Physiology, brief anatomy of respiratory system

1. By Gunchmaa.N

2. 4 main stages
1. Ventilation
2. Diffusion (alveoli/blood)
3. Transport of O2 and
CO2
4. Exchange (tissue/blood)

3. Non-respiratory functions
• Moistens inspired air
• Maintains pH
• Vocalization
• Modifies various materials
• Enhances venous return

6. The Pleura
• The pleura separates
each lung from the
thoracic wall and other
structures
• Secretes a thin
intrapleural fluid which
lubricates the pleural
surfaces as they
slide past each other

7. Different Pressures
• Atmospheric pressure = 760 mm Hg
• Intra-alveolar pressure - pressure within
the alveoli
• Intrapleural pressure - pressure exerted
within the thoracic cavity /756 mm Hg/

8. Transmural Pressure Gradient
4 mm Hg difference in pressure enables
lungs to expand and shrink

9. Basic concept
• Intra-alveolar P < atmospheric P =
inspiration
• Intra-alveolar P > atmospheric P =
expiration

10. Major respiratory muscles
• Diaphragm
• External intercostal
• Internal intercostal
• Abdominal muscles
• Sternocleidomastoideous
• Scalenus

13. Movement of rib and sternum

14. Pulmonary surfactant
• A complex mixture of lipids and proteins
secreted by the Type II alveolar cells
• Lowers alveolar surface tension
• Decreases hydrogen bonding at the alveolar
air–water interface
• More crowded in small alveoli

15. Law of LaPlace
The smaller alveolus has a tendency
(without pulmonary surfactant) to collapse and
empty its air into the larger alveolus.
Surfactant avoids this!

17. • Surfactant proteins - synthesized in
polyribosomes, modified in the ER, GA and
stored in lamellar bodies before secretion.
• Surfactant phospholipids - synthesized in the
ER and packaged into lamellar bodies. After
exocytosis of lamellar bodies, it’s organized
into tubular myelin

18. Alveolar interdependence
When an alveolus in a group of alveoli collapses, the
surrounding alveoli are stretched. As the other alveoli
recoil in resistance, they pull outward on the collapsing
alveolus.

19. Variations in lung volume

22. Anatomical Dead Space
Not all the inspired air
gets down to
the alveoli. Part
remains in the
conducting airways,
where it is not
available for gas
exchange. The volume
averages about 150 ml.

23. Effects of CO2 and O2

24. Gas transport
• Oxygen is present in the blood in two forms:
physically dissolved and chemically bound to
hemoglobin
• Deoxyhemoglobin/oxyhemoglobin
• The saturation, measures the Hb combined
with O2 and can vary from 0% to 100%.
• PO2 of the blood determines saturation

25. CO2 transport in blood

26. This reaction takes place slowly in the plasma,
but it’s catalyzed by erythrocyte enzyme
carbonic anhydrase.

27. Haldane effect
Removing O2 from Hb increases the ability of
Hb to pick up CO2 and CO2-generated H ion

28. Components of neural control of
respiration
1. Factors that generate respiratory rhythm
2. Factors that regulate the magnitude of
ventilation
3. Factors that modify respiratory activity to
serve other purposes.

29. Medullary Respiratory Center
• Dorsal respiratory group consists of inspiratory
neurons. When active inspiration occurs.
• Ventral respiratory group is composed of
inspiratory neurons and expiratory neurons.
Activates when demands for ventilation are
increased.

30. Pre-Bötzinger complex
A region located near the end of the medullary
respiratory center. Displays pacemaker activity.

31. Apneustic center
Prevents the inspiratory
neurons from
being switched off.

32. Hering–Breuer reflex
Prevents overinflation of the lungs. Pulmonary
stretch receptors’ action potentials travel
through afferent nerve fibers to the medullary
center and inhibit the inspiratory neurons.

34. Peripheral chemoreceptors
• Carotid/aortic
bodies
• Responds to
chemical
changes in
arterial blood

36. Other ventilation factors
• Protective reflexes such as sneezing and
coughing
• Inhalation of noxious agents triggers cessation
of ventilation.
• The expression of various emotional states,
such as laughing, crying, sighing.
• Hiccups
• The respiratory center is reflexly inhibited
during swallowing

37. Thank You