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Male Physiology Flashcards

1
Q

What are the key hormones secreted by the hypothalamus, anterior pituitary, and Leydig and Sertoli cells of the testes?

A

GnRH, LH, FSH, testosterone, inhibin

These hormones play crucial roles in male reproductive development and function.

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2
Q

Describe the general structure of testosterone.

A

Testosterone is a steroid hormone synthesized from cholesterol, with a specific configuration of four fused carbon rings.

Testosterone is essential for male secondary sexual characteristics and reproductive functions.

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3
Q

What is spermatogenesis?

A

The process in which spermatozoa are produced from male primordial germ cells via mitosis and meiosis.

Includes stages such as spermatocytogenesis and spermiogenesis.

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4
Q

Differentiate the mechanisms that produce erection, ejaculation, and erectile dysfunction.

A

Erection involves vascular changes, ejaculation is a reflex action, and erectile dysfunction is the inability to achieve or maintain an erection.

Each mechanism is regulated by different physiological processes.

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5
Q

What are the major elements of the male anatomy?

A
  • Testes
  • Epididymis
  • Vas deferens
  • Seminal vesicles
  • Prostate
  • Bulbourethral glands
  • Urethra
  • Penis

These structures are essential for reproduction and hormone secretion.

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6
Q

What is the Pampiniform plexus?

A

A network of veins in the male spermatic cord that helps regulate temperature in the testes.

It acts as a heat exchanger, cooling arterial blood before it reaches the testes.

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7
Q

What are the three stages of spermatogenesis?

A
  • Spermatocytogenesis
  • Meiosis
  • Spermiogenesis

Each stage has distinct processes leading to the formation of mature spermatozoa.

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8
Q

What does the Hypothalamic-Pituitary Axis control?

A

Production of gametes and sex steroid biosynthesis.

It is the central regulator of the male reproductive system.

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9
Q

How is GnRH produced and what is its function?

A

GnRH is produced by hypothalamic neurons and stimulates the anterior pituitary to release LH and FSH.

It is secreted in a pulsatile manner to regulate gonadotropin release.

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10
Q

What is the role of Leydig cells in the male reproductive system?

A

Leydig cells produce testosterone in response to LH stimulation.

They are crucial for testosterone synthesis and the maintenance of male reproductive functions.

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11
Q

What do Sertoli cells secrete?

A
  • Anti-müllerian hormone (AMH)
  • Androgen-binding protein (ABP)
  • Estradiol
  • Inhibin

These secretions support sperm development and regulate hormonal feedback.

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12
Q

What is the feedback mechanism of testosterone and inhibin?

A

Testosterone inhibits GnRH and LH secretion; inhibin inhibits FSH secretion.

This feedback controls the levels of hormones in the reproductive axis.

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13
Q

What is the significance of dihydrotestosterone (DHT)?

A

DHT is more potent than testosterone and is crucial for the masculinization of external genitalia and prostate development.

It has biological activities that are 30-50 times higher than testosterone.

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14
Q

Fill in the blank: The principal target of LH in the male reproductive system is the ______.

A

Leydig cells

These cells are responsible for testosterone secretion.

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15
Q

True or False: FSH and LH are co-secreted in equimolar amounts.

A

False

They are segregated into different secretory granules for independent regulation.

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16
Q

What is Dihydrotestosterone (DHT)?

A

A more potent hormone with biological activity 30-50X higher than testosterone

DHT is primarily produced in extra-testicular tissue and has similar activities to testosterone.

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17
Q

What are the functions of DHT?

A

Required for masculinization of external genitalia and changes associated with puberty, including:
* Differentiation and growth of penis, scrotum, and prostate (early)
* Prostate growth, balding, sebaceous gland activity (late)

DHT plays a crucial role in both prenatal and postnatal development.

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18
Q

What is Androstenedione?

A

A precursor for testosterone and a weak androgen receptor agonist

It can be converted back to testosterone and is involved in extra-glandular estrogen formation.

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19
Q

What significant legislation was passed regarding Androstenedione?

A

The Anabolic Steroid Control Act of 2004 reclassified it as a Schedule III controlled substance

It is banned by the NCAA.

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20
Q

What is Dehydroepiandrosterone (DHEA)?

A

A precursor for testosterone and a weak androgen receptor agonist, sourced from the adrenal gland

All DHEA in male plasma originates from the adrenals.

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21
Q

What is the primary binding protein for testosterone in circulation?

A

Sex hormone-binding globulin (SHBG)

Approximately 45% of testosterone is bound to SHBG.

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22
Q

What percentage of testosterone in circulation is free (unbound)?

