3.2 Gametogenesis

Question 1

Name the 3/4 things that germ cells do after colonising the gonad

Answer 1

Proliferate by mitosis
Reshuffle genetically
Reduce to haploid by meiosis
Cytodifferentiate

Question 2

Compare oogenesis and spermatogenesis (simple)

Answer 2

Oogenesis

• Few gametes 400
• Intermittent production 1/month

Spermatogenesis

• Lots 200/day
• Continuous production
• Disposable

Question 3

2 main functions of meiosis

Answer 3

Reduce chromosome number to 23

Genetically unique gametes

Question 4

3 sources of genetic variation

Answer 4

Crossing over

Independent assortment

Random segregation

Question 5

Which two types of spermatogonium are produced by mitosis in spermatogenesis?

Answer 5

Ad - resting

Ap - active
Ap produce type b spermatogonia which give rise to primary spermocytes which divide by meiosis to make secondary -> 4 haploid spermatids

Question 6

Define spermiogenesis

Answer 6

Process by which the 4 haploid spermatids formed from each primary spermatocyte DIFFERENTIATE into spermatozoa

Question 7

Define spermatogenic cycle

Answer 7

Time taken for reappearance of the same stage (of spermatogenesis) within a given segment of the tubule
About 16 days

Question 8

Define Spermatogenic wave

Answer 8

Distance between the same stage of spermatogenesis

Question 9

What is spermiation?

Answer 9

Spermatids released into lumen of seminiferous tubules

Question 10

What 4 things make up semen?

Answer 10

Seminal vesicles secretions 70%
Secretions of prostate 25%
Sperm via vas deferens
Bulbourethral gland secretions

Question 11

What is the other name for the bulbourethral gland?

What does the secretions do?

Answer 11

Cowper gland

Mucoproteins to lubricate and neutralise acidic urine in distal urethra

Question 12

What happens in capacitation?

Answer 12

In female reproductive tract

• removal of glycoproteins and cholesterol from sperm membrane
• activation of signalling pathways
• allow sperm to bind to zone pellucida (acrosome reaction)

Question 13

How many chromosomes and chromatids are there in an oogonium and in a primary oocyte?

Answer 13

Oogonium
- 46 chromosomes, 46 chromatids

Primary oocyte
- 46 chromosomes , 96 chromatids

Question 14

What is a primordial follicle?

Answer 14

Primary oocyte in meiosis I surrounded by layer of flat epithelial cells called follicular cells

Question 15

3 stages of maturation at puberty

Answer 15

1) Pre-Antral
2) Amtrak
3) Pre-ovulatory

Question 16

Describe the preantral stage

Answer 16

Primordial follicle grows
Follicular cells change from flat to cuboidal
Follicular cells proliferate to form stratified epithelium of granulosa cells

Question 17

What do granulosa cells do in the preantral stage?

Answer 17

Secrete layer of glycoproteins on oocyte to form zona pellucida

Question 18

Describe Antral stage

Answer 18

Fluid filled spaces appear between granulosa cells

Spaces join to make antrum

Question 19

What stimulates preovulatory stage?

Answer 19

LH surge

Question 20

Describe preovulatory stage

Answer 20

One larger daughter cell enters meiosis II but arrests in metaphase
Only completed upon fertilisation

Question 21

What is a mature follicle called?

Answer 21

Graafian follicle 2.5cm

Mature due to FSH and LH

Question 22

What does LH surge cause during ovulation?

Answer 22

Increased collegenase activity
Increased prostaglandins which cause contractions in ovarian wall
Get ovulation
Promotes development of CL

Question 23

How is corpus luteum formed?

Answer 23

Granulosa and theca interna cells become vascularises

Change into luteum cells

Question 24

What does corpus luteum do?

Answer 24

Secrete oestrogen and progesterone
Cause uterine muscosa to enter secretory stage to prepare for implantation

Dies after 14 days

Question 25

How is the oocyte transported?

Answer 25

Fimbriae
Cilia
Peristalsis

Question 26

What happens if no fertilisation occurs?

Answer 26

CL degenerates into CA
Progesterone decreases
Menstruation

Question 27

What happens if fertilisation occurs?

Answer 27

HCG from embryo maintains CL
Forms CL graviditatis
4th month, progesterone secretion taken over by placenta