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GIGU > Male Reproductive Physiology > Flashcards

Male Reproductive Physiology Flashcards

1
Q

What determines genetic sex?

A

XX or XY

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2
Q

Why is there a delay in formation of testes vs ovaries?

A

there is no anti-mullerian hormone production, so the mullerian tract can form to make the internal genitalia

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3
Q

What week is the fetus bipotential (neither m or f)?

A

week 5

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4
Q

When do the testes begin to develop?

A

weeks 6-7 d/t production of anti-mullerian hormone

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5
Q

When do ovaries begin to develop?

A

week 9

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6
Q

What determines gonadal sex?

A

testes or ovaries

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7
Q

What determines phenotypic sex?

A

physical characteristics of internal and external genitalia

**determined by HORMONAL output from gonads

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8
Q

When does GnRH (and subsequently FSH and LH) begin to rise after birth?

A

puberty

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9
Q

What initiates puberty in terms of hormones?

A

pulsatile secretion of GnRH–> pulsatile FSH and LH

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10
Q

What are responsible for appearance of secondary sex characteristics?

A

increased circulating levels of sex steroid hormones

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11
Q

What stimulates secretion of gonadal steroid hormones: testosterone and estradiol?

A

pulsatile secretions of FSH and LH

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12
Q

How did they discover pulsatile GnRH was necessary to start puberty?

A

GnRH analogue given:

  • pulsatile: puberty initiated, reproductive fxn established
  • long acting: no puberty
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13
Q

What are the 2 main fxns of the testes?

A
  • spermatogenesis

- secretion of testosterone

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14
Q

What is the main fxn of the scrotum?

A

maintain lower temperature (1-2 below BT) for spermatogenesis

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15
Q

What is the main fxn of the epididymis?

A

primary location for maturation and storage of sperm

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16
Q

What is the fxn of the prostate gland?

A

secretes milky aqueous solution rich in citrate, Ca2+ and enzymes

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17
Q

What is the fxn of the vas deferens?

A
  • ampulla provides another storage area for sperm

- secretes fluid rich in fructose and citrate

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18
Q

What is the fxn of seminal vesicles?

A

secretes fluid rich in FRUCTOSE, citrate, prostaglandins and fibrinogen

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19
Q

Where are Leydig cells located?

A

between seminiferous tubules in testes

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20
Q

What is the anatomical make-up of the adult testis?

A

80% seminiferous tubules

20% CT interspersed with Leydig cells

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21
Q

What are seminiferous tubules?

A

epithelium formed by Sertoli cells with interspersed germ cells

–>contain spermatogonia and spermatozoa

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22
Q

What are spermatogonia?

A

immature germ cells located near PERIPHERY of seminiferous tubule in testis

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23
Q

What are spermatozoa?

A

mature germ cells located near LUMEN of seminiferous tubule of tesis

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24
Q

Where are spermatogonia and spermatozoa located in seminiferous tubules?

A

ogonia at periphery, ozoa near lumen

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25
Q

What is the general fxn of Leydig cells?

A

synthesize and secrete testosterone

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26
Q

What are the general fxns of Sertoli Cells?

A
  • provide nutrients to differentiating sperm
  • form tight jxn with each other for blood barrier b/t blood and testes
  • secrete aqueous fluid into lumen of seminiferous tubules to help transport sperm to epididymis
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27
Q

What androgens are secreted by the testes?

A

testosterone (most abundant)

dihydrotestosterone

androstenedione

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28
Q

What is testosterone converted to in target tissues?

A

dihydrotestosterone (DHT)

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29
Q

What is the major androgenic hormone that is synthesized and secreted by Leydig cells of testes?

A

testosterone

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30
Q

What do testes lack so they can’t synthesize gluco- or mineralocorticoids?

A

21B and 11B-hydroxylase

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31
Q

What enzyme do testes have that converts androstenedionen to testosterone?

A

17B-hydroxysteroid dehydrogenase

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32
Q

What is the end product of steroid synthesis in the testes?

A

Testosterone

–>not DHEA and androstenedione like in adrenal gland

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33
Q

Where is testosterone concentrated and bound to androgen binding protein (ABP)?

A

lumen of seminiferous tubules

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34
Q

What enzyme is in peripheral tissue that converts testosterone to dihydrotestosterone?

