NDA Biology · Human Physiology
Excretion and Reproduction
The nephron filters blood at Bowman's capsule to make urine; the kidney also releases renin to control blood pressure; sperm form through meiosis from the primary spermatocyte.
Why this matters
3 PYQs — small but reliable. Two anchors: Bowman's capsule is the filtration site of the nephron, and the kidney's enzyme renin starts the blood-pressure cascade. One reproduction fact: the first meiotic division of spermatogenesis occurs in the primary spermatocyte.
Concept 1 of 2: The nephron — filtration and renin
Definition
The nephron's key parts and the renin role:
- Bowman's capsule (+ glomerulus) — the site of ultrafiltration; blood is filtered here.
- Tubule (PCT, loop of Henle, DCT) + collecting duct — reabsorb water, salts and useful molecules; the rest becomes urine.
- Renin — an enzyme secreted by the kidney that converts plasma angiotensinogen → angiotensin, raising blood pressure (the RAAS cascade).
Worked example
Practice this conceptself-check · 3 quick reps
The same idea in a real exam question:
Example 1 · Human Physiology · Excretory and Reproductive Anatomy
Bowman's capsule filters; it doesn't carry urine away
Concept 2 of 2: Spermatogenesis — where meiosis happens
Definition
The sequence and the meiosis checkpoint:
- Spermatogonium (diploid) — divides by mitosis.
- Primary spermatocyte — undergoes meiosis I (the FIRST meiotic division) → two secondary spermatocytes.
- Secondary spermatocyte — undergoes meiosis II → spermatids → mature sperm.
- Sertoli cells — nurse cells that nourish developing sperm (they do not divide into sperm).
Worked example
Practice this concept3 quick reps
The same idea in a real exam question:
Example 2 · Human Physiology · Excretory and Reproductive Anatomy
Summary — formulas & gotchas at a glance
A revision cheat-sheet for the formulas and gotchas above. Click any concept name to jump back to its full explanation.
Watch out for (1)
- Bowman's capsule filters; it doesn't carry urine away→ The nephron — filtration and renin
Test yourself on Human Physiology
15 past NDA questions from this chapter, timed at 15 minutes and marked the way the exam marks it. You see your score and every answer the moment you finish. Free to start.