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LCRS > Endocrinology 10 - The Gonads 1 & 2 > Flashcards

Endocrinology 10 - The Gonads 1 & 2 Flashcards

1
Q

What are the functions of the gonads?

A
  • In males, undergo spermatogenesis and produce androgens (as well as oestrogens and progestogens)
  • In females, oogenesis as well as produce oestrogen, progestogen (and androgens)
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2
Q

Describe the production of spermatogonia throughout life.

A
  • Sperm is produced to 6 million before birth

- This number remains relatively constant throughout life

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3
Q

Describe the production of oogonia throughout life

A
  • All of the eggs are produced in the foetus

- They then rapidly decrease in number until menopause

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4
Q

Describe the stages of spermatogenesis

A
  • Germ cell to spermatogonia
  • Mitotic division to primary spermatocytes. Some are recycled to reform spermatogonia.
  • First meiotic division to seconday spermatocytes
  • Second meiotic division to spermatids
  • Mature to spermatozoa (22x or 22y)
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5
Q

When does gametogenesis begin in males?

A

At puberty, following FSH stimulation.

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6
Q

Describe the stages of oogenesis.

A
  • Germ cell to oogonia
  • Mitotic division to primary oocytes
  • First meiotic division begins but does not end, there is meiotic arrest until puberty or even for 50 years
  • At puberty, secondary oocytes and the first polar body are made
  • Second meiotic division makes the ovum and second polar body (only at fertilisation)
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7
Q

What are polar bodies?

A
  • They are formed because the oocyte does not divide evenly
  • They are non-functioning egg cells that cant be fertilised
  • They are smaller, haploid cells, which get less of the cytoplasm than the ovum
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8
Q

Describe the anatomy of the testes

A
  • The many coiled semineferous tubules lead to the Rete testis
  • Sperm travels down the epididymis from the Vasa efferentia to the vasa deferens
  • The vasa deferens is surrounded by smooth muscle, so ejaculation to the urethra can occur
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9
Q

Describe the anatomy of the seminiferous tubules of the testes.

A
  • The outside contains spermatogonia
  • Spermatozoa are in the lumen
  • Sertoli cells form the seminiferous tubules
  • The leydig cells are found around the outside of seminiferous tubules
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10
Q

Describe the function of the sertoli cells

A

-Synthesise FSH and androgen receptors
in response to FSH
- Produce various molecules including INHIBIN
- Are intimately associated with developing spermatocytes

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11
Q

Describe the function of Leydig cells

A
  • Synthesise LH receptors

- In response to LH are the principal source of testicular androgens (mainly testosterone)

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12
Q

Describe the structure of the ovaries

A
  • The graafian follicle contains the ovum, granulosa cells and thecal cells
  • There are many follicles undergoing atresia (unfertilised)
  • Ovarian stroma is the fluid
  • There is a corpus luteum
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13
Q

Describe the pathway of synthesis of androgens, oestrogen and progesterone

A
  • Progesterone is produced first
  • Then testosterone
  • Testosterone can be converted to dihydrotestosterone (more potent than testosterone) or oestradiol (main human oestrogen)
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14
Q

How is testosterone transported around the body?

A
  • In the blood via sex hormone binding globulin (60%)
  • 38% in the blood bound to albumin
  • 2% in the blood is bioactive
  • In the seminiferous fluid, it is carried by androgen binding globulin
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15
Q

List the principle actions of androgens in the fetus

A
  • Development of male genitalia

- Fetal growth (by acting on other hormones)

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16
Q

List the principle actions of androgens in the adult.

A
  • Spermatogenesis
  • Growth and development of male genitalia and secondary sex characteristics
  • Protein and bone anabolism
  • Male sexual behaviour
  • Growth spurt at puberty
17
Q

Define an oestrogen

A

Any substance which induces mitosis in the endometrium

18
Q

What is the main human oestrogen?

