Physiology of the respiratory system

Physiology, brief anatomy of respiratory system

1. By Gunchmaa.N

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

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

4. The Pleura T he 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

5. 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/

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

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

8. Major respiratory muscles Diaphragm External intercostal Internal intercostal Abdominal muscles Sternocleidomastoideous Scalenus

9. Movement of rib and sternum

10. 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

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

12. S urfactant 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

13. 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.

14. Variations in lung volume

15. 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.

16. Effects of CO2 and O2

17. 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 %. P O2 of the blood determines saturation

18. CO2 transport in blood

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

20. Haldane effect R emoving O2 from Hb increases the ability of Hb to pick up CO2 and CO2-generated H ion

21. Components of neural control of respiration Factors that generate respiratory rhythm F actors that regulate the magnitude of ventilation F actors that modify respiratory activity to serve other purposes .

22. Medullary Respiratory Center D orsal respiratory group consists of inspiratory neurons . When active inspiration occurs. V entral respiratory group is composed of inspiratory neurons and expiratory neurons. Activates when demands for ventilation are increased.

23. P re- Bötzinger complex A region located near the end of the medullary respiratory center. Displays pacemaker activity.

24. Apneustic center P revents the inspiratory neurons from being switched off.

25. 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.

26. P eripheral chemoreceptors Carotid/aortic bodies Responds to chemical changes in arterial blood

27. 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

28. Thank You