A

5a-reductase

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35
Q

What is most of circulating testosterone bound to?

A

sex hormone binding globulin (SHBG)

plasma proteins

albumin

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36
Q

Is testosterone active in all tissues?

A

NO–>prostate gland, external genitalia of male fetus, skin and liver use DHT

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37
Q

What are the main steroidogenic cells in the testis?

A

Leydig cells

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38
Q

Where is cholesterol synthesized in testes?

A

Leydig cells de novo

–>can also get LDL and HDL via circulation

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39
Q

What lipase generates free cholesterol in Leydig cells?

A

hormone-sensitive lipase (HSL)

–>converts cholesterol esters to free cholesterol

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40
Q

What is cholesterol converted to in Leydig cells?

A

pregnenolone for androgen production

–>transferred within mito membranes via StAR

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41
Q

Are estrogens formed in males?

A

Yes, small amounts via Sertoli cells (product of testosterone–>estradiol)

–>high amounts in seminiferous tubules d/t role in spermatogenesis

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42
Q

What accounts for more than 80% of total male estrogen production?

A

as product of testosterone and androstenediol via tissues, especially ADIPOSE TISSUE

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43
Q

What is the RLS in synthesis of testosterone?

A

conversion of cholesterol to pregnenolone in Leydig cells

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44
Q

What is the mito pathway in testosterone synthesis?

A

CYT P450 cleaves side chain from carbon @ 20 of cholesterol

–>cholesterol to pregenolone

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45
Q

What carries testosterone into peripheral circulation?

A

bound to ABP in seminiferous tubules–> carried into circulation by SHBG and albumin

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46
Q

What regulates the overall rate of testosterone synthesis?

A

LH

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47
Q

What stimulates the conversion of cholesterol to pregnenolone in Leydig cells?

A

LH

–>increases affinity of P450 for cholesterol

–>stimulates synthesis of P450 enzyme

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48
Q

When does testosterone production begin in fetus?

A

Week 7-8

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49
Q

Where are androgen receptors located?

A

Males: prostate, testis (sertoli, leydig, myoid), epididymis, seminal vesicles

Females: ovary, mammary glands, uterus

Non-repro: CNS, AP, thyroid, skin, liver, etc.

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50
Q

What is the fxn of androgen receptor complex?

A

directs protein synthesis via nuclear receptor

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51
Q

Does testosterone or DHT bind androgen receptors with higher affinity?

A

DHT

52
Q

Deficiency of what enzyme results in ambiguous external genitalia?

A

5a-reductase

–>DHT plays important role in causing changes at puberty

53
Q

What is the most important biological form of testosterone?

A

free testosterone (2% blood)

  • ->68% circulating bound to SHBG
  • -> 38% bound to albumin
54
Q

How is testosterone excreted?

A

urine as 17-ketosteroids

55
Q

Peripheral tissues convert testosterone to what?

A

convert it to estradiol via aromatase

56
Q

Testes convert testosterone to what?

A

convert to DHT via 5a-reductase

57
Q

If testosterone is present in the fetus, what develops?

A

penis, scrotum

58
Q

If there is not testosterone present in the fetus, what develops?

A

clitoris, vagina

59
Q

Fetal actions based on testosterone

A

differentiation of internal male genital tract (epididymis, vas deferens, seminal vesicles)

60
Q

What causes descent of testes into scrotum during last 2-3 months of pregnancy?

A

testosterone

61
Q

What is the term for lack of testes descent?

A

cryptorchidism

62
Q

What are actions of testosterone @ puberty?

A
  • increase muscle mass
  • pubertal growth spurt
  • closure of epiphyseal plates
  • growth of penis and seminal vesicles
  • deepening of voice
  • spermatogenesis
  • libido
63
Q

What is responsible for fetal differentiation of the external male genitalia?

A

DHT

–>penis, scrotum, prostate

64
Q

What action does DHT have in males?

A

male hair distribution
–>male pattern baldness
sebaceous gland activity
growth of prostate

65
Q

What can 5a-reductase inhibitors be used for?

A

treat male pattern baldness and BPH

–>DHT causes male pattern baldness and prostate growth

66
Q

What are anabolic actions of androgens?

