Body Fluids and Circulation Class 11 NCERT Solutions Study Material Free PDF

UNIT 1 - RESPIRATORY SYSTEM I
UNIT 2 - RESPIRATORY SYSTEM II
UNIT 3 - BODY FLUIDS
UNIT 4 - CARDIOVASCULAR SYSTEM
UNIT 5 - LYMPHATIC SYSTEM
HUMANPHYSIOLOGY:BREATHING ANDEXCHANGE
OFGASES,BODYFLUIDANDCIRCULATION

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1.1 INTRODUCTION
Respiration is the transport of oxygen from the air to the cell in the tissue, and the removal of
carbon dioxide in the opposite direction. The aerobic metabolic pathway of conversion of nutrients
to energy requires oxygen, for example:
C6
H12
O6
+ O2
 CO2
+ 6H2
O + energy as ATP
Because the cells require a continuous supply of ATP, the body, in turn, needs a constant intake of
oxygen and method for removal of carbon dioxide. Our respiratory system functions to accomplish
these necessary gas exchanges.
1.2 GROSS ANATOMY
1.2.1. Upper respiratory tract
A. Nose
The external portion of the nose begins at the base of the frontal bone and extends over the maxilla,
with the nasal bone providing the bridge of the nose. Extending from the nasal bone is a collection
of hyaline cartilages that make up the bulk of the nose. The medial region of the nose consists of
a central septal cartilage with two lateral processes. The tip of the nose contains the major alar
cartilage. Two minor alar cartilages are found at the sides and base of the lateral septal cartilages.
Dense fibrous connective tissue is found under the skin of the sides lateral aspects the nose, away
from the cartilage. Variations in the size of a person’s nose, or its form, are due to differences in the
various cartilages.
The openings to the nose, the nares, are lined with coarse hairs to aid in filtration of particulate
matter. The area immediately inside the nares, the vestibule, contains a large number of sebaceous
glands, sweat glands, and hair follicles. In rabbit, at the apex of nose, a pair of external-nares is
present. This is termed as Dirhynous condition.
The nasal cavity is divided into right and left sides by the nasal septum. This dividing wall’s anterior
portion is made of cartilage. Its floor, the palate, forms the roof of the mouth. It is separated into the
hard and soft palate. The anterior hard palate is formed from the maxillary process of the palatine
bone. The posterior soft palate does not contain bone and moves during swallowing to close off the
nasal cavity to prevent material from entering it from the mouth.
Extending from the nasal septum are three pairs of C-shaped structures called conchae/ turbinates.
The superior, middle, and inferior conchae extend the length of the nasal cavity. They are covered
by a mucus membrane. The conchae serve as baffles to increase the surface area of the nasal
cavity. The mucus glands and blood vessels aid in humidifying and warming the air coming into the
body.
There are two types of epithelial coverings in the nasal cavity: respiratory epithelium and olfactory
epithelium. The olfactory mucosa found in the roof of the cavity detects odors. The respiratory
UNIT 1 - RESPIRATORY SYSTEM I

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epithelium that covers the rest of the nasal cavity is also found through most of the respiratory tract
and is pseudostratified, ciliated, columnar epithelia. This is called pseudostratified columnar ciliated
glandular epithelium (PSCCGE).
Functional divisions of nasal passage:
 Vestibular region: Skin, hairs, sebaceous glands.
 Respiratory region: PSCCGE, Goblet cells.
 Olfactory region: Schneiderian membrane or neuro sensory epithelium.
B. Paranasal sinuses
Within the bones surrounding the nasal cavity are paranasal sinuses (a sinus is a hollow area),
which function to make the skull lighter as well as moisten and warm incoming air. These sinuses
frequently become filled with excess fluid when a person has a head cold. Since the paranasal
sinuses serve as resonators for speech and sound it is not surprising that the sound of the voice
becomes altered when they are filled with fluid or swollen.
C. Pharynx
As the air passes posteriorly through the nasal cavity, it enters the pharynx which encompasses 3
distinct areas and connects the nasal passage to the larynx in the throat. It extends about 13 cm
from the base of the skull to the level of the 6th
cervical vertebrae. The wall of all 3 portions contains
two layers of skeletal muscle: inner layer arranged in circular pattern and outer layer arranged
longitudinally.
Nasopharynx: The superior section of the pharynx, posterior to the nasal cavity and inferior to the
sphenoid bone. It acts only as a conduit for air and closes off during swallowing by raising the soft
palate. The paired pharyngeal tonsils, also known as the adenoids, lie in the posterior wall of the
nasopharynx.
Oropharynx: The opening from the oral cavity and the second portion of the pharynx, runs from the
soft palate to the epiglottis and is posterior to the oral cavity. In comparison to the nasopharynx,
which is lined with columnar epithelia, the oropharynx is covered by stratified squamous epithelia,
that are often found covering areas which are subject to a great deal of frictional wear.
Laryngopharynx: The third and shortest portion of the pharynx, runs inferiorly from epiglottis and
ends superior to the esophagus. It carries both air and food and is lined with stratified squamous
epithelia.
Pharynx is the only part where food and air passage mix together.
D. Larynx
It is a complex structure (about 5 cm (2 in.) long) extending from the laryngopharynx and the hyoid
bone to the trachea. It is in addition to providing a passageway for air, it directs air and food to their
appropriate tubes. The vocal cords, which are used in making sound and speech, can be found

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within the larynx. The epithelial lining of the
larynx exhibits two different arrangements.
Initially, stratified squamous epithelia lines
laryngopharynx to the vocal cords. Inferior to
the vocal cords, the epithelial lining shifts to
pseudostratified, ciliated, columnar epithelia.
The nine cartilage structures found in the
larynx provide key anatomical landmarks.
They function to maintain an open airway.
Eight of the cartilages are composed of
hyaline cartilage.
Epiglottis: It is made of elastic cartilage and
covered with stratified squamous epithelia. It
connects loosely to the tongue, the hyoid
bone, and the rim of the thyroid cartilage. The
epiglottis is normally open, allowing air to
freely flow into the rest of the larynx and the trachea. When a person swallows, the front of the
epiglottis is raised, and the posterior portion descends, covering the glottis, which is the opening to
the vocal cords and trachea. This movement directs food and water to the esophagus and prevents
it from entering the bottom portion of the larynx and the upper trachea.
Thyroid cartilage: The largest cartilage of the larynx and found at the front. This roughly triangularly
shaped cartilage contains the laryngeal prominence, commonly known as the “Adam’s apple” which
is more prominent in males (during puberty as the larynx widens, the voice deepens). The thyroid
cartilage connects to the hyoid bone by the thyrohyoid membrane or ligament.
Cricoid cartilage: Inferior to the thyroid cartilage, connects superiorly to the thyroid cartilage by the
cricothyroid ligament and inferiorly to the trachea by the cricotracheal ligament. When an occlusion
of the upper respiratory tract occurs and a tracheostomy is performed to facilitate breathing, the
cricothyroid ligament must be punctured.
Arytenoids cartilages, cuneiform cartilages, corniculate cartilages: The next six cartilages are
found in three pairs. Arytenoids cartilages anchor the true vocal cords. All pairs are found in lateral
and posterior walls of larynx. Except for the epiglottis, the arrangement of the cartilages of the
larynx ensures that the passages through the larynx remain open.
Vocal cords: Two pairs of folded tissue immediately inferior to the epiglottis: the false and true
vocal cords. The false vocal cords do not function in making sounds or speech but aid in closing the
glottis. The true vocal cords run from the arytenoids to the thyroid cartilage, are reinforced with
elastic fibers and vibrate when adequate air is forced through the gap between them, resulting in
sound. Pitch control is achieved by adjusting the tension on the cords. Lessening the tension lowers
the pitch.
Cricoid
cartilage
Hyoid bone Epiglottis
Thyrohyoid
membrane
False vocal
cords
True vocal
cords
Thyroid
cartilage
Ventricle
Vocalis
muscle
Trachea

6
Actual speech is achieved with the coordination of muscles in the pharynx, face, tongue, soft palate,
and lips.
1.2.2. Lower respiratory tract
A. Trachea
It is about 10 cm long and 2 cm wide, extends from the larynx to the level of the 5th
thoracic vertebrae.
The presence of 16-20 C-shaped dorsally incomplete rings of hyaline cartilage located along the
trachea prevents this airway from collapsing.
The last cartilage in the trachea exhibits a projection called carina, from the anterior surface that
extends into the lumen. It is very sensitive to particulate material and causes coughing when
stimulated.
The openings of the C-shaped cartilages face the posterior of the trachea and contain the trachealis
smooth muscle which constricts when someone coughs, increasing the force of the cough. The
trachealis muscle also constricts during an asthmatic reaction, shrinking the airway and making it
harder to breathe.
Structurally, trachea consists of 3 concentric tissue layers:
 Mucosa: Has 3 sublayers
• Epithelium - PSCCGE
• Lamina propria - Reticular fibrous connective tissue.
• Muscularis mucosa - Longitudinal and circular muscle fibers.
 Submucosa: Areolar connective tissue.
 Tunica adventia: White fibrous connective tissue.
B. Bronchi and Bronchioles
Branching of the trachea into the right and
left primary bronchi occurs after the last
cartilage in the trachea at the level of the 7th
thoracic vertebrae. The right primary
bronchus is wider, shorter, and more vertical
than the left primary bronchus because the
left primary bronchus and lung must
accommodate the heart. The primary
bronchi branch to form the secondary or
lobar bronchi. There are three secondary
bronchi on the right and two on the left. The
secondary bronchi continue to branch into
the tertiary or segmented bronchi, which
also continue the branching pattern.
Tertiary
bronchus
Bronchiole
Terminal
bronchiole
Alveoli
Secondary
bronchus
Primary
bronchus
Alveoli enlarged

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Approximately 23 successive branches lead to the bronchioles.
A bronchiole is a tube with a diameter of less than 1 millimeter (mm). When the measurement
reaches less than 0.5 mm, a bronchiole is termed a terminal bronchiole. Plates of cartilage are
found in the walls of the bronchial tree, with the amount of cartilage and the number of plates
decreasing as the bronchi and bronchioles become smaller. The terminal bronchioles do not contain
cartilage plates, these tubes are small enough to stay open without cartilage. Smooth muscle is
found throughout the system, even into the respiratory zone.
C. Lungs
Along with the heart, the lungs take up nearly all of the space in the thorax, superior to the diaphragm.
As an organ, the lung is made up of airway tubes and alveoli, giving it little weight. Elastic connective
tissues in the stroma of the lungs allow them to expand with incoming air and recoil when expelling
air. The lungs contain a large amount of surface area in order to efficiently support the exchange of
oxygen and carbon dioxide.
The hilus (meaning depression of pit) of the lungs is an indentation on the medial side of the lungs
and the point of entry of blood vessels, primary bronchi, nerves, and lymphatics. This collection of
vessels and nerves makes up the root of the lung. The tip or apex of the lungs is a blunted point
found just above the clavicles. The posterior, lateral and anterior sides of the lungs are surrounded
by the ribs. These areas are called the costal surfaces of the lungs referring to the costal cartilage
surrounding them. The flat inferior surface of the lungs is found superior to the diaphragm and
referred to as the base of the lung. Since, the liver is found on the right side of the body and inferior
to the diaphragm, the insertion of the diaphragm is slightly raised on the right. Consequently the
right lung is usually slightly shorter than the left. The lungs extend from the first costal cartilage to
the tenth thoracic vertebrae.
The lungs consist of a right lung and a left lung. Even though the right lung is slightly shorter than the
left, the left lung has about 10% less mass than the right due to the cardiac notch on the medial side
of the left lung. The heart is tucked into this notch. The heart, the right lung, and the left lung are
each located in their own anatomical compartments in the upper thorax. The right lung is divided
into three lobes. A horizontal fissure separates the superior and middle lobes, and an oblique fissure
separates the middle and inferior lobes. The smaller left lung contains only two lobes. An oblique
fissure separates the superior and inferior lobes on this side.
Each lobe is divided into bronchopulmonary segments separated by connective tissue septa.
There are a total of 10 of these segments and each contains a tertiary bronchiole, a pulmonary and
bronchial artery, and a lymphatic branch. The presence of these segments aids in further isolating
parts of the lungs to prevent the spread of infection or disease. Connective tissue further divides the
segments into lung lobules, the smallest anatomical unit in the lungs. A lobule is hexagonal in shape
and less than a centimeter in diameter. Each lobule contains a terminal bronchiole and its associated
alveoli. The connective tissue associated with lobules may be blackened by tobacco smoke or
pollution from the environment.

