2. The materials which provide the two primary requirements of life, namely,
energy andraw materials (matter) are called nutrients
The processes which are responsible for providing energy are
nutrition and respiration.
Nutrition is the sum total of all processes through which the food is taken in,
digested, absorbed, and utilized and finally, the undigested matter is
eliminated outside the body.
Thus, nutrition includes the processes like ingestion, digestion, absorption,
assimilation and egestion (defecation).
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3. the process in which food is taken inside the body. This
Ingestion
ingested food is then digested.
process during which complex, non-diffusible and non-
N absorbable food substances are converted into simple,
Digestion
U diffusible and absorbable substances by enzymes. .
T
process in which the simple substances get diffused into
R the blood. Thus, the absorbed food is now carried to
Absorption
I each and every tissue cell of the body where it is
T assimilated
I the process by which the protoplasm is synthesized into
Assimilation
O each cell of the body by utilizing simple food substances.
N
process of the elimination of the indigestible remains of
Egestion the food from the alimentary canal (defecation or
evacuation)..
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5. HUMAN DIGESTIVE SYSTEM
Alimentary Canal Accessory Glands
Mouth parotid
Salivary
Palate Sub lingual
Glands
Buccal Cavity Tongue Sub mandibular
Teeth
Naso-Pharynx
Pancreas
Pharynx Oro-Pharynx (Exocrine part)
Laryngo-Pharynx Liver
Oesophagus
Cardiac
Stomach Fundus
Pylorus
Duodenum
Small Int Jejunum
Ileum
Caecum
Large Int Colon
Anus Rectum
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6. MOUTH
Uppermost Transverse slit-like opening of alimentary canal
Bounded by 2 fleshy lips
Leads to a large cavity called ORAL or BUCCAL CAVITY
BUCCAL CAVITY
Large space bounded : above by the Palate
sides by the Jaws ( they bear the teeth)
below by the Throat ( they support the tongue)
Lined by : Squamous epithelium and mucous membrane
Presence of : TONGUE, TEETH & SALIVARY GLANDS
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7. TONGUE
--Thick muscular protrusible organ
--Att. To the floor of buccal cavity by a : fold of mucous membrane – LINGUAL FRENULUM
bony attachments – styloid process and hyoid bone
--Upper surface shows presence of numerous raised projections called PAPPILAE
which contain sensory receptors for taste (gustatory receptors)
--USES : 1. Taste
2. Mixing of food with saliva
3. Deglutition ie swallowing
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8.
9. TEETH
Present on both the upper and the lower jaw
The following terminologies describe the teeth :
1. THECODONT : Fixed in the sockets of jaw bones
2. HETERODONT : Different types of teeth
a) Incisors - chisel shaped , for biting, cutting and gnawing
b) Canines – Pointed, used for ripping and shredding
c) Premolars – for grinding
d) Molars – for grinding
3. DIPHYODONT : Teeth appear twice during lifetime
2 (I) 1 (C) 0 (PM) 2 (M)
a) Decidious : 20 in number 2 1 0 2
2 (I) 1 (C) 2 (PM) 3 (M)
b) Permenant : 32 in number 2 1 2 3
12. CLINICAL APPLICATION : ROOT CANAL THERAPY
Root canal therapy is a multistep procedure in which all traces of pulp tissue are
removed from the pulp cavity and root canals of a badly diseased tooth.
After a hole is made in the tooth, the canal are filed out and irrigated to remove
the bacteria
Then the canals are treated with medication and sealed tightly.
