Respiratory Physiology

Respiratory Physiology

1. Respiratory System:

The respiratory system consists of:

• Airways:

• Upper airways: Nose, pharynx, larynx

• Lower airways: Trachea, bronchial tree

• Lungs

• Thoracic cage

• Respiratory muscles

2. Functions of the Airways:

• Air conduction

• Protection: Prevents entry of large dust particles (> 5um) with the help of nasal hairs and mucus

• Warming and humidification of air due to capillaries and glands

3. Functional Unit for Gas Exchange:

• Alveoli:

• Type 1 alveoli (smaller)

• Type 2 alveoli (larger)

4. Characteristics of Large Alveolar Cells:

• Two types:

• Type with abundant mitochondria in the cytoplasm

• Type with abundant lysosomes in the cytoplasm

5. Which Alveolar Cells Secrete Surfactant?

• Type 2 alveoli

6. Respiratory Unit of Alveoli:

• Respiratory membrane: Composed of 6 layers:

• Surfactant layer

• Alveolar epithelium layer

• Basement membrane of epithelium

• Interstitial space

• Basement membrane of capillaries

• Endothelial cells

7. Respiratory Membrane Area in Adults:

• 50-100 m2

8. Thin Pleura Contains:

• Fibroblasts, macrophages

9. Nerve Innervation of Parietal Pleura:

• Phrenic and intercostal nerves

10. Nerve Innervation of Visceral Pleura:

• Sympathetic and parasympathetic nerve branches

11. Primary Factor Creating Negative Pressure in the Pleural Cavity:

• Elasticity of lungs and thoracic cage

12. Negative Pressure in the Pleural Cavity:

• At the end of normal expiration: -4 mmHg

• At the end of normal inspiration: -7 mmHg

• At the end of forced expiration: -1 mmHg

• At the end of forced inspiration: -30 mmHg

13. Significance of Negative Pressure in the Pleural Cavity:

• Parietal pleura adheres to the visceral pleura, allowing lungs to follow the movements of the thoracic cage

• Makes the intrathoracic pressure lower than other areas

• Facilitates blood return to the heart and to the lungs, reducing workload on the right ventricle

• Maximum gas exchange efficiency during inspiration

14. Function of the Respiratory System (CNTK):

• To deliver oxygen-rich air from the environment to the alveoli and expel carbon dioxide from the alveoli

15. Inspiration:

• Active process, requiring energy expenditure

• Muscles involved: Diaphragm, scalene muscles, serratus anterior, intercostal muscles (internal and external)

• Lowering the diaphragm by 1cm increases thoracic volume by 250 cm3

• Accessory inspiratory muscles participate during forced inspiration: Sternocleidomastoid, pectoral muscles, oblique muscles

• Forced inspiration can add around 1500-2000 ml to the lungs

16. Expiration:

• Passive process, no energy expenditure

• Forced expiration: Mainly due to abdominal muscles, active process requiring energy

17. Special Respiratory Movements:

• Straining, coughing, speaking, sneezing

18. Tidal Volume (TV):

• Volume of air inhaled or exhaled in a single breath

• In adults: 400-500ml (accounts for 12% of vital capacity)

19. Ventilation Ratio:

• Amount of alveolar air that is renewed

20. Inspiratory Reserve Volume (IRV):

• Volume of air that can be inhaled after a normal inspiration

21. Expiratory Reserve Volume (ERV):

• Volume of air that can be exhaled after a normal expiration

22. Residual Volume (RV):

• Volume of air remaining in the lungs after a forced expiration

23. Vital Capacity (VC):

• Volume of air that can be exhaled after a forced inspiration

• VC = TV+ IRV + ERV

24. Forced Vital Capacity (FVC):

• Volume of air exhaled as forcefully and rapidly as possible after a full inspiration

• FVC is significantly reduced in individuals with airway obstruction

25. Functional Residual Capacity (FRC):

• Volume of air in the lungs at the end of normal expiration

26. Total Lung Capacity (TLC):

• Total volume of air in the lungs after a maximal inspiration

• TLC = VC + RV

27. Respiratory Flow Rate:

• Volume of air moved in a unit of time (liters/minute)

• Indicates the patency of the airways

28. FEV1:

• Maximum volume of air that can be exhaled in the first second

• FEV1 accounts for 75% of VC

29. Tiffeneau Ratio:

• FEV1/VC .100%

30. Obstructive Ventilation Dysfunction:

• FEV1 < 75% or Tiffeneau ratio < 75%

31. Respiratory Indices:

• Total lung capacity: 5l

• IRV volume: 1500-2000 ml (accounts for 56% of VC)

• ERV volume: 1100-1500ml

• RV volume: 1000- 1200ml

32. Gas Transport by Blood:

• Blood transports O2 from the lungs to the tissues

• Blood transports CO2 from the tissues to the lungs

• Gas exchange in the lungs

33. Oxygen Transport in Blood:

• Dissolved form: Accounts for 3%

• Bound form: Bound to hemoglobin

34. Barcroft Curve:

• Represents the percentage of hemoglobin bound to oxygen compared to the total amount of hemoglobin in blood

• Dependent on partial pressure of O2

35. Lowest Partial Pressure of O2:

• In the tissues

36. Oxygen Binding Reaction in Tissues:

• Reversible, dissociates into Hb and O2

37. Factors Affecting Oxygen-Hemoglobin Dissociation:

• Partial pressure of O2

• Partial pressure of CO2

• Blood temperature

• 2,3-DPG concentration

38. Carbon Dioxide Transport in Blood:

• Dissolved form

• Bound to hemoglobin to form carbaminohemoglobin

• Bound to protein

• Bound to alkali salts

39. Haldane Effect:

• Increased partial pressure of O2 decreases CO2 transport

40. Hamburger Phenomenon:

• Exchange of Cl ions in plasma with HCO3 ions in red blood cells

41. Respiratory Center:

• Group of symmetrical neurons located on both sides of the medulla oblongata and pons

42. Respiratory Neuron Groups:

• Dorsal respiratory group: Causes inspiration, regulates respiratory rhythm

• Ventral respiratory group: Causes inspiration or expiration depending on the neuron

43. Respiratory Regulatory Center:

• Located in the dorsal and superior regions of the pons

• Regulates respiratory frequency and breathing patterns