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Physiology > Male Physiology > Flashcards

Male Physiology Flashcards

1
Q

What are the two metabolic products of testosterone?

A

Dihydrotestosterone and estradiol

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2
Q

The production of sperm and testosterone in the testes is regulated by what part of the brain?

A

The hypothalamic-pituitary-testicular axis

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3
Q

What does the epididymis connect?

A

Rete testis and vas deferens

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4
Q

What keeps sperm in an inactive state in the epididymis?

A

The cells of the epididymis secrete H+ to acidify the luminal fluid, which keeps sperm in an inactive state

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5
Q

The vas deferens connects what two places?

A

epididymis and the seminal vesicles

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6
Q

What is the enlarged space located at the juncture between the vas deferens and the seminal vesicles, and what is its function?

A

the ampulla Store sperm

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7
Q

What is the path of travel of sperm from the seminiferous tubules to the urethra? (7, starting at and including the seminiferous tubules)

A

Seminiferous tubules Rete testes Epididymis Vas Deferens Ampulla Ejaculatory duct Urethra

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8
Q

Where are aging sperm reabsorbed?

A

Epididymis

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9
Q

Where are sperm stored?

A

Vas deferens

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10
Q

What are the two erectile tissues in the penis?

A

1 x Corpus spongiosum 2x Corpus cavernosum

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11
Q

What part of the male genitalia produces the largest portion of semen?

A

Seminal vesicles (60%)

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12
Q

What is in seminal fluid that provides energy for sperm?

A

Fructose

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13
Q

What is in seminal fluid that causes the cervical environment to be more favorable for sperm survival and promotes peristalsis in the uterus and fallopian tubes?

A

Prostagladins

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14
Q

What is in seminal fluid that causes semen to coagulate after ejaculation? Why is coagulation important?

A

Fibrinogen Aids in holding the semen in deeper regions of the vagina, closer to the cervix

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15
Q

What attaches to sperm and serves to suppress motility of sperm in the coagulated semen?

A

Seminogelin

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16
Q

What is the main function of the prostate?

A

Secretes fluid for semen

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17
Q

Prostatic fluid constitutes approx. what % of the volume of semen?

A

39%

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18
Q

What is the function of prostatic acid phosphatase that the prostate secretes?

A

Unknown

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19
Q

What is the function of profibrinolysin (Plasminogen) that the prostate secretes?

A

dissolves coagulated semen

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20
Q

What is the function of the HCO3 that the prostate secretes?

A

Neutralizes acidic environment of the cervix

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21
Q

What is the function of PSA that the prostate secretes?

A

PSA hydrolyzes seminogelin, which increases sperm motility.

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22
Q

The prostate is an androgen sensitive tissue. Over 90% of testosterone that enters prostatic cells is converted to what? What does this do?

A

dihydrotestosterone (DHT) by 5α-reductase. DHT is the primary regulator of prostatic growth

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23
Q

What is the function of the bulbourethral glands?

A

Secretes mucus into the urethra upon arousal

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24
Q

What is the function of the ampulla?

A

Hold sperm Contracts to propel sperm

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25
Q

What are the three accessory glands of the male reproductive system?

A

Seminal vesicle Prostate Cowper glands

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26
Q

What are the three different portions of the epididymis?

A

Cauda Corpus Caput

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27
Q

In what third of the epididymis are sperm most mature?

A

Cauda

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28
Q

What are the cells in the testes that produce testosterone from cholesterol?

A

Cells of Leydig

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29
Q

Where are the leydig cells located?

A

In the peritubular compartment of the testes

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30
Q

Where are the sertoli cells located?

A

in the intratubular compartment

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31
Q

What are the functions of the sertoli cells? (3)

A

Provide environment for germ cells to develop Stem cell niche Produce and secrete androgen

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32
Q

Is spermatogenesis synchronous or asynchronous?

A

asynchronous

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33
Q

GnRH is secreted in a pulsatile fashion. What controls the frequency of these pulsations?

A

Pulse generator of the Hypothalamus

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34
Q

What are the steps of the hypothalamic-pituitary-gonadal axis?

A
  1. GnRH secreted to pituitary gonadotrophs, which secrete LH and FSH
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35
Q

What is the path of LH production?

A

Sent to Leydig cells, where they increase testosterone synthesis

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36
Q

What is the path of FSH?

A

Go to sertoli cells, to produce ABP

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37
Q

What hormone controls sertoli cell proliferation and seminiferous tubule growth?

A

FSH

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38
Q

Why is it important to have a pulsatile secretion of GnRH?

A

Desensitization of the gonadotroph cells

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39
Q

Once LH is secreted into the circulation, it travels to the testes and binds to what?

A

G protein-coupled receptors on Leydig cells

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40
Q

Activation of LH receptors increases what? What does this lead to?

A

Activation of LH receptors increases intracellular cAMP levels, which leads to an increase in the synthesis of steroidogenic enzymes that control the production of testosterone

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41
Q

Where is the testes are the blood vessels, macrophages, CT etc: the peritubular space, or the intratubular

A

Peritubular

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42
Q

What are the cells that produce the androgen binding protein, and what are they signalled by?

