Pocket Notes — Human Reproduction
Male anatomy quick facts
- Testes in scrotum, ~2–2.5°C cooler than body.
- Sertoli cells: nurse germ cells (FSH target).
- Leydig cells: secrete testosterone (LH target).
- Duct route: rete testis → vasa efferentia → epididymis → vas deferens → ejaculatory duct → urethra.
Female anatomy quick facts
- Ovary: 1–2 lakh primary follicles at birth.
- Oviduct parts (ovary → uterus): infundibulum → ampulla → isthmus.
- Uterus wall: perimetrium · myometrium · endometrium.
- Fertilisation site: ampullary-isthmic junction.
Hormones cheat sheet
| Hormone | Source | Function |
|---|
| GnRH | Hypothalamus | Stimulates pituitary → FSH & LH |
| FSH | Ant. pituitary | Sperm production; follicle growth |
| LH | Ant. pituitary | Testosterone (Leydig); ovulation surge |
| Testosterone | Leydig cells | Male 2° characters, spermatogenesis |
| Oestrogen | Ovarian follicle | Endometrium proliferation, female 2° characters |
| Progesterone | Corpus luteum | Endometrium secretory, maintains pregnancy |
| hCG | Trophoblast | Maintains corpus luteum; pregnancy test |
| hPL | Placenta | Metabolic changes in mother |
| Relaxin | Placenta (late) | Relaxes pelvic ligaments for parturition |
| Oxytocin | Post. pituitary | Uterine contractions; milk ejection |
| Prolactin | Ant. pituitary | Milk production |
Gametogenesis numbers
| Process | Precursor | Product |
|---|
| Spermatogenesis | 1 primary spermatocyte (2n) | 4 sperms (n) |
| Oogenesis | 1 primary oocyte (2n) | 1 ovum + 3 polar bodies |
- Oogenesis starts in foetal life, pauses at prophase I of meiosis I.
- Secondary oocyte pauses at metaphase II; completes meiosis only after fertilisation.
Sperm structure
Head (nucleus + acrosome) · neck · middle piece (mitochondria = energy) · tail (flagellum).
Semen benchmarks (WHO / NCERT)
- ~200–300 million sperms per ejaculation.
- ≥60% normal morphology, ≥40% motile for normal fertility.
Menstrual cycle (28-day)
| Days | Phase | Key event |
|---|
| 1–5 | Menstrual | Endometrium shedding |
| 6–13 | Follicular / Proliferative | FSH ↑, follicles grow, oestrogen ↑ |
| ~14 | Ovulation | LH surge → Graafian follicle ruptures |
| 15–28 | Luteal / Secretory | Corpus luteum → progesterone ↑ |
- Menarche = first period. Menopause ~45–50 yr.
From fertilisation to implantation
- Fertilisation: ampullary-isthmic junction.
- Acrosomal enzymes dissolve zona pellucida.
- Zygote (2n) → cleavage → morula (8/16 cells) → blastocyst (trophoblast + inner cell mass).
- Implantation ~day 7 of blastocyst life; ~day 21 of cycle.
Placenta functions (mnemonic: NREST)
Nutrition · Respiratory gas exchange · Excretion · Secretion of hormones (hCG, hPL, oestrogen, progesterone, relaxin) · Transport barrier.
Development milestones
- Month 1 — heart beats.
- Month 3 — limbs & digits.
- Month 4 — sex identifiable via ultrasound.
- Month 5 — hair on head.
- Month 6 — mostly developed.
- ~280 days from LMP → parturition.
Parturition & lactation
- Foetal ejection reflex → oxytocin → contractions → positive feedback → birth.
- Colostrum = first milk, rich in IgA antibodies.
- Prolactin → milk synthesis · oxytocin → milk ejection.
FAQ
- Why is scrotum outside body? — Testes need cooler temp for spermatogenesis.
- Why is oogenesis discontinuous? — Meiosis pauses at prophase I (foetal life) and metaphase II (until fertilisation).
- Which cell fertilises? — Secondary oocyte (not mature ovum yet).
- What triggers ovulation? — LH surge around day 14.
