Human reproduction is a fundamental chapter in Class 12 Biology and a crucial part of the NEET 2026 syllabus. Understanding it requires knowledge of anatomical structures, physiology, hormonal regulation, and developmental biology. This complete note is suitable for NEET aspirants as well as students pursuing higher secondary biology.

Human Reproduction – Complete NEET 2026 Notes

1. Male Reproductive System

The male reproductive system is specialized for sperm production and delivery.

Key Structures:

• Testes (2): Primary sex organs located in the scrotum. Each testis is covered by a tough capsule called tunica albuginea.
• Internal structure: Divided into 250–300 compartments called testicular lobules, each containing 1–3 seminiferous tubules.
• Seminiferous tubules: Site of spermatogenesis (sperm formation). Contains two types of cells:
• Spermatogenic cells: Developing sperm cells.
• Sertoli cells: Provide nutrition and hormonal support.
• Interstitial (Leydig) cells: Located between tubules. Secrete testosterone, responsible for male secondary sexual characters.

Accessory Ducts:

Rete testis → Vasa efferentia → Epididymis → Vas deferens

These ducts help in storage, maturation, and transport of sperm.

Accessory Glands:

• Seminal vesicles: Secrete fructose-rich fluid (70% of semen).
• Prostate gland: Secretes alkaline fluid to neutralize vaginal acidity.
• Bulbourethral glands: Secrete mucus for lubrication.

2. Female Reproductive System

Designed for ovum production, fertilization, implantation, and fetal development.

Key Structures:

• Ovaries (2): Almond-shaped primary sex organs producing ova and female hormones (estrogen & progesterone).
• Fallopian Tubes (oviducts): Extend from ovaries to uterus.
• Divided into: Infundibulum, Ampulla (site of fertilization), Isthmus, and Uterine part.
• Uterus: Hollow, muscular organ. Wall layers:
• Perimetrium (outer)
• Myometrium (middle muscular)
• Endometrium (inner lining) – prepares for implantation.
• Cervix: Lower narrow part of uterus.
• Vagina: Muscular canal, also called the birth canal.

3. Microscopic Anatomy of Testis and Ovary

Testis (under microscope):

• Seminiferous tubules: Sperm cells in different stages of development.
• Sertoli cells: Support spermatogenesis.
• Leydig cells: Produce testosterone.

Ovary:

• Contains ovarian follicles in different stages.
• Primary follicle → Secondary follicle → Graafian follicle (mature).
• At ovulation, Graafian follicle ruptures and releases the ovum.

4. Gametogenesis

Spermatogenesis:

• Process of sperm production inside seminiferous tubules.
• Begins at puberty and continues throughout life.

Stages:

• Spermatogonia (2n) → Mitosis → Primary spermatocytes (2n)
• Meiosis I → Secondary spermatocytes (n)
• Meiosis II → Spermatids (n)
• Spermiogenesis → Spermatids mature into spermatozoa

Oogenesis:

Begins during fetal life; primary oocytes remain arrested in meiosis-I until puberty.

Stages:

• Oogonia (2n) → Primary oocyte (arrested)
• Meiosis I (at puberty) → Secondary oocyte + Polar body
• Meiosis II (completed only after fertilization)

5. Menstrual Cycle

• A cyclic change in the reproductive tract, lasting ~28 days
• Regulated by FSH, LH, Estrogen, and Progesterone.

Phases:

• Menstrual Phase (1–5 days): Shedding of endometrium.
• Follicular Phase (6–14 days): Follicle grows, estrogen increases.
• Ovulation (~Day 14): LH surge leads to ovum release.
• Luteal Phase (15–28 days): Corpus luteum forms; progesterone prepares uterus.

6. Fertilization

• Occurs in the ampulla of the fallopian tube.
• Sperm binds to the zona pellucida of ovum → Acrosomal reaction → Sperm enters → Nucleus fusion → Zygote (2n) is formed.
• Sex of the baby is determined by sperm (X or Y chromosome).

7. Embryo Development up to Blastocyst

• Zygote → 2-cell → 4-cell → Morula → Blastocyst.

Blastocyst contains:

• Trophoblast (outer layer): Forms placenta.
• Inner cell mass: Forms embryo.

8. Implantation

• Blastocyst attaches to endometrium (~7 days after fertilization).
• Endometrium becomes decidua after implantation.

9. Pregnancy & Placenta Formation (Elementary Idea)

Pregnancy: Period of embryo development inside the uterus.

Placenta: 

• Temporary organ connecting mother and fetus.
• Transfers nutrients, gases, and removes wastes.
• Secretes hCG, hPL, estrogen, and progesterone.

10. Parturition (Elementary Idea)

• Process of childbirth.
• Triggered by uterine contractions, oxytocin, and prostaglandins.
• Positive feedback mechanism.

11. Lactation (Elementary Idea)

• Milk production stimulated by prolactin.
• Milk ejection controlled by oxytocin.
• First milk = Colostrum, rich in antibodies (IgA) – essential for immunity.

NEET Key Highlights:

Final Tip:

Revise this chapter along with diagrams, flowcharts, and hormone timelines. Practice previous year NEET MCQs, as many questions are directly based on NCERT lines.

Thank You Note

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