The bulk of the glomerular filtrate is reabsorbed in__________________?
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Answer: D. Proximal segment
Explanation
The vast majority of water and solutes are reabsorbed in the proximal convoluted tubule. Specialized transport proteins actively move sodium and glucose out of the tubular lumen constantly. Water follows these reabsorbed solutes passively to maintain overall osmotic and fluid balance equilibrium. The proximal segment features a brush border with microvilli providing massive surface area for absorption. Epithelial cells here contain numerous mitochondria supplying the ATP needed for active transport mechanisms. Approximately sixty to seventy percent of filtered glomerular filtrate is recovered in this region.
This massive reabsorption capacity protects the body from rapidly losing vital electrolytes and water. Clinical disorders affecting this tubule segment cause severe wasting of nutrients and systemic dehydration. Pharmaceutical agents targeting this region can alter systemic fluid balance and blood pressure effectively. The loop of Henle primarily concentrates urine rather than reabsorbing the bulk of the filtrate. The distal convoluted tubule handles fine-tuning of electrolyte balance rather than bulk fluid reabsorption. The collecting duct responds to hormonal signals for final water conservation rather than primary reabsorption.
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