Question

1. A. Describe the negative feedback cascade of hormones in the male reproductive system that regulate spermatogenesis and testosterone levels once puberty has been reached.

B. Name three male secondary sexual characteristics influenced by testosterone.

C. Describe the steps of spermatogenesis plus the numbers of cells and chromosomes involved during each stage.

2. A. Name the segments of the menstrual cycle and, for each segment, list the female reproductive hormones that are being released and their sites of origin.

B. Describe the uterine responses during each phase of the menstrual cycle.

C. List the four extraembryonic membranes and one function for each.

Answer 1

1.

A. B. Secondary sexual characteristics:

• Enlargement of primary sexual organ (testes) and secondary sexual organs.

• Development of a low voice.

• Growth of hair in pubic regions, armpits and face.

C. SPERMATOGENESIS

The process of formation of sperms is called spermatogenesis.

It involves 3 phases-

• multiplication phase

• growth phase

•maturation phase.

1. Multiplication phase: Male germ cells/spermatogonia undergo mitotic divisions to form a large number of spermatogonia.

2. Growth phase: Spermatogonia increases their size by accumulation of nutrition in the cytoplasm and are ready for first meitoic division. Here, the spermatocytes are referred as primary spermatocytes (46 chromosomes).

3. Maturation phase: A primary spermatocyte completes the first meiotic division which leads to formation of two haploid cells called secondary spermatocytes (23 chromosomes each) These secondary spermatocytes undergo the second meiotic division to produce four haploid spermatids (23 chromosomes).

- Spermiogenesis:

The spermatids are transformed into spermatozoa (23 chromosomes).

Thereafter, sperm heads become embedded in the Sertoli cells and are released into the lumen from Seminiferous tubules. This process is called spermiation.

2.

A. Menstrual cycle and Hormones.

Menstruation: Low level of every hormones.

Follicular phase/ Proliferative phase: Estrogen released from theca interna. A slight rise in FSH and somewhat LHS is seen, secretd by pituitary gland.

Ovulation: LH surge is seen. FSH is also high. They are released from Pituitary gland.

Secretory phase/ Luteal phase: Progesterone and Estrogen are released from Corpus luteum.

B. Menstrual cycle and uterine wall.

Menstruation: Thickened uterine wall sheds off as menses due to low level of progesterone as Corpus luteum degenerates.

Follicular phase: Regeneration of normal thickness of uterine wall due to oestrogen released from theca interna.

Secretory phase: Uterine wall gets thickened due to progesterone released from Corpus luteum.

C. Extraembryonic layers.

1. Amnion: It encloses amniotic fluid which helps in the protection of embryo.

2. Chorion: It helps in the formation of placenta and thus is responsible for exchange of gases nutrients antibodies between mother and foetus.

3. Allantois: disposes of waste products and contributes to gas exchange.

4. Yolk sac: It encloses the yolk and helps in nutrient supply for early embryo.