All about respiratory system

1. Respiratory system - 2

2. Regulation of respiration
The DRG and
VRG are the
respiratory
rhythm centres
located in the
medulla

3. • Also there is a
chemosensitive area in
the medulla which can
detect CO2 levels and H+
ion levels. This centre
has control over the
respiratory rhythm
centres in the medulla

4. Respiratory membrane

5. Factors affecting transport of gases
• Pressure/concentration gradient of gases
• Solubility of gases
• Thickness of membranes
• Surface area of respiratory membrane

7. Partial pressures in mm of Hg of CO2 and O2 at different areas of circulation
Respiratory
gas
Atmospheric
air (inspired
air)
Expired air Alveolar air Blood
(deoxygenated)
Blood
(oxygenated)
Tissues
O2 159 116 104 40 95 40 (20-40)
CO2 0.3 32 40 45 40 45 (45-52)

8. Transport of oxygen in blood
In 2 ways:-
1. As dissolved form in Plasma (dissolved in the water) – 3%
2. Bound to Hb as Oxy-Hb – 97%

9. Transport of carbon dioxide in blood
In 3 ways:-
1. Bound to Hb as carbamino-Hb – 23% (Hb has more affinity to CO2 than O2)
2. Dissolved in plasma – 7% (CO2 is 20 times more soluble in water than O2)
3. As bicarbonate ions – 70%
Affinity of Hb with various gases
CO >>> CO2 >> O2
Affinity of Hb to CO2 is 20x more than the affinity to O2 (forms carboxy Hb)
Affinity of Hb to O2 is 200x more than the affinity to O2

10. • O-Hb forms at lungs and not
CO2-Hb as pO2 at lungs is very
high
• O2 is released by Hb (by
dissosciation) and it binds to
CO2 to form CO2-Hb at tissue
level as pO2 is less, pCO2 is
high and affinity of Hb is more
to CO2 than to O2

11. Transport of CO2 as HCO3
- ions

12. Carbonic anhydrase
• Very high conc in RBCs than in plasma
• Can catalyse the reaction of 36,000,000 CO2 molecules per minute
• As more HCO3
- forms more in RBCs than plasma, it will move out into the plasma where it will bind to Na+
ions to form NaHCO3 (KHCO3 forms in less amount)
• The forward and backward nature of the CA catalysed reaction depends on the pO2 levels at tissue and
alveoli
• As the HCO3
- ions move into plasma, the total CO2 transport in plasma is 77% and not 7%

13. Transport of CO2 as HCO3
- ions