Gas Exchange: Alveoli and Diffusion — NEET Biology
📚 Practice ConceptAlveoli are the primary sites of exchange of gases. Exchange of gases also occur between blood and tissues. O₂ and CO₂ are exchanged in these sites by simple diffusion mainly based on pressure/concentration gradient. Solubility of the gases as well as the thickness of the membranes involved in diffusion are also some important factors that can affect the rate of diffusion.
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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