S3.2 Gametogenesis

Question 1

What is spermatogenesis?

Answer 1

Primary spermatocytes divide by meiosis, giving rise to 2 secondary spermatocytes and then to 4 haploid spermatids which differentiate (spermiogenesis) into spermatozoa.

Question 2

What is spermiogenesis?

Answer 2

Differentiation of spermatids into spermatozoa.

Question 3

Describe sperm capactiation

Answer 3

Conditions in female genital tract stimulate:
Removal of glycoproteins and cholesterol from sperm membrane.
Tail movement changes from beat to whip-like action.
Allow sperm to bind to zona pellucida of oocyte and initiate acrosome reaction.

Question 4

Describe oogenesis

Answer 4

Oogonia becomes a primary oocyte, then a secondary oocyte + first polar body, then the ovum + 3 secondary polar bodies

Question 5

From puberty onwards ~15-20 oocytes start to mature each month passing through what 3 stages?

Answer 5

Preantral – surrounding follicular cells become granulosa cells
Antral – fluid filled spaces appear between granulosa cells forming the antrum
Preovulatory - LH surge induces meiosis 1 forming 2 haploid daughter cells. Cells then enter Meiosis 2 and arrest, meiosis 2 completed if fertilisation occurs.

Question 6

What occurs during ovulation?

Answer 6

FSH and LH stimulate follicle growth.
LH surge increases collagenase activity, and prostaglandins cause muscular contractions in ovarian walls.
Oocyte extruded and breaks free from ovary

Question 7

What are the functions of the corpus luteum?

Answer 7

Follicle is lutenized by LH forming corpus luteum.
CL secretes oestrogen and progesterone to stimulate uterine mucosa to enter secretory stage in preparation for embryo implantation.

Question 8

What happens to the corpus luteum in pregnancy?

Answer 8

If fertilisation doesn’t occur, CL degenerates into corpus albicans, PG production decreases and menstruation occurs
If fertilization occurs, the Syncytiotrophoblast from embryo releases HCG preventing CL degeneration, then CL forms CL Graviditatis