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2.9.5Structure & Functions in Living Organisms

Nephron Structure — Edexcel International GCSE Biology 4BI1 Revision Notes & Topical Questions

5 min read 3 parts Lesson 19 of 21 Unit quiz

📚 Edexcel International GCSE Biology 4BI1 Hub / Topical Revision
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Part 1 of 4Regions of the Kidney

2.9.5 Nephron Structure

A section through a kidney shows three main regions.

Regions of the Kidney
Cortex
  • The outer layer of the kidney, where the filtering units begin and where the glomeruli and convoluted tubules are found.
Medulla
  • The inner region containing the loops of Henle and collecting ducts, which appear as pyramid-shaped areas.
Renal pelvis
  • A funnel-shaped cavity that collects urine from the collecting ducts and passes it into the ureter.
Nephrons
  • Each kidney contains about a million of these tiny tubes, which are the functional units that filter blood and form urine.

Part 2 of 4Parts of the Nephron

Filtrate flows through the nephron in a fixed order.

1
The glomerulus is a knot of capillaries that receives blood from a wide vessel and leaves through a narrower one, raising the pressure.
2
The Bowman's capsule is a cup-shaped structure surrounding the glomerulus that collects the fluid filtered from the blood.
3
The proximal convoluted tubule (PCT) is the coiled first section, with cells containing many mitochondria and a surface folded into microvilli.
4
The loop of Henle dips down into the medulla and back up, and is where more water can be reabsorbed.
5
The distal convoluted tubule (DCT) is a second coiled section in the cortex that leads to the collecting duct.
6
The collecting duct passes through the medulla, where the final amount of water reabsorbed is controlled, and carries urine to the renal pelvis.

Part 3 of 4Location Summary

Cortex
  • Glomerulus, Bowman's capsule, proximal convoluted tubule and distal convoluted tubule lie in the cortex.
Medulla
  • Loops of Henle and collecting ducts run through the medulla towards the renal pelvis.
Blood vessels
  • Capillaries wrap around the tubules, so that reabsorbed substances can move back into the blood.
Pressure
  • The vessel leaving the glomerulus is narrower than the one entering it, which keeps the filtering pressure high.
PartRegion of kidney
Bowman's capsule and glomerulusCortex
Proximal convoluted tubuleCortex
Loop of HenleMedulla
Collecting ductMedulla

Part 4 of 4Exam Checklist & Tips

2.9.5 – Key Points for the Exam

  • Nephron The functional unit of the kidney that filters blood and forms urine.
  • Glomerulus A knot of capillaries inside the Bowman's capsule where filtration of blood takes place.
  • Bowman's capsule The cup-shaped start of the nephron that collects the filtrate.
  • Loop of Henle The hairpin-shaped part of the nephron that extends into the medulla.
  • Collecting duct The tube that receives urine from several nephrons and passes it to the renal pelvis.

Common Mistakes

  • Placing the loop of Henle in the cortex; it lies mainly in the medulla.
  • Calling the glomerulus a part of the tubule; it is a capillary network, not a tube.
  • Forgetting the correct ordercapsule, PCT, loop of Henle, DCT, collecting duct.
  • Confusing the renal pelvis, which collects urine, with the nephron, which makes it.

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