A

2% free

The majority of testosterone is bound to proteins in circulation.

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23
Q

What is the role of the androgen receptor (AR)?

A

A high-affinity ligand-activated transcription factor that interacts with protein coactivators and binds to androgen response elements in nuclear DNA

The androgen-AR complex functions as a transcription factor.

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24
Q

What factors determine the quantity of testosterone entering a cell?

A

Plasma concentration and intracellular milieu of enzymes and binding proteins

These factors influence whether testosterone binds to AR or is converted to DHT.

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25
What metabolic fate does most urinary testosterone undergo?
Unchanged urinary testosterone accounts for approximately 2% of daily production ## Footnote The rest undergoes various metabolic pathways.
26
Which enzymes are involved in the conversion of testosterone?
17β-hydroxysteroid dehydrogenase and 3β-hydroxysteroid dehydrogenase ## Footnote These enzymes play roles in the synthesis and degradation of androgens.
27
What are the mechanisms discussed regarding erectile function?
Mechanisms of synthesis and degradation of androgens, and mechanisms that produce erection and ejaculation ## Footnote Pathophysiological mechanisms underlying erectile dysfunction were also discussed.
28
when does spermatoCYTOgenesis occur?
at puberty
29
describe the process of spermatocytogenesis.
spermatogonia undergo mitotic division to produce spermatocytes
30
describe the Meiotic stage of sperm maturation.
the diploid spermatocytes divide into haploid spermatids
31
describe the process of spermatogenesis.
maturation of the spermatids into mature spermatozoa
32
what kind of receptors do GnRH molecules attach to?
Gq
33
T or F: pulsatile secretion desensitizes the gonadotropes to GnRH.
false pulsatile stimulates constant exposure will desensitize
34
What AP hormones does GnRH preferentially target at high and low frequency pulses
higher frequency: LH secretion 1 pul/hr lower frequency: FSH secretion- 1 pul/3 hr.
35
where in the brain is the pulse generator for GnRH located?
arcuate nucleus of the medial basal hypothalamus
36
what NTs stimulate GnRH pulse frequency?
kisspeptin and glutamate GABA inhibits
37
LH and FSH receptors are what kind?
Gs
38
what is the role of ABP secretion?
keeps local testosterone levels high
39
estradiol is secreted via what enzymes?
P-450 aromatases
40
T or F: Inhibin is a member of the TGFbeta superfamily.
true
41
Inhibin inhibits the release of what HPA hormone?
FSH-AP only
42
T or F: high testosterone will decrease LH and FSH secretion.
true
43
T or F: testosterone is stored in Sertoli cells.
false it is produced and stored in leydig cells
44
once testosterone enters the sertoli cell, what different things can it be used for
metabolized by aromatase to produce estradiol OR binds to an ABP for lumenal storage to mediate spermatogenesis
45
what is estradiol used for in leydig cells?
production of enzymes required for cholesterol conversion to testosterone
46
what effects does testosterone have on skin
enhances sebaceous gland secretion and skin thickening
47
what is the ideal ratio of intratesticular to circulating testosterone for optimal spermatogenesis
IT > Cir.
48
what are the physiologic consequences of abusing steroids for their anabolic effects?
decreased IT > Cir. ratio is sufficient to inhibit LH but not sufficient enough for normal spermatogenesis also, excess testosterones gets converted to estrogen in several different tissues throughout the body
49
what enzyme produces DHT?
5-alpha reductase
50
Compare and contrast the different roles Type I and Type 2 SER play in male maturity?
Type 1: not expressed until puberty drives secondary sexual characteristics especially the skin changes Type 2: liver hair follicles genital skin male UG tract
51
androstenedione is a precursor for what?
extra-glandular estrogen formation
52
T or F: DHEA can be sold OTC.
true
53
what is the primary endogenous source for DHEA production?
adrenal glands
54
what happens to testosterone once it binds to its target cell?
it is either converted to DHT or used to stimulate certain cellular metabolic pathways
55
T or F: ARs also serve as transcription factors to activate gene expression of their target proteins
true
56
What are the key hormones secreted by Leydig cells?
Testosterone ## Footnote Leydig cells primarily secrete testosterone, which plays a crucial role in male reproductive development and function.
57
What hormone is secreted by Sertoli cells?
Inhibin ## Footnote Sertoli cells secrete inhibin, which helps regulate spermatogenesis.
58
What are the main steps involved in spermatogenesis?
1. Mitotic divisions of spermatogonia 2. Meiotic divisions of spermatocytes to spermatids 3. Maturation to spermatozoa
