🌟 In the cortex
The Bowman's capsule and glomerulus, the proximal convoluted tubule and the distal convoluted tubule are all in the cortex.
Excretion » Structure of a Nephron
What you'll learn this session
Study time: 30 minutes
Edexcel spec: 2.74
- The parts of a nephron, in order, from the Bowman's capsule to the collecting duct
- Which parts sit in the cortex and which dip into the medulla
- A one-line job for each part
- How to label a diagram of a nephron
Note: this lesson is Paper 2 only. It will not be asked on Paper 1.
🔒 Unlock Full Course Content
Sign up to access the complete lesson and track your progress!
Unlock This CourseWhat is a nephron?
In the lesson The Urinary System and Kidney Roles you saw that the kidney cleans the blood and makes urine. But how does one organ do all that? The answer is that each kidney is packed with about a million tiny tubes. Each tube is a working unit of the kidney.
Key terms:
- Nephron: one of the tiny tubes in the kidney that filters the blood and makes urine.
- Cortex: the outer layer of the kidney.
- Medulla: the inner part of the kidney, inside the cortex.
A nephron is a long, thin tube with a closed cup at one end. It twists and turns, and different sections of it have different jobs. Each section has its own name, and you need to know them in order.
The parts of a nephron, in order
Follow the liquid as it travels along the tube. There are five parts to learn.
- Bowman's capsule with its glomerulus
- Proximal convoluted tubule
- Loop of Henle
- Distal convoluted tubule
- Collecting duct
Key terms:
- Bowman's capsule: a cup-shaped structure at the start of the nephron.
- Glomerulus: a tangled ball of tiny blood vessels (capillaries) sitting inside the Bowman's capsule.
- Convoluted tubule: a tube that is tightly coiled and twisted. There are two in each nephron.
- Loop of Henle: a long, hairpin-shaped section of the tube.
- Collecting duct: a wider tube that several nephrons empty into.
A memory trick
Proximal means near and distal means far. The proximal tubule is the one nearer to the start of the nephron, and the distal tubule is the one further along.
Where each part sits
A kidney has two layers you can see if you cut it open. The outer layer is the cortex and the inner part is the medulla. The nephron is not all in one place. It crosses from one layer to the other and back again.
🔻 Dipping into the medulla
The loop of Henle goes down into the medulla and comes back up. The collecting duct runs down through the medulla too.
So the journey is: start in the cortex, dive into the medulla and return to the cortex, then finish by running down through the medulla.
A quick job for each part
You will learn each job in detail in the next two lessons, Ultrafiltration and Glucose Reabsorption, and Water Reabsorption, ADH and Urine. For now, here is a one-line preview so the names make sense.
🔄 Bowman's capsule and glomerulus
Where blood is filtered and liquid first enters the nephron.
🥣 Proximal convoluted tubule
Where useful substances are taken back into the blood.
💧 Loop of Henle
The hairpin that dips into the medulla. Its part in making urine comes in a later lesson.
⚖️ Distal convoluted tubule
Where the liquid is adjusted before it passes to the collecting duct.
📦 Collecting duct
Collects the liquid, now urine, from several nephrons and carries it towards the ureter.
Remember that the kidney sends urine out through the ureter, as you saw in The Urinary System and Kidney Roles. The collecting ducts are where that urine begins its journey out of the kidney.
Labelling a nephron
In the exam you may be given a drawing of a nephron and asked to name parts. Use these clues.
- A cup with a ball of capillaries inside is the Bowman's capsule and glomerulus.
- A tightly coiled tube is a convoluted tubule. The one joined to the cup is the proximal one. The one after the loop is the distal one.
- A hairpin bend is the loop of Henle.
- A straight, wide tube that the distal convoluted tubules of several nephrons drain into is the collecting duct.
Worked example
Question: Put these parts of a nephron in the order that liquid passes through them: distal convoluted tubule, Bowman's capsule, collecting duct, loop of Henle, proximal convoluted tubule.
Answer: Bowman's capsule, proximal convoluted tubule, loop of Henle, distal convoluted tubule, collecting duct.
Common mistakes
Mixing up proximal and distal. Remember that proximal is near the start and distal is far. Another slip is putting the whole nephron in the medulla. Only the loop of Henle and the collecting duct go into the medulla. Finally, do not call the glomerulus a tube. It is a ball of capillaries, so it carries blood.
Exam-style question
(a) Name the part of the nephron that contains the glomerulus. [1 mark]
(b) Name the two parts of the nephron that are shaped like a coiled tube. [2 marks]
(c) State which part of the nephron goes down into the medulla and back up again. [1 mark]
(d) Describe where the collecting duct sits in the kidney. [1 mark]
Model answer
(a) The Bowman's capsule. (1)
(b) The proximal convoluted tubule (1) and the distal convoluted tubule. (1)
(c) The loop of Henle. (1)
(d) It runs down through the medulla. (1)
Exam tip
When a question asks for a part of the nephron, write its full name, for example "proximal convoluted tubule", not just "tubule", so the examiner can see which one you mean.