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Endocrinology BM > Gonads (1) 10 > Flashcards

Gonads (1) 10 Flashcards

1
Q

What are the functions of the gonads?

A

1) gametogenesis

2) steroidogenesis

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2
Q

What is atresia?

A

When germ cells degenerate and die

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3
Q

What is the order in spermatogenesis?

A

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

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4
Q

Spermatogonesis background:

A
  • 70 days
  • occurs after puberty when FSH is first released
  • high numbers throughout life
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5
Q

Describe Sequence of Oogenesis

A

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

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6
Q

Oogenesis background:

A
  • Primary oocytes are formed before birth (2 million)
  • meiosis completed during ovulation
  • by puberty there is only 0.5million
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7
Q

What steroids to the testes produce?

A

Mainly androgens

small amounts of oestrogen and progesterones

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8
Q

What steroids do the ovaries produce?

A

Mainly oestrogens and progesterones

small amounts of androgens

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9
Q

Where does spermatogenesis take place in the testes?

A

Semineferous tubules

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10
Q

What is the pathway after spermatogenesis?

A

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

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11
Q

Where are the spermatozoa stored?

A

Epididymis

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12
Q

Where do the testes develop?

A

In the abdomen and descend into the scrotum just before birth

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13
Q

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

A

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.

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14
Q

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

A

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

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15
Q

What is the function of Leydig cells?

A

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

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16
Q

What are the differences between Sertoli and Leydig cells?

A

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

17
Q

Describe the structure of the Graffarian Follicle

A

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

18
Q

Ovaries and atresia use?

A

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

19
Q

What are steroids synthesised from?

A

Cholesterol

20
Q

What is the follicle developed into after ovulation?

A

Corpus luteum

21
Q

What steroids are formed in the gonads?

A
  • Progestogens (C21)
  • Androgens (C19)
  • Oestrogens (C18)
22
Q

Common development between gonads and adrenals?

A

The first four reactions from cholesterol to form steroid hormones

23
Q

What are the gonadal end products of steroid formation?

A
  • porgesterone
  • 17beta-oestradiol
  • testosterone and subsequently dihydrotestosterone
24
Q

How long does the menstrual cycle take?

A

28 days with ovulation occurring at day 14

25
Q

What are the two events in the menstrual cycle?

A
  • Ovarian cycle and endometrial cycle
26
Q

Occurrences in ovarian cycle:

A

1) follicular phase
2) ovulation
3) luteal phase

27
Q

Occurrences in endometrial cycle:

A

1) proliferative phase

2) secretory phase

28
Q

What are the layers of the endometrium?

A

Superificial epithelial layer and a deeper stromal layer

29
Q

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

A

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

30
Q

What is the split of the ovarian cycle?

A

1st 14 days = follicular phase

2nd 14 days = luteal phase

31
Q

Describe the hormone level variations in the menstrual cycle:

A

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

32
Q

Describe follicle sequence of events:

A

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

33
Q

What stimulates ovum to complete first meiosis?

A

Surge of LH

34
Q

Difference between thecal and granulosa cells?

A

Thecal cells (outer) have LH receptors

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

35
Q

What is the difference between Proliferative and Secretory phases?

A

Proliferative - oestrogen is the dominant influence

Secretoy - progesterone is the dominant influence

Endocrinology BM (12 decks)

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