59
Differentiate between spermatogenesis and spermiogenesis.
Spermatogenesis: Formation of sperm cells Spermiogenesis: Maturation of spermatids into spermatozoa
60
What regulates testosterone secretion?
Hypothalamic-pituitary axis ## Footnote The regulation involves GnRH, LH, and FSH.
61
Describe the general structure of testosterone.
Testosterone is a steroid hormone ## Footnote It has a four-ring carbon structure typical of steroid hormones.
62
What is the role of hCG in male fetal development?
Stimulates testosterone synthesis by the testes ## Footnote hCG acts as an LH receptor agonist.
63
What is the function of Müllerian Inhibiting Substance?
Stimulates regression of paramesonephric ducts ## Footnote Secreted by Sertoli cells in male fetuses.
64
What happens during adrenarche?
Increased production of adrenal androgens ## Footnote Occurs during the prepubertal period.
65
What is gonadarche?
Physical and functional maturation of the gonads ## Footnote Induced by production of FSH and LH.
66
What changes occur in males during puberty?
Enlargement of testes, penis, scrotum, voice deepening, and increased hair growth
67
What is the primary function of the seminal vesicles?
Produce fluid containing fructose, prostaglandins, and fibrinogen ## Footnote They contribute about 70% of semen volume.
68
What are the contributions to seminal fluid from different glands?
Seminal vesicles: 70% Prostate gland: 25% Bulbourethral glands: 5%
69
What is the approximate pH of semen?
7.5 (range 7.0 – 8.0) ## Footnote This pH helps maintain sperm viability.
70
How long can sperm remain viable in the female reproductive tract?
1-3 days ## Footnote Most sperm die within 12 hours.
71
What is capacitation?
Conversion of non-fertile to fertile sperm ## Footnote It occurs after ejaculation in the female reproductive tract.
72
What role do Sertoli cells play in spermatogenesis?
Support and nourish developing sperm cells ## Footnote They also secrete inhibin to regulate spermatogenesis.
73
What is the function of the prostate gland?
Secretes fluid that nourishes and protects sperm Ca citric acid plasminogen/pro-fibronolysin ## Footnote It contributes about 30% to the total volume of semen.
74
What is the function of the bulbourethral (Cowper's) gland?
Secretes pre-ejaculatory fluid ## Footnote Helps lubricate the urethra during ejaculation.
75
List the three stages of spermatogenesis.
* Mitotic divisions of spermatogonia * Meiotic divisions of spermatocytes to spermatids * Maturation to spermatozoa
76
What is the average concentration of sperm in semen?
120 million/ml ## Footnote Normal range is 35-200 million/ml.
77
What physiological changes occur in sperm during spermiogenesis?
Cyto­plasmic reduction, chromatin condensation, nuclear elongation ## Footnote These changes prepare sperm for fertilization.
78
True or False: Sperm are motile when they leave the epididymis.
False ## Footnote Sperm become motile after maturation in the female reproductive tract.
79
What is capacitation?
Conversion of non-fertile to fertile sperm ## Footnote Sperm is made competent to fertilize an ovum
80
Where does capacitation occur?
After ejaculation in the female reproductive tract
81
What changes occur during capacitation?
Changes in or removal of components of the outer acrosome
82
How long does capacitation require in the female tract?
1 to 10 hours
83
What is the effect of capacitation on sperm motility?
Inactivation of inhibitor proteins blocking motility
84
What happens to the head of sperm during capacitation?
Becomes more permeable to Ca +2
85
What is the result of increased motility of the flagellum?
Capacitated sperm
86
What are the motor pathways involved in the control of erection?
3 motor & 1 afferent sensory pathway
87
Which neurons are primarily involved in the sympathetic control of erection?
Sympathetic neurons (T1-T12, L1-L3)
88
What is the role of parasympathetic neurons in erection?
Primarily under parasympathetic control, relax smooth muscles
89
What neurotransmitter is involved in the erection process?
Acetylcholine (Ach)
90
What is the function of nitric oxide (NO) in erection?
Released by nonadrenergic-noncholinergic neurons
91
What does emission refer to in male sexual function?
Movement of the ejaculate into the prostatic or proximal part of the urethra
92
What phase is emission primarily under?
Sympathetic control
93
What prevents retrograde ejaculation?
Contraction of the internal urethral sphincter
94
What is ejaculation?
Forceful expulsion of semen from the urethra
95
What triggers the desire for expulsion during ejaculation?
Fluid in internal urethra
96
What muscles are involved in the expulsion of semen?
Ischiocavernosus and bulbocavernosus skeletal muscles
97
What is the cognitive correlation of ejaculation in males?
Orgasm
98
List the phases of the male sexual response.
