Chapter 3: Human Reproduction

Q1. What are the functions of the following: (i) Corpus luteum (ii) Fimbriae (iii) Acrosome

Solution

(i) Corpus luteum: Secretes progesterone to maintain endometrium for implantation
(ii) Fimbriae: Finger-like projections that catch the ovum from ovary
(iii) Acrosome: Contains enzymes to help sperm penetrate the ovum

Q2. Describe the menstrual cycle with its phases.

Solution

Phase 1 - Menstrual (1-5 days): Shedding of endometrium
Phase 2 - Follicular (6-13 days): FSH stimulates follicle growth, endometrium rebuilds
Phase 3 - Ovulatory (14th day): LH surge causes ovulation
Phase 4 - Luteal (15-28 days): Corpus luteum secretes progesterone

Q3. What is the role of HCG during pregnancy?

Solution

Human Chorionic Gonadotropin (HCG) is secreted by the placenta. It maintains the corpus luteum, which continues to secrete progesterone needed to maintain the endometrium during pregnancy.

Q4. What are the changes that occur in the uterus during the menstrual cycle?

Solution

Menstrual phase: Endometrium breaks down, bleeding occurs
Follicular phase: Endometrium regenerates, becomes thick and vascular
Luteal phase: Endometrium becomes highly vascular and glandular, ready for implantation

Q5. Name the hormones involved in parturition.

Solution

Oxytocin: Stimulates uterine contractions
Relaxin: Relaxes the cervix and ligaments
Prolactin: Stimulates milk production after birth

Q6. Describe the process of spermatogenesis.

Solution

Stages: (1) Spermatogonia (2n) undergo mitosis to produce primary spermatocytes (2n) (2) Primary spermatocytes undergo meiosis I to form secondary spermatocytes (n) (3) Secondary spermatocytes undergo meiosis II to form spermatids (n) (4) Spermatids differentiate into spermatozoa - spermiogenesis

Q7. What is oogenesis? How is it different from spermatogenesis?

Solution

Oogenesis: Begins in fetal life, produces one ovum from one oocyte, unequal cytokinesis, occurs in ovary
Spermatogenesis: Begins at puberty, produces four sperm from one spermatocyte, equal cytokinesis, occurs in testis

Q8. Describe the process of fertilization in humans.

Solution

Process: (1) Sperm travels through cervix and uterus (2) Capacitation occurs in female tract (3) Acrosome reaction releases enzymes to penetrate corona radiata and zona pellucida (4) Sperm fuses with ovum membrane (5) Cortical reaction prevents polyspermy (6) Fusion of pronuclei forms zygote

Q9. What is the structure of the placenta? What are its functions?

Solution

Functions: (1) Nutrient and oxygen supply to fetus (2) Removal of CO₂ and waste (3) Secretes HCG, progesterone, and estrogen (4) Acts as barrier to some pathogens (5) Provides passive immunity through IgG

Q10. What is colostrum? Why is it important for newborns?

Solution

Importance: (1) Rich in IgA antibodies for passive immunity (2) High in protein, low in fat (3) Contains growth factors (4) Protects newborn from infections (5) Acts as laxative to remove meconium

Q11. Describe the events during parturition.

Solution

Events: (1) Hormonal signals from fetus trigger uterine contractions (2) Oxytocin stimulates strong uterine contractions (positive feedback) (3) Cervix dilates (4) Baby is pushed out through birth canal (5) Placenta is expelled after delivery

Q12. What is the difference between a primary follicle and a Graafian follicle?

Solution

Primary follicle: Oocyte surrounded by single layer of cuboidal cells
Graafian follicle: Mature follicle with large antrum (fluid-filled cavity), ready for ovulation

Q13. What are the hormones secreted by the testes?

Solution

Testosterone (Leydig cells): Development of secondary sexual characters, spermatogenesis
Inhibin (Sertoli cells): Inhibits FSH secretion (negative feedback)
Androgen-binding protein (Sertoli cells): Maintains high testosterone in seminiferous tubules

Q14. What is the role of the corpus luteum in the menstrual cycle?

Solution

(1) Forms from ruptured Graafian follicle after ovulation
(2) Secretes progesterone to maintain endometrium
(3) If fertilization occurs, maintained by HCG
(4) If no fertilization, degenerates into corpus albicans
(5) Progesterone drop triggers menstruation

Q15. What is the difference between implantation and gastrulation?

Solution

Implantation: Embedding of blastocyst into uterine endometrium (about 7th day)
Gastrulation: Formation of three germ layers (ectoderm, mesoderm, endoderm) from blastula

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