Human reproduction involves spermatogenesis (seminiferous tubules; Sertoli cells support; Leydig cells secrete testosterone; 64 days; 4 sperm per spermatogonium) and oogenesis (starts fetal life; primary oocyte arrested prophase I at birth; 2 million primary oocytes at birth; secondary oocyte arrested metaphase II at ovulation; meiosis II only at fertilization; 1 ovum per cycle).
The menstrual cycle (28 days): FSH drives follicular growth (days 6–13); LH surge triggers ovulation (day 14); corpus luteum produces progesterone (days 15–28); no pregnancy → progesterone falls → menstruation.
Fertilization (in the ampulla): acrosomal reaction + cortical reaction (polyspermy block) + meiosis II completion → zygote. Cleavage → morula (16 cells) → blastocyst (trophoblast + ICM). Implantation day 6–7 post-fertilization. Trophoblast secretes hCG → corpus luteum maintained → pregnancy established. Pregnancy = 266 days. Parturition = oxytocin positive feedback loop. Lactation = prolactin (production) + oxytocin (ejection).
The three most critical NEET facts for REP-02:
- Primary oocyte → prophase I; secondary oocyte → metaphase II; meiosis II at fertilization only
- Fertilization = ampulla; implantation = endometrium
- LH surge (not FSH) = ovulation trigger