* Orgasm * Excitement * Plateau * Resolution * Refractory Period
99
What is erectile dysfunction?
Inability to attain or maintain erection sufficiently firm for satisfactory sexual performance
100
What is the prevalence of erectile dysfunction in men < 40 years?
5%
101
What is the prevalence of erectile dysfunction in men 75-80 years?
55-75%
102
What are physiological causes of erectile dysfunction?
* Impedance of blood entering and being retained in the penis * Failure of internal urethral sphincter to constrict (retrograde ejaculation)
103
What are psychological causes of erectile dysfunction?
Erection or penetration fails due to thoughts or feelings
104
What are some risk factors for erectile dysfunction?
* Vascular Disease * Diabetes * Cigarette smoking * Hypercholesterolemia * Age
105
What types of medications can contribute to erectile dysfunction?
* Antihypertensive drugs * Antidepressant, antipsychotic & anticonvulsant drugs * H2 receptor blocking drugs * Oral hypolipidemic drugs
106
What endocrine abnormalities can lead to erectile dysfunction?
* Hypogonadotropic hypogonadism * Hyper/hypothyroidism * Hyperprolactinemia
107
What types of physical and psychological pathology are associated with erectile dysfunction?
* Pelvic/spinal chord injury
108
What was discussed regarding the male reproductive system in the lecture summary?
* Basic anatomical organization * Hormonal regulation * Mechanisms of erection & ejaculation * Pathophysiological mechanisms of erectile dysfunction
109
hCG serves as a what?
LH receptor agonist both hcG and LH stimulate the synthesis of testosterone during fetal development
110
what are the primary target cells for FSH?
sertoli cells
111
T or F: during puberty the sertoli cells become more sensitive to FSH.
false sertoli cells become more dependent on testosterone production coming from the leydig cells
112
T or F: FSH indirectly increases the # of leydig cells during development
true
113
What physiologic changes occur during adenarche (6-8 yrs. old) for both sexes?
increased production of DHEA & androstenedione by the adrenal cortex
114
T or F: absence of adrenarche does not prevent gonadarche or the attainment of reproductive competence.
true
115
The increased levels of adrenal androgens induces what during adenarche?
induce pubarche or growth of pubic hair
116
List the clinical manifestations of the early phases of gonadarche (11-13 yrs. old).
pubarche enlargement of testis, penis, and scrotum voice deepens
117
list the clinical manifestations of the middle phase of gonadarche (14-16yrs. old)
first ejaculation height spurt adult pubic and axillary hair growth enlargement of the sebaceous glands
118
At what age does the facial and body hair start to develop?
17-19 yrs. old
119
What do the daughter cells of the Type A spermatogonia do during spermatogenesis?
both complete the mitotic phase- 1 gets recycled back into a spermatogonium- the other goes on to the meiotic phases to become a mature spermatid
120
describe the process of spermiogenesis.
transformation of spermatids into spermatozoa occurs in the epididymis undergo-cytoplasmic reduction, chromatin condensation, nuclear elongation, and differentiation of the body and tail pieces
121
what does the acrosome/head of the spermatozoa contain?
protolytic enzymes
122
what part of the spermatozoa is rich in mitochondria?
the body of the tail
123
1 primary spermatocyte produces how many spermatozoa?
4: 2 XX & 2 XY
124
what important roles does the epididymis play?
acidification of luminal fluid capacitation reservoir for sperm phagocytosis of aging sperm cells
125
fibrinogen comes from what accessory gland?
the seminal vesicle
126
what is the primary function of fibrinogen?
forms fibrin which creates a weak coagulum hat holds sperm in the vagina
127
sperm are viable in the female repro. tract for how long?
1-3 days but most are gone after 12 hrs.
128
Why is the acidic environment of the vagina important for sperm viability?
vaginal secretions will mix w/ semen to provide an optimal pH for sperm viability at 6-6.5
129
where are the preganglionic nerve fibers for the sympathetics located?
synapse in celiac, mesenteric plexus, hypogastric & pelvic ganglia
130
where do the preganglionic parasympathetic nerve fibers synapse?
pelvic plexus
131
what nerve contains the postganglionic nerve fibers for both para & sympathetics?
cavernous nerve
132
what nerve holds the afferent sensory neurons?
pudendal nerve
133
where are the somatic motor nerve fibers located?
sacral spine
134
what muscles relax during erection?
the corpora cavernosa and corpus spongiosum
135
What types of receptors are involved in the Acetylcholine mediated process of erection?
M3 Gq
136
vasorelaxation during erection increases blood flow to the sinusoids leading to the collapse of what?
venous return

Reproductive Medicine (17 decks)

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