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Human Physiology - Hormones and Health > Sex Determination and Differentiation > Flashcards

Sex Determination and Differentiation Flashcards

1
Q

What are the aims of the male reproductive system?

A
  • to produce, maintain, transport and nourish sperm an semen
  • to discharge sperm within the female reproductive tract
  • to produce and secrete male sex hormones
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2
Q

What are the male external genitalia?

A

penis and scrotum

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3
Q

What is the male gonad?

A

testis

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4
Q

What are the male internal genitalia?

A
  • seminal vesicle
  • ejaculatory duct
  • vas deferens
  • epididymis
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5
Q

What are the aims of the female reproductive system?

A
  • to release eggs, which can potentially be fertilised by sperm
  • to produce and secrete female sex hormones
  • to provide an environment for a fertilised egg to develop during pregnancy
  • to facilitate labour and childbirth
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6
Q

What are the female external genitalia?

A
  • clitoris
  • labia
  • vagina
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7
Q

What is the female gonad?

A

ovary

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8
Q

What are the female internal genitalia?

A
  • uterine duct
  • uterus
  • vagina (upper 1/3)
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9
Q

What are the 3 levels that determine the sex of a person?

A
  1. genetic sex
  2. gonadal sex
  3. phenotype sex
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10
Q

When is genetic sex determined?

A

at the time of fertilisation

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11
Q

How many chromosomes do somatic and gamete cells have respectively?

A
  • somatic = 46 (23 pairs)
  • gamete = 23
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12
Q

What are the sex chromosomes in males and females respectively?

A
  • male = XY
  • female = XX
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13
Q

What does genetic sex determine?

A

gonadal sex

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14
Q

What determines gonadal differentiation?

A

presence or absence of a Y chromosome

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15
Q

What can the gonadal ridge form?

A

either ovary or testis

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16
Q

What happens at 1.5 months of gestation?

A
  • all embryos have a potential to differentiate along either male or female lines
  • the developing reproductive tissues of both sexes are identical and undifferentiated
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17
Q

When is gonadal sex determined in males and females respectively?

A
  • males = week 7
  • females = week 9
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18
Q

What is the SRY gene?

A

the sex determining region of the short arm of the Y chromosome that encodes the protein TDF (testis-determining factor)

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19
Q

What does TDF do?

A

act as a TF for the genes necessary for testicular differentiation, including MIF and androgen receptors

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20
Q

What does MIF do?

A

initiate the development of male glands

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21
Q

Why do females not produce TDF?

A

they lack the SRY gene

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22
Q

What does the cloaca form?

A

the male and female external genitalia

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23
Q

Which ducts form the male and female internal genitalia?

A
  • male = Wolffian
  • female = Müllerian
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24
Q

What happens if the undifferentiated glands are removed before testes have developed at 7 weeks?

A

the Wolffian gland development is inhibited and so no MIF is produced and ovaries form

25
Q

What is required for male differentiation?

A
  • Y chromosome must be present
  • SRY gene must work to produce MIF
  • hormones must be present
26
Q

What does testosterone do?

A

convert to DHT which allows the Cloaca to form the external male genitalia

27
Q

What enzyme converts testosterone to DHT?

A

5α reductase

28
Q

What is aneuploidy?

A

abnormal number of chromosomes

29
Q

What causes Turner’s syndrome?

A

having a single X chromosome

30
Q

What are the symptoms of Turner’s syndrome?

A

webbed feet, short stature, failure of ovaries to develop, absence of menstrual cycle

31
Q

Give an example of a gonadal sex disorder

A

abnormal development of gonads (incomplete differentiation) and so not functional to induce puberty

32
Q

Give an example of a phenotypic sex disorder

A

male/female pseudo hermaphroditism

33
Q

What is pseudo hermaphroditism?

A

a condition in which an organism is born with secondary sex characteristics or a phenotype that is different from what would be expected on the basis of the gonadal tissue (ovary or testis)

34
Q

What is an hermaphrodite?

A

one bearing characteristics of both sexes

35
Q

What is lacking in male pseudo hermaphroditism?

A
  • hormones (testosterone, MIF)
  • enzymes (5α-reductase, enzymes involved in steroid synthesis)
  • receptors (androgen receptors, LH receptor)
36
Q

What does female pseudo hermaphroditism arise from?

A

exposure to androgens (male sex hormone) by maternal exposure or androgen excess in foetus

37
Q

What are the symptoms of 21-hydroxylase deficiency in females?

A
  • abnormal menstrual periods
  • deep voice
  • early appearance of pubic and armpit hair
  • excessive hair growth and facial hair
  • failure to menstruate
  • genitals that look both male and female (ambiguous genitalia), often appearing more male than female
38
Q

What is a significant stage in sexual development of males?

A

descent of the testes in the 7th month of gestation

39
Q

What is undescended testes into adulthood and what is its incidence?

A

cryptorchidism and its incidence is 3% of full-term babies and 30% of premature babies

40
Q

What is spermatogenesis dependent on?

A

temperature (needs to occur 2ºC cooler than normal body temperature)

41
Q

How long does spermatogenesis take?

A

64 days

42
Q

What cell type produces testosterone?

A

Leydig cells

43
Q

What provides nutrients and support for spermatogenesis?

A

Sertoli cells

44
Q

What does the hypothalamus do at puberty?

A

secrete GnRH to stimulate the anterior pituitary to make and release LH and FSH

45
Q

How are LH and FSH secreted?

A

in a pulsatile manner ~every 1-3 hours

46
Q

What happens if there is continuous exposure of gonadotrophs to GnRH?

A

desensitisation of GnRH receptors, leading to a decrease in LH and FSH release

47
Q

How is GnRH a tropic hormone?

A

it stimulates the testes to make testosterone

48
Q

What does the negative feedback loop of testosterone levels do?

A

decrease GnRH release by acting on the hypothalamus to indirectly decrease both LH and FSH release

49
Q

How does testosterone work?

A

by binding to plasma proteins in circulation (can also bind to albumin but not with the same affinity)

50
Q

What are the effects of testosterone?

A
  • internal male genitalia (differentiation)
  • pubertal growth spurt
  • penis (growth)
  • deepening of voice
  • spermatogenesis
  • libido
  • muscle mass and recovery
51
Q

What are the effects of taking exogenous hormone (anabolic steroid)?

A

the testes would not achieve normal testosterone levels since they are not receiving normal stimulatory input causing testosterone secretion and sperm production to decrease and the testes to shrink

52
Q

How much more active is DHT than testosterone?

A

more than 2x

53
Q

Where is 5α-reductase high?

A

skin, prostate gland, seminal vesicle, epididymis, testes and liver

54
Q

What are the effects of DHT?

A
  • external male genitalia (differentiation)
  • sebaceous glands
  • prostate (growth)
  • male hair pattern baldness
55
Q

What does DHT do to hair?

A

cause shrinkage in the overly sensitive hair follicles which causes them to fall out

56
Q

What is spermatogenesis?

A

production of sperm

57
Q

Give an example of a post testicular abnormality

A

failure in sperm storage, transport, nourishment, and release

58
Q

Give an example of a pretesticular abnormality

A
  • failure in the entire male repo functions
  • GnRH deficiency

Human Physiology - Hormones and Health (14 decks)

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