Exam Frequency Analysis
Past paper frequency (2018 to 2024)
This topic accounts for approximately 12% of your exam marks.
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Stable12%
The kidney and urea production appear regularly; dialysis is a common application question.
The nephron is the functional unit of the kidney: every step of urine formation happens along its length. A single nephron has these parts, in order along the route the filtrate takes:
- Bowman's capsule: a cup-shaped structure in the cortex that surrounds the glomerulus, a tight knot of capillaries. The Bowman's capsule is where blood is filtered (ultrafiltration, section 6).
- Proximal convoluted tubule (PCT): a coiled tube also in the cortex. Selective reabsorption of glucose happens here.
- Loop of Henle: a long hairpin loop that dips deep down into the medulla and back up. Reabsorbs some water and salts.
- Distal convoluted tubule (DCT): a second coiled tube, back in the cortex. Fine-tunes the salt content of the filtrate.
- Collecting duct: runs back down through the medulla to the renal pelvis. The site of most water reabsorption, controlled by the hormone ADH (section 7).
Around each nephron runs a dense network of capillaries that picks up the substances reabsorbed from the filtrate and returns them to the bloodstream.
