Gonads (1) 10

Question 1

What are the functions of the gonads?

Answer 1

1) gametogenesis

2) steroidogenesis

Question 2

What is atresia?

Answer 2

When germ cells degenerate and die

Question 3

What is the order in spermatogenesis?

Answer 3

1) Germ cell
2) Spermatogonia
3) Primary spermatocytes
4) Secondary spermatocytes (haploid)
5) Spermatids
6) Spermatozoa

Question 4

Spermatogonesis background:

Answer 4

• 70 days
• occurs after puberty when FSH is first released
• high numbers throughout life

Question 5

Describe Sequence of Oogenesis

Answer 5

1) Germ cell
2) oogonia
3) Primary oocytes
4) Secondary oocyte + polar body (haploid)
5) Ovum + 2nd Polar body

Question 6

Oogenesis background:

Answer 6

• Primary oocytes are formed before birth (2 million)
• meiosis completed during ovulation
• by puberty there is only 0.5million

Question 7

What steroids to the testes produce?

Answer 7

Mainly androgens

small amounts of oestrogen and progesterones

Question 8

What steroids do the ovaries produce?

Answer 8

Mainly oestrogens and progesterones

small amounts of androgens

Question 9

Where does spermatogenesis take place in the testes?

Answer 9

Semineferous tubules

Question 10

What is the pathway after spermatogenesis?

Answer 10

1) Seminiferous tubules
2) Rete Testis
3) Vasa efferentia
4) Vas deferens
5) urethra

Question 11

Where are the spermatozoa stored?

Answer 11

Epididymis

Question 12

Where do the testes develop?

Answer 12

In the abdomen and descend into the scrotum just before birth

Question 13

What is the function of Sertoli cells in the seiniferous tubules?

Answer 13

They are connected together via tight junctions that keep a blood-testis barrier to keep out large proteins such as antibodies. Therefore, spermatozoa are protected from immune reactions.

Question 14

How do spermacytes move from behind the Sertoli cells to the tubule?

Answer 14

Spermatogonia are engulfed and enclosed within the cytoplasm where the rest of spermatogenesis actually occurs. The sertoli cells provide structural and metabolic support

Question 15

What is the function of Leydig cells?

Answer 15

These are steroidogenic cells that contain enzymes allowing synthesis and excytosis of testosterone. testosterone is needed for spermatogenesis to occur.

Question 16

What are the differences between Sertoli and Leydig cells?

Answer 16

Sertoli:
- synthesis FSH and androgen receptors. In response to FSH, they produce Inhibin that has -ve feedback on FSH production.

Leydig:
- synthesis LH receptors and produce androgens (testosterone) in response to LH

Question 17

Describe the structure of the Graffarian Follicle

Answer 17

Ovum surrounded by follicular fluid surrounded by granulosa cells surrounded by thecal cells

Question 18

Ovaries and atresia use?

Answer 18

In the ovaries, there are follicles at various stages of development and atresia at all times.

Question 19

What are steroids synthesised from?

Answer 19

Cholesterol

Question 20

What is the follicle developed into after ovulation?

Answer 20

Corpus luteum

Question 21

What steroids are formed in the gonads?

Answer 21

• Progestogens (C21)
• Androgens (C19)
• Oestrogens (C18)

Question 22

Common development between gonads and adrenals?

Answer 22

The first four reactions from cholesterol to form steroid hormones

Question 23

What are the gonadal end products of steroid formation?

Answer 23

• porgesterone
• 17beta-oestradiol
• testosterone and subsequently dihydrotestosterone

Question 24

How long does the menstrual cycle take?

Answer 24

28 days with ovulation occurring at day 14

Question 25

What are the two events in the menstrual cycle?

Answer 25

- Ovarian cycle and endometrial cycle

Question 26

Occurrences in ovarian cycle:

Answer 26

1) follicular phase 2) ovulation 3) luteal phase

Question 27

Occurrences in endometrial cycle:

Answer 27

1) proliferative phase | 2) secretory phase

Question 28

What are the layers of the endometrium?

Answer 28

Superificial epithelial layer and a deeper stromal layer

Question 29

Which hormones and when do they cause the link between the ovarian and the endometrial cycles?

Answer 29

17b-oestrodiol from the follicular phase causes the proliferative phase. Then, 17b-oestrodiol and progesterone from the luteal phase cause the secretory phase in the endometrial phase

Question 30

What is the split of the ovarian cycle?

Answer 30

1st 14 days = follicular phase | 2nd 14 days = luteal phase

Question 31

Describe the hormone level variations in the menstrual cycle:

Answer 31

1) FSH levels slightly raised at start to encourage development 2) As follicles start growing, 17b-oestrodiol is produced. this has a -ve feedback on gondaotrophin release (LH/FSH) 3) As the follicles grow, one becomes dominant and the others undergo atresia. This follicle then produces lots of oestrogen 4) If oestrogens are high enough for >36 hours, there is a switch from the -ve to the +ve feedback. this induces a surge of gonadotrophins (LH/FSH) 5) This surge induces ovulation 6) after ovulation, follicle forms corpus luteum which continues to form 17b-oestrodiol and progesterone in large quantities 7) progesterone and oestrogen have a -ve feedback on gondatrophins 8) if ovum is not fertilised, oestrogens/progesterones start to fall causing menstration of the endometrium 9) There is less -ve feedback so LH/FSH levels start to rise 10) as gonadotrophins rise, may be a small surge of 17-hydroxyprogesterone which adds to =ve feedback of oestrogen 11) an increase in body temperature can be measured after ovulation

Question 32

Describe follicle sequence of events:

Answer 32

1) Pre-antral follicle (containing ovum) 2) Early-antral follcile (containing ovum/thecal/granulosa) 3) Late-antral follicle (containing ovum/thecal/granulosa but larger) 4) Graffarian follicle (see above with follicular fluid) 5) ovum (after ovulation) and corpus luteum

Question 33

What stimulates ovum to complete first meiosis?

Answer 33

Surge of LH

Question 34

Difference between thecal and granulosa cells?

Answer 34

Thecal cells (outer) have LH receptors Granulosa cells (inner) have FSH receptors. Granulosa cells contain aromatase which converts androgens into 17b-oestrodiol

Question 35

What is the difference between Proliferative and Secretory phases?

Answer 35

Proliferative - oestrogen is the dominant influence Secretoy - progesterone is the dominant influence