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Human Reproduction

NCERT Class 12 Biology Chapter 2

Human Reproduction for Class 12 Biology and NEET: reproductive systems, gametogenesis, menstrual cycle, fertilisation, pregnancy, parturition, lactation.

7 topics Updated 8 Nov 2026

For: Class 12 and NEET

In the syllabus: NEET Class 12 syllabus

With your textbook

NCERT Biology (Class 12), Chapter 2 “Human Reproduction”, reprint 2026-27.

Open the official NCERT chapter (PDF, 64.5 MB, ncert.nic.in)

Checked on 19 Oct 2026.

Learn in this order

  1. The male reproductive system

    Male reproductive system for Class 12 Biology and NEET: labelled diagram, testes, seminiferous tubules, Sertoli and Leydig cells, ducts and glands.

    NCERT Section 2.1 10 min read 3 solved examples 8 practice questions

  2. The female reproductive system

    Female reproductive system for Class 12 Biology and NEET: labelled diagram, ovaries, fallopian tube parts, layers of the uterus and the mammary glands.

    NCERT Section 2.2 10 min read 3 solved examples 7 practice questions

  3. Gametogenesis

    Gametogenesis for Class 12 Biology and NEET: spermatogenesis, spermiogenesis, hormones, sperm structure, oogenesis and follicles, with labelled diagrams.

    NCERT Section 2.3 15 min read 4 solved examples 9 practice questions

  4. Menstrual cycle

    Menstrual cycle for Class 12 Biology and NEET: menarche, menopause, the four phases with a hormone graph, the LH surge, the corpus luteum and hygiene.

    NCERT Section 2.4 11 min read 3 solved examples 6 practice questions

  5. Fertilisation and implantation

    Fertilisation and implantation for Class 12 Biology and NEET: how a sperm fertilises the ovum, the sex of the baby, morula and blastocyst, with diagrams.

    NCERT Section 2.5 13 min read 4 solved examples 8 practice questions

  6. Pregnancy and embryonic development

    Pregnancy and embryonic development for Class 12 Biology and NEET: placenta formation, hCG and other hormones, germ layers, monthly growth, with diagrams.

    NCERT Section 2.6 10 min read 3 solved examples 7 practice questions

  7. Parturition and lactation

    Parturition and lactation for Class 12 Biology and NEET: gestation period, foetal ejection reflex, oxytocin, colostrum and milk hormones, with a diagram.

    NCERT Section 2.7 8 min read 3 solved examples 6 practice questions

Key formulas in this chapter

The male reproductive system

  • testis: about 250 lobules, 1 to 3 seminiferous tubules each
  • scrotum: 2–2.5 °C below body temperature
  • Sertoli cells: nourish germ cells; Leydig cells: androgens
  • tubules → rete testis → vasa efferentia → epididymis
  • epididymis → vas deferens → ejaculatory duct → urethra
  • seminal plasma: fructose, calcium, enzymes
  • semen = seminal plasma + sperms

The female reproductive system

  • ovary: 2 to 4 cm; cortex outside, medulla inside
  • fallopian tube: 10–12 cm; fimbriae at the infundibulum; infundibulum → ampulla → isthmus → uterus
  • uterine wall: perimetrium, myometrium, endometrium
  • birth canal = cervical canal + vagina
  • milk: alveoli → branching ducts → nipple (NCERT additionally labels an ampulla)

Gametogenesis

  • primary spermatocyte (2n, 46) → 2 secondary spermatocytes (n, 23) → 4 spermatids (n, 23) → 4 sperms
  • primary oocyte (2n) → 1 ovum (n) + polar bodies
  • GnRH → LH → Leydig cells → androgens → spermatogenesis
  • GnRH → FSH → Sertoli cells → spermiogenesis
  • sperm: head (acrosome), neck, middle piece (mitochondria), tail
  • follicle stages: primary, secondary, tertiary (antrum), Graafian

Menstrual cycle

  • textbook model: 28/29-day cycle; ovulation near day 14, with real variation
  • menstrual phase: functional endometrium sheds; ovarian follicular phase has begun
  • follicular phase: Graafian follicle, estrogens, endometrium proliferates
  • LH surge → rupture of Graafian follicle → ovulation
  • luteal phase: corpus luteum → progesterone → endometrium maintained
  • no hCG rescue: corpus luteum regresses → hormones fall → menstruation

Fertilisation and implantation

  • fertilisation: in the ampulla; one sperm per ovum
  • ovum (n, X) + sperm (n, X or Y) → zygote (2n, XX or XY)
  • XX → female; XY → male
  • zygote → 2 → 4 → 8–16 (morula) → blastocyst
  • blastocyst: trophoblast + inner cell mass
  • trophoblast attaches to the endometrium; blastocyst embeds: implantation, then pregnancy

Pregnancy and embryonic development

  • chorionic villi + uterine tissue = placenta
  • placental hormones: hCG, hPL, estrogens, progestogens
  • relaxin: ovarian source in NCERT; not exclusive to late pregnancy
  • inner cell mass → epiblast/hypoblast; epiblast → three definitive germ layers
  • clinical trimesters: through 13w6d; 14–27w6d; 28 weeks onward

Parturition and lactation

  • gestation period: about 9 months
  • foetal ejection reflex → oxytocin release → stronger contractions → more oxytocin
  • parturition hormones (NCERT Summary): cortisol, estrogens, oxytocin
  • colostrum: first milk, rich in antibodies

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