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Each lobule is further divided into several air-sacs and in the end each air-sac is lastly divided into
3 or 4 alveoli, the structural and functional units of lungs. Approximately 300 million alveoli are
present in both lungs. Inner (alveolar) surface area of both lungs is approximately 100 m2
. Wall of
alveoli consist of two layers: outer layer is composed of yellow fibrous CT while inner layer iscomposed
of simple squamous epithelium. Squamous cells are called as pneumocytes which help in gaseous
exchange (pneumocyte-I) while few pneumocytes (pneumocyte-II, larger in size) secrete lecithin
(phospholipid) that acts as surfactant preventing the alveoli from remaining collapse by reducing its
surface tension.
Alveoli internal surface, the respiratory surface is derived from the endoderm of the embryo. The
middle part of alveoli wall is made up of CT, richly supplied with a dense network of blood capillaries.
There are small pores, pores of Kohn, present in the walls of alveoli that make gas diffusion easy.
This is the characteristic feature of mammalian lungs, that there is no central cavity, mammalian
lungs are solid and spongy. Muscles are absent in the lungs of mammals. So the power of self-
contraction and self-expansion is absent in these lungs (sunken lungs).
Each lung is found in a pleural cavity bounded by the pleural membrane, a double sided membrane
that contains a thin layer of pleural fluid. The visceral pleural is a mucus membrane that covers the
lungs and folds over at the hilus. The folded membrane continues and becomes the parietal pleura,
which lines the inner wall of the thoracic cavity. The space between the two membranes is called the
pleural cavity or space. From 1 to 15 ml of pleural fluid is found on the facing surfaces of the
pleural membranes. This fluid helps to lubricate the membrane surfaces so that the movement of
the lungs during inhaling and exhaling does not cause frictional damage to the tissues. The fluid
also lightly holds the two membranes together so that they move together as the chest wall expands
and contracts.
The pleural sac extends below the lungs, to the level of the twelfth thoracic vertebrae. Samples of
the pleural fluid can be safely taken from this area. Normal pleural fluid is clear and pale yellow in
color. It has very few cells free in the fluid. The majority (75%) of these cells are macrophages.
About 23% of the cells are lymphocytes, with an assortment of cells making up the remaining 2%.
Sometimes due to bacterial infection the amount of pleural fluid increases and the organism feels
difficulty in breathing (dyspnoea), this is termed as pleural effusion disease.

Trachea
Apex
Upper lobe
Oblique fissure
Upper lobe
Horizontal fissure
Oblique fissure
Lower lobe
Cardiac notch
Middle lobe
Lower lobe
Lung
Intercostal
muscle
Pleural sac
Trachea
Anterior azygous
lobe
Bronchus
Left anterior
lobe
Left posterior
lobe
Posterior azygous
lobe
Right posterior
lobe
Rabbit
Right anterior
Terminal
bronchiole
Atria
Air saccules
Alveoli
Respiratory
bronchiole
Alveolar ducts
Man
D. Blood and nerve supply
The lungs have a dual blood supply. The pulmonary artery brings oxygen-poor blood from the
right ventricle of the heart. This blood passes through the pulmonary capillaries, where some
carbon
RABBIT HUMAN
Right lung Left lung Right lung (625 gm) Left lung (575 gm)
4 lobes 2 lobes 3 lobes 2 lobes
Anterior azygous Left anterior Anterior lobe Left anterior
Right anterior Left posterior Middle lobe Left posterior
Right posterior Posterior lobe
Posterior azygous

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dioxide will leave the blood and a large amount of oxygen will be acquired. The newly oxygenated
blood enters the pulmonary veins and returns back to the left side of the heart. The pulmonary
circulation holds about 500 milliliters (ml) of blood, or about 10% of the body’s supply. About 75 ml
of blood is in the pulmonary capillaries for gas exchange at any one time. The blood supply that
nourishes the tissues of the lungs arrives through the bronchial artery, which branches off of the
aorta and carries oxygen-rich blood to support the lung tissues. The bronchial supply anastomoses
with the pulmonary vessels, and a mixture of blood leaves through the bronchial and pulmonary
veins. Blood passes through the lungs at a rate equal to cardiac output, or about five liters per
minute.
Nerves from the pulmonary plexus enter the lungs at the hilus. These nerves contain a mixture of
visceral sensory and autonomic nerve fibers that follow the bronchial tree and blood vessels.
Parasympathetic nerve stimulation results in bronchoconstriction, constriction of the bronchioles,
while sympathetic nerve stimulation results in bronchodilation, dilation of the bronchioles.
E. Thoracic cage
Coverings of thoracic cavity makes thoracic cage.
Anterior surface: Clavicle bones, neck.
Posterior surface: Diaphragm.
Dorsal surface: Vertebral column and ribs.
Ventral surface: Sternum and ribs.
Lateral surface: Ribs.
F. Diaphragm
A muscular septum which is found only in mammals (and crocodile). Normal shape of it is dome like
which divides body cavity in two parts upper thoracic cavity and lower abdominal cavity. In central
region of diaphragm, central tendon is present. It is pierced by three structures:
(i) Oesophagus (ii) Aorta (iii) Posterior vena cava
Radial muscles are present in diaphragm. They originate from periphery and inserted in central
region of diaphragm. By the contraction in these muscles, diaphragm become flatten in shape, so,
volume of thoracic cavity increases. Therefore, diaphragm helps in inspiration.
G. Intercostal muscles (ICM)
Space between two ribs is called intercostal space in which 2 types of muscles are present: external
ICM (EICM) and internal ICM (IICM).
EICM: They originate from dorsal part of upper rib and insert on ventral part of lower rib. By the
contraction in these muscles, ribs and sternum shift upward and outward. So they help in inspiration.
IICM: They originate from dorsal part of lower rib and insert in ventral part of upper rib. By the
contraction in these muscles, ribs and sternum shift downward and inward respectively. So it helps
Inspiration
Sternum
Ribs
Vertebral
column
Expiration
Position of ribs
(Thoracic respiration)

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in forceful expiration which is a voluntary activity. So contraction of IICM is under the control of
cerebrum.
1.3 RESPIRATORY FUNCTIONS
1.3.1 Zones of respiratory system
A. Conducting zone
The conducting zone of the
respiratory system brings gases
into and out of the respiratory
system. In addition, the organs
and tissues along this path warm
the incoming air to approximately
body temperature, moisten the air
to about 100% humidity, and begin
filtering out any harmful
microorganisms or particles that
may be suspended in the inhaled
air.
If the air in the respiratory zone is
not near 100% humidity, the thin
walled alveoli can become
dehydrated and may deteriorate.
B. Respiratory zone
A transition occurs in the
composition of the epithelial lining
at the end of the terminal
bronchioles. The epithelial lining
changes to simple cuboidal cells
without any intermixed goblet
cells. The walls of the tubes at this
point become very thin and are
called respiratory bronchioles.
The loss of the goblet cells means
that no mucus is secreted into the
bronchioles at this point, but the
cilia are still present to sweep
away any mucusthat should come
down into them. Some portions of
External nostrils
Vestibule
Nasal chamber
Internal nares
Nasopharynx
Pharynx
Glottis
Larynx
Trachea
Bronchial tree
Trachea
Primary bronchus
Secondary bronchus
Tertiary/Segmental bronchus
Total pulmonary bronchioles
Terminal bronchiole
Respiratory bronchiole
Alveolar duct
Atria
Alveolar sac
Alveoli
Conducting
zone
Exchange zone
Respiratory tree
Bronchial
tree

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the respiratory bronchioles are not completely covered by cilia, and a number of phagocytic
macrophages are found in this area to compensate for the loss of the cilia. Some gas exchange can
occur through the walls of the respiratory bronchioles.
Respiratory bronchioles lead into the alveolar ducts, which still have smooth muscle and some
elastic fibers in the walls. Alveolar sacs occur as clusters of alveoli (singular alveolus) sharing a
common chamber along the alveolar ducts.
1.3.2 Respiratory pulmonary ventilation
Pulmonary ventilation brings in air with a new supply of oxygen and a very small amount of carbon
dioxide from the atmosphere into the alveoli. This mixture then participates in external respiration,
the exchange of oxygen and carbon dioxide between the alveoli and pulmonary capillary blood
across the respiratory membrane. Internal respiration is the exchange of gases between the tissues
of the body and the blood, which provides oxygen for aerobic cellular respiration and removes
carbon dioxide. Aerobic cellular respiration refers to the intracellular use of oxygen and the
generation of carbon dioxide waste through metabolic pathways.
Inspiration
Inspiration occurs by increasing the volume of the thorax. This active process involves the use of
chest and neck muscles. Resting inspiration is achieved mostly by movement of the diaphragm.
The relaxed shape of the diaphragm resembles a shallow dome with the apex pointing towards the
lungs, similar to the shape of an open umbrella. When the diaphragm contracts, it tends to flatten
out, expanding the volume of the thorax in an inferior direction. Consequently, the intrapleural and
intrapulmonary pressures decrease below atmospheric pressure resulting in air being pulled through
the conducting zone and into the lungs. The external intercostal muscles work in conjunction with
the diaphragm. The normal orientation of the ribs is around the side of the thorax and angled inferiorly
to the sternum. When the external intercostal muscles contract, the ribs are pulled up, also expanding
the thoracic cavity in a horizontal direction. In adults, ventilation occurs about 12 times a minute and
moves roughly 500 ml of air during each breath. Normally it takes around 2 seconds.
Expiration
Resting expiration is a passive process. The muscles used during inspiration relax, and allow the
chest wall and the diaphragm to move back to their original position, thus decreasing the volume of
the thorax and forcing air from the lungs. The compression of the chest wall also aids in moving
blood and lymph through the vessels that drain the lungs. Expiration becomes an active process
when a more forceful exhale is required. The internal intercostal muscles pull the ribs down, helping
to compress the chest. The external and internal oblique and transverse abdominal muscles press
on the abdominal organs, which move them up against the diaphragm and force the diaphragm
higher than it would normally go on relaxation, further decreasing the volume of the thoracic cavity.
Normal breathing is also called abdominal breathing and it takes around 3 seconds.

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Air enters
Ribcage moves
up and out
Lungs
expand
Diaphragm
moves down
Inhalation
Air leaves
Ribcage moves
down and in
Lungs get
smaller
Diaphragm
moves up
Exhalation
1.3.3 Regulation of respiration
The respiratory rhythm is controlled by the nervous system. The rate of respiration can be enhanced
as per demand of the body during strenuous physical exercises. A number of groups of neurons
located bilaterally in the medulla oblongata control the respiration. These are called respiratory
centers. Three groups of respiratory centers have been identified, namely: dorsal respiratory group,
ventral respiratory group and pneumotaxic center.
The dorsal respiratory group is present in the dorsal portion of medulla oblongata. The signals
from these neurons generate the basic respiratory rhythm. The nervous signal released from this
group is transmitted to the diaphragm and EICM.
The ventral respiratory group of neurons are located anterolateral to the dorsal respiratory group.
During normal respiration, this remains inactive and even does not play any role.
In the enhanced respiratory drive, the respiratory signal of this group contributes to fulfill the demand
by regulating both inspiration and expiration. Few of the neurons of this group control inspiration,
while few other control expiration, thus regulating both. The pneumotaxic center is located dorsally
in the upper pons. It transmits signals to the inspiratory area. Primarily, it controls the switch off point
of inspiration. When this signal is strong (high frequency), the inspiration lasts for a shorter duration
and lungs are filled partially. During weak pneumotaxic signal, inspiration lasts for a longer duration
resulting into complete filling of lungs. The strong signal (high frequency) causes increased rate of
breathing, because duration of inspiration as well as expiration, is shortened. The concentration of

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CO2
and H+
cause increased strength of inspiratory, as well as expiratory signal. However, oxygen
has no such direct effect.
Hering Breuer reflex arch
In the walls of terminal bronchioles and atria stretch receptors are present, which are normally
inactive but they become active when the lungs are excessively inflated due to failure of switch off
of inspiration. The Hering Breuer reflex arch now becomes activated and sends inhibitory signals to
the inspiratory center to switch off inspiration. This prevents the alveoli from over stretching and
bursting. Thus Hering Breuer reflex arch is a protective reflex which works only when normal
mechanism of switch off of inspiration does not work timely due to any reason.
1.3.4 Factors affecting breathing
A. Chemical factors
There are so many factors which affect the activity of respiratory center. Respiratory center is sensitive
to CO2
concentration in the blood and pH of blood. Respiratory center is not sensitive for O2
concentration in blood. Whenever, in the blood, CO2
concentration is increased, or pH is decreased,
or acidity is increased, then respiratory center becomes more activated and increases the rate of
respiration. Normal breathing rate of rabbit is 36 to 38 per minute. For human it is 12 to 18 per
minute.
B. Physical factors
The activity of respiratory center is also affected by body temperature and blood pressure. Whenever
body temperature is increased or blood pressure goes high, respiratory center becomes more
activated and this increases the respiration rate.
C. Sensory factors
A sensory organ – carotid labyrinth is found in the walls of carotid arteries. This is sensitive for O2
concentration in blood. Whenever O2
concentration in the blood is reduced, this sensory organ
becomes activated and sends sensory impulse to respiratory center. As a result respiratory center,
becomes activated and this increases the rate of respiration. This center also can recognize changes
in CO2
and H+
concentration.
1.3.5 Respiratory volumes, capacities and function tests
Various lung volumes, capacities (capacities are combinations of lung volumes) and flow rates can
be evaluated through a process called spirometry. The patient breathes in and out under controlled
conditions, and the amount of air passing through the system, as well as the time it takes for air
passage is measured. The values for these measurements depend on lung function and the size of
the patient.