Pocket Notes — Human Reproduction
Male anatomy quick facts
- Testes in scrotum, ~2–2.5°C cooler than body.
- Sertoli cells: nurse germ cells (FSH target).
- Leydig cells: secrete testosterone (LH target).
- Duct route: rete testis → vasa efferentia → epididymis → vas deferens → ejaculatory duct → urethra.
Female anatomy quick facts
- Ovary: 1–2 lakh primary follicles at birth.
- Oviduct parts (ovary → uterus): infundibulum → ampulla → isthmus.
- Uterus wall: perimetrium · myometrium · endometrium.
- Fertilisation site: ampullary-isthmic junction.
Hormones cheat sheet
| Hormone | Source | Function |
|---|
| GnRH | Hypothalamus | Stimulates pituitary → FSH & LH |
| FSH | Ant. pituitary | Sperm production; follicle growth |
| LH | Ant. pituitary | Testosterone (Leydig); ovulation surge |
| Testosterone | Leydig cells | Male 2° characters, spermatogenesis |
| Oestrogen | Ovarian follicle | Endometrium proliferation, female 2° characters |
| Progesterone | Corpus luteum | Endometrium secretory, maintains pregnancy |
| hCG | Trophoblast | Maintains corpus luteum; pregnancy test |
| hPL | Placenta | Metabolic changes in mother |
| Relaxin | Placenta (late) | Relaxes pelvic ligaments for parturition |
| Oxytocin | Post. pituitary | Uterine contractions; milk ejection |
| Prolactin | Ant. pituitary | Milk production |
Gametogenesis numbers
| Process | Precursor | Product |
|---|
| Spermatogenesis | 1 primary spermatocyte (2n) | 4 sperms (n) |
| Oogenesis | 1 primary oocyte (2n) | 1 ovum + 3 polar bodies |
- Oogenesis starts in foetal life, pauses at prophase I of meiosis I.
- Secondary oocyte pauses at metaphase II; completes meiosis only after fertilisation.
Sperm structure
Head (nucleus + acrosome) · neck · middle piece (mitochondria = energy) · tail (flagellum).
Semen benchmarks (WHO / NCERT)
- ~200–300 million sperms per ejaculation.
- ≥60% normal morphology, ≥40% motile for normal fertility.
Menstrual cycle (28-day)
| Days | Phase | Key event |
|---|
| 1–5 | Menstrual | Endometrium shedding |
| 6–13 | Follicular / Proliferative | FSH ↑, follicles grow, oestrogen ↑ |
| ~14 | Ovulation | LH surge → Graafian follicle ruptures |
| 15–28 | Luteal / Secretory | Corpus luteum → progesterone ↑ |
- Menarche = first period. Menopause ~45–50 yr.
From fertilisation to implantation
- Fertilisation: ampullary-isthmic junction.
- Acrosomal enzymes dissolve zona pellucida.
- Zygote (2n) → cleavage → morula (8/16 cells) → blastocyst (trophoblast + inner cell mass).
- Implantation ~day 7 of blastocyst life; ~day 21 of cycle.
Placenta functions (mnemonic: NREST)
Nutrition · Respiratory gas exchange · Excretion · Secretion of hormones (hCG, hPL, oestrogen, progesterone, relaxin) · Transport barrier.
Development milestones
- Month 1 — heart beats.
- Month 3 — limbs & digits.
- Month 4 — sex identifiable via ultrasound.
- Month 5 — hair on head.
- Month 6 — mostly developed.
- ~280 days from LMP → parturition.
Parturition & lactation
- Foetal ejection reflex → oxytocin → contractions → positive feedback → birth.
- Colostrum = first milk, rich in IgA antibodies.
- Prolactin → milk synthesis · oxytocin → milk ejection.
FAQ
- Why is scrotum outside body? — Testes need cooler temp for spermatogenesis.
- Why is oogenesis discontinuous? — Meiosis pauses at prophase I (foetal life) and metaphase II (until fertilisation).
- Which cell fertilises? — Secondary oocyte (not mature ovum yet).
- What triggers ovulation? — LH surge around day 14.