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Human Reproduction
Biology · Class 12pp. 26–382 sets × 25 questionsFree
Key facts and formulas for Human Reproduction, three worked sample questions, and two full practice sets. Every question has a hint, a reason for every option and a step-by-step solution, with a calculator or animation where one helps. English and Hinglish.
Key facts for this chapter
| Idea | Rule or fact |
|---|
| Male gamete path | Seminiferous tubules → rete testis → vasa efferentia → epididymis → vas deferens → ejaculatory duct → urethra |
| Testis cells and glands | Leydig cells make androgens; Sertoli cells nourish germ cells and make inhibin; accessory glands: seminal vesicles (2), prostate (1), bulbourethral (2) |
| Scrotum | Testes lie 2–2.5 °C below body temperature; dartos and cremaster adjust position |
| Spermatogenesis counts | Spermatogonium 46 → primary spermatocyte 46 → secondary spermatocyte 23 → spermatid 23; 1 primary spermatocyte gives 4 sperms |
| Oogenesis | 1 primary oocyte gives 1 ovum plus polar bodies; ovulated cell is a secondary oocyte arrested at metaphase II; meiosis II finishes after sperm entry |
| Uterus and oviduct | Layers outside in: perimetrium, myometrium, endometrium; oviduct: infundibulum, ampulla (wider), isthmus (narrow) |
| Menstrual cycle | Menstrual days 1–5; LH surge near day 14 (estrogen positive feedback); luteal phase: corpus luteum secretes progesterone |
| Fertilisation to implantation | Fertilisation in ampulla; cleavage 1→2→4→8→16; blastocyst: trophoblast attaches to endometrium, inner cell mass forms embryo |
| Pregnancy hormones | hCG, hPL and relaxin occur only in pregnancy; hCG keeps the corpus luteum active; oxytocin drives positive feedback in labour |
| Placenta and cord | Cord has 2 arteries and 1 vein; maternal and foetal blood do not mix; first foetal movements in the fifth month |
Three sample questions
Q1. Consider these statements.
I. Humans are viviparous.
II. Sperm formation continues in old age, but ovum formation stops at about 50 years.
III. The events of reproduction begin at birth.
Which are correct?
- I and III only
- I and II only
- II and III only
- I, II and III
Hint and solution
Hint: Reproductive events need sexual maturity. Ask whether a newborn can already make gametes and reproduce.
- Humans: viviparous, give birth to young — Statement I is true. Human females give birth to young ones, so humans are viviparous.
- Sperms: till old age; ova: stop near 50 y — Statement II is true. Men keep forming sperms in old age, while women stop forming ova at about 50 years.
- Reproductive events begin at puberty — Statement III is false. Gametogenesis and the related hormones start only at puberty, not at birth.
- I and II are correct — So only statements I and II are correct. Option B.
Answer: B. Reproductive events begin only after puberty, so III is wrong.
Q2. Assertion (A): The testes of humans lie outside the abdominal cavity.
Reason (R): Spermatogenesis needs a temperature 2–2.5 °C lower than the normal internal body temperature.
- Both A and R are true but R is not the correct explanation of A
- A is true but R is false
- A is false but R is true
- Both A and R are true and R is the correct explanation of A
Hint and solution
Hint: Check each statement separately, then ask why the testes hang outside the body.
- Testes lie in the scrotum, outside abdomen — Assertion A is true. The testes are located in the scrotal sac, outside the abdominal cavity.
- Spermatogenesis needs 2–2.5 °C below body temp — Reason R is also true. Sperm formation works properly only at a temperature slightly lower than the body core.
- Cooler site is the reason for the outside position — The scrotum provides this lower temperature. So R is the cause behind A.
- Both true, R explains A — So both are true and R is the correct explanation. Option D.
Answer: D. The scrotum gives the cooler temperature that sperm formation needs. R explains A.
Q3. Which is the correct path of sperms from the testis to the urethra?
- Seminiferous tubules → rete testis → vasa efferentia → epididymis → vas deferens → ejaculatory duct
- Seminiferous tubules → vasa efferentia → rete testis → vas deferens → epididymis → ejaculatory duct
- Rete testis → seminiferous tubules → epididymis → vasa efferentia → vas deferens → ejaculatory duct
- Seminiferous tubules → epididymis → rete testis → vasa efferentia → ejaculatory duct → vas deferens
Hint and solution
Hint: Sperms are made in the tubules, collected in a network, then leave the testis through small ducts before reaching the long coiled tube.
- Seminiferous tubules → rete testis — Sperms are made in the seminiferous tubules, which open into a network called the rete testis.
- Rete testis → vasa efferentia → epididymis — Fine ducts called vasa efferentia leave the testis and open into the epididymis.
- Epididymis → vas deferens → ejaculatory duct — The epididymis leads to the vas deferens, which joins the seminal vesicle duct to form the ejaculatory duct.
- Match the order with the options — Only the first option has this exact order. Option A.
Answer: A. The tubules open into the rete testis, then vasa efferentia lead to the epididymis, then the vas deferens and the ejaculatory duct.
How to use this chapter
Read the NCERT pages first, then attempt Set 1 without the hints. Note every wrong answer in a mistake list, read the reason for each option, and retry Set 2 two days later. A topic is solid when you can say why each wrong option is wrong.