15
Expiratory
reserve volume
Residual
volume
Expiration
Time
1000
2000
3000
4000
5000
6000
Lung
volume
(ml)
Functional
residual
capacity
Tidal
volume
Total lung
capacity
Vital
capacity
Inspiratory
capacity
Inspiratory
reserve
volume
Inspiration
Diagram showing respiratory excursions during normal breathing and during maximal
inspiration and maximal expiration
Several respiratory capacities can be calculated from the volumes listed above.
 Inspiratory capacity: The amount of air (about 3500 milliliters) a person can breathe in,
beginning at the normal expiratory level and distending the lungs to the maximum amount.
 Functional residual capacity: The amount of air that remains in the lungs at the end of
normal expiration (about 2300 milliliters).
 Vital capacity: This is the maximum amount of air a person can expel from the lungs after
first filling the lungs to their maximum extent and then expiring to the maximum extent (about
4600 milliliters).
Respiratory volumes Description Normal adult values
Tidal Volume (TV) Volume of a resting breath 500 ml/breath
Inspiratory Reserve Maximum volume that can be inhaled after a 1900-3300 ml
Volume (IRV) normal inhale
Expiratory Reserve Maximum volume that can be exhaled after a 700-1200 ml
Volume (ERV) normal exhale
Residual Volume (RV) Air left in the lungs after exhaling completely 1200 ml
(i.e. after an ERV)
Dead Space Air inhaled during breathing that stays in the 150 ml
conducting zone

16
 Total lung capacity: The maximum volume to which the lungs can be expanded with the
greatest possible effort (about 5800 milliliters).
All pulmonary volumes and capacities are about 20-25% less in women than in men, and they are
greater in large and athletic people than in small and asthenic people.
Besides volumes and capacities, flow rates are often measured to assess a person’s lung function.
Flow rates are important because although changes in airway resistance will not usually change
volumes, they will affect the rate of air movement through the system. To assess flow rates, the
individual takes as deep a breath as possible (gets to VC) and then exhales maximally and as
quickly as possible. The time it takes to bring the lung volume down to RV provides information
about airway resistance. Flow rates are used to assess asthma and related conditions.
Lung volumes and flow rates can be used to differentiate between obstructive and restrictive
pulmonary diseases. Obstructive pulmonary disorders are those that increase the resistance to
airflow, thus increasing the time it takes to move air in and out of the lungs. Examples of obstructive
disorders include bronchitis and asthma. Restrictive pulmonary disorders are those that affect the
compliance of the lung or affect the ability of the chest wall to expand and relax normally. Such
disorders lead to lower lung volumes than would be expected based upon a person’s size. Examples
of restrictive pulmonary disorders include those that lead to structural or functional changes in the
lung tissue (tuberculosis, fibrosis) or those that impede normal muscular function (such as muscular
dystrophy) or function of motor nerves (such as multiple sclerosis and ALS).
TARGET POINTS
Spirometry is the measuring of breath and is one of the most common tests of pulmonary function.
These tests are collectively known as PFTs (pulmonary function tests) and are used to measure
and assess the ventilation of the lungs. Spirometry can measure the volume of air moving in and out
of lungs and the speed of airflow in and out of the lungs. The most common features measured in
spirometry are the vital capacity, the forced vital capacity, and forced expiratory volume.
Respiratory capacities Description Normal adult values
Inspiratory Capacity (IC) TV + IRV 2400 - 3800 ml
Functional Residual Capacity (FRC) RV + ERV 1800 - 2200 ml
Vital Capacity (VC) TV + IRV + ERV 3000 - 4600 ml
Total Lung Capacity (TLC) TV + IRV + ERV + RV 4200 - 6000 ml

17
1. The diagram shows organs associated with
breathing in humans
D
A
B
C
What are the numbered structures?
a) A- Bronchus, B - Bronchioles, C - Larynx,
D - Trachea
b) A- Bronchioles, B - Bronchus, C - Larynx,
D - Trachea
c) A- Larynx, B - Trachea, C - Bronchus,
D - Bronchiole
d) A- Trachea, B - Bronchus,
C - Bronchiole, D - Larynx
2. Which features distinguish bronchioles from
bronchi?
a) Bronchioles are less than 1 mm in
diameter
b) Bronchioles have cartilage in their walls
c) Larger bronchioles are supported by
connective tissue alone which extend
from the interlobular septa
d) Both (a) and (b)
3. By the contraction in diaphragm volume of
thoracic chamber increases in the
a) Dorso-ventral axis
b) Antero-posterior axis
c) Dorso-posterior axis
d) Antero-ventral axis
4. The most important muscular structure in
respiratory system of rabbit is
a) External intercostal muscle
b) Internal intercostal muscle
c) Diaphragm
d) Vertebral column
Simple Questions
5. A wall of alveoli is composed of
a) Simple squamous epithelium
b) Simple cuboidal epithelium
c) Pseudostratified epithelium
d) Simple columnar epithelium
6. Which of the following steps not involved in
respiration?
a) Diffusion of gases across alveolar
membrane
b) Transport of gases by the blood
c) Provide nutrients, O2
to all the living cells
of body
d) Utilization of O2
by the cells for catabolic
reactions and resultant release of CO2
7. Which of the following is not a structural
feature of the left lung?
a) Superior lobe b) Cardiac notch
c) Inferior lobe d) Middle lobe
8. Very high number of alveoli present in a lung
is meant for
a) More space for increasing volume of
inspired air
b) More area for diffusion
c) Making the organ spongy
d) Increasing nerve supply
9. Life without air would be
a) Reductional
b) Free from oxidative damage
c) Impossible
d) Anaerobic
10. During normal respiration, without any effort,
the volume of air inspired or expired iscalled
a) Tidal volume b) Reserve volume
c) Residual volume d) None of these
11. After deep inspiration, capacity of maximum
expiration of lung is called
a) Total lung capacity
b) Functional residual capacity
c) Vital capacity
d) Inspiratory capacity

18
12. The impulse for voluntary forced breathing
starts in
a) Medulla
b) Vagus
c) Cerebral hemisphere
d) Spinal cord
13. Inhibition of respiratory center is termed
a) Bradypnoea b) Apnoea
c) Anoxia d) Tachypnoea
14. Hiccough (hiccup) is due to activity of
a) Intercostal muscle
b) Food in air tract
c) Diaphragm
d) Inadequate oxygen in environment
15. During inspiration, the diaphragm
a) Expands
b) Shows no change
c) Contracts and flattens
d) Relaxes to become dome shaped
16. A person breathes in some volume of air by
forced inspiration after having a forced
expiration. This quantity of air taken in is
a) Total lung capacity
b) Tidal volume
c) Vital capacity
d) Inspiratory capacity
17. Which is not a structure of the respiratory
system?
a) The pharynx b) The bronchus
c) The larynx d) The hyoid
18. Lungs of rabbit and man are
a) Sunken lungs b) Pressure lungs
c) Aquatic lungs d) None
19. Cilia of trachea transfers
a) Mucous into pharynx
b) Mucous into lungs
c) Air into lungs
d) Air into pharynx
20. In lungs air is separated from venous blood
by
a) Squamous epithelium + tunica externa
of blood vessel
b) Squamous epithelium + endothelium of
blood vessel
c) Transitional epithelium + tunica media
of blood vessel
d) Columnar epithelium + 3 layered wall of
blood vessel
21. Which structure is not related to respiration
in frog?
a) Diaphragm b) Skin
c) Buccal cavity d) Lungs
22. Signet ring cartilage of larynx is
a) Cricoid b) Arytenoid
c) Thyroid d) All
23. Which one protects the lungs?
a) Rib b) Vertebral column
c) Sternum d) All above
24. Rate of breathing in rabbit
a) 12 / min b) 36 - 38 / min
c) 100 / min d) 300 / min
25. Lung recoil occurs because of elastic fibers
in the alveolar walls and
a) Barometric pressure
b) Pleural pressure
c) Surface tension of fluid that lines the
alveoli
d) Surfactant secretion in the alveoli
26. Surfactant
a) Reduces surface tension of the fluid
lining the alveoli
b) Increases pleural pressure
c) Decreases alveolar pressure
d) Makes inspiration more difficult

19
27. If a pneumothorax occurs, pleural pressure
and alveolar pressure become ____
barometric pressure
a) Equal to
b) Greater than
c) Lesser than
d) Cannot be determined
28. If compliance increases, lung expansion is
a) Easier b) More difficult
c) Unaffected d) None of these
29. If a person's vital capacity is 4000 ml, her
ERV is 1000 ml and her IRV is 2500 ml and
her TV is
a) 3500 ml b) 3000 ml
c) 500 ml d) 1500 ml
30. If the total pressure of a gas is 700 mmHg
and its composition is 20% O2
, 0.03% CO2
,
75% N2
, and 5% water vapor, the partial
pressure of O2
(pO2
)
a) 140 mmHg b) 105 mmHg
c) 20 mmHg d) 1600 mmHg
Difficult Questions
1. Match the following columns
Codes
A B C D E
a) 3 4 2 1 5
b) 3 1 2 5 4
c) 3 1 4 5 4
d) 5 4 2 1 2
2. The air that enters our lungs is characterized
that
I) It is warm
II) It is filtered
III) Some oxygen is extracted from it
IV)Some carbon dioxide is added to it
The correct answer is
a) I, II, III and IV b) I and II
c) II and IV d) III and IV
Column I Column II
A. Tidal volume 1. 2500 to 3000 mL of air
B. Inspiratory reserve 2. 1000 mL of air
volume
C. Expiratory reserve 3. 500 mL of air
volume
D. Residual volume 4. 3400 to 4800 mL of air
E. Vital capacity 5. 1200 mL of air
3. The following diagram shows a section of
an alveolus in a human lung
Air flow Alveolus
Blood flow
Blood capillary
Which conditions would result in the
maximum rate of diffusion of oxygen from
the alveolus into the blood capillary?
Amount of Amount of Rate of
oxygen in oxygen blood
alveolar air in blood flow
a) Small Large Fast
b) Small Large Slow
c) Large Small Fast
d) Large Small Slow

20
4. Which is correct?
a) Respiratory centers are not affected by
CO2
.
b) In humans vital capacity is just double
the expiratory volume.
c) A human lung has 103
alveoli.
d) During inspiration the lungs act as
suction pump.
5. Which one of the following statement is
correct?
a) Chest expands because air enters into
the lungs
b) Air enters into the lungs because chest
expands
c) The muscles of the diaphragm contacts
because air enters into the lungs
d) All of the above statements are correct
6. Which part of thyroid cartilage in larynx is
closed?
a) Dorsal b) Ventral
c) Anterior d) Posterior
7. Neither the trachea nor the bronchi contain
a) Hyaline cartilage
b) Ciliated columnar epithelium
c) Goblet cells
d) Simple squamous epithelium
8. In man, the structure which functions similar
to spiracles of cockroach are
a) Lungs b) Alveoli
c) Bronchioles d) Nostrils
9. Among mammals, the efficiency of
ventilation of lungs as compared to reptiles
and birds is better developed by the
presence of
a) Ribs and costal muscles
b) Only ribs
c) Only costal muscles
d) Diaphragm
10. Listed below are four respiratory capacities
(a-d) and four jumbled respiratory volumes
of a normal human adult
Respiratory Respiratory
capacities volumes
A) Residual volume 2500 ml
B) Vital capacity 3500 ml
C) Inspiratory reserve 1200 ml
volume
D) Inspiratory capacity 4500 ml
Which one of the following is the correct
matching of two capacities and volumes?
a) A) 4500 ml B) 3500 ml
b) B) 2500 ml C) 4500 ml
c) C) 1200 ml D) 2500 ml
d) D) 3500 ml A) 1200 ml
11. If the thoracic wall but not the lungs are
punctured
a) The lungs get inflated
b) The man dies as the lungs get collapsed
c) The breathing rate decreases
d) The breathing rate increases
12. One of the following is a difference between
pulmonary respiration of frog and human
a) Diaphragm and ribs play role in breathing
b) Lungs are respiratory organs
c) Respiration occurs due to pressure
gradient
d) None of the above
13. A person met with an accident and died
instantly without any injury to heart, brain,
stomach and kidney. One of the following
is a reason for his death
a) Intestine got twisted
b) RBCs became coagulated
c) Stomach stopped digestion
d) Diaphragm got punctured

