CBSE Class 12 Biology – Human Reproduction

NCERT-aligned chapter resource | Biology Code 044

1. Male Reproductive System

The male system includes testes, accessory ducts, glands and external genitalia. Seminiferous tubules in the testes are the site of spermatogenesis. Sertoli cells support developing germ cells, while Leydig cells produce androgens.

2. Female Reproductive System

The female system includes ovaries, oviducts, uterus, cervix, vagina and external genitalia. The ovaries produce ova and ovarian hormones. The oviduct provides the usual site for fertilisation.

3. Spermatogenesis

Spermatogenesis begins at puberty. Spermatogonia undergo mitosis and differentiation; primary spermatocytes undergo meiosis I and secondary spermatocytes undergo meiosis II, producing haploid spermatids. Spermiogenesis converts spermatids into spermatozoa, followed by their release through spermiation.

4. Oogenesis

Oogenesis begins during embryonic development. Primary oocytes remain arrested until puberty. During each ovarian cycle, usually one secondary oocyte is released at ovulation. Completion of meiosis II occurs only after fertilisation.

5. Menstrual Cycle

Around the middle of a typical cycle, the LH surge triggers ovulation. After ovulation, the corpus luteum secretes progesterone and helps maintain the endometrium.

6. Fertilisation and Implantation

Fertilisation normally occurs in the ampullary region of the oviduct. Fusion of sperm and ovum forms the zygote. Cleavage produces the morula and then blastocyst, which implants in the uterine endometrium.

7. Pregnancy and Parturition

The placenta forms an important exchange interface between mother and foetus and also functions as an endocrine tissue. Near parturition, hormonal signals involving oxytocin and prostaglandins contribute to uterine contractions.

8. Lactation

After childbirth, prolactin supports milk production and oxytocin promotes milk ejection. Colostrum is rich in antibodies and provides important early immune protection.

Diagram Practice

• Male reproductive system
• Female reproductive system
• Spermatogenesis
• Oogenesis
• Menstrual cycle
• Blastocyst implantation

Chapter-Specific MCQs

1. Which cells produce androgens in the testes? (A) Sertoli cells (B) Leydig cells (C) Spermatids (D) Oogonia. Answer: B.
2. Ovulation is triggered by a surge of: (A) FSH only (B) LH (C) progesterone only (D) prolactin. Answer: B.
3. Implantation occurs when the blastocyst attaches to the: (A) ovary (B) endometrium (C) cervix (D) oviduct wall. Answer: B.

Competency Questions

1. Why is completion of meiosis II in the secondary oocyte linked to fertilisation?
2. Explain how hormonal changes coordinate the menstrual cycle.
3. Why is the placenta considered both an exchange organ and an endocrine tissue?