Gametogenesis

Question 1

Describe the stages of sperm production. (14)

Answer 1

Spermatogonia 
Mitosis 
1 Ad spermatogonium (replace the original one) and 1 Ap spermatogonium. 
Mitosis 
B spermatogonia 
Mitosis
Primary spermocytes 
Meiosis
Secondary spermocytes
Development
Spermatids
Spermiogenesis 
Spermatozoa.

Question 2

Describe the spermatic wave and the spermatic cycle. (4)

Answer 2

Not all of the stages are visible at once in one seminiferous tubules.
The spermatic cycle is the amount of time that it takes for the the same stage to reappear anywhere within the tubule.
But the developmental stages always happen in different parts of the tubule.
The spermatic wave is how long it takes for the same stage of development to appear in the exact same bit of the tubule.

Question 3

Describe spermiogenesis. (3)

Answer 3

The process of spermation - remodelling the spermatids as they pass through the testes into the epididymis, in which they become motile.

Question 4

Describe the capitation of sperm. (4)

Answer 4

Conditions in the female genital tract prompt the removal of glycoproteins and cholesterol from the membrane, activating signalling pathways. This allows sperm to bind to the Zona Pellucida of oocyte and initiate the acrosome reaction.

Question 5

Describe the production of primordial follicles. (5)

Answer 5

Germ cells colonise the gonadal cortex before birth, and differentiate into oogonia. They enter meiosis and arrest at prophase I to be called primary oocytes. They are surrounded by flat epithetlial cells called follicular cells, and so are now called primordial follicles.

Question 6

Describe the phases a primordial follicle undergoes to be ovulated. (9)

Answer 6

Preantral stage - the epithelium changes from flat to cuboidal and produces granulosa cells which secrete the zona pellucida.
Antral stage - fluid filled spaces appear between granulosa cells which coalesce to form the antrum.
Preovulatory stage - LH surge induces growth, meiosis I produces two haploid daughter cells (one polar body one oocyte). It then arrests at the start of meiosis II only to start again if fertilisised.

Question 7

Describe ovulation. (4)

Answer 7

FSH and LH stimulate rapid follicle growth. LH stimulates increased collagenase activity, and prostaglandins cause ovarian wall contraction. Oocyte extruded.

Question 8

Describe the corpus luteum. (4)

Answer 8

Remaining granulosa and theca interna cells become the corpus luteum which secretes oestrogen and progesterone. Stimulates the uterine mucosa to enter secretory stage to prepare for implantation, and if it doesn’t receive hCG stimulation from the embryo, it dies.

Question 9

Describe the corpus albicans. (2)

Answer 9

If no fertilisation occurs, the corpus luteum degenerates, and forms the bpfibrotic corpus albicans. Progesterone decreases, precipitating menses.

Question 10

Describe when the oocyte goes through the two stages of meiosis (4)

Answer 10

First part of meiosis I - in utero
Second part of meiosis I - preovulatory stage
First part of meiosis II - preovulatory stage
Second part of meiosis II - only on fertilisation.

Question 11

Describe 6 differences between oogenesis and spermatogenesis. (12)

Answer 11

Approx 200 million sperm per day vs 1 ovum per 28 day cycle.
4 spermatids produced vs 1 ovum and 3 polar bodies.
Male starts at puberty vs female starts in utero.
Male never ends vs female ends at menopause.
Male has motile gametes vs female non-motile
Male has all stages complete in the seminiferous tubules of the testes vs last stage in female taking place on fertilisation in the Fallopian tube.