The damaged crown is repaired
14. PHARYNX
The buccal cavity leads in to the pharynx. It can be divided into 3 regions
1. NASOPHARYNX : lies behind the nasal cavities having the internal nares and
Eustachian canals
2. OROPHARYNX : lies behind the buccal cavity and forms the passage for the
bolus of food
3. LARYNGOPHARYNX : lowest part of Pharynx and has 2 openings
a) Glottis which leads to the trachea
b) Gullet which leads to the oesophagus
16. OESOPHAGUS
The oesophagus is 25 cm long, narrow, muscular
tube connecting the pharynx to the stomach
It is lined by stratified squamous epithelium
containing mucous glands
Food moves through the oesophagus due to
rhythmic contractions of the longitudinal and
circular muscles
This movement is called as PERISTALSIS
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17. CLINICAL APPLICATION :CARDIA ACHLASIA
Failure of the sphincter to relax causes impediment for the
food to pass through the oesophagus. Distention of
oesphagus can lead to pain which is often confused
with heart pain
18. CLINICAL APPLICATION :HEARTBURN
Failure of the sphincter to close after the passage of food in
the stomach can cause the contents of the stomach to revert
back in the oesophagus thereby leading to irritation of
oesophageal wall causing a burning sensation called as Heartburn
19. STOMACH
Sac like , ‘J’ shaped, 25-30 cms long
3 parts : i) Cardiac
ii)Fundus
iii) Pyloric
Sphincters at both the ends of stomach
i) Cardiac Sphincter : prevents
regurgitation of food back into the
buccal cavity
ii) Pyloric Sphincter : Regulates the
passage of food into the duodenum
FUNCTIONS :
i) Churns the food ie breaks the food into
smaller pieces which facilitates the mixing
of food with gastric juice
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20. SMALL INTESTINE
Longest part of the Digestive system, it is 6m long
and 2.5 cms broad .
It is compactly coiled in the abdominal cavity
The coils are held together by connective tissue
membranes called mesenteries supporting
the blood vessels, lymph vessels and nerves
3 parts:
i) DOUDENUM : U-shaped about 25 cms long
Bile duct and pancreatic duct opens in the
duodenum
ii) JEJUNUM : 2.5 m long and narrower than
duodenum
iii) ILEUM : Lower part of the small
intestine 3.5 m long and opens in the large
intestine
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21. 1.5 m long, arranged around the mass of small
LARGE INTESTINE intestine in the form of a ? mark
i) CAECUM : small blind sac off the colon,
Present at the junction of ileum and colon. At
the junction is a ileocaecal valve that
regulates passage of substances from the
small to the large intestine. Caecum bears a
small worm like vestigial organ called as
appendix(functional in herbivores for the
digestion of cellulose)
ii) COLON : Anterior region divided into 3
parts a) Ascending colon
b) Transverse colon
c) Descending colon
iii) RECTUM : Posterior region, about 15 – 20
cms long. The rectum has longitudinal
folds and large blood vessels.
Undigested matter called faecal matter is
temporarily stored before egestion
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22. ANUS
The rectum opens to the outside by the opening called ANUS . It is guarded by a
sphincter. It removes undigested matter outside by a process known as
DEFEACATION
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23. HUMAN DIGESTIVE SYSTEM
Alimentary Canal Accessory Glands
Mouth parotid
Salivary
Palate Sub lingual
Glands
Buccal Cavity Tongue Sub mandibular
Teeth
Naso-Pharynx
Pancreas
Pharynx Oro-Pharynx (Exocrine part)
Laryngo-Pharynx Liver
Oesophagus
Cardiac
Stomach Fundus
Pylorus
Duodenum
Small Int Jejunum
Ileum
Caecum
Large Int Colon
Anus Rectum dr. aarif
24. SALIVARY GLANDS
1. SUBLINGUAL GLAND
2. SUBMANDIBULAR GLAND
3. PAROTID
The Salivary glands have 2 types of secretory cells :
a) Serous cells : produces a watery fluid containing enzyme SALIVARY AMYLASE or
PTYALIN
b) Mucous cells : produces mucous. It binds the food, makes it slippery so that it can be
easily swallowed
25. LIVER
-Largest gland of the body.
-Reddish brown in colour
-Weighing about 1.5 kgs in adult
-Located on the right side, just below the
diaphragm
-Made up of 2 lobes
-Produces bile juice which gets stored in a
small bag-like structure called gall-bladder
Functions of the liver:
-Liver secretes bile which emulsifies fats and makes the food alkaline.
-It stores excess of glucose in the form of glycogen which is used during starvation.
-In liver, excess amino acids are converted into ammonia by the process called deamination.
-It synthesizes vitamin A, D, K and B12.
-Blood proteins like prothrombin and fibrinogen are formed in the liver.
-It produces red blood cells during early development thus working as a hematopoietic organ.
