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LSM3214 > Sex determination > Flashcards

Sex determination Flashcards

1
Q

What is the genetic sex phase of sex determination?

A

Sex is dependent on the chromosomes (i.e. XX or XY)

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2
Q

What is the gonadal sex phase of sex determination?

A

Phase in which the testes or ovaries develop

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3
Q

When does an embryo start to be sexually differentiated?

A

After 5-6 weeks. Before that, it is sexually undifferentiated with ducts and potential gonads of both gender.

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4
Q

When does gonadal specificity appear in the embryo?

A

After 7 weeks - testes develop in males
After 9 weeks in females; no formation of testes automatically leads to formation of ovaries

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5
Q

How do testes develop?

A

Y chromosome has SRY which codes for TDF, acting as a transcription factor for testes development

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6
Q

What is the phenotypic sex phase of sex determination?

A

Development of external genitalia and the reproductive tract

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7
Q

What is the function of leydig cells?

A

Secretes testosterone which promotes wolffian duct development

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8
Q

What is the function of sertoli cells?

A

Secretes MIF, which causes the mullerian duct to regress

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9
Q

How is testosterone converted into di-hydrotestosterone (DHT)?

A

Via 5alpha-reductase enzyme

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10
Q

What is the function of DHT?

A

Initiates formation and development of external genitalia

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11
Q

Is an OX or OY a lethal genotype in which the individual can never be born?

A

OY

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12
Q

What happens with an OX genotype?

A

Female with turner’s syndrone - non-working ovaries and no menstruation!

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13
Q

When does the testes descend into the scrotum?

A

By the 7th month

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14
Q

What is cryptorchidism?

A

Case of hidden testes where testes are undescended and hence cannot produce viable sperm

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15
Q

Why is testes descending important?

A

Temperature in the scrotum is 2˚ < body temperature and spermatogenesis is temperature dependent

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16
Q

What is the function of sertoli cells with regards to testes descending?

A

Sertoli cells provide nutrients and support for spermatogenesis

17
Q

What occurs in puberty?

A

Onset of spermatogenesis with testes enlargement and development of secondary characteristics (e.g. pubic hair)

18
Q

What hormone is secreted in puberty?

A

The hypothalamus secretes GnRH which triggers LH and FSH secretion by the anterior pituitary gland

19
Q

What is the function of LH in male reproduction?

A

LH stimulates the Leydig cells in the testes to produce and secrete testosterone

20
Q

What is the function of FSH in male reproduction?

A

FSH plays a role in sperm production (spermatogenesis) in the testes.

21
Q

How are GnRH, LH and FSH secreted and why?

A

Pulsatile manner, as continuous exposure of gonadotrophs to GnRH leads to desensitisation that will decrease LH and FSH release

22
Q

What is the function of inhibin and what is it secreted by?

A

Inhibin inhibits FSH secretion and is secreted by sertoli cells

23
Q

What feedback does testosterone have?

A

Testosterone has negative feedback on GnRH release

24
Q

What is the effect of FSH in female reproductive system?

A

Aids follicle growth and maturation

25
Q

What is the function of LH in female reproductive system?

A

Stimulates the follicle to burst and release the egg

26
Q

What are the 2 phases in the ovarian cycle?

A

Follicular & luteal phase

27
Q

What is the flow of hormones in the follicular phase of the ovarian cycle?

A

GnRH secreted = LH & FSH production which stimulates estrogen release

Increased FSH = increased estrogen = FSH inhibition + LH production = follicle bursts open

28
Q

Why is FSH secretion inhibited?

A

To prevent multiple ovulations!

29
Q

What is the hormone regulation in the luteal phase of the ovarian cycle?

A

Corpus luteum secretes estrogen and progesterone; increased progesterone = inhibits FSH and LH;

no pregnancy = decreased progesterone = LH and FSH secretion.

30
Q

What is the function of progesterone?

A

Supports the ovum in preparation of fertilisation

31
Q

What are the 3 phases of the uterine cycle?

A

Menstrual, proliferative, secretory

32
Q

What occurs in the menstrual phase?

A

Low progesterone and estrogen levels and endometrium is not nourished as there is no embryo

33
Q

What occurs in the proliferative phase?

A

Estrogen levels increase to promote endometrium thickening (rebuilding of endometrium walls)

34
Q

What occurs in the secretory phase?

A

Progesterone levels increase to cause endometrium thickening to provide nutrients for the embryo (e.g. more blood vessels and secretory glands)

LSM3214 (5 decks)

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