By the end of this lesson
- Identify named nephron regions.
- Trace filtrate through a nephron.
- Relate each region to its main role.
BIG QUESTION
How can a microscopic tube turn filtered plasma into urine?
Successive nephron regions filter, reabsorb and fine-tune different parts of the fluid.
Filtration begins in the renal corpuscle
A knot of capillaries called the glomerulusA knot of capillaries inside the Bowman's capsule where blood is filtered under high pressure (ultrafiltration). lies inside Bowman's capsuleThe cup-shaped start of a nephron that surrounds the glomerulus and collects the filtrate.. Pressure forces water and small solutes across a filtration barrier into the capsule.
Blood cells and large plasma proteins normally remain in capillaries.
Convoluted tubules recover solutes
The proximal convoluted tubuleThe first coiled part of a nephron, where all the glucose and much of the water and salts are reabsorbed into the blood (selective reabsorption). has a large epithelial surface and many mitochondria for selective reabsorption, including glucose.
The distal convoluted tubuleThe coiled part of a nephron after the loop of Henle, where the reabsorption of ions and water is adjusted. contributes to regulated ion and water handling before fluid enters a collecting duct.
The loop and collecting duct shape concentration
The loop of HenleThe U-shaped part of a nephron that passes into the medulla and sets up a gradient that helps the kidney conserve water and make concentrated urine. passes into the medulla and helps establish a gradient that enables water conservation.
The collecting ductA tube that receives fluid from several nephrons, where the amount of water reabsorbed into the blood is controlled by ADH. receives fluid from several nephrons. Its water permeability varies with ADH, changing final urine concentration.
Blood vessels follow the tubule
An efferent arteriole leaves the glomerulus and forms capillaries around tubules, providing a short route for reabsorbed substances to return to blood.
Nephron structure therefore coordinates filtration and reabsorption.
Nephron regions and roles
Trace filtrate in sequence.
| Region | Position in route | Main role |
|---|---|---|
| Bowman’s capsule + glomerulus | Start. | Ultrafiltration. |
| Proximal convoluted tubule | After capsule. | Most selective reabsorption, including glucose. |
| Loop of Henle | Between convoluted regions. | Builds medullary concentration gradient. |
| Distal convoluted tubule | Before collecting duct. | Further regulated ion/water handling. |
| Collecting duct | Final shared tube. | ADH-regulated water reabsorption. |
Language that earns precision
- nephron
- Microscopic functional unit of a kidney.
- glomerulus
- Capillary knot where ultrafiltration occurs.
- Bowman’s capsule
- Cup-shaped nephron region receiving glomerular filtrate.
- collecting duct
- Tube receiving filtrate from nephrons and adjusting water reabsorption.
Common misconceptions
Claim: The glomerulus is a kidney tubule.
Correction: It is a capillary network inside Bowman’s capsule.
Claim: Each collecting duct belongs to only one nephron.
Correction: A collecting duct receives fluid from several nephrons.
Claim: Urine flows through renal blood vessels.
Correction: Filtrate follows nephron tubules; blood remains in vessels.
Match the answer to the command word
Include all five named structures and follow the filtrate route.
Separate glomerular filtration from tubular reabsorption.
Recall, apply, then justify
Describe the route of filtrate through a nephron.
Hint
Start at the capsule and keep the tubules in order.
Suggested marking points
- Bowman’s capsule.
- Proximal convoluted tubule.
- Loop of Henle.
- Distal convoluted tubule.
- Collecting duct.
Explain why capillaries closely surround nephron tubules.
Hint
Short path and maintained gradients.
Suggested marking points
- Reabsorbed substances have a short diffusion/transport distance to blood.
- Blood flow carries recovered substances away.
- This helps maintain gradients and restore water/solutes to circulation.
Explain how nephron structure permits both bulk filtration and precise regulation.
Planning hint
Different regions specialise.
What a strong design includes
- Glomerular pressure produces rapid bulk filtration of small substances.
- The filtration barrier retains cells and large proteins.
- A long tubule provides large area for reabsorption.
- Different segments express different transport proteins/permeabilities.
- The loop establishes a medullary gradient.
- The collecting duct responds to ADH, allowing variable final water recovery.