-Kupffer cells digest old R.B.C.’s
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26. PANCREAS
It is a leaf-shaped gland lying in the gap
between the duodenum and the stomach.
It is a mixed gland because some part of it
is exocrine in function, i.e. its secretion is
carried by the ducts, while the other part is
endocrine, i.e. its secretion is directly
poured into the blood stream.
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29. SEROSA:
Outer protective covering of the stomach.
Outer layer of squamous epithelium (mesothelium)
Inner layer of connective tissue.
MUSCULARIS :
Thick layer made up of 3 kinds of muscles
1. Outer longitudinal muscles
2. Middle circular muscles and
3. Inner oblique smooth muscles.
This muscular layer is the thickest part responsible for the churning movement in the
stomach.
SUBMUCOSA:
Connective tissue layer containing blood vessels, lymph vessels and nerves.
It supports mucosa
MUCOSA:
It is the innermost layer thrown into large folds called rugae. It is made up of three
parts:
Muscularis mucosa: It is prominent and formed of outer longitudinal and inner
circular muscles.
Lamina Propria: It contains the gastric glands.
Epithelium: It is columnar and folded to form gastric glands. dr. aarif
30. GASTRIC GLAND
These are simple, tubular, branched or un-branched glands, embedded in the lamina propria.
Each is made up of the following 3 types of cells
MUCOUS CELLS:
They are present in the neck region and
secrete mucous.
PARIETAL CELLS (OXYNTIC CELLS):
large oval cells.
secrete dilute HCI and an intrinsic
factor [necessary for absorption of
Vitamin B12.(def .of B12 leads to
pernicious anaemia)]
CHIEF CELLS (PEPTIC CELLS):
They are pyramid shaped
Present deep in the base of the glands.
Secretes enzyme pepsinogen
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35. HISTOLOGY OF PANCREAS The exocrine part is made up of pancreatic
lobules called acini. They are flask-shaped
and formed of a single layer of large
glandular pyramid-shaped cells. These cells
secrete the pancreatic juice. This juice is
alkaline in nature with pH of 8.8. About a
litre of pancreatic juice is secreted each day.
The endocrine part is made up of groups of
cells present in the connective tissue
between the acini. These are called Islets of
Langerhans.
1. ‘A’ or alpha α cells that secrete glucagon
2. ‘B’ or beta β cells that secrete insulin.
Both these hormones together control the
blood sugar level.
3. delta cells secrete somatostatin hormone,
which decreases glucagon and insulin
secretion.
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36. PHYSIOLOGY OF DIGESTION
PHYSICAL CHANGES + CHEMICAL CHANGES
breaking up of the food Chemical changes are
into smaller finer particles brought about by the
mastication, action of different
churning and enzymes.
peristaltic movements
The food eaten is insoluble and it cannot become a part of our body. The
food undergoes many physical and chemical changes so that it is converted
into the simple soluble absorbable form. This is absorbed into the mucosa
cells of the alimentary canal and then diffused into the blood capillaries
37. DIGESTION IN BUCCAL CAVITY
MASTICATION will break down the food in to smaller particles
TONGUE mixes the food with SALIVA secreted from the SALIVARY GLANDS
PTYALIN SALIVA LYSOZYME
STARCH MALTOSE
Anti-bacterial
(Poly) pH 6.8 (Di)
Prevents Infections
(30% of starch is hydrolysed)
The bolus , formed is then pushed into the oesophagus by the action of the tongue.
The tongue presses against the palate and pushes the bolus into the pharynx.
This is called swallowing or deglutition
Food is swallowed too quickly for all the starch to be reduced to maltose
Ptyalin in the swallowed food continues its action for 15-20 min in the stomach
before it is inactivated by the acid of the stomach
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39. DIGESTION IN STOMACH
GASTRIC JUICE
HCl PEPSINOGEN MUCOUS
1. Stops the action of Pepsinogen HCl Pepsin Mucous and
salivary amylase. (Inactive) (Active) bicarbonates
2. Provides the acidic forms a
medium (pH 1.8) required to Pepsin protective layer
convert inactive pepsinogen Proteins Peptones + Proteoses on the mucosa
to active proteolytic enzyme of the stomach
pepsin to prevent the
3. It kills the germs that may action of HCl.
enter along with the food.