A

Sertoli cell, receive signal via FSH from pituitary gonadotropes

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43
Q

How does LH increase the production of testosterone from the Leydig cells?

A

increasing the expression of cholesterol side chain cleavage enzyme, thereby, increasing conversion of cholesterol into pregnenolone

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44
Q

How does testosterone increase sperm synthesis?

A

diffuses into sertoli cells

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45
Q

What is the feedback mechanism for testosterone?

A

directly inhibits the secretion of both LH and FSH from the pituitary gonadotropes

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46
Q

How does testosterone inhibit the secretion of LH? (2)

A

Can change to DHT and E2, and inhibitsecretion of GnRH and LH from the hypothalamus and pituitary gland, respectively.

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47
Q

How does FSH exert its effects on the sertoli cells?

A

Inducing the synthesis and secretion of androgen binding protein (ABP) by the Sertoli cells

48
Q

How does ABP facilitate spermatogenesis?

A

by concentrating testosterone at the site of spermatogenesis

49
Q

The testosterone concentration is 100-fold greater the area surrounding the developing sperm than in the blood stream. What allows for this wicked increase?

A

Androgen binding protein

50
Q

How do Sertoli cells inhibit the production of FSH?

A

Produce inhibin, which can travel in the blood stream to the anterior pituitary, where it selectively inhibits FSH production.

51
Q

What are the two, broad categories of androgen effects?

A
  1. Androgenic functions 2. Metabolic functions
52
Q

What are the androgenic functions of testosterone?

A

actions on the male reproductive tract and main secondary male sexual characteristics

53
Q

What are the metabolic functions of testosterone?

A

actions on the nonreproductive tissues such as muscle, bone, bone marrow, kidney, and liver

54
Q

What is inhibin produced by, and what does it act on to inhibit FSH secretion?

A

Produced by sertoli cells, and inhibits Pituitary gonadotrops

55
Q

GnRH agonists are used to reduce androgen synthesis in prostate CA. What is the MOA behind this?

A

Causes desensitization in the gonadotrophs in the pituitary,

56
Q

LH binds to what type of G protein on Leydig cells? (Gs, Gi, or Gq)?

A

Gs

57
Q

When testosterone diffuses from the Leydig cells into the sertoli cells, it is acted upon by what enzyme? What does this produce?

A

Aromatase, producing estradiol

58
Q

Draw out the cholesterol synthesis pathway.

A
59
Q

What is the rate limiting step of the testosterone synthesis pathway? (include substrate, enzyme and product)

A

Cholesterol to pregnenolone via cholesterol desmolase

60
Q

LH increases the expression of which enzyme in the testosterone synthesis pathway?

A

Cholesterol desmolase (also called cholesterol desmolase or P450scc)

61
Q

What is the enzyme found in places such as the prostate, that converts testosterone into the more potent hormone dihydroxytestosterone (DHT)?

A

5alpha-reductase

62
Q

What is the enzyme that converts testosterone into estradiol in places like the brain, adipose tissue, testes, and liver?

A

Aromatase

63
Q

What are the two ways in which LH regulates the production of testosterone?

A
  1. Expression of cholesterol desmolase 2. Increases the rate of transport of cholesterol into the mitochondria
64
Q

When do the first two spikes of testosterone occur in a male?

A

fetal, and neofetal

65
Q

What causes testosterone to fluctuate throughout the day?

A

The pulsatile nature of GnRH

66
Q

What are the two major proteins in the blood stream that binds to testosterone?

A

sex hormone binding globulin (SHBG) and albumin (40/60 split)

67
Q

Is testosterone that is bound to albumin available to a cell? How about if bound to SHBG?

A

Available only if bound to albumin, NOT SHBG

68
Q

What are the two factors that decrease the circulating amount of testosterone in the blood as men age?

A

Decreased synthesis Increased SHBG

69
Q

Testosterone freely crosses the cell membrane and into the cell because of its lipophilicity. Once in the cell, what does it do/bind to? Where is this?

A

Binds to androgen receptor in the cytoplasm. This complex can then go into the nucleus, and increase transcription

70
Q

What is the enzyme found in the cytoplasm of cells that converts testosterone to estradiol?

A

p450 aromatase

71
Q

What is the relative binding affinity of DHT for the androgen receptor protein compared to testosterone?

A

DHT have much higher affinity

72
Q

What are the two main androgens produced in the adrenal glands?

A

Androstenedione and DHEA

73
Q

Androstenedione and DHEA are not very potent hormones relative to testosterone, but they can be converted to testosterone in some tissues. What is the enzyme that does this?

A

17beta-OHD

74
Q

What are the three main effects of testosterone?

A
  1. Internal genitalia 2. Increases muscle 3. Erythropoiesis
75
Q

What are the two main effects of DHT?

A

Do stuff to external genitalia Increase hair follicles

76
Q

What is the main effect of estradiol?

A

Bone development

77
Q

What are the two main metabolic effects of testosterone?

A
  1. Increases metabolic rate 2. Inhibits lipid accumulation
78
Q

How are the spermatogonia developed in the male fetus?

