The Structure of The Kidney and The Nephron
Laura Armstrong
Teacher
Contents
Recall Questions
This topic requires prior knowledge of the kidney from GCSE. You can test your knowledge below.
What is the main function of the kidney?
To filter blood and remove waste products such as urea.
What would your urine be like on a hot day where you have been producing a lot of sweat?
More concentrated, with smaller volumes produced.
Which organ transports urine from the kidneys to the bladder?
The ureters.
Topic Explainer Video
Check out this @LauraDoesBiology video that explains the structure of the kidney and the nephron or read the full notes below. Once you've gone through the whole note, try out the practice questions!
The Role of the Kidney
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The kidneys maintain homeostasis by:
- Removing waste products (e.g. urea).
- Regulating water potential and ion balance in the blood.
- Producing urine which is excreted via the bladder.
Structure of the Kidney
| Region | Description & Function |
| Cortex | Outer region of the kidney; contains the glomerulus + Bowman’s capsule, the proximal convoluted tubules and the distal convoluted tubules. |
| Medulla | Inner region; contains loops of Henle and collecting ducts. |
| Renal Pelvis | Central area that collects urine from collecting ducts and funnels it into ureter. |
| Ureter | Tube that carries urine from kidney to bladder. |
| Renal artery | Brings oxygenated blood to kidney for filtration. |
| Renal vein | Carries deoxygenated, filtered blood away from the kidney. |
Structure of the Nephron
The nephron is the functional unit of the kidney. Each kidney contains millions of nephrons.
Key Components & Their Roles:
| Nephron Part | Function |
| Bowman’s capsule | Collects filtrate from glomerulus during ultrafiltration. |
| Glomerulus | High-pressure capillary knot that forces small molecules out of blood. |
| Proximal convoluted tubule (PCT) | Site of selective reabsorption of glucose, amino acids, ions, and water. |
| Loop of Henle | Creates a water potential gradient in medulla for water reabsorption. |
| Distal convoluted tubule (DCT) | Involved in fine-tuning salt and water reabsorption. |
| Collecting duct | Site of ADH-regulated water reabsorption. Urine is concentrated here. |
Blood Flow Through the Nephron
- Blood enters via renal artery → afferent arteriole → glomerulus.
- Blood is filtered → filtrate enters Bowman’s capsule.
- Filtered blood leaves glomerulus via efferent arteriole → capillaries (which wrap around the nephron).
- Reabsorbed substances (e.g. glucose, water) re-enter blood in capillaries.
- Remaining filtrate is excreted as urine.
- Urine contains urea, excess water and excess mineral ions.
Key Terms
- Nephron: The functional unit of the kidney that filters blood and forms urine.
- Ultrafiltration: High-pressure filtration of blood in the glomerulus.
- Selective reabsorption: Reabsorption of useful molecules like glucose from the PCT.
- Loop of Henle: Creates a low water potential in the medulla to aid water reabsorption.
- ADH: Hormone that controls permeability of the collecting duct to water.
No answer provided.
Exam Tip
Make sure you can label the nephron and describe the role of each section. See further study notes for more detail on this!
No answer provided.
Label the nephron. (2 marks)
- Bowman’s capsule
- Proximal convoluted tubule
- Loop of Henle
- Distal convoluted tubule
- Collecting duct
All correct = 2 marks
3/4 correct = 1 mark
Practice Question 1
Try to answer the practice question from the TikTok on your own, then watch the video to see how well you did!
Practice Question 2
If you want to try out another one, check this video out and see how you do!