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GIGU > Male Reproductive Physiology > Flashcards

Male Reproductive Physiology Flashcards

1
Q

Describe the Gonadotropin secretion over the lifetime

A 
Fetus: small increase
Childhood: Low and constant
Puberty: Starts to increase
Adult life: PULSATILE
Old age: slow increase
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2
Q

How is puberty initiated by GnRH?

A

GnRH is secreted in a pulsatile manner

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3
Q

Pulsatile secretion of GnRH drives the pulsatile secretion of?

A

FSH and LH

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4
Q

What do FSH and LH stimulate secretions of?

A

Steroid sex hormones - Testosterone and Estradiol

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5
Q

Increased levels of steroid sex hormones (Testosterone and Estradiol) result in the appearance of what at puberty?

A

Secondary sex characteristics at puberty

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6
Q

_______ secretion rate of GnRH is necessary for reproductive function and puberty

A

Pulsatile

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7
Q

If a constant GnRH analogue is administered, what occurs?

A

NO puberty or reproductive function will be initiated!

– must be pulsatile

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8
Q

Main function of the Testes?

A

Spermatogenesis

Testosterone secretion

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9
Q

Why is the scrotum a lower temperature?

A

It is necessary for spermatogenesis within the testes

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10
Q

Where are sperm matured and stored?

A

Epididymis

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11
Q

The vas deferens ____ can also serve as a sperm storage site

A

Ampulla

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12
Q

Adult testis are ______ seminiferous tubules and _____ CT with leydig cells

A

80%

20%

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13
Q

Main function of the sertoli cells

A

Provide nutrients to differentiating sperm and create the blood-testis barrier

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14
Q

Main function of leydig cells

A

Synthesis and secretion of testosterone

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15
Q

3 main androgens secreted from testes?

A

Testosterone (main one)
DHT
Androstenedione

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16
Q

Where is the majority of Testosterone converted to DHT?

A

Peripheral tissues

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17
Q

What enzyme in the testes can convert Androstenedione to Testosterone?

A

17beta - hydroxysteroid dehydrogenase

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18
Q

What enzyme in testes and in peripheral tissues can convert Testosterone to DHT (dihydrotestosterone)?

A

5alpha - reductase

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19
Q

DHT binds to the androgen receptor in target tissues with a _____ affinity than testosterone?

A

Higher

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20
Q

What can the circulating testosterone be bound to in the blood?

A

Free
Albumin
SHBG (sex hormone binding globulin)

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21
Q

What binds to circulating testosterone in the blood the majority of the time?

A

SHBG

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22
Q

The most biologically important form of testosterone is bound to?

A

Nothing - free

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23
Q

DHT is important for what changes associated with puberty?

A

External male genitalia

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24
Q

If there is a 5alpha - reductase deficiency, what can become ambiguous?

A

External male genitalia due to low levels of DHT

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25
Q

What are the 2 sources for male estrogen?

A

Sertoli cells in seminiferous tubules

Adipose tissue

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26
Q

Estrogen can potentially have a role in what for males?

A

Spermatogenesis because sperm cells express an estrogen receptor

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27
Q

______ forms 80% of all male estrogen

A

Adipose tissue

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28
Q

Testosterone is converted to Estradiol with what enzyme?

A

Aromatase (CYP19)

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29
Q

Rate limiting step in testosterone synthesis?

A

Cholesterol –> Pregnenolone using the Desmolase enzyme

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30
Q

What is the main steriodogenic cell in the testes and why?

A

Leydig cells because they can synthesize and store cholesterol (precursor for testosterone)

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31
Q

What hormone acts on leydig cells to control their rate of testosterone synthesis?

A

LH

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32
Q

3 main actions of DHT

A
  1. External male genitalia formation
  2. Male hair distribution and its loss
  3. Prostate growth
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33
Q

Potential treatment for male pattern hair loss?

A

5alpha-reductase inhibitors to stop the formation of excess DHT

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34
Q

Benign Prostatic Hyperplasia (BPH)

A

Excessive urination, difficulty urinating, urinary urgency and dribbling
- majority of males over 80 have this

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35
Q

Describe DHT levels in males with BPH

A

NOT HIGHER than a regular male - normal levels

36
Q

What may men with BPH have more of?

A

DHT receptors which will cause a larger enlargement of the prostate that compresses the prostatic urethra

37
Q

LH binds to what cell?

A

Leydig cell

38
Q

From the leydig cell, where can testosterone go?

A

Circulation or Sertoli cell (seminiferous tubule)

39
Q

FSH binds to what cell?

A

Sertoli cell

40
Q

What 3 products (besides mature sperm) can sertoli cells produce in response to FSH?

A
  1. Aromatase (testosterone –> estradiol)
  2. ABP (androgen binding protein, binds testosterone in the lumen of the sertoli cells)
  3. Inhibin (inhibits more FSH release)
41
Q

What intracellular pathway is activated with LH or FSH bind to either leydig cells or sertoli cells?