21
14. Division of mammalian lungs into a very
large number of tiny alveoli around alveolar
ducts opening into bronchioles is
a) An inefficient system of ventilation of
alveoli through with very little residual air
b) An inefficient system of ventilation of
alveoli resulting in very high percentage
of residual air in the lungs
c) A very efficient system of ventilation of
alveoli with no residual air
d) An efficient system of ventilation of
alveoli with little or no residual air
15. Which of the following factor can affect the
rate of diffusion of gases?
a) Thickness of the membranes involved
in diffusion
b) Solubility of the gases
c) Pressure of the gases
d) All of these
16. Residual air mostly occurs in
a) Alveoli b) Bronchus
c) Nostrils d) Trachea
17. When there is no air in initial bronchioles,
they does not collapse. It is due to
a) Presence of lecithin
b) Presence of incomplete cartilaginous
rings
c) Presence of complete cartilaginous
rings
d) Presence of mucous
18. Breathing differs from respiration by
a) Both are same and there is no
difference
b) Breathing refers to respiration in human
beings whereas respiration occurs in rest
of the animals and plants
c) Breathing refers to chest movements
due to inhalation of oxygen and
exhalation of carbon dioxide, whereas
respiration refers to gaseous exchanges.
19. Adam's apple represents
a) Arytenoid cartilage of larynx
b) Cricoid cartilage of larynx
c) Thyroid cartilage of larynx
d) All of the above
20. Common factor in the trachea of mammals
and insects is
a) Ciliated inner lining
b) Non-collapsible wall
c) Paired nature
d) Origin from head region
21. The impulse for voluntary muscles for
forced breathing starts in
a) Medulla oblongata
b) Vagus nerve
c) Cerebellum
d) Cerebrum
22. The function of tracheal cilia is to
a) Pass mucus out b) Pass mucus in
c) Pass air out d) Pass air in
23. Expiration involves
a) Relaxation of diaphragm and intercostal
muscles
b) Contraction of diaphragm and intercostal
muscles
c) Contraction of diaphragm muscles
d) Contraction of intercostal muscles
24. If expiratory reserve volume is 1100 ml,
residual volume is 1200 ml and tidal volume
is 500 ml, what shall be the functional
residual capacity?
a) 1600 ml b) 2800 ml
c) 2300 ml d) 1200 ml
25. Which is not a function of the paranasal
sinuses?
a) Warm inhaled air
b) Responsible for sound resonance
c) Gas exchange
d) Humidify inhaled air

22
26. The respiratory system assists the
cardiovascular and lymphatic systems in
a) Regulating blood volume
b) Regulating blood pressure
c) Controlling body fluid pH
d) All of the above
27. Which one of the following does not
accurately characterize the epithelial lining
of the respiratory tract?
a) It is mostly pseudostratified ciliated
columnar epithelium with numerous
goblet cells.
b) Cilia in the larger passageways sweep
trapped debris towards the pharynx,
where it is swallowed.
c) It changes from simple columnar to
simple cuboidal epithelium within
progressively smaller bronchioles.
d) Goblet cells and mucous glands in the
lamina propria secrete a watery,
lubricating fluid
28. Which paranasal sinuses are located
deepest within the skull, or farthest posterior
to the face?
a) Ethmoidal b) Frontal
c) Sphenoid d) Maxillary
29. Even if all the defenses in the conducting
portion of the respiratory tract fail, ______
may still destroy pathogens before they can
enter the body fluids
a) Macrophages in the pulmonary lymph
nodes
b) NK cells in the elastic tissues of the
lungs
c) Cytotoxic T- lymphocytes
d) Alveolar macrophages
30. Autonomic stimulation via the vagus nerves
causes what response within the lungs?
a) Deeper inhalation
b) Forced exhalation
c) Bronchodilation
d) Bronchoconstriction
31. Babies that sleep on their stomachs are now
known to be at greater risk of
a) Asphyxiation
b) SIDS (crib death)
c) Developmental delays
d) All of the above
32. Ultimately, the harmful effects of cystic
fibrosis are attributable to _____ caused by
a defective gene
a) Excessive, dilute mucus in the lungs
b) Hyposecretion of pancreatic enzymes
c) Hypersecretion of sodium chloride
d) Osmotic imbalance in gland cells
33. In prematurely born infants, hyaline
membrane disease is associated with
inadequate production of _______ by
_______ cells
a) Lysozyme: Mucus glands
b) Mucin: Goblet
c) Glycoproteins: Alveolar type I
d) Surfactant: Alveolar type II
34. According to Boyle's law, intrapulmonary
pressure should ____ when the diaphragm
or external intercostal muscle contract
a) Increase
b) Decrease
c) Remain constant
d) Equal atmospheric pressure

23
ANSWER KEYS
Simple Questions
1.d 2.d 3.b 4.c 5.a 6.c 7.d 8.b 9.d 10.a 11.c 12.c
13.b 14.c 15.c 16.a 17.d 18.a 19.a 20.b 21.a 22.a 23.d 24.b
25.c 26.a 27.a 28.a 29.c 30.a
Difficult Questions
1.b 2.a 3.c 4.d 5.b 6.b 7.d 8.d 9.d 10.d 11.b 12.a
13.d 14.d 15.d 16.a 17.b 18.c 19.c 20.b 21.d 22.a 23.a 24.c
25.c 26.d 27.d 28.c 29.d 30.d 31.b 32.d 33.d 34.b

24
1. Dead space air is the
a) Amount of air remaining in the alveoli
b) Amount of air left behind in lungs at the
end of deep expiration
c) Amount of air taken in and out
d) Air left in the bronchial tree
2. Vital capacity of lung is
a) Inspiratory Reserve Volume (IRV) +
Expiratory Reserve Volume (ERV) + Tidal
Volume (TV) + Residual Volume (RV).
b) IRV + ERV + TV
c) IRV + ERV
d) IRV + ERV + TV-RV
3. Whether a child died after normal birth or
died before birth can be confirmed by
measuring
a) Tidal volume of air
b) Residual volume of air
c) The weight of the child
d) The dead space air
4. Respiratory rhythm center is present in
a) Pons region b) Aortic arch
c) Medulla region d) Carotid artery
5. The function of conducting part in
respiratory system of human is
a) Clear foreign particles
b) Humidifies atmospheric air
c) Brings the air to body temperature
d) All of the above
DPP - 1
6. Arrange the following in the order of
increasing volume
I) Tidal volume
II) Residual volume
III) Expiratory reserve volume
IV)Vital capacity
a) I < II < III < IV b) I < III < II < IV
c) I < IV < III < II d) I < IV < II < III
7. Respiratory center in brain occurs in
a) Medulla oblongata
b) Cerebellum
c) Hypothalamus
d) Pericardium
8. Vital capacity of lungs of an average human
is
a) 3000 to 4500 ml b) 1500 to 1800 ml
c) 2000 to 2500 ml d) 500 to 1000 ml
9. During hibernation period, frog's respiration
is
a) Cutaneous
b) Pulmonary
c) Pharyngeal
d) Buccopharyngeal
10. Type of cartilage seen in tracheal wall is
a) Hyaline cartilage
b) Fibrocartilage
c) Elastic cartilage
d) None of these

2.1 RESPIRATORY LEVELS OF ORGANIZATION
 Chemical level - oxygen, carbon dioxide, bicarbonate and hydrogen ions.
 Macromolecular level - hemoglobin, mucus and surfactant.
 Cellular level - ciliated cells, goblet cells, alveolar cells, and macrophages.
 Tissue level - Stratified to pseudostratified to simple squamous epithelium.
 Organ level - Upper respiratory tract, bronchial tree and lungs.
 Organ system level - integration of organs for gas exchange.
2.2 HOW GASES EXCHANGE
The respiratory system brings in oxygen and exchanges it for carbon dioxide. Oxygen makes up
21% of the air we breathe while carbon dioxide is found at very low levels (0.039%). The diffusion of
gases across membranes follows the same principles as the diffusion of solutes in solution across
membranes, basically molecules move down a gradient. The difference is that gases in solution are
measured in terms of partial pressure.
Partial pressure is the pressure that a given gas in a mixture contributes to the total pressure
inside the container or in the atmosphere. The partial pressure is equal to the total pressure times
the fraction of the gas.
Table of partial pressures and percentage concentrations (in brackets) of gases in various airs
Thus partial pressure of O2
in pure blood pO2
= 104 mmHg and pCO2
= 40 mmHg.
Pure blood goes to tissues from heart. Inspirated air contains 19.6% oxygen and expirated air has
15.7% O2
. So, approximately 4% oxygen goes to blood from air. In the same way inspirated air contains
0.04% CO2
and expirated air has 3.6% CO2
so approximately 3.56% CO2
goes to air from blood.
Henry's Law, explains that the amount of dissolved gas found in liquid is proportionate to the gas
phase partial pressure as well as the molecules solubility in a specific liquid. For example,
considering
UNIT 2 - RESPIRATORY SYSTEM II
Gas Atmospheric air Functional residual Expired air
alveolar air
O2
159.0 (20.84%) 104.0 (13.6%) 120.0 (15.7%)
CO2
0.3 (0.04%) 40.0 (5.3%) 27.0 (3.6%)
Partial Pulmonary Pulmonary Tissue fluid Inside of cell
Pressure Arterial Blood Venous Blood
(Deoxygenated blood) (Oxygenated blood)
pO2
40 mmHg 95-104 mmHg 40 mmHg 20 mmHg
pO2
45-46 mmHg 40 mmHg 45 mmHg 50 mmHg

26
partial pressures alone it would be expected that oxygen would readily diffuse from the alveoli
because there is a high partial pressure gradient between alveoli and blood. However, oxygen has
very low solubility in plasma, so even with the large gradient between the two very little of oxygen
leaves the alveoli and dissolves directly into the plasma. Instead most of the dissolved oxygen
found in the blood is attached to the hemoglobin molecules found inside the red blood cells. On the
other hand carbon dioxide is very soluble in plasma (over 20 times more soluble than oxygen), so
significant amounts can be found directly in
dissolved form. Because of its high solubility, large
amounts of carbon dioxide can move between air
and liquid compartments even with small partial
pressure gradients.
Diffusing capacity: Volume of gas diffusing
through the membrane per minute for a difference
or 1 mmHg. It is 21 ml/mt/mmHg for O2
.
At high altitudes, the fraction of oxygen in the
atmosphere is the same (21%), but the total
atmospheric pressure is less. This causes the
partial pressure of the oxygen we breathe in to be
significantly less than that at sea level, making it
much harder to move oxygen from the air into our
plasma.
Respiratory membrane (0.2 mm thick): Alveolar
epithelium + Epithelial basement membrane + thin
interstitial spaces + capillary basement membrane
+ capillary endothelial membrane.
2.2.1 External respiration
The partial pressure of oxygen in the alveoli is slightly lower than the partial pressure of oxygen
found in the atmosphere. Air taken into the lungs (tidal volume minus the volume of the conduction
zone) mixes with air that is already in the lungs (functional residual volume). Because gas exchange
is constantly occurring (even between breaths, when we hold our breath, etc), the air making up the
functional residual volume has had some oxygen removed from it and some carbon dioxide added
to it. When a new tidal volume of air is inhaled, the portion of this air that enters the alveoli mixes
with the functional residual volume and effectively lowers the fraction of oxygen in this alveolar air.
Inhaled air at sea level typically has a partial pressure of oxygen near 160 mmHg. In the alveoli, the
partial pressure of oxygen would vary with our ventilation pattern, but typically equilibrates at about
105 mmHg. It is the difference between alveolar oxygen partial pressure and the plasma oxygen
partial pressure that drives external respiration across the alveolar membrane. Blood coming through
the pulmonary arterial circulation is lower in oxygen, with a typical partial pressure of 40 mmHg. The
Interstitial
space
Epithelial
basement
membrane
Alveolar
epithelial
wall
Alveolus Capillary
Diffusion
of O2
Diffusion
of CO2
Capillary basement membrane
Capillary
endothelium