4. It helps to soften the food
Rennin is a proteolytic enzyme found in gastric juice of infants which helps in the digestion of
milk proteins
After digestion in the stomach, food is converted into a semisolid mass called chyme. Acidic
chyme travels into the duodenum through the pyloric sphincter
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40. DIGESTION IN SMALL INTESTINE
PANCREATIC
JUICE
FOOD IN DUODENUM
(chyme)
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41. BILE
Bile helps to neutralize the acidic chyme.
Bile juice is a yellowish green liquid.
It is made up of water, cholesterol, bile salts, bile pigments and phospholipids but
no enzymes.
Bile salts Bile Pigments
Brings about emulsification of fats, i.e., (bilirubin and biliverdin) are produced as a
breaking down of the fats into very small result of breakdown of haemoglobin.
micelles.
They give colour to faecal matter
Bile also activates lipases
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42. PANCREATIC
JUICE
Amylase acts on the starch to form disaccharides maltose
.
AMYLASES Starch pancreatic amylase Maltose
alkaline medium
Lipase with the help of Bile converts lipids into fatty acids and glycerol
.
LIPASES Lipids pancreatic lipase fatty acids + glycerol
alkaline medium
Nucleases in the pancreatic juiceacts on nucleic acids to form
nucleotidesand nucleosides
NUCLEASES .
Nucleic Acids Nucleases Nucleotides + Nucleosides
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43. PANCREATIC
INACTIVE TRYPSINOGEN & CHYMOTRYPSINOGEN
JUICE
Inactive trypsinogen is converted to trypsin by enterokinase from intestinal juice.
Enterokinase
TRYPSINOGEN TRYPSIN
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44. INTESTINAL Secretion of Secretion of brush
= +
JUICE Goblet cells border cells
Succus Mucous Disaccharidases
entericus Dipeptidases
Lipases
Nucleosidases
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46. BUCCAL CAVITY
Bolus
STOMACH
Chyme
SMALL
INTESTINE
Chyle
LARGE
INTESTINE
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47. ABSORPTION
Absorption is the process by which the end products of digestion pass through the
intestinal mucosa into the blood or lymph.
It is carried out by passive, active or facilitated transport mechanisms.
ABSORPTION
Passive Active Facilitated
Transport
Along the conc gradient Against the conc gradient Same as passive but
No energy required energy required Requires the presence of
some carrier substances
like Na+
Water, short chain fatty Glucose, galactose, Na+, Fructose, some amino
Acids, water sol vitamins Amono acids acids
52. NUTRITIONAL IMBALANCE
DEFICIENCY OVERINTAKE
Deficiency disorder affects the structure Excess of nutrients is also harmful
and function of the part which depends Animal fats --- Cardiovascular diseases
upon that nutrient Proteins ---- cancer of large intestine
Vit A / D ---- Hypervitaminosis
Results in Deficiency disorders
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54. KWASHIORKOR
-It is a protein deficiency disease. Commonly affects infants and children between 1 to 3
years of age.
SYMPTOMS:
The common symptoms of Kwashiorkor are underweight, stunted growth, poor brain
development, loss of appetite, anaemia, protruding belly, slender legs and bulging eyes.
Oedema of lower legs and face and change in skin and hair colour may also occur in
Kwashiorkor.
CAUSES:
The basic causes of the disease are:
Protein-deficient or inadequate diet due to ignorance or poverty
Infectious disease such as diarrhoea, measles, respiratory infections, intestinal worms,
which weaken the child.
CURE:
The proteins are the building blocks of food, and are essential for growth and repair of the
tissues and also for the body defence. Therefore, adequate amounts of proteins must be
present in the diet. For normal health, daily diet should contain one gram of proteins per kg.
body weight in the case of adults and two grams of proteins per kg. body weight in the case
of growing children. The sources of protein are cereals, pulses, meat, fish, milk, cheese,
leafy vegetables, groundnut, peas and beans. dr. aarif
55. MARASMUS
It is a form of prolonged protein energy malnutrition (PEM).