A

cAMP - protein kinase A pathway

42
Q

ABP action

A

Androgen binding protein
- Binds testosterone in the lumen of the seminiferous tubule to provide local testosterone source for developing spermatogonia

43
Q

Aromatase action

A

Testosterone converted to estradiol

44
Q

Inhibin action

A

Inhibits more FSH release from the anterior pituitary

45
Q

3 phases of spermatogenesis?

A
  1. Mitotic phase
  2. Meiotic phase
  3. Spermiogenesis
46
Q

Mitosis takes spermatogonia to?

A

Type A and Type B spermatogonia each with 2N DNA

47
Q

Meiosis 1 takes Type B spermatogonia (2N) to?

A 
Primary spermatocytes (4N) and then to
Secondary spermatocytes (2N)
48
Q

Meiosis 2 takes secondary spermatocytes (2N) to?

A

4 spermatids (1N)

49
Q

Spermiogenesis takes spermatids to?

A

Spermatozoa

50
Q

Where in the mature sperm is there mitochondria?

A

Middle piece

51
Q

Residual body of the sperm is phagocytized by?

A

Sertoli cells

52
Q

What is necessary for early division of sperm and without it, spermatogenesis will not occur?

A

Growth hormone

53
Q

Sertoli cells need ____ to form sperm

A

FSH

54
Q

Leydig cells need _____ to form testosterone

A

LH

55
Q

What steroid hormones are essential for spermatogenesis?

A

Testosterone (leydig) and Estrogen (sertoli)

56
Q

What does exogenous administration of androgens cause?

A

(-) feedback on pituitary to release less LH/FSH which DECREASES spermatogenesis

57
Q

Job of seminal vesicals

A

Secrete nutrients, fructose and prostaglandins for sperm

58
Q

What do prostaglandins do from the seminal vesical?

A
  • make female mucous less thick so sperm can travel

- reverse peristaltic contractions in the female to move sperm from the uterus to the uterine tubes

59
Q

Job of prostate gland

A

Secrete alkaline fluid to help neutralize acidic environment of vagina

60
Q

Semen is composed of sperm and fluid from?

A

Vas deferens
Seminal vesicals
Prostate gland
Bulbourethral glands

61
Q

What is the final pH of semen?

A

7.5

62
Q

Less than _____ sperm = infertile

A

20 million

63
Q

During flaccid state, blood flow to erectile tissue is?

A

Minimal

64
Q

What is the main innervation during erection?

A

Parasympathetics

65
Q

During erection, parasympathetic nerves cause the helicine arteries to release?

A

NO - nitric oxide

66
Q

Helicine arteries supply?

A

Cavernous spaces

67
Q

Once the helicine arteries release NO, what happens?

A

Guanylyl cyclase
Increased cGMP
Decreased calcium
= Relaxation of smooth muscle in the helicine arteries and blood can flow into cavernous spaces

68
Q

Emission

A

Movement of semen from epididymis, vas deferens, seminal vesicals and prostate gland to ejaculatory duct

69
Q

During emission, what is the main innervation?

A

Sympathetic

70
Q

During emission, sympathetic control causes what 2 things?

A
  1. Peristaltic contractions of vas deferens

2. Closure of internal sphincter of bladder

71
Q

Why is it important to close the internal sphincter of bladder during emission and with what surgery can the internal sphincter of the bladder be damaged?

A

To prevent retrograde ejaculation into the bladder

- Prostatectomy can damage this sphincter and cause retrograde ejaculation into the bladder

72
Q

Ejaculation

A

Propulsion of semen out of male urethra

73
Q

Contractions of what muscles cause ejaculation?

A

Bulbospongiosus

Ischiocavernosus

74
Q

Ambiguity of external genitalia - testosterone age deficiency?

A

Early gestation

75
Q

Inadequate testicular descent - testosterone age deficiency?

A

Late gestation

76
Q

Poor secondary sexual development - testosterone age deficiency?

A

Puberty

77
Q

Decreased libido, Decreased hair growth, and erectile dysfunction - testosterone age deficiency

A

Post-puberty

78
Q

Kallman’s syndrome

A

GnRH neurons fail to migrate to hypothalamus during development

79
Q

Symptoms of Kallman’s syndrome

A

Delayed or absent puberty and altered sense of smell

80
Q

Klinefelter syndrome

A

47, XXY

- Phenotypically male but at puberty failure to induce normal testicular growth and spermatogenesis

81
Q

Primary hypogonadism

A

Decreased testosterone

- klinefelter

82
Q

Secondary hypogonadism

A

Decreased testosterone

Decreased LH/FSH

83
Q

Tertiary hypogonadism

A

Decreased testosterone
Decreased LH/FSH
Decreased GnRH
- Kallman

84
Q

Hyperprolactinemia inhibits?

A

FSH and LH secretion

85
Q

Andropause

A

Gonadal sensitivity to LH and FSH decreases as you age which causes increased levels of LH and FSH and less androgen production

GIGU (29 decks)

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