Ultrafiltration in the glomerulus is driven by
Correct answer: B. the high hydrostatic pressure caused by the efferent arteriole being narrower than the afferent
- A. active transport using ATP from the capsule cells
- B. the high hydrostatic pressure caused by the efferent arteriole being narrower than the afferent
- C. osmosis from the tubule into the capillary
- D. the beating of cilia in the capsule
Explanation
Blood enters the glomerulus through a wide afferent arteriole and leaves through a narrower efferent one, so pressure builds up and forces water and small solutes through the capillary pores and the basement membrane into the capsule. The process is purely physical and uses no ATP, which is why it is called filtration rather than transport. Roughly 125 cm3 of filtrate is formed every minute.
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The kidney and urinary system remove nitrogenous wastes, regulate water and ion balance, and help maintain blood pH through filtration, selective reabsorption and secretion. Questions cover nephron structure, ultrafiltration, the loop of Henle, collecting ducts, urine formation and the roles of ADH and aldosterone, while distinguishing excretion from egestion.
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