27
differential concentration gradient for oxygen to move from the alveolar air into the capillary blood
starts at about 65 mmHg (105 mmHg in the alveoli minus 40 mmHg in blood), providing enough of
a difference in partial pressures for oxygen to diffuse from the alveoli into the capillary. Diffusion will
occur along the length of the pulmonary capillary until the partial pressures come into equilibrium
near 105 mmHg.
The functioning of the pressure gradient for carbon dioxide works in reverse of that for oxygen, with
the carbon dioxide partial pressure being higher in the pulmonary arterial blood than in the alveoli.
Even with a much smaller gradient for carbon dioxide than for oxygen, nearly as much carbon
dioxide diffuses from the blood to the alveoli as oxygen diffuses from the alveoli to the blood because
of the much higher solubility of carbon dioxide in the plasma.
Alveolus wall
Capillary wall
Deoxygenated
blood cell
Oxygenated
blood cell
Carbon dioxide
Oxygen
2.2.2 Internal respiration
Internal respiration occurs between the blood and systemic tissues of the body. The systemic arteries
carry essentially the same concentration of oxygen and carbon dioxide as the pulmonary veins.
Oxygen is continually being used by the tissues, and the partial pressure of oxygen in active cells
remains below 40 mmHg. Oxygen circulating in the systemic arterial blood readily diffuses across
the membranes of the blood vessels into the tissues, replenishing the supply of oxygen in the cells.
The final concentration of oxygen and carbon dioxide in the systemic veins is essentially the same
as it is in the pulmonary arteries.
Just as the tissues are continually using up the oxygen, they are continually producing carbon dioxide.
The partial pressure of carbon dioxide in tissues is always greater than 45 mmHg. This accounts for
the diffusion of carbon dioxide into the systemic capillaries, raising the pressure to 45 mmHg.
Blood
Cells
CO2
O2
External respiration: pulmonary pO2
pCO2
Pulmonary arteries leading to 40 45
capillaries
Alveoli 105 40
Pulmonary veins 100 40
Internal respiration: tissues pO2
pCO2
Systemic arteries leading to capillaries 100 40
Metabolically active tissues < 40 > 45
Systemic veins 40 45

28
2.3 TRANSPORT OF GASES
Here are a few of symbols you will see:
 Deoxyhemoglobin (HHb): A hemoglobin molecule that has been reduced and does not
have a full complement of oxygen molecules attached to it.
 Oxygen (O2
): A gas that is required for converting nutrients into cellular energy.
 Oxyhemoglobin (HbO2
): A hemoglobin molecule that has been oxidized and is bound to
four oxygen molecules.
 Carbon dioxide (CO2
): A gas that is released as a waste product during the breakdown of
glucose to release energy.
 2,3 bisphosphoglycerate (BPG): It is a molecule found in red blood cells that can bind to
hemoglobin and decrease its affinity for oxygen.
 Carbonic acid (H2
CO3
): It is formed as an intermediate step in the transportation of carbon
dioxide. Carbonic anhydrase is an enzyme that will speed up the formation of carbonic acid
from water and carbon dioxide.
 Bicarbonate (HCO3
–
): Carbonic acid can quickly convert to bicarbonate and a hydrogen ion.
Bicarbonate plays a huge role in transporting carbon dioxide and maintaining blood pH.
2.3.1 Transport of oxygen
As much oxygen comes in the blood from air, it is approximately 3% dissolved in the blood plasma.
Remaining 97% oxygen combines with hemoglobin to form Oxyhemoglobin. One molecule of
hemoglobin combines with 4 molecules of oxygen. Hemoglobin is made up of 4 units. Every unit of
it, reacts with one molecule of oxygen. 1 gm hemoglobin transports 1.34 ml oxygen. 100 ml (1 dL) of
blood contains normally 15 gm of hemoglobin. So, 100 ml blood transports approximately 20 ml
oxygen. Oxygen does not oxidise hemoglobin. Formation of oxyhemoglobin is a process of
oxygenation. The valency of iron is 2 in oxyhemoglobin. Some gases (eg. ozone) oxidise hemoglobin.
This oxidized hemoglobin is called methemoglobin. This is a colorless compound. This types of
gases are environmental pollutant. At the time, oxyhemoglobin reaches upto the tissues it dissociates.
O2
freed from it goes into the tissue fluid from blood.
In a conducting cycle blood gives its 25% O2
to tissues. Dissociation of oxyhemoglobin is affected
by so many factors
 Low partial pressure of oxygen: Combination of oxygen with hemoglobin is a reversible
reaction. Low partial pressure of O2
activates dissociation of oxyhemoglobin.
 High concentration of CO2
: High concentration of CO2
also activates the dissociation of
oxyhemoglobin. The effect of CO2
concentration on dissociation of oxyhemoglobin is called
Bohr's effect.
 Low pH value of tissue fluid: Acidity activates dissociation of oxyhemoglobin. The effect of
pH on dissociation of oxyhemoglobin is called Root effect.

29
A graph is plotted between O2
concentration and percentage saturation of hemoglobin with oxygen
(we get a sigmoid curve), this curve is called dissociation curve. As the concentration of CO2
increases, saturation of hemoglobin with oxygen decreases. At higher CO2
concentration, dissociation
curve shifts towards right. This effect is called Bohr's effect.
The meaning of right side shifting of dissociation curve is that, O2
is readily dissociating from
oxyhemoglobin.
Shift to left means increase in
affinity between O2
and Hb (which
may be due to  pH,  temperature,
 CO2
).
Shift to right means decrease in
affinity between O2
and Hb. (which
may be due to  pH,  temperature,
 CO2
).
Hb cannot take up O2
beyond a
saturation level of 97%. Hb is 50%
saturated with O2
at 30 mm Hg.
P50
value - pO2
at which the Hb is
50% saturated with O2
. Higher the
P50
lower is the affinity of Hb for O2
.
2, 3 diphosphoglycerate (2, 3 DPG)
- a substance formed during
glycolysis.  2,3 DPG will cause shift
t
to right.
Transport of O2
during strenuous exercise
Normally: 5 ml O2
/ 100 ml is delivered.
During heavy exercise: Muscle cells
use O2
at a rapid rate.  Interstitial fluid
pO2
falls as low as 15 mmHg.
 Only 4.4 ml O2
remains bound to Hb.
 19.4 - 4.4 = 15 ml O2
/ 100 ml blood is
delivered to muscle. Also cardiac output
can reach maximum 7 times the (normal) value. Therefore O2
delivery maximum limit which we can
achieve is 20 - 21 times the normal.
100
90
80
70
60
50
40
30
20
10
0
10 20 30 40 50 60 70 80 90 100
pO (mmHg)
2
Oxyhemoglobin
(%
saturation)
Decreased temp
Decreased 2-3 DPG
Decreased [H
CO
+
]
Right shift
(reduced affinity)
Increased temp
Increased 2-3 DPG
Increased [H
+
]
HbO dissociation curve
2
19.4 ml O /100 ml
2
Saturation of Hb
with oxygen is 97% (Artery)
14.4 ml O /100 ml
2
(Vein)
Organ
Saturation of Hb
with oxygen is 75%

30
2.3.2 Transport of carbon dioxide
Carbon dioxide is carried in the blood in three forms: dissolved, attached to hemoglobin, and converted
to bicarbonate ions. Dissolved CO2
accounts for 7 to 10% of the carbon dioxide carried in the blood.
This is also the only form of carbon dioxide that diffuses from the tissues into the blood and from the
blood into the alveoli for expulsion from the body.
Carbaminohemoglobin
Carbon dioxide can bind to any protein and form a carbamate compound. 20 to 23% of the CO2
carried in the blood is bound to hemoglobin in the form of Carbaminohemoglobin. In the capillaries
of the systemic tissues, CO2
molecules attach to the terminal amino acids of the alpha and beta
chains of the hemoglobin molecule. Deoxygenated hemoglobin such as that found in metabolically
active tissues, binds CO2
easily. In the capillaries of the lungs, the elevated levels of oxygen found
in alveoli force the carbon dioxide off the hemoglobin molecule and oxidize the protein, freeing up
hydrogen ions. Although some carbon dioxide is transported as Carbaminohemoglobin, the majority,
about 70%, is dissolved in the blood as bicarbonate ions that arise from the reversible reactions.
Bicarbonate
Carbon dioxide in the presence of water can be reversibly converted to carbonic acid. Carbonic acid is
not very stable and readily dissociates into a hydrogen ion and a bicarbonate ion. Red blood cells
contain an enzyme calledcarbonic anhydrase (CA), which iscapable of facilitating one million reactions
per second per enzyme molecule. Because of the enzyme, most of the CO2
dissolved in the blood is
quickly converted to carbonic acid which breaks down to form, hydrogen ions, and bicarbonate ions.
77% CO2
CO2
7% CO is carried
dissolved in plasma
2
23% CO2
Tissue
level
70% diffuses inside RBC
CO + H O
2 2 H CO
2 3
C.A.
H CO
2 3 H + HCO
+ –
3
KHbO2 KHb + O2
KHb K + Hb
+
H + Hb
+
H.Hb
CO + HHb, NH
2 2 H.Hb.NHCOOH
K + Cl
+ –
KCl
HCO3
Cl
–
NaCl Na + Cl
+ –
HCO + Na
3
– +
NaHCO3
CO H H HCO
2 2 2 3 3
+ –
(in the presence of CA) + O CO H +
The oxyhemoglobin (HbO2
) of the erythrocytes is weekly acidic and remains in association with K+
ions as KHbO2
. The hydrogen ions (H+
) released from carbonic acid combine with hemoglobin after
its dissociation from the potassium ions.

31
The majority of bicarbonate ions (HCO3
–
) formed within the erythrocytes diffuses out into the plasma
along a concentration gradient. H+
combine with hemoglobin to form the hemoglobinic acid (H.Hb)
In response, chloride ions (Cl–
) diffuse from plasma into the erythrocytes to maintain the ionic balance.
Thus, electrochemical neutrality is maintained. This is called Chloride shift or Hamburger
phenomenon. The chloride ions (Cl–
) inside RBC combine with potassium ions (K+
) to form potassium
chloride (KCl). Whereas hydrogen carbonate ions (HCO3
–
) in the plasma combine with Na+
to form
sodium bicarbonate (NaHCO3
). Nearly 70% of carbon dioxide is transported from tissues to the
lungs in this form.
Release of carbon dioxide in the alveoli of lung: When the deoxygenated blood reaches the
alveoli of the lung, It contains carbon dioxide as dissolved in plasma, as carbaminohemoglobin, and
as bicarbonate ions in the pulmonary capillaries. The carbon dioxide dissolved in plasma diffuses
into alveoli. Carbaminohemoglobin also splits into carbon dioxide and hemoglobin. For the release
of carbon dioxide from the bicarbonate, a small series of reverse reactions takes place. When the
hemoglobin in the pulmonary blood takes up oxygen, the H+
is released from it. Then the Cl–
and
HCO3
–
ions are released from KCl in RBC, and NaHCO3
in the plasma, respectively. Then HCO3
–
reacts with H+
to form H2
CO3
, ultimately, then splits into carbon dioxide and water in the presence of
carbonic anhydrase enzyme and carbon dioxide is released into lungs.
When bicarbonates and carbamino compounds reach in the lungs, then they dissociate. Thus CO2
is formed. This dissociation is stimulated by oxyhemoglobin. This CO2
freed from blood goes into
atmosphere. The effect of oxyhemoglobin on the dissociation of these compounds is known as
Haldane-effect. In this reaction oxyhemoglobin acts like a strong acid i.e. it frees H+
in the medium.
These H+
combine with bicarbonates and thus their dissociation is stimulated, in this way transportation
of CO2
is completed.
2.4 RESPIRATORY DISORDERS
A. Bronchial asthma: This is characterized by the spasm of the smooth muscles present in the walls
of the bronchiole. It is generally caused due to the hypersensitivity of the bronchiole to the foreign
substances present in the air passing through it. The symptoms of the disease may be coughing or
difficulty in breathing mainly during expiration. The mucous membranes on the wallsof the air passage
start secreting excess amount of mucous, which may clog the bronchi, as well as bronchiole.
B. Bronchitis: It isthe inflammation of thebronchi, whichischaracterizedby hypertrophy and hyperplasia
of seromucous gland and goblet cells lining the bronchi. The symptom is regular coughing, with thick
greenish yellow sputum that indicates the underlying infection, resulting into excessive secretion of
mucous. It may also be caused by cigarette smoking and exposure to air pollutantslike carbonmonoxide.
C. Emphysema: It is an inflation or abnormal distension of the bronchiole or alveolar sac, which
results into the loss of elasticity of these parts. As a result the alveolar sac remains filled with air
even after expiration and ultimately, the lung size increases. The reason for such a condition can be
assigned to cigarette smoking and chronic bronchitis.