A

17 beta-oestradiol

19
Q

List the effects of oestrogen

A
  • Stimulates mitosis of the endometrium
  • Triggers LH surge resulting in ovulation
  • Growth of breasts
  • Feedback on gonadotroph releasing horomone
  • Stimulates osteoblasts (results in osteoporosis after menopause)
  • Metabolic actions
  • Female behaviors
20
Q

Define progestogen

A

Any substance (natural or synthetic) inducing secretory changes in the endometrium

21
Q

What is the main progestogen in humans?

A

Progesterone

22
Q

What are the effects of progestogens?

A
  • Stimulates secretory activity in the endometrium and cervix
  • Negative feedback
  • Increases basal body temperature
  • Growth of breast
23
Q

Describe the feedback in the hypothalamo-pituitary-testicular axis

A
  • Leydig cell produces testosterone (stimulated by LH), which performs negative feedback
  • The sertoli cell produces inhibin (stimlated by FSH) which perfoms negative feedback
  • Feedback is on hypothalamus (makes GnRH) and anterior pituitary (makes LH and FSH)
24
Q

Describe the process that occurs in the early follicular phase.

A
  • New follicles begin growing under the influence of FSH

- These follicles begin to produce oestrodiol. As levels are only low, LH and FSH remains to stimulate growing

25
Q

What happens during the early mid follicular phase of the menstrual cycle?

A
  • Oestradiol levels increase due to follicles growing, causing proliferation in the endometrium, as well as increasing the number of receptors for oestrogen and progesterone in the uterus
  • This causes one of the follicles to become larger
  • This follicle begins to produce large amounts of oestrogen, causing positive feedback - granulosa cells surrounding it are stimulated to produce more oestrogen.
  • LH and FSH are reduced by the high oestrogen levels, which results in only the graafian follicle surviving. The graafian follicle is no longer controlled by FSH
26
Q

What happens in the late follicular phase of the menstrual cycle?

A
  • Oestrogen reaches a threshold where positive feedback in the hypothalamus/pituitary occur, and high levels of LH and FSH are produced
  • The LH surge triggers the egg to be released
27
Q

What happens in the luteal phase of the menstrual cycle?

A
  • Once the egg is released, the corpus luteum is left. This produces progesterone
  • When there is no fertilisation, progesterone makes the womb lining thicker.
  • Negative feedback of LH and FSH occurs. This causes luteolysis and menstruation
28
Q

Describe the process that occurs in the endometrial cycle.

A
  • In the proliferative phase, oestrogen is dominant, and the endometrium thickens. Glands enlargen
  • In the secretory phase, progesterone is dominant and this causes the endometrium to become secretory, secreting glycogen and the mucosa becomes engorged with blood
  • It then becomes necrotic and the lining is shed
29
Q

What is amenorrhoea?

A

The absense of the menstrual cycle

30
Q

What is the difference between primary and secondary amenorrhoea?

A
  • Primary is where a woman has never had a period

- Secondary is where a woman has had periods but they stopped

31
Q

What is oligomenorrhoea?

A

Ingrequent cycles

32
Q

Define infertility

A

A couple cant get pregnant following 12 months of regular unprotected sex

33
Q

List the causes of infertility

A
  • Pituitary failure
  • Prolactinoma
  • Testicular failure e.g. mumps, Klinefelter syndrome (XXY)
  • Ovarian failure e.g. Turner syndrome (XO)
  • Polycystic ovarian syndrome (PCOS)
34
Q

How many carbons are in cholesterol?

A

27

35
Q

What converts testosterone to oestrogen?

A

Aromatase

36
Q

What coverts testosterone to dihydrotestosterone?

A

5-alpha reductase

37
Q

What is the function of granulosa cells?

A

Produce oestrogen, stimulated by FSH.

38
Q

What is the function of thecal cells?

A

Stimulated by LH to produce the precursor for oestrogen, androstenedione.

LCRS (24 decks)

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