Question

discuss the gas exchange mechanism in the body

Answer 1

Respiration is an active process in humans in which O₂ is taken in and CO₂ is given out. This is an active process as it needs energy. Lungs are most important structure play important role in the respiration.

Respiratory tract is formed by :

• nose,
• pharynx,
• larynx,
• trachea,
• bronchi and
• alveoli in lungs.

The respiration is regulated by neural and chemical mechanism. In human brain respiratory centre’s are bilaterally situated in reticular formation of the brainstem. These are

1. Medullary centres : Medullary centres are diffusely situated in nucleus tractus solitarius which is present in medulla oblongata collectively known as inspiratory centers
2. Pontine centres:Pontine centers located in the brain and present in pons.

During respiration, O₂ and CO₂ exchange takes place between the alveoli and the blood capillaries. Exchange of gases in lung is mainly depends on Partial pressure of both O₂ and CO₂. The air taken in and out depends on method of expiration or inspiration, depth of respiration, partial pressure of gases in atmosphere. Diffusion capacity is the factor determines the gas exchange in lungs tissues. It is denoted as volume of gas that diffuses the respiratory membrane each minute for a pressure gradient of 1mm Hg. Diffusion of oxygen from the atmospheric air into the alveoli when the partial pressure is 159mmHg and in the alveoli is 104mmHg. When the blood is flowing through capillaries near lung alveoli , RBC is exchanges O₂ from the alveoli and when the O₂ partial pressure reaches 40mm Hg, in the alveoli ,partial pressure of O₂ is 104mm Hg. This gradient difference cause diffusion of oxygen into blood.

In blood, hemoglobin carrys the oxygen to the tissues. It is dependent on the O₂ - CO₂ dissociation curve. Diffusion of CO₂ from blood into alveoli when the partial pressure is 40 mm Hg in alveoli where in the blood it is 46mm Hg. After it enters into lung alveoli carbon dioxide expelled out from blood capillaries into the alveoli when it’s pressure reaches 40mm Hg. In blood oxygen transported in the form oxyhemoglobin and CO₂ in the form of carbaminohemoglobin .