Human Reproduction

NCERT Line-by-Line Breakdown for NEET 2026

Unit 1: Reproduction

Humans are sexually reproducing and viviparous. The reproductive events include Gametogenesis, Insemination, Fertilization, Implantation, Gestation, and Parturition.

1. Male Reproductive System

Located in the pelvis region. Includes a pair of testes, accessory ducts, glands, and external genitalia.

[Image of male reproductive system diagram]

A. Testes

Location: Outside abdominal cavity within Scrotum (Maintains temp 2-2.5°C lower than body temp for spermatogenesis).
Structure: Oval shape. Covered by dense covering. Contains ~250 compartments called Testicular Lobules.
Seminiferous Tubules: Each lobule has 1-3 tubules. Lined by:
- Male Germ Cells (Spermatogonia): Undergo meiosis to form sperm.
- Sertoli Cells: Provide nutrition to germ cells.
Interstitial Space: Outside tubules. Contains Leydig Cells (Synthesize Androgens/Testosterone).

B. Accessory Ducts & Glands

Path of Sperm: Rete Testis → Vasa Efferentia → Epididymis → Vas Deferens → Ejaculatory Duct → Urethra.

Glands: Seminal Vesicles (Paired), Prostate (Single), Bulbourethral (Paired). Secretions constitute Seminal Plasma (Rich in Fructose, Calcium, Enzymes).

2. Female Reproductive System

Located in the pelvic region. Includes ovaries, oviducts, uterus, cervix, vagina, and external genitalia.

[Image of female reproductive system diagram]

A. Ovaries (Primary Sex Organs)

Produce ovum and steroid hormones. Covered by epithelium enclosing ovarian stroma (Cortex + Medulla).

B. Accessory Ducts

Fallopian Tubes (Oviducts): 10-12 cm long. Parts: Infundibulum (funnel shape with Fimbriae), Ampulla (Wider part), Isthmus (Narrow).
Fertilization occurs in the Ampullary region.
Uterus (Womb): Inverted pear shape. Wall layers: Perimetrium (External), Myometrium (Muscular – contractions during delivery), Endometrium (Glandular – cyclic changes).

C. Mammary Glands

Functional mammary glands are characteristic of all female mammals. Glandular tissue divided into 15-20 Mammary Lobes containing Alveoli (secrete milk).

3. Gametogenesis

♂️ Spermatogenesis

Starts at puberty.

Spermatogonia (2n) → Mitosis → Primary Spermatocyte (2n).
Meiosis I → Secondary Spermatocytes (n).
Meiosis II → Spermatids (n).
Spermiogenesis → Spermatozoa (Sperm).

Spermiation: Release of sperm from Sertoli cells.

♀️ Oogenesis

Initiated during embryonic development ( fetal life).

Oogonia → Primary Oocyte (2n) arrested at Prophase I.
Puberty: Meiosis I completes (Unequal division) → Secondary Oocyte (n) + Polar Body.
Fertilization: Meiosis II completes → Ovum (n) + 2nd Polar Body.

4. Menstrual Cycle

Reproductive cycle in female primates. Average duration 28/29 days.

[Image of menstrual cycle phases hormone levels]

Phase	Days	Events
Menstrual	1-5	Breakdown of endometrium. Low levels of LH, FSH, Estrogen, Progesterone.
Follicular (Proliferative)	6-13	Primary follicle matures into Graafian follicle. Endometrium regenerates. Rise in FSH, LH, Estrogen.
Ovulatory	14	LH Surge induces rupture of Graafian follicle (Ovulation).
Luteal (Secretory)	15-28	Formation of Corpus Luteum. Secretes high Progesterone (maintains endometrium).

5. Fertilization, Pregnancy & Parturition

A. Fertilization

Sperm comes in contact with Zona Pellucida layer of ovum. Induces changes to block entry of additional sperms (Block to Polyspermy). Acrosome secretions help sperm enter cytoplasm.

B. Implantation

Zygote divides (Cleavage) → Morula (8-16 blastomeres) → Blastocyst. Blastocyst implants in Endometrium. Outer layer is Trophoblast; Inner group is Inner Cell Mass.

[Image of blastocyst implantation stages]

C. Parturition (Childbirth)

Induced by complex neuroendocrine mechanism. Signals originate from fully developed fetus and placenta (Fetal Ejection Reflex). Triggers release of Oxytocin from maternal pituitary → Strong uterine contractions.

📝 Rapid Fire MCQs

Q1. Sertoli cells are regulated by the pituitary hormone:

A) LH
B) FSH
C) GH
D) Prolactin

Click to check Answer

Answer: B) FSH (Follicle Stimulating Hormone).

Q2. The hormone releasing IUD is:

A) Lippes Loop
B) Multiload 375
C) LNG-20
D) Vaults