A

Primordial germ cells migrate to the basal compartment of the testes and line the seminiferous tubules

79
Q

What is the immunoprivileged site in the testes? What prevents the immune system from entering?

A

between the Sertoli cells–adluminal compartment of the seminiferous tubule Tight junction between sertoli cells

80
Q

What happens to spermatogonia as they migrate up the sides of the Sertoli cells in the space between them, towards the seminiferous tubule?

A

Maturation to spermatocytes

81
Q

What are the maturation stages of spermatogonia to sperm?

A
  1. Spermatogonia 2. Primary spermatocytes 3. Secondary spermatocytes 4. Spermatids
82
Q

What is spermiogenesis?

A

WHen spermatids gain flagella and mature to sperm

83
Q

What is spermiation?

A

Release of spermatids into the seminiferous tubules

84
Q

What are the two main hormones that act to produce sperm?

A
  1. Testosterone 2. FSH
85
Q

What are the two roles that testosterone plays in the development of sperm?

A
  1. Stimulates transcription of genes in sertoli cells 2. Converted to estradiol
86
Q

What are the three roles of FSH in spermatogenesis?

A
  1. Increase ABP 2. Increases aromatase 3. Stimulates growth factors in Sertoli cells
87
Q

Why can anabolic steroid administration reduce spermatogenesis?

A

Feedback to inhibit LH and FSH production **Loss of FSH** despite presence of testosterone

88
Q

What hormone is the main regulator of spermatogenesis?

A

FSH

89
Q

What is the first step of spermiogenesis?

A

Golgi buds off acrosomal vesicle

90
Q

What is the next step in spermatogenesis after the Golgi produces the acrosomal vesicle?

A

Acrosomal vesicle moves to one pole of the elongating nucleus forming the acrosomal cap

91
Q

What is the next step in spermatogenesis after the acrosomal vesicle moves to one pole of the elongating nucleus forming the acrosomal cap?

A

Centrioles migrate to the end of opposite to the cap and form the flagellum.

92
Q

What is the next step in spermatogenesis after the centrioles migrate to the end of opposite to the cap and form the flagellum?

A

Flagellum elongates

93
Q

What is the next step in spermiogenesis after the flagella elongates?

A

Mitochondria migrate to the tail end of the sperm

94
Q

What is the next step in spermiogenesis after the mitochondria migrate to the flagellar end of the sperm?

A

Sertoli cells phagocytose excess cytoplasm

95
Q

What is the function of the blood testes barrier beside immunoprivilege?

A

Maintenance of fluid composition

96
Q

What does hypergonadism lead to?

A

Precocious puberty

97
Q

What are the two tumor causes of hypergonadism?

A

Hypotahalmic or androgen producing tumors

98
Q

What are the two non-tumor causes of Hypergonadism?

A

LH receptor mutations Congenital adrenal hyperplasia

99
Q

What, generally, is hypogonadism?

A

Androgen deficiency

100
Q

What is the cause of primary hypogonadism? Why is there higher levels of FSH and LH?

A

Testicular dysfunction leads to a decrease in testosterone production (hypergonadotropic hypogonadism) Higher levels d/t lack of feedback via testosterone

101
Q

What are the two disease processes discussed in class that lead to primary hypogonadism?

A

Cryptorchidism Klinefelter syndrome (XXY)

102
Q

What is secondary hypogonadism?

A

Decrease in circulating gonadotropins (hypotrophic hypogonadism)

103
Q

hypergonadotropic hypogonadism = ? Hypogonadotropic hypogonadism = ? (primary vs secondary)

A

hypergonadotropic hypogonadism = primary Hypogonadotropic hypogonadism = Secondary

104
Q

What is Kallmann syndrome? MOA?

A

Secondary hypogonadotropic hypogonadism inherited malfunction of GnRH neurons

105
Q

Parasympathetic or sympathetic: male erection?

A

Para

106
Q

Parasympathetic or sympathetic: luberication?

A

Para

107
Q

Parasympathetic or sympathetic: emission?

A

Symp

108
Q

What lubricates the urethra?

A

Bulbourethral glands secrete mucus

109
Q

What happens during the emission stage of male sexual arousal? (3)

A
  1. Ampulla contracts 2. Seminal vesicles contract 3. Bladder sphincter contracts
110
Q

What is the mechanism behind an erection?

A

Vasodilation, sinusoidal spaces fill with blood, and compress veins

111
Q

What causes the vasodilation in an erection? (3 chemicals)

A

Parasympathetic nerve terminals release acetylcholine, nitric oxide (NO), and vasoactive intestinal peptide (VIP).

112
Q

What is the effect of Ach in an erection?

A

Triggers NO release

113
Q

What is the MOA of NO?

A

INduces G protein and cGMP, causing relaxation of smooth muscles of arterioles

114
Q

What terminates an erection?

A

Sympathetic nerve activity which promotes arterial constriction

115
Q

What is the MOA of viagra?

A

Inhibits the phosphodiesterase the degrades cGMP

Physiology (75 decks)

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