32
D. Chronic Obstructive Pulmonary Disease (COPD): Chronic obstructive pulmonary disease
(COPD) is a chronic, debilitating disease. COPD is a set of symptoms that can develop as a result
of either chronic bronchitis or emphysema. People with chronic bronchitis constantly produce mucus
in the conducting division in response to inhaled irritants or mild infections emphysema which is
permanent results from the progressive destruction of lung tissue. It is typically a more severe form
of COPD than bronchitis, and may lead to death. The leading cause of both conditions is tobacco
smoke, inhaled as either firsthand or secondhand smoke. Occasionally, emphysema can develop
as a result of exposure to gases or fumes in the workplace. There is a low incidence of COPD
resulting from a deficiency of the protein alpha-1-antitrypsin.
The symptoms of COPD include a cough with or without mucus, fatigue, frequent respiratory
infections, shortness of breath (dyspnea), the inability to catch one’s breath, and wheezing. As the
disease progresses, patients may have more symptoms which can progress in severity. Evaluating
lung sounds and x rays are not necessarily useful in establishing a diagnosis for COPD. Spirometry
and the examination of arterial blood gases to determine the blood concentrations of oxygen and
carbon dioxide provide much better diagnostic tools.
As COPD worsens, blood oxygen levels decrease and blood carbon dioxide level increase. The
decreased oxygen leads to the fatigue, dizziness and decreased activity tolerance these people
often experience. The increase in carbon dioxide can lead to respiratory acidosis, ultimately
contributing to dysfunction in many of the body’s metabolic pathways.
There is no cure for COPD, but medications can help alleviate its effects. Inhalers that cause
bronchodilation and contain steroids to reduce inflammation and mucus secretion are effective in
many cases. Other anti – inflammatory may also help. If the conditions become severe, steroids
can be administered orally or by intravenous methods. Oxygen may be needed, and mechanical
breathing assistance may be used.
E. Occupational lung disease: It is caused because of the exposure to potentially harmful
substances, such as gas, fumes of dusts present in the environment where a person works, silicosis
and asbestosis are the common examples which occur due to chronic exposure of silica and asbestos
dust in the mining industry. It is characterized by fibrosis (proliferation of fibrous connective tissue)
of upper part of lung, causing inflammation.
F. Decompression sickness: During deep sea diving the diver inhales gases at an increased
pressure in depth, as a result the nitrogen also gets dissolved in the blood. When the diver comes
back to the surface, where the pressure has again decreased, the dissolved nitrogen start getting
released from blood in the form of bubbles which cause a number of problems, example air embolism
infarction due to blocked vessel etc.
G. Altitude sickness: Also called acute mountain sickness, can strike people climbing to elevations
above 8000 feet. At elevations high above sea level, there is much less atmospheric pressure which
lowers the partial pressure of the oxygen being inhaled so less oxygen enters the body. If the body
does not adapt well, a person can experience altitude sickness ranging from mild to severe forms.

33
TARGET NOTES
 Eupnoea: It is the state of normal breathing. In humans, rate of normal breathing is 12 to 16 per
minute. In infants rate of breathing is 44 per minute. Rate of breathing is slowest while sleeping.
 Bradypnoea or hyponoea: It is the state of slow breathing.
 Tachypnoea or hypernoea: It is the state of fast breathing.
 Apnoea: It is the state of stoppage of breathing temporarily.
 Dyspnoea: It is the state of discomfort due to difficulty in breathing.
 Asphyxia: It is the state of suffocation due to high CO2
concentration or low O2
concentration.
 Anoxia: It is the absence of O2
supply to tissues.
 Hypocapnoea: It is the state of reduced CO2
concentration in blood.
 Hypercapnoea: It is the state of increased CO2
concentration in blood
 Pathological dead space: If due to disease of circulatory origin the air is filling in the alveolis but
the blood circulation or perfusion in the capillaries of wall of alveoli is absent or low then this air
also gets wasted as there is no blood present to whom it may oxygenate. This amount of air is
pathological dead space. in a normal person this is zero.
Total dead space = Anatomical dead space + pathological dead space.
 Alveolar perfusion: The amount of blood that enters the wall of the alveoli via capillaries to
participate in exchange of gases. This is denoted as ‘Q’.
 Physiological shunt: Not entire amount of blood which enters the lungs via pulmonary arteries
actually reaches the walls of alveoli. 2% of the total blood actually never passes through the
walls, instead it enters the venule side from arteriole side via the conduction zone in lungs. So
this blood never gets oxygenated. This is shunted blood (2% of total). This means that only 98%
blood which enters the lungs actually gets oxygenated. This phenomenon of bypass of alveoli by
2% of total blood is called as physiological shunt. It is normally present in all human beings.
 Pathological shunt: If due to presence of some respiratory disease, alveoli do not get filled up
with air and remain collapse, then blood which passes through the walls of these alveoli does not
get oxygenated. This portion of blood is called pathological shunt. So greater is the pathological
shunt, greater will be the amount of a blood which falls to get oxygenated as it passes through
lungs. The pathological shunt is zero in lungs of normal human beings.
Total shunt = physiological shunt + pathological shunt.
• One molecule of hemoglobin combines with four molecules of carbon monoxide to form
carboxyhemoglobin. Its color is cherry red.
• One molecule of hemoglobin has 4 Fe++
ions metal. Only one ion of iron metal is present in
myoglobin.
• In normal conditions – frogs show 35% - cutaneous respiration, 9% - buccopharyngeal
respiration and 56% pulmonary respiration.
In frog, sternohyal and mylohyal (petrohyal) muscles are related with the process of respiration.

34
1. Oxygen hemoglobin dissociation curve will
shift to right on decrease of
a) Acidity
b) Carbon dioxide concentration
c) Both (a) and (b)
d) pH
2. “ Emphysema” is a condition in which
a) Respiratory center is inhibited
b) Lot of fluid is in the lungs
c) The walls separating the alveoli breaks
d) Lungs have more oxygen
3. Respiratory centre of brain is stimulated by
a) Carbon dioxide content in venous blood
b) Carbon dioxide content in arterial blood
c) Oxygen content in venous blood
d) Oxygen content in arterial blood
4. Which of the following changes (I-IV) usually
tend to occur in the plain dwellers when they
move to high altitudes (3,500 m or more)?
I) Increase in red blood cell size
II) Increase in red blood cell production
III) Increased breathing rate
IV)Increase in thrombocyte count
Changes occurring are
a) II and III b) III and IV
c) I and IV d) I and II
5. Determination of oxygen carried by
hemoglobin is done by
a) pH
b) Partial pressure of oxygen
c) Partial pressure of carbon dioxide
d) All the above
6. What is true about RBCs in humans?
a) They do not carry CO2
at all
b) They carry about 20 to 25% of CO2
c) They transport 99.5% of O2
d) They transport about 80% oxygen only
and the rest 20% of it is transported in
dissolved state in blood plasma
Simple Questions
7. Amount of oxygen present in one gram if
hemoglobin is
a) 20 ml
b) 1.34 ml
c) 13.4 ml
d) None of these
8. During transport of CO2
blood does not
become acidic due to
a) Neutralisation of H2
CO3
by Na2
CO3
b) Absorption of leukocytes
c) Blood buffers
d) Non-accumulation
9. If a man from sea coast goes to Everest
mountain peak, his
a) Breathing and heart beat will increase
b) Breathing and heart beat will decrease
c) Respiratory rate will decrease
d) Heart beat will decrease
10. If a reduced oxygen supply weakens the
heart cells but does not actually kill them,
the condition is called
a) Myocardial infarction
b) Tachycardia
c) Bradycardia
d) Ischemia
11. Which of the following statement correctly
defines Bohr’s effect?
a) Rise in P50
with a decrease in CO2
concentration
b) Rise in P50
with a decrease in pH
c) Rise in P50
with increase in pH
d) Fall in P50
with a decrease in pH
12. A stage when lung collapsed, especially the
alveoli are
a) Atelectasis
b) Poliomyelitis
c) Asthma
d) Epistaxis

35
13. Body tissues obtain O2
from hemoglobin
because of its dissociation in tissues caused
by
a) Low oxygen concentration and high CO2
concentration
b) High O2
concentration
c) Low CO2
concentration
d) High CO2
concentration
14. Hering Breuer reflex is related to
a) Effect of pH on respiratory center
b) Effect of CO2
on respiratory center
c) Effect of nerves on respiratory center
d) Effect of temperature on respiratory
center
15. Effect of CO2
concentration on dissociation
of oxyhemoglobin is called
a) Bohr’s effect
b) Haldane effect
c) Hamburger effect
d) Gaudi Kov’s effect
16. The state, during which the respiratory
center is inhibited, is termed as
a) Asphyxia b) Choking
c) Anoxia d) Suffocation
17. In the process of transport of CO2
which
phenomenon occurs between RBCs and
plasma
a) Osmosis b) Adsorption
c) Chloride shift d) Absorption
18. Carbonic anhydrase is found in
a) WBC b) RBC
c) Blood plasma d) All
19. The chloride shift is movement of Cl–
a) From plasma to RBC
b) From WBC to plasma
c) Both
d) None
20. When temperature decreases oxy-
hemoglobin curve will become
a) More steep b) Straight
c) Parabola d) None of the above
21. Inflammation of the lung covering causing
severe chest pain in
a) Emphysema b) Pleurisy
c) Asphyxia d) Hypoxia
22. Partial pressure of oxygen in the inspired
and expired air is respectively
a) 158 and 116 mmHg
b) 158 and 40 mmHg
c) 100 and 95 mmHg
d) 40 and 95 mmHg
23. Hamburger’s phenomenon is also called
a) HCO3
shift b) Chloride shift
c) Hydrogen shift d) None of these
24. After taking a long deep breath, we do not
respire for some seconds due to
a) More CO2
in blood
b) More O2
in blood
c) Less CO2
in blood
d) Less O2
in blood
25. Increased asthmatic attacks in certain
seasons are related to
a) Hot and humid environment
b) Eating fruits preserved in tin containers
c) Inhalation of seasonal pollen
d) Low temperature
26. All are the disease of lungs except
a) Asthma b) Bronchitis
c) Encephalitis d) Pneumonia
27. When carbon dioxide concentration in blood
increases, breathing becomes
a) Shallower and slow.
b) There is no effect on breathing
c) Slow and deep
d) Faster and deeper

36
28. Blood analysis of a patient reveals an
unusually high quantity of
carboxyhemoglobin content. Which of the
following conclusions is most likely to be
correct? The patient has been inhaling
polluted air containing usually high content
of
a) Carbon disulphide
b) Chloroform
c) Carbon dioxide
d) Carbon monoxide
29. Carbon monoxide prevents transport of
oxygen by
a) Forming stable compound with
hemoglobin
b) Destroying hemoglobin
c) Forming carbon dioxide with oxygen
d) Destroying RBCs
30. CO2
is carried in blood in physical solution,
in the form of carbaminohemoglobin and in
the form of HCO3
–
, the proportion of CO2
in
different forms respectively is
a) 5%, 10%, 85% b) 5%, 85%, 10%
c) 85%, 5%, 10% d) 10%, 85%, 5%
31. In rabbit respiration takes place in
a) Cells lining the lungs cavity
b) Cells found in blood
c) All living cells of the body
d) Only RBC
32. Asthma is a respiratory disease caused due
to
a) Infection of trachea
b) Infection of lungs
c) Bleeding into pleural cavity
d) Spasm in bronchial muscles
33. Low O2
concentration causes
a) Emphysema
b) Pleurisy
c) Asphyxia
d) Hypoxia
34. In fever breathing rate
a) Increases
b) Decreases
c) Stop
d) None
Difficult Questions
1. What is true about hemoglobin?
a) It is a dipeptide and present in red blood
corpuscles in blood warm.
b) It is present in the dissolved state in
blood plasma in earthworm.
c) It is a dipeptide in mammals and
localized in red blood corpuscles.
d) It is present in dissolved state in blood
plasma in scorpions.
2. Which one of the following is the correct
statement for respiration in humans?
a) Cigarette smoking may lead to
inflammation of bronchi.
b) Neural signals from penumotoxic center
in pons region of brain can increase the
duration of inspiration.
c) Workers in grinding and stone breaking
industries may suffer, from lung fibrosis.
d) About 90% of CO2
is carried
by hemoglobin as Carbamino-
hemoglobin.