A
    • RBC production
    • sebaceous gland secretion
  • controls protein anabolic effects
    • linear body growth and closure of epiphyses
    • ABP synthesis
  • maintains secretions of sex glands
  • regulates behavioral effects (libido)
67
Q

Are concentrations of DHT in protatic tissue higher in men with BPH?

A

NO

68
Q

What are classic signs and sx of BPH?

A

urinary frequency, urgency, nocturia

–>difficulty initiating or maintaining a stream

–>dribbling and feeling of postvoid fullness in bladder

69
Q

What men develop BPH?

A

older men

–>80% by age 80

70
Q

What stimulates Sertoli cells to produce inhibin, ABP, aromatase and protein synthesis?

A

testosterone and FSH

71
Q

What does inhibin do?

A

inhibits FSH release

72
Q

What provides local testosterone supply to developing spermatogonia?

A

binding of testosterone to ABP in lumen of seminiferous tubules

73
Q

What cell produces antimullerian hormone?

A

sertoli cells

74
Q

Where does spermatogenesis occur?

A

along seminiferous tubules

75
Q

What distinct populations of cells line the seminiferous tubules?

A
  • spermatogenic cells
  • –>develop into spermatozoa
  • Sertoli cells
  • ->supportive and nutrient fxn
76
Q

How long does spermatogenesis take?

A

64 days

–>staggered to allow maturation in stages every 16 days

77
Q

What are the 3 stages of spermatogenesis?

A

1: mitotic divisions
2: meiotic divisions
3: spermiogenesis

78
Q

What line the basement membrane of seminiferous tubules?

A

spermatogonia

–>end product of mitotic division

79
Q

Describe pathway from primary spermatocyte to spermatozoa

A 
-Primary spermatocyte (diploid)
   complete Meiosis 1
-Secondary spermatocyte (haploid)
    complete Meiosis 2
-Spermatids
    spermiogenesis
-Spermatozoa
80
Q

Why do spermatids undergo spermiogenesis?

A

to mature into spermatozoa

–>ends in testis with release from sertoli cells

81
Q

What is the proliferative phase at puberty that results in primary spermatocytes?

A

mitotic division

–>stem cells divide to produce daughter spermatogonia–> primary spermatocytes

82
Q

What occurs in meiosis of spermatogenesis?

A
  • primary spermatocytes undergo 2 meiotic divisions
    1: produces 2 secondary spermatocytes (haploid duplicated)
    2: spermatocytes produce 2 spermatids (haploid unduplicated)
83
Q

As spermatids mature to spermatozoa, what destroys the residual body?

A

Sertoli cells phagocytize

84
Q

What is secreted by anterior pituitary and stimulates Leydig cells to secrete testosterone?

A

LH

85
Q

What is secreted by anterior pituitary and stimulates Sertoli cells to nurse and form sperm?

A

FSH

86
Q

Spermiogenesis won’t occur without what stimulation?

A

FSH

spermiogenesis=maturation

87
Q

What hormone is necessary for controlling background metabolic fxn of testes?

A

growth hormone

88
Q

Lack of what hormone causes deficient or absent spermatogenesis–>infertilitly?

A

growth hormone

89
Q

What hormone promotes early division of sperm?

A

growth hormone

90
Q

What is essential for growth and division of testicular germinal cells (beginning of sperm formation)?

A

testosterone

91
Q

What might be essential for spermatogenesis and is formed by testosterone when + by FSH?

A

estrogens

92
Q

What role do FSH and LH play in the stimulation of spermatogenesis?

A

FSH + primary spermatocyte

LH–> Leydig cell–> testosterone–> secondary spermatocyte

93
Q

What effect does administration of exogenous testosterone have on spermatogenesis?

A

insufficient spermatogenesis d/t LH at lower than nml levels

–>androgens exert greater negative feedback on HPT axis

94
Q

Where do sperm spend a month in for maturation after release from testis?

A

epididymis

–>increase motility

95
Q

Where does decapacitation occur?

A

epididymis

–>prevents acrosomal reaction before contact with egg

96
Q

Where can mature sperm be stored for several months?

A

epididymis

97
Q

How do prostaglandins from seminal vesicles aid in fertilization?

A
  • makes cervical mucus less thick so sperm can more easily

- causes reverse peristaltic contractions in uterus and tubes so sperm can move toward ovaries

98
Q

What is the final pH of semen?

