Trace a nephron and its associated blood vessels
Keep capillary blood and tubule contents in separate routes.
Exam scope and assessment notes
Extended only (Supplement) · Biology 0970, 2026–2028. Use the stated specimen features and evidence. Diagrams are schematic. Written practice is self-checked; human subject-teacher review, supervised practical competence and cumulative assessment remain pending. Cambridge states that IGCSE 0970 has the same subject content as IGCSE 0610, with 9–1 grading. This StudyForA pathway maps the 2026–2028 syllabus only. This 9–1 graded qualification is available only in a limited number of administrative zones. Confirm that your centre can enter you for this code and exam series with Cambridge International. Cambridge has published a separate syllabus for 2029. StudyForA has not reconciled that version yet; this page supports exams in 2026, 2027 and 2028 only.
Before you begin
- Recall cell metabolism, blood transport, amino acids and the distinction between excretion and egestion.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
What is a glomerulus in this outline?
What you will learn
- Locate filtration in the blood-tubule relationship
- Follow return to blood and urine outflow
Trace a nephron and its associated blood vessels
| Feature | Meaning |
|---|---|
| Blood route | Glomerulus then associated blood vessels |
| Filtration | Blood → nephron fluid |
| Reabsorption | Nephron contents → blood |
| Urine route | Processed tubule contents → collection |
Locate filtration in the blood-tubule relationship
A nephron is a kidney processing unit with a tubule associated with blood vessels. In the simplified diagram, an incoming blood vessel supplies the glomerulus, a capillary network at the start of the filtration region. Fluid filtered from blood enters the tubule route, while blood remains in its own vessel system.
The blood route continues from the glomerulus into vessels associated with the tubule and returns towards the circulation. Those vessels allow reabsorbed materials to return to blood. The tubule route carries filtered contents through processing and towards the urine collection route. An arrow crossing from tubule to blood therefore has a different meaning from blood flowing through a vessel.
Follow return to blood and urine outflow
The required outline concerns glomerular filtration of water, glucose, urea and ions; reabsorption of all glucose, some ions and most water; and urine containing urea and excess water and ions. Detailed pressures, individual transport mechanisms and every named tubule segment are beyond this stated requirement, so the model labels the key structures and routes without demanding an advanced mechanism.
Do not confuse a nephron tubule with the ureter between kidney and bladder, or the glomerulus with the whole kidney. The original figure enlarges microscopic routes schematically and is not a single-scale photograph. A learner should trace blood and tubule contents separately, locate their exchange relationships and avoid saying blood simply pours unchanged into urine.
Pause and explain
Where do reabsorbed substances return?
Worked example
In the original nephron model, which blood network performs the required initial filtration?
Show the worked solution
- Find the capillary network at the tubule start.
- It is the glomerulus.
Answer The glomerulus filters the specified small substances from blood into the tubule route.
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Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
Outline the distinct blood and tubule routes in the nephron model.
Give me a hint
Track each route through its own structures.
Compare my reasoning
- Blood passes through glomerular and associated vessel routes.
- Filtered fluid enters the tubule and later the urine collection route.
Blood remains in its vessel route; filtered fluid enters the nephron tubule, where processing and return of useful substances occur before urine collection.
Look for these in your work
- Separate both routes
- Locate filtration and return
Explain why a nephron tubule is not the ureter.
Give me a hint
Compare scale and endpoints.
Compare my reasoning
- The nephron tubule is a kidney processing structure.
- A ureter carries urine from the whole kidney to the bladder.
The nephron tubule is part of kidney processing; the ureter is the separate kidney-to-bladder urine tube.
Look for these in your work
- Separate structures
- Use their functions and endpoints
A model arrow points from tubule contents into an associated capillary. Is it urine flowing to the bladder?
Give me a hint
Read the arrow destination.
Compare my reasoning
- Its destination is blood.
- This models reabsorption, not urinary outflow.
No; the arrow shows reabsorption back into blood, whereas urine outflow follows the tubule collection route towards the ureter.
Look for these in your work
- Give the return direction
- Distinguish urine outflow
Common mistakes
- Calling the nephron tubule a ureter.
- Merging blood and tubule contents into one route.
What can you explain now?
Where do reabsorbed substances return?
Compare with the explanation
From the tubule contents to blood
Return direction is essential.
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Make it stick
Trace separate blood and tubule routes and identify the glomerulus.
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