37
3. The apparatus shown is used to investigate
gas exchange during breathing:
M
T
Limewater
solution
X Y
Which one of the following would occur
when a person blows through tube M?
a) The solution in X and Y both turns cloudy
b) The solution in X remains clear, but that
in Y turns cloudy
c) The solution in X turns cloudy, but that
in Y remains clear
d) The solution in X is forced out through
the tube T
4. During strenuous exercise, which of the
following change occurs?
a) Glucose is converted into glycogen
b) Glucose is converted into pyruvic acid
c) Starch is converted into glucose
d) Pyruvic acid is converted into lactic acid
5. Complete bronchus obstruction results in
a) Collapse of the portion of the lung
supplied by the bronchus
b) A rise in intrapleural pressure on the
affected side
c) An increase in physiological dead space.
d) Vasodilation of alveoli supplied by the
bronchus
6. The compound soluble in water but does
not impede the oxygen transportation is
a) SO3
b) SO2
c) NO d) CO
7. For proper transport of O2
and CO2
blood
should be
a) Slightly acidic b) Strongly acidic
c) Strongly alkaline d) Slightly alkaline
8. What would happen when blood is acidic?
a) Binding of oxygen with hemoglobin
increases
b) Red blood corpuscles are formed in
higher number
c) Binding of oxygen with hemoglobin
decreases
d) There is no change in oxygen binding
nor number of RBC
9. Intra-aortic balloon pump is inflated by
a) Hydrogen b) Oxygen
c) Helium d) Chlorine
10. The ‘blue baby’ syndrome results from
a) Excess of dissolved oxygen
b) Excess of TDS (total dissolved solids)
c) Excess of chloride
d) Methemoglobin
11. Which of the following statement is / are
correct?
1) A high concentration of carbonic
anhydrase is present in RBC
2) Minute quantities of carbonic anhydrase
are present in plasma.
3) Every 100 ml blood delivers
approximately 4 ml of CO2
to the alveoli.
4) 20 to 25% CO2
is carried by hemoglobin
as carbaminohemoglobin.
a) 1, 3 and 4 b) 1 and 4
c) 1, 2, 3 and 4 d) Only 1
12. Which of the following can cause
atelectasis?
a) Blockage of small bronchi with mucus.
b) Obstruction of major bronchus.
c) Lack of surfactant in fluids lining the
alveoli
d) All of the above

38
13. At what pCO2
death may occur?
a) 50 mm Hg
b) 100 to 150 mm Hg
c) > 500 mm Hg
d) Does not occur at any pCO2
14. Mark the incorrect statement
a) Respiratory centers are found in medulla
oblongata
b) Near lungs Cl-
moves out of the RBC
c) RBC of deoxygenated blood are slightly
bigger than that of oxygenated blood
15. A large proportion of oxygen is left unused
in the human blood even after its uptake by
the body tissues. This O2
a) Raises the pCO2
of blood to 75 mm of
Hg
b) Is enough to keep oxyhemoglobin
c) Helps in releasing more O2
to the
epithelial tissues
d) Acts as a reserve during muscular
exercises
16. The decompression sickness is
a) Respiration under depression
b) Sickness develops after coming over the
sea surface from a great depth
c) Sickness develops after attaining a high
altitude
d) Sickness develops after coming on earth
surface from the mines
17. Combination of hemoglobin with oxygen in
lungs can be promoted by
a) Increasing carbon dioxide concentration
in blood
b) Increasing oxygen concentration in
blood
c) Decreasing oxygen concentration in
blood
d) Introducing carbon monoxide in blood
18. After fast running, man has fast heart beat,
slow pulse and shallow breathing, in such
conditions, he has
a) Oxygen debt
b) Poisoning due to lactic acid
c) No pulmonary pressure
d) Weak heart
19. Oxyhemoglobin dissociatesinto oxygen and
deoxyhemoglobin at
a) Low oxygen pressure in tissues
b) High oxygen pressure in tissue
c) Equal oxygen pressure inside and
outside tissue
d) All times irrespective of oxygen pressure
20. When blood CO2
level rises
a) Only the rate of breathing decreases
b) Respiratory acidosis may occur
c) Peripheral pressure receptors respond
d) Both the rate and depth of breathing
decrease
21. What is incorrect about oxygen binding with
hemoglobin?
a) The bond between oxygen and
hemoglobin is very loose
b) Oxygen becomes ionic when it binds to
hemoglobin
c) Hb and oxygen is readily reversible
combinations
22. Minimum concentration and pressure of CO
in alveoli of lungs that would be dangerous
to man
a) 1%, 0 – 7 mm Hg
b) 0 – 4%, 0 – 7 mm Hg
c) 2 – 7%, 0 – 4 mm Hg
d) 0 – 3%, 0 – 4 mm Hg

39
23. If a large number of people are enclosed in
a room, then
a) Oxygen decreases and carbon dioxide
increases
b) Oxygen increases and carbon dioxide
decreases
c) Both oxygen and carbon dioxide
decreases
d) Both Oxygen and carbon dioxide
increases
24. Rate of respiration is directly affected by
a) CO2
concentration
b) O2
in trachea
c) Concentration of O2
d) Diaphragm expansion
25. Diffusion of gases along the respiratory
surface occurs because
a) pCO2
is more in alveoli than blood
b) pO2
is more in alveoli than blood
c) pCO2
is more in blood than in tissues
d) pO2
is more in blood than in tissues
26. Ratio of oxyhemoglobin and hemoglobin in
blood is based upon
a) Oxygen tension
b) Carbon dioxide tension
c) Carbonate tension
d) Bicarbonate tension
27. Artificial respiration at the rate of 10 to 15
times per minute is being given to a man
saved from drowning. This is because
a) The water in the respiratory passage is
cleared fast at this rate
b) It is the normal rate of breathing
c) Choking is least at this rate
d) The lungs are ventilated best at this rate
28. Which forms stable compound with
hemoglobin?
a) O2
b) CO2
c) CO
d) All
29. Iron free compound of hemoglobin is
a) Hemotoxin
b) Bilirubin
c) Haematin
d) Globin
30. The diabetic patient shows
a) High respiratory quotient
b) Low respiratory quotient
c) Zero respiratory quotient
ANSWER KEYS
Simple Questions
1.d 2.c 3.b 4.a 5.d 6.b 7.b 8.c 9.a 10.d 11.a 12.a
13.a 14.c 15.a 16.c 17.c 18.b 19.a 20.a 21.b 22.a 23.b 24.c
25.c 26.c 27.d 28.d 29.a 30.a 31.c 32.d 33.c 34.a
Difficult Questions
1.c 2.c 3.b 4.d 5.a 6.b 7.d 8.c 9.c 10.d 11.c 12.d
13.b 14.d 15.d 16.b 17.c 18.a 19.a 20.b 21.b 22.a 23.a 24.a
25.b 26.a 27.a 28.c 29.d 30.b

40
1. Amount of oxygen supplied by 100 ml
arterial blood while passing through the
tissues is
a) 0.4 to 0.6 ml b) 4 to 6 ml
c) 14 to 15 ml d) 19 to 20 ml
2. Which of the following is correct in mmHg?
Alveoli Deoxyge- Tissue
nated blood
a) pO2
= 159 pCO2
= 40 pCO2
= 20
b) pCO2
= 40 pO2
= 95 pO2
= 40
c) pO2
= 104 pCO2
= 45 pCO2
= 45
d) pO2
= 40 pO2
= 40 pCO2
= 45
3. During rest, the metabolic needs of the body
are at their minimum. Which of the following
is indicative of this situation?
a) Rate of breathing
b) Pulse rate
c) O2
intake and CO2
output
d) All of these
4. Which of the following factors raise the P50
value and shifts the HbO2
dissociation curve
to right and vice versa?
1) Rise in pCO2
2) Fall in temperature
3) Raise in H+
(fall in pH)
4) Fall in diphosphoglyceric acid
a) 1 and 2 are correct
b) 2 and 4 are correct
c) 1 and 3 are correct
d) 1, 2 and 3 are correct
5. If O2
concentration in tissues was almost
as high as at the respiratory surface then
a) Oxyhemoglobin would dissociate to
supply to the tissue
b) Hemoglobin would combine with more
O2
at respiratory surface
c) Oxyhemoglobin would not dissociate to
supply O2
to the tissue
d) CO2
will interfere the O2
transport
DPP - 2
6. People living at sea level have around 5
million RBCs per cubic millimeter of their
blood, whereas those living at an altitude of
5400 m have around 8 million. This is
because at high altitude
a) People get pollution free air to breath and
more oxygen available
b) Atmospheric oxygen level is less and
hence, more RBCs are needed to
absorb the required amount of O2
to
survive
c) There is more UV radiation, which
enhances RBC production
d) People eat more nutritive food, therefore,
more RBCs are formed
7. People who have migrated from the planes
to an area adjoining Rohtang pass about
six months back
a) Have more RBCs and their Hb has a
lower binding affinity to O2
b) Are not physically fit to play games like
football
c) Suffer from altitude sickness with
symptoms like nausea, fatigue etc
d) Have the usual RBC count, but their Hb
has very high binding affinity to O2
8. Ratio of oxyhemoglobin and hemoglobin in
the blood is based upon
a) Bicarbonate tension
b) Carbon dioxide tension
c) Carbonate tension
d) Oxygen tension
9. A chemosensitive area is situated adjacent
to respiratory rhythm center. Which is highly
sensitive to _____ and ______ ions?
a) O2
, H+
b) CO2
, OH-
c) CO2
, H+
d) CO2
, O2
10. O2
dissociation curve is
a) Sigmoid b) Parabolic
c) Hyperbolic d) Straight line

41
3.1 BODY FLUIDS AND CELL’S ENVIRONMENT
 Cell, tissue and organs are
immersed in body fluids which
make sure that all the cells has
the right assortment of
nutrients, ions, etc.
 Body keep both cells and the
fluid surrounding the cells in a
dynamically stable environment
via a process called
homeostasis.
3.2 WATER
 About 60% of the body is water.
– Blood is 83% water.
– Muscle is 75% water.
– Brain is 74% water.
– Bone is 22% water.
 Total body water depend on amount of
fat in the body.
– Obese animal can have as low as 45%
TBF.
– Lean animal can have as high as 70%
TBF.
 2/3 of total body water (i.e. 40% of TBW)
is found within cells so we refer to it as
intracellular fluid (ICF).
 The other 1/3 (i.e. 20% of TBW) is
outside cells so we call it extracellular
fluid (ECF).
 The 3 main types of ECF are:
i) The fluid that surrounds the cells –
the tissue fluid or interstitial fluid
(ISF) (~ 15% of TBW).
UNIT 3 - BODY FLUIDS
Regulates body
temperature
Lubricates joints
Lessens the burden
on the kidneys and
liver by flushing out
waste products
Carries nutrients and
oxygen to cells
Moistens tissues such
as those in the mouth,
eyes and nose
Protects body organs
and tissues
Helps prevent
constipation
Helps dissolve
minerals and
other nutrients
to make them
accessible to
the body
Function of body fluid
Composition of human body
Substance Male Female
Water 62 59
Protein 18 15
Lipid 14 20
Carbohydrates 1 1
Other (electrolytes, 5 5
nucleic acids)
IVF ISF ICF
Water
Proteins
Capillary wall Cell membrane
Water
Water
Urea Urea
Urea
Glucose
Glucose
Na+
Na+

42
ii) The fluid in blood plasma – the intravascular fluid (IVF) (~5% of TBW).
iii) The fluid in body cavities – the transcellular fluid (TCF) (<1% of TBW).
– Cerebrospinal fluid (CSF)
– Intraocular fluid.
– Fluid in digestive tract.
Ion compositon of body fluids
Interstitium
Cations Anions Cations
Cytosol
Anions
Na
+
CI–
Ca , Mg
2+ 2+
HCO3
–
K
+
Proteins, phosphates,
etc.
K+
Proteins–
Ca , Mg
2+ 2+
Na
+
Misc
HCO3
–
Inorganic
phospate
 Water balance: Body must gain water to balance the lost water.
 Water turnover: Amount of water gained by body to balance that which is lost.
 Water requirement depend on: Caloric expenditure, basal metabolism condition, body surface
area.
mval/L (mmol/L)
Ion Plasma Serum Interstitium Cytosol
Na+
142 153 145 ca. 12
K+
4.3 4.6 4.4 ca. 140
Free Ca2+
2.6 (1.3*) 2.8 (1.3) 2.5 (1.5) <0.001
Free Mg2+
1.0 (0.5**) 1.0 (0.5) 0.9 (0.45) 1.6
Sum 150 162 153 ca. 152
CI
–
104 112 117 ca. 3
HCO3
–
24 36 27 10
Inorganic phosphate 2 2.2 2.3 ca. 30
Proteins 14 15 0.4 ca. 54
Misc. 5.9 6.3 6.2 ca. 54
Sum 150 162 153 ca. 152
*) Total plasma Ca: 2.5 mmol/L; **) Total plasma Mg: 0.9 mmol/L
Anions
Cations

43
 Metabolic water: Water derived from metabolic reactions in cell. 100 g of protein, carbohydrate
and fat yield 40, 60 and 110 ml of water
Failure of water balance
 Dehydration:
– Occur when water losses exceed water gain.
– Mild – thirst mechanism re-establish the water balance.
– Moderate to severe (>10% of body weight) – therapy required.
 During dehydration
– Immediate source of water – ECF.
– Kidney also excrete electrolyte and ions to maintain the osmolarity.
– So, rehydration requires not only water but also electrolytes.
Kinds of electrolytes
 Acid: Carbonic acid, hydrochloric acid, acetic acid, phosphoric acid.
 Base: Sodium hydroxide, potassium hydroxide, magnesium hydroxide, aluminum hydroxide.
 Salt: Sodium chloride, aluminum chloride, magnesium sulphate.
TARGET POINTS
 It is because of the more limited reserves (e.g. ECF) associated with their relatively higher needs
that young baby become distressed more quickly in conditions of uncontrolled water loss (e.g.
Diarrhea).
 Adaptation to water lack
 Camel, sheep, donkey etc.
– Can endure dehydration ~ 30% of their body weight (other animal ~ 10%).
– Can drink ~ 25% of their body weight at one time without any harmful effect.
– Excrete dry feces and concentrated urine.
– Metabolic water from stored fat.

