physiology of respiration is divide into two phases.
External respiration: The exchange of gases(CO2 & O2) between the alveoli of the lungs and blood in pulmonary is referred to external respiration.
- The deoxygenated blood is pumped from the right ventricle to the pulmonary artery, which circulated the deoxygenated blood in to the capillaries surrounding the alveoli. At the same time the inspired atmospheric the alveoli.
- at the particular situation the
The partial pressure of O2 in alveolar air is=105mm Hg and partial pressure of O2 in capillary blood is =40mm Hg
- Due to this difference in the partial pressure of oxygen, diffuses out from the alveolar air into the capillary blood. At the same there is a net diffusion of CO2 from the capillary blood to the alveoli.
The factors affecting the partial pressure are:
- partial pressure difference between the atmospheric gases.
- Thickness of the respiration membrane.
- Surface area of the respiratory membrane.
- solubility and molecular weight of the gases.
Thus is the exchanges of gases by diffusion between the blood in the capillaries and the body cells.
- The oxygenated blood is collected from the pulmonary capillaries through the pulmonary veins and is brought to the heart and through which it is circulated to the entire body.
- At this situation the partial pressure of O2 in the blood is 100 mmHg and the partial pressure of O2 in the tissues is only 40 mm Hg this difference in the partial pressure of oxygen leads to the diffusion of oxygen from the blood to the tissues cells.
- Conversely the partial pressure of CO2 in the tissues cells is 45 mm Hg, whereas the partial pressure of CO2 in the capillary blood is about 40mm Hg and therefore the CO2 diffuses from tissues capillaries to blood. This deoxygenated blood is then carried back to the heart where it is pumped into the lungs for oxygenation.