Gametogenesis

Question 1

What determines the sex of the offspring?

Answer 1

Whether the sperm contains an X or Y chromosome

Question 2

What is the function of meiosis?

Answer 2

Reduce chromosome number to 23

Ensures genetically unique

Crossing over

Produces 4 daughter cells (3 are polar bodies in females)

Question 3

How does genetic variation arise?

Answer 3

Crossing over

Independent assortment

Random segregation

Question 4

Outline spermatogenesis

Answer 4

Occurs in the seminiferous tubules

Spermatogonia divide by mitosis = 1) AD spermatogonium: reserve stock, 2) AP spermatogonium: give rise to type B spermatogonia which give rise to primary spermatocyte

Primary spermatocytes divide my meiosis = secondary spermatocytes then = spermatids

Question 5

What is the spermatogenic cycle?

Answer 5

Time taken for reappearance of the same stage within a given segment of tubule

~16 days

Question 6

What is the spermatogenic wave?

Answer 6

Distance down the length of the seminiferous tubule, between the same stage

Question 7

Outline the role of the rete testis

Answer 7

Concentrate the spermatozoa

Question 8

Describe the role of the epididymis

Answer 8

Storage tube for sperm

Question 9

What is the role of the vas deferens?

Answer 9

Tube carrying sperm from epididymis to the urethra

Question 10

What is the basal compartment of the testes?

Answer 10

Spermatogonia (germ cells) reside

Question 11

Define spermiation

Answer 11

Spermatids being released into the lumen of the seminiferous tubule

Question 12

Outline the journey of the sperm

Answer 12

Seminiferous tubule

Rete testis

Ductuli efferentes

Epididymis

Vas deferens

Urethra

Question 13

Outline the role of the seminal vesicle

Answer 13

65% vol

Secrete = AA, citrate, fructose, prostaglandins

Question 14

What is the role of the prostate?

Answer 14

25% vol

Secrete = proteolytic enzymes, zinc

Question 15

What is the role of the bulbourethral glands?

Answer 15

1% vol

Secrete = mucoproteins: help lubricate and neutralise acidic urine in distal urethra

Question 16

What is capacitation?

Answer 16

Final maturation step required before sperm becomes fertile

= removal of glycoproteins/cholesterol = allow sperm to bind zona pellucida and initiate acrosome reaction

Question 17

Outline the maturation of oocytes before birth

Answer 17

Germ cells diff into oogonia

Oogonia divide by mitosis

Some enter meiosis but arrest in prophase of meiosis I = primary oocytes

Become surrounded by follicular cells = primordial follicle

Question 18

What are the stages of an oocyte maturing at puberty?

Answer 18

Preantral

Antral

Preovulatory

Question 19

Outline the preantral stage

Answer 19

follicular cells change into stratified ep of granulosa cells = primary follicle

Question 20

Outline the antral stage

Answer 20

theca cell present (prod androgens)

space appears between granulosa cells called antrum = sec follicle

Question 21

Outline the preovulatory stage

Answer 21

meiosis I now complete giving 2 daughter cells

enters meiosis II but arrests in metaphase

finishes meiosis II if fertilised

if not fertilised cell degenerates

Question 22

Briefly outline ovulation

Answer 22

FSH + LH stimulate rapid growth of follicle

LH surge = collagenase activity

Prostaglandins = local contractions of ovarian wall

Oocyte extruded

Question 23

What happens to the follicle once ovulation has occurred?

Answer 23

Granulosa and theca cells become vascularised = corpus luteum

Secrete oestrogen and progesterone

Question 24

What happens if the oocyte isnt fertilised ?

Answer 24

Corpus luteum degenerates = corpus albicans

Question 25

What happens to the corpus luteum of the oocyte if fertilisation occurs?

Answer 25

Corpus luteum grows = corpus luteum graviditatis

Question 26

Very briefly outline the cell stages of the ovarian cycle

Answer 26

Primary follicle
Secondary follicle
Ovulation (LH surge)
Corpus luteum
Corpus albicans