It affects infants under one year of age
CAUSES:
Marasmus is caused by simultaneous deficiency of proteins and total food caloric value,
that is, deficiency of all nutrients. It affects the infant if mother's milk is replaced too early
with foods having low protein content and caloric value. This often happens when the
mother conceives before her infant is ready for weaning
SYMPTOMS:
Due to protein-deficient diet, stored fats and tissue proteins are used as sources of energy.
This impairs physical growth and retards mental development. Subcutaneous fat
disappears, ribs become very prominent, limbs become thin and skin becomes dry, thin and
wrinkled. There is emaciation (extreme leanness) and loss of weight. Digestion and
absorption of food stop due to atrophy of digestive glands and intestinal mucosa. This leads
to diarrhoea. There is no oedema, characteristic of Kwashiorkor
CURE:
Diet with adequate proteins and proper calorific value should be given to the infants.
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56. INDIGESTION
It is a nonspecific term that includes a variety of upper abdominal complaints including
heart burn, regurgitation and dyspepsia (upper abdominal discomfort or pain).
-These symptoms are due to gastro-oesophageal reflux disease. It occurs as a
consequence of acid reflux into the oesophagus from the stomach. This may occur due to
a large meal or acid hyper secretion.
-Some other factors include physical position such as lying down, bending over, increased
pressure on the stomach (tight clothes obesity) and loss of lower oesophageal sphincter
tone.
-Indigestion can be improved with avoidance of large meals, smoking, alcohol, fatty food
and weight reduction and taking antacids.
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57. CONSTIPATION
It is defined as decrease in the frequency of stools to less than one per week or difficulty
in defeacation which may result in abdominal pain, distortion and a rarely perforation.
Some contributory factors may include inactivity, low fibre diet etc.
Specific causes of constipation may include affected colonic mobility due to neurological
dysfunction e.g. diabetes mellitus, spinal cord injury.
Constipation may improve with increased dietary fibres, increased fluid intake and
exercises.
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58. JAUNDICE
This is not a disease in itself, but is a sign of abnormal bilirubin metabolism and excretion.
Jaundice develops when there is an abnormality at some stage in the metabolic sequence
caused by excess haemolysis of red blood cells with the production of more bilirubin than
the liver can deal with, obstruction to the flow of bile from the liver to the duodenum
(gall bladder stones) and abnormal liver function (hepatitis viruses).
Bilirubin, produced from the breakdown of haemoglobin is usually conjugated. The
bilirubin is water soluble and can be excreted. (Conjugation is a process of adding certain
groups to bilirubin to make it water soluble).
Unconjugated bilirubin is fat soluble and has a toxic effect on the brain cells. Serum
bilirubin may rise to 40 to 50 μmol/l before the yellow coloration of skin and conjunctiva is
seen (Normal value is 3 to 13 μmol/l).
Effects of raised bilirubin include pruritus (itching) caused by the irritating effects of bile
salts on the skin, pale face, dark urine and whitish stool.
There is no specific drug to prevent jaundice. Mainly, the treatment involves supportive
care, bed rest and treatment of cause.
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59. CARBOHYDRATES
1. Carbohydrates are chemically composed of carbon, hydrogen and oxygen.
(These are polyhydroxyaldehydic or ketonic organic compounds.)
2. They are the main sources of energy. Carbohydrates form more than half of our diet, but
form only 1% of our total weight.
This shows that they are primarily fuel foods and are rapidly oxidized to supply energy for
body activities.
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60. Carbohydrates can be classified into 3 categories:
Monosaccharides:
These are made up of simple sugars like glucose and fructose which are found in fruits and
honey.
Disaccharides:
1. These are composed of two molecules of simple sugars.
2. These include sucrose, lactose and maltose.
3. Sucrose is found in sugarcane, lactose in milk; however, maltose doesn’t occur free in
nature.
Polysaccharides:
1. These are made up of a number of molecules of simple sugars.
2. They include starch, glycogen and cellulose.
3. Starch is present in staple foods such as rice, wheat, maize, jowar, potato etc.
4. Glycogen is the main reserve food material of animal cells. It is also known as animal
starch. Glycogen is stored in the muscles and liver.
5. Cellulose is found in green vegetables. It is an indigestible fibrous carbohydrate that is
necessary as roughage for the smooth movement of food through the alimentary canal.
