Gas Diffusion at Alveoli and Tissues — NEET Biology
📚 Practice ConceptExchange of O₂ and CO₂ at the alveoli and tissues occur by diffusion. Rate of diffusion is dependent on the partial pressure gradients of O₂ (pO₂) and CO₂ (pCO₂), their solubility as well as the thickness of the diffusion surface. These factors in our body facilitate diffusion of O₂ from the alveoli to the deoxygenated blood as well as from the oxygenated blood to the tissues. The factors are favourable for the diffusion of CO₂ in the opposite direction, i.e., from tissues to alveoli.
Which of the above statements are correct? S1: The rate of diffusion of gases across the alveolar membrane is directly proportional to the partial pressure gradient and solubility of the gas. S2: In patients with alveolar fibrosis, the total thickness of the diffusion membrane significantly decreases, thereby facilitating more efficient oxygen uptake. S3: A higher partial pressure of CO₂ in the blood, as seen in active tissues, shifts the oxygen dissociation curve to the right, promoting oxygen release from oxyhaemoglobin. S4: Under normal physiological conditions, every 100 ml of deoxygenated blood delivers approximately 5 ml of O₂ to the tissues. S5: The diffusion membrane is composed of three major layers: the thin squamous epithelium of alveoli, the endothelium of alveolar capillaries, and the basement substance between them. S6: Increasing the partial pressure of inspired oxygen, such as through oxygen therapy, helps to compensate for reduced oxygen diffusion in conditions of increased diffusion membrane thickness.
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