Exercises :
1. Fill in the blanks
(a) Humans reproduce sexually
(b) Humans are viviparous
(c) Fertilisation is internal in humans
(d) Male and female gametes are haploid
(e) Zygote is diploid
(f) The process of release of ovum is called ovulation
(g) Ovulation is induced by hormone LH (Luteinizing Hormone)
(h) Fusion of male and female gametes is called fertilisation
(i) Fertilisation takes place in fallopian tube
(j) Zygote divides to form embryo
(k) Structure is called placenta
2. Draw a labelled diagram of male reproductive system.
Answer:
A labelled diagram should include: testis, scrotum, vas deferens, urethra, penis, seminal vesicle, prostate gland.
3. Draw a labelled diagram of female reproductive system.
Answer:
A labelled diagram should include: ovary, fallopian tube, uterus, cervix, vagina.
4. Write two major functions each of testis and ovary.
Answer:
Testis:
Produces sperms
Secretes testosterone
Ovary:
Produces ova (eggs)
Secretes estrogen and progesterone
5. Describe the structure of a seminiferous tubule.
Answer:
Seminiferous tubules are highly coiled structures present in testis. They contain germ cells that produce sperms and Sertoli cells that provide nourishment.
6. What is spermatogenesis? Briefly describe the process.
Answer: Spermatogenesis is the process by which male gametes (sperms) are formed from germ cells in the testes.
Where does it occur?
It takes place in the seminiferous tubules of the testes.
Process of spermatogenesis (brief):
Multiplication phase:
Germ cells called spermatogonia (2n) divide by mitosis to produce more spermatogonia.
Growth phase:
Some spermatogonia grow in size and become primary spermatocytes (2n).
Maturation phase:
Primary spermatocytes undergo meiosis I to form two secondary spermatocytes (n).
Each secondary spermatocyte undergoes meiosis II to produce four spermatids (n).
Transformation (Spermiogenesis):
Spermatids differentiate into spermatozoa (mature sperms) with a head, middle piece, and tail.
Result:
One primary spermatocyte produces four haploid sperms.
7. Name the hormones involved in regulation of spermatogenesis.
Answer:
FSH, LH and testosterone.
8. Define spermiogenesis and spermiation.
Answer:
Spermiogenesis: Transformation of spermatids into sperms.
Spermiation: Release of sperms from Sertoli cells.
9. Draw a labelled diagram of sperm.
Answer:
Diagram should include: head, acrosome, nucleus, middle piece, tail.
10. What are the major components of seminal plasma?
Answer:
Fructose, calcium, enzymes and mucus.
11. What are the major functions of male accessory ducts and glands?
Answer:
They help in transport of sperms and provide nutrition and fluid to form semen.
12. What is oogenesis? Give a brief account.
Answer: Oogenesis is the process by which female gametes (ova/eggs) are formed in the ovaries.
Where does it occur?
It takes place in the ovaries.
Process of oogenesis (brief):
Multiplication phase:
Germ cells called oogonia (2n) multiply by mitosis during fetal life.
Growth phase:
Oogonia grow and become primary oocytes (2n).
These remain arrested in prophase I for a long time (until puberty).
Maturation phase:
At puberty, during each menstrual cycle:
A primary oocyte completes meiosis I to form:
One secondary oocyte (n)
One first polar body (n)
The secondary oocyte begins meiosis II but stops at metaphase II.
It completes meiosis II only if fertilization occurs, forming:
One ovum (n)
One second polar body (n)
Result:
From one primary oocyte, only one functional ovum is formed (others become polar bodies).
13. Draw a labelled diagram of a section through ovary.
Answer:
Diagram should show: follicles, oocyte, stroma, corpus luteum.
14. Draw a labelled diagram of a Graafian follicle.
Answer:
Diagram should show: antrum, oocyte, granulosa cells, theca layers.
15. Name the functions of the following:
(a) Corpus luteum
Answer: Secretes progesterone.
(b) Endometrium
Answer: Supports implantation of embryo.
(c) Acrosome
Answer: Helps sperm to penetrate ovum.
(d) Sperm tail
Answer: Helps in movement of sperm.
(e) Fimbriae
Answer: Collects ovum after ovulation.
16. Identify True/False statements. Correct each false statement.
(a) Androgens are produced by Sertoli cells.
Answer: False (Produced by Leydig cells)
(b) Spermatozoa get nutrition from Sertoli cells.
Answer: True
(c) Leydig cells are found in ovary.
Answer: False (Found in testis)
(d) Leydig cells synthesise androgens.
Answer: True
(e) Oogenesis takes place in corpus luteum.
Answer: False (Takes place in ovary)
(f) Menstrual cycle ceases during pregnancy.
Answer: True
(g) Presence or absence of hymen is not a reliable indicator of virginity.
Answer: True
17. What is menstrual cycle? Which hormones regulate it?
Answer:
Menstrual cycle is a monthly cycle in females involving changes in ovary and uterus. It is regulated by FSH, LH, estrogen and progesterone.
18. What is parturition? Which hormones are involved?
Answer:
Parturition is the process of childbirth. It is controlled by oxytocin and relaxin hormones.
19. In our society women are often blamed for giving birth to daughters. Explain why this is incorrect.
Answer:
The sex of a child is determined by the sperm of the male (X or Y chromosome). Therefore, women are not responsible.
20. How many eggs are released by a human ovary in a month? What about twins?
Answer:
Normally one egg is released per month.
Identical twins: one egg
Fraternal twins: two eggs
21. How many eggs were released by a female dog that gave birth to 6 puppies?
Answer:
Six eggs were released.