44
3.3 BLOOD
Along with lymph, blood is a vascular connective tissue whose matrix is liquid and fiber free.
Blood
Blood cells Blood platelets Plasma
Erythrocytes Leukocytes
Granulocytes Agranulocytes
Neutrophils Eosinophils Basophils Monocytes Lymphocytes
3.3.1 Salient features
 Color: red
 pH: 7.4 (slightly alkaline)
 By weight: 7 to 8% of body weight
 By volume: 5 to 6 liters in male and 4 to 5 liters in
female.
 Blood is a false CT because:
– Cells of blood have no power of division.
– Fibers are completely absent in blood.
– Matrix of blood is produced and synthesized by
liver and lymphoid organs.
 Composition:
Liquid part – matrix – plasma 55%
Solid part – blood corpuscles – 45% (RBC, WBC and platelets) [formed elements]
TARGET POINTS
 Study of blood – haematology.
 Haemopoiesis: Process of blood formation.
 Packed cell volume – (PVC)% volume or total number of blood corpuscles is blood.
 Haematocrit volume: %volume or only number of RBC in blood.
 PVC ~ HV because 99% of packed cell volume is completed by RBC and in rest 1% WBC and
platelets are present.
Plasma
(55% of total blood)
Buffy coat
leukocytes and platelets
(<1% of total blood)
Erythrocytes
(45% of total blood)

45
3.3.2 Plasma (blood matrix)
Reabsorb in blood
Gives colour to plasma
Dead
RBC
Haem
Globin Iron
Porphyrin
Bilirubin
(Yellow)
Biliverdin
(Green)
Bile
juice
Stercobilinogen
Gives colour
to stool
Urobilinogen
 Pale yellow in color due to urobilinogen (bilirubin).
 Composition: Water (90 – 92%), solid part (8 – 10%) containsinorganic and organic compounds
 Inorganic components (0.9%):
1. Ions – Na+
, K+
, Ca++
, Cl–
, HCO3
–
, SO4
2–
, PO4
3–
, Cl–
> Na+
.
2. Salts – NaCl, KCl, NaHCO3
, KHCO3
, [maximum: NaCl (also called as common salt).]
3. Gases – O2
, CO2
, N2
, [each100 ml of plasma contains 0.29% O2
, 0.5% N2
, 5% CO2
present
in dissolved form.]
 Organic compounds (7 – 9%):
A. Proteins (6-7% maximum): albumin, globulin, prothrombin, fibrinogen.
B. Digested nutrients:
Amino acid
Glucose
Fatty acid
Glycerol
Cholesterol
Vitamins
If exceeds 180 mg/100ml
= Appears in urine = Glucosuria
70 - 110 m/dI = Fasting Glucose
110 - 140 mg/dI = Glucose PP
(Blood cholesterol level - 80 - 180 mg/100ml)
(Blood Glucose level - 80 - 100 mg %)
C. Waste products: Urea, uric acid, creatine, creatinine.
Normal blood urea level 17 – 30 mg%. If blood urea becomes more than 40 mg this condition
is called uremia in which RBC becomes irregular in shape called burr cell which are
destroyed in spleen so uremia is a type of anaemia.
D. Anticoagulant: Heparin (a mucopolysaccharide that prevents clotting of blood in blood
vessels.)
E. Protective compounds: Lysozyme (an enzyme which dissolves the cell wall of bacteria
and destroy them) and properdin (large protein molecules, destroy toxins synthesized by
bacteria or viruses).

46
F. Hormones: Secreted by endocrine glands which are transported by blood plasma.
 Proteins of plasma:
A. Albumin (4% maximum):
 Produced and synthesized by liver.
 Smallest plasma protein.
 Responsible to maintain BCOP (28 – 32 mmHg).
B. Globulin (2 – 2.5%):
 Ratio of albumin and globulin is 2:1.
 Produce and secreted by liver and lymphoid organs.
 Transport or carry substance in body.
 Destroy bacteria virus and toxic substances.
 In blood 3 types of globulins are present.
i) -Globulin: Produced by liver. e.g. Ceruloplasmin – Cu carrying protein.
ii) -Globulin: Produced by liver. e.g. Transferin – Fe carrying protein.
iii) -Globulin: Produced by lymphoid organs. Present in the form of antibodies which
destroy bacteria, virus and toxic substance. Also called immunoglobulins. These
are of 5 types.
a) IgG (-immunoglobulin)- (75%): Maximum in quantity and smallest in size, molecular
weight 1,46,000 dalton, single antibody to cross placenta which mother gives to child
during embryonic life.
b) IgA (- immunoglobulin) – (10 – 15%): Molecular weight 1,70,000 dalton, secretory
antibody because it is present in glandular secretions like milk or intestinal secretion.
After birth mother gives to child immunoglobulin A.
Colostrum – 1st
milk after parturition in which more IgA is present.
c) IgM (- immunoglobulin) (5 – 10%): Molecular weight 9,60,000 dalton, produced
and synthesized at the time of recent infection of bacteria and viruses, largest, heaviest
and oldest antibody.
d) IgD (- immunoglobulin) (1- 3%): Molecular weight 1,84,000 dalton, surface antibody.
Present on the surface of B lymphocyte.
e) IgE (-Immunoglobulin) (0.005%): Molecular weight 1,88,000 dalton, produced at
time of severe allergy.
C. Prothrombin (0.3%): Produced by liver.
D. Fibrinogen (0.3%): Produced by liver, it is the largest plasma protein and helps in blood
clotting.

47
BLOOD CORPUSCLES
Red blood cell Platelet White blood cell
Multipotential hematopoietic
stem cell (Hemocytoblast)
Common myeloid progenitor Common lymphoid progenitor
Erythrocyte Mast cell Myeloblast
Megakaryocyte
Thrombocytes
Basophil Neutrophil Eosinophil Monocyte
Macrophage
Plasma cell
B lymphocyte
T lymphocyte
Small lymphocyte
Natural killer cell
(Large granular lymphocyte)
Hematopoiesis and stem cells
During embryonic development the formation of blood cells occurs in the liver, spleen, and yolk sac.
However, after birth, the infant’s liver and spleen become the locations for destroying blood cells. All
blood cells, whether they end up in the myeloid or lymphoid family, begin as hemocytoblasts, stem
cells that develop from embryonic mesenchyme.
3.3.3 Red blood cells (RBCs) or erythrocytes
 Size
– Human – 7.5 Rabbit – 6.9 Frog – 35

48
– Largest RBC – Amphiuma, 75 – 80 (class: amphibia).
– Smallest RBC – Musk deer, 2.5(class: mammalia).
– Largest RBC among all mammals is elephant, 9 – 11
– Change in the size of RBC is called as anisocytosis.
1. Due to Vitamin B12
deficiency RBC becomes larger in size called as macrocytes. These
are immature RBCs which are destroyed in spleen. In these RBCs amount of hemoglobin
is normal.
2. Due to Fe deficiency RBCs become smaller in size called as microcytes. They are also
destroyed in spleen. In these RBCs amount of hemoglobin is less.
 Shape:
– Biconcave.
– Change in the shape of RBC is called as poikilocytosis.
– Uremia – RBC becomes irregular in shape.
– Sickle cell anaemia – RBC becomes sickle shaped.
– If RBC is kept in hypertonic solution it will shrink (crenation).
– In hypotonic solution it will burst.
– 0.8 – 1% NaCl solution is isotonic for RBC (0.9% of NaCl).
– 80 – 100 mg% of glucose is also isotonic.
 Mammalian RBC’s are biconcave, circular and non-nucleated. At the time of origin, nucleus
is present in RBCs but it degenerates during maturation. Biconcave shape increases the
surface area. Absence of nucleus and biconcavity allow more hemoglobin to be filled in RBC.
Exception: Camel and Lamma are mammals with biconvex, oval shaped.
 Endoplasmic reticulum is absent; endoskeleton is composed of structural protein, fats and
cholesterol in the form of network called stromatin which is a spongy cytoskeleton. Plasma
membrane of RBC is called Donnan’s membrane. It is highly permeable to some ions like
Cl–
and HCO3
–
and impermeable to Na+
and K+
. This is called Donnan’s phenomenon. Due
to presence of stromatin spongy cytoskeleton and flexible plasma membrane, RBC (7.5 m)
can pass through less diameter blood capillaries (5 m).
 Higher cell organelles like mitochondria and Golgi complex are absent and thus, anaerobic
respiration takes place in RBC. Enzymes of glycolysis are present while enzymes of Kreb’s
cycle are absent. Carbonic anhydrase enzyme is present which increases the rate of formation
and dissociation of carbonic acid by 5000 times (fastest catalyst (with zinc)).
 Antigen of blood group is present on the surface of RBC. If Rh antigen is present then it is
also found on the surface.
 Single RBC is pale yellow while groups of RBCs appear red.

49
 In each RBC, 26.5 crores molecules of hemoglobin (mol. wt. 67, 200 Da) are present.
 Composition: Water (60%), solid part (40%). Only Hb constitutes 36% of total weight of
RBC and 90% on dry weight.
 Hemoglobin: Haem (5%) and Globin (95% protein part)
A. Haem (iron and porphyrin):
– Iron present in the form of Fe+2
– While in muscles, myoglobin is present where iron is present in the form of Fe+3
.
– Porphyrin is composed of acetic acid and glycine amino acid.
– Each molecule of Hb carries 4 molecules of O2
, 1 gm Hb carries 1.34 ml of O2
, 100 ml
blood contain 15 gm Hb, 100 ml blood transport 20 ml O2
.
B. Globin:
– Each molecule of globin protein is composed of 4 polypeptide chains. Polypeptide chains
are of 4 types:
i) polypeptide chain having 141 amino acids.
ii) polypeptide chain having 146 amino acids.
iii)  polypeptide chain having 146 amino acids.
iv)  polypeptide chain having 146 amino acids.
On the basis of these polypeptide chains 3 types of Hb are formed in human.
– HbA (adult Hb) – 2 + 2
– HbA2
(adult-2) – 2 + 2
– HbF (foetal Hb) – 2 + 2
(oxygen binding capacity of foetal Hb is more than
adult Hb)
 RBCs formation:
– RBC formation is erythropoiesis and the producing organs are called erythropoietic
organs. Hormone which stimulates erythropoiesis is erythropoietin synthesized by the
kidney.
– 1st RBC is produced by yolk sac. During embryonic life, RBCs are produced by liver,
spleen, placenta and thymus gland. In adult stage, red bone marrow (filled in trabeculae of
spongy bones) produce RBCs. Kidney is an erythropoietic organ in frog.
– 1% RBCs are destroyed daily but in same number new RBCs enter in the blood. Destruction
occurs in spleen (the graveyard of RBC). Spleen also stores excess blood corpuscles,
also called as ‘the blood bank of body’.
Chain
Heme
Fe
2+
Chain

Body Fluids and Circulation Class 11 NCERT Solutions Study Material Free PDF

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