Two nephrons are drawn. Nephron X has its corpuscle high in the cortex and a very short loop of…
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Two nephrons are drawn. Nephron X has its corpuscle high in the cortex and a very short loop of Henle. Nephron Y has its corpuscle deep in the cortex and a very long loop that runs far into the medulla.
- Name each kind of nephron.
- Which one has a well developed vasa recta?
- Which kind is more common in the human kidney?
- A student predicts that an animal with a very concentrated urine has more nephrons of type Y. Explain why this is a reasonable prediction.
Need a reminder? The key ideaShow
A nephron is a glomerulus and a renal tubule. The tubule runs from the Bowman's capsule through the proximal convoluted tubule, the loop of Henle (descending then ascending limb) and the distal convoluted tubule to the collecting duct. The corpuscle, the PCT and the DCT lie in the cortex, the loop in the medulla. The efferent arteriole forms the peritubular capillaries and the vasa recta. Cortical nephrons have short loops. Juxtamedullary nephrons have long loops.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. (a) X is a cortical nephron. Y is a juxtamedullary nephron.
Step 2. (b) Nephron Y. The vasa recta is absent or reduced in the cortical nephron.
Step 3. (c) The cortical nephron is the more common kind.
Step 4. (d) A long loop and its vasa recta reach deep into the medulla, where the interstitial fluid is the most concentrated. A tubule that runs there can lose much water to it. So more long loops allow a more concentrated urine.
Answer: (a) X cortical, Y juxtamedullary; (b) Y; (c) cortical; (d) long loops reach the saltiest region, so more water can be taken from the filtrate.
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