61. PROTEINS
1. Proteins are chemically composed of carbon, hydrogen, oxygen, nitrogen, sulphur and
phosphorous.
2. Proteins are natural polymers that are ranked first amongst the chemical substances
essential for growth and maintenance of life.
3. Each protein is made up of numerous monomers, the amino acids which are joined
together by peptide bonds.
There are 22 amino acids, out of which eight are said to be essential amino acids as these
cannot be synthesized in the body.
Animal proteins like meat, milk, egg, fish, etc. contain all the essential amino acids and
hence are known as complete proteins.
4. Proteins cannot be stored in the body. Excess of proteins are deaminated (broken down) in
the liver, to produce urea which is eliminated by kidneys (excretion).
Functions:
a. Proteins help in repair of wear and tear of the body.
b. Proteins aid the formation of enzymes, hormones, antibodies etc.
62. FATS (LIPIDS)
Fats are chemically composed of carbon, hydrogen and oxygen.
They comprise of heterogeneous organic compounds which are insoluble in water but readily
soluble in non-polar organic solvents like ether, chloroform, benzene, etc. On hydrolysis,
lipids yield fatty acids which are utilized by the living organisms.
(The fats present in our diet, after being processed in the alimentary canal and liver are
supplied to the tissues as glycerides. Fats are also formed from glucose and amino acids.
Thus, carbohydrates are fattening. This is why a lamb or pig fed on a starch-rich diet (grams
and cereals) puts on fat.)
Fats are solid or liquid. The fats which are liquid at room temperature are known as oils. Fats
are the richest source of energy. These are present in butter, cream, nuts, meat, fish and egg-
yolk.
A normal person needs 10%-25% of fats in his diet. Athletes need more than 40% fats.
Deficiency of fats causes dry and rough skin while excess of fats results in obesity, high blood
pressure and heart diseases.
Functions:
They protect the body from shocks and jerks.
They form the cell membrane.
They act as solvents for vitamins like vitamin A, D, E and K.
They make food tasty and palatable.
63. MINERALS
Minerals are inorganic substances required in very small quantities.
Minerals have small molecules and do not require digestion.
Various minerals are present in our diet.
Some of these minerals are sodium, calcium, phosphorous, potassium, iron, iodine etc.
Sodium, potassium and chloride ions maintain the osmotic balance of blood plasma. These
are obtained from common salt, sea foods and leafy vegetables.
Calcium and phosphorous are necessary for the development of bones, teeth, heart action,
nerve action and clotting of blood. Pregnant women and children need more calcium.
Sources of calcium are milk, eggs, fish and leafy vegetables.
Iron is necessary for formation of haemoglobin. Lack of iron leads to anemia. Sources of iron
are fish, liver, meat, tomatoes, cabbage, leafy vegetables etc.
Iodine is necessary for the proper functioning of the thyroid glands (production of
thyroxine). Its deficiency leads to a disease of the thyroid called goiter. The sources of iodine
are iodized salt and sea foods.
64. Name of the vitamin Source Effects of deficiency
Vitamin A Liver, milk, egg yolk, Night blindness, dry scaly
(Retinol) tomato, carrot and papaya skin, defective teeth
Vitamin B1 Yeast, whole grains, milk, Beriberi, loss of appetite,
(Thiamine) meat and green vegetables nerve disorders
Vitamin B2 Meat, milk, egg white, Loss of body weight, mental
(Riboflavin) soyabean and green leafy confusion, rough skin of
vegetables. exposed parts
Vitamin B3 Fish, meat, potato, green Skin irritation, mental
(Niacin) leafy vegetables disorder (pellagra)
Vitamin B12 Liver and green vegetables Megaloblastic anaemia,
(Cynocobalamine) digestive disorders
Vitamin C Citrus fruits, tomato, Scurvy (disease of gums)
(Ascorbic Acid) cabbage, amla delayed wound healing
Vitamin D Fish liver oil, milk, action of Rickets, tooth decay
(Calciferol) sunlight on the skin
Vitamin E Wheat-germ oil, milk, meat Sterility, muscular
(Tocopherol) and leafy vegetables disorder
Vitamin K Green leafy vegetables, Bleeder’s disease, clotting
(Phylloquinone) tomatoes, cabbage disorder
