Physiology of respiration in human

The following steps are involved in mechanism of respiration:

1. Breathing
2. Exchanges of gases on the alveolar surface
3. Cellular or internal respiration

Breathing 

Inhale fresh air into lung and expel out air from lung, called breathing. 

it completed in two steps:

• Inspiration
• Expiration

Inspiration 

Inhalation of fresh air into lung. It is an active process.

Physiology of respiration in human Flow Chart

Expiration 

Air expelling out air from lungs. It is a passive process.

Physiology of respiration in Human Exhalation Flow Chart

Exchange of gases

• Exchange of gases at the level of lungs between the alveoli and capillaries.
• Exchange of gases at the level of tissue between the capillaries and various body cells.
• Exchange of gases occurs due to different partial pressure of gases.
• Release of carbon dioxide, which occurs at alveolar level.

Transport of oxygen

• Transport of oxygen by RBCs respiratory pigment, called Hemoglobin.
• Hemoglobin has 4 iron atoms; each iron atom attaches one oxygen atom.

1 gram of hemoglobin transports 1.34 ml oxygen.

Physiology of respiration in human reaction

In alveoli, the partial pressure of carbon dioxide (PCO2) is low as compared to partial pressure of in de-oxygenated blood. 

PCO2 in alveoli is ↓ and ↑ PCO2 in deoxygenated blood.

The CO2 present in carbonic acid and carbamino hemoglobin would split because of low PCO2 in alveolar air and dissociation of CO2 into the alveolar (from the capillary) would occur.

Transport of carbon dioxide (CO2)

CO2 is carried in blood in 3 major forms:-

• Carbonic acid: around 5-10% of the total of CO2 is transported in this form.
• Carbamino haemoglobin: around 10% of the total of CO2 is transported in this way.
• Hydrogencarbonate ions: around 85% of the total of CO2 is transported in the blood as this form.

Cellular or internal respiration

It is a very complex process. Internal respiration involves in various process by which food elements are oxidized in cells.