A

7.5 to neutralize acidity

99
Q

What is maximal live span of ejaculated sperm?

A

24-48 hrs @ rt

–>2-6ml of 20-200 million sperm

100
Q

What is the pathway of sperm from testis to penis?

A

efferent ductules of testis–> epididymis–> vas deferens–> ejaculatory duct–> prostatic urethra–> membranous urethra–> penile urethra

101
Q

What are the 2 main difference between the male and female repro tracts?

A

1: males have continuous lumen from seminiferous tubules to end of male tract (tip of penile urethra)
2: male tract connects to the distal urinary tract (male urethra)

102
Q

Describe blood flow to the penis during the flaccid state

A

blood flow minimal d/t vasoconstriction of vasculature

103
Q

What are the 3 erectile bodies of the penis?

A

2 corpora cavernosa, 1 corpus spongiosum

–>anastomosing network of vascular spaces and loose CT

104
Q

What do parasymp neurons innervating SM of penis release during erection?

A

NO

–>increases cGMP–> decreases intracellular Ca2+ so vasculature relaxes–> flow of blood into penis for engorgement and erection

105
Q

How is venous drainage reduced during erection?

A

engorged tissue d/t vasodilation presses veins against noncompliant outer fascia

106
Q

What does somatic stimulation do during erection?

A

increases contraction of muscles at base of penis to further promote erection

107
Q

What neuro control is the movement of semen under?

A

sympathetic

–>closes internal sphincter of bladder to prevent retrograde flow via contraction of vas deferens SM

108
Q

What is destroyed in a prostatectomy that results in retrograde ejaculation?

A

internal sphincter of bladder

109
Q

What causes ejaculation of sperm?

A

rhythmic contraction of bulbospongiosus and ischiocavernous muscles that surround base of penis

–>innervated by somatic motor nerves

110
Q

What occurs during capacitation?

A

uterine and fallopian tubes wash away inhibitory factors

loss of cholesterol @ head of acrosome makes it weaker

membrane of sperm more permeable to calcium–>increases motility

111
Q

What is the fxn of hyaluronidase in the acrosome of sperm?

A

depolymerizes polymers that hold ovarian granulosa cells together

–>digest proteins in structural elements of tissue cells that adhere to ovum

112
Q

What does testosterone deficiency in the 2-3 month of gestation lead to?

A

ambiguity in male genitalia

–>male pseudohermaphrodism

113
Q

What does testosterone deficiency in the 3rd trimester of pregnancy lead to?

A

cryptorchidism, micropenis

114
Q

What does testosterone deficiency in puberty lead to?

A

poor secondary sexual development, overall eunuchoid features

–>persistence of prepubertal characteristics (typical of opposite sex)

115
Q

What does testosterone deficiency post-puberty lead to?

A

decreased libido, erectile dysfunction, decreased facial and body hair growth, low energy, infertility

116
Q

What occurs when GnRH neurons fail to migrate into the hypothalamus during embryo development?

A

Kallman’s syndrome

117
Q

What is characterized by delayed or absent puberty and impaired sense of smell?

A

Kallman’s syndrome

–>form of hypogonadotropic hypogonadism

m>f

118
Q

What is Klinefelter syndrome

A

seminiferous tubular dysgenesis (extra X)

–>phenotypically male because of Y chromosome

@ puberty, failure to induce normal testicular growth and spermatogenesis

low androgen production–> primary hypogonadism

infertility d/t destroying of seminiferous tubules

119
Q

How to classify primary hypogonadism?

A

decreased testosterone

increased LH

120
Q

What are the testosterone/LH levels in Klinefelter’s syndrome?

A

decreased testosterone

increased LH

121
Q

What are the testosterone/LH levels in Kallmann’s syndrome?

A
  • decreased GnRH
  • decreased or nml LH
  • decreased testosterone
122
Q

What can androgen receptor antagonist be used to treat?

A

prostate cancer

123
Q

What do tumors of testis produce large amounts of?

A

testosterone

124
Q

What do germinal epithelial tumors produce?

A

don’t produce any hormones

125
Q

What happens to androgen production, LH and FSH levels as men age?

A

gonadal sensitivity to LH decreases
androgen production drops

FSH>LH

126
Q

What does hyperprolactinemia suppress?

A

FSH and LH secretion

GIGU (37 decks)

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