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SFIV Test 3 > Male Reproductive System I > Flashcards

Male Reproductive System I Flashcards

1
Q

What are the major functions of the adult testes and where do they occur?

A

Spermatogenesis - seminiferous tubules

Steroid hormone synthesis - Leydig cells

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2
Q

Where is the majority of estradiol in males made?

A

Made in adipose tissue from testosterone

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3
Q

How is testosterone transported in the blood?

A

40-60% bound to sex hormone-binding globulin

Bound to albumin

2-3% free

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4
Q

What is bioavailable testosterone?

A

Both free and albumin-bound

Albumin-bound testosterone readily dissociates

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5
Q

What pathway is activated in Leydig cells to activated steroidogenesis via what hormone?

A

LH activates a G-protein coupled receptor

cAMP signaling pathway

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6
Q

What is the function of 5a-reductase and what is a clinical use for inhibitors of this enzyme?

A

Converts testosterone to dihydrostestosterone

5a-reductase inhibitors are useful in treating benign prostatic hyperplasia and prostate cancer

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7
Q

What is the action of aromatase?

A

Metabolizes testosterone to estradiol

Occurs in certain CNS nuclei, Leydig and Sertolie cells, and adipose tissue

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8
Q

What are excretory metabolites?

A

Biologically inactive forms of testosterone

Occurs primarily in the liver

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9
Q

What is the reason for the rise in testosterone production at puberty?

A

Rise in plasma LH concentrations

LH promotes androgen biosynthesis in Leydig cells

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10
Q

Describe the plasma testosterone profile during the male lifespan

A

Childhood - testosterone relatively low

Adolescent - increase in production during puberty

Older adult - age related decline at 4th or 5th decade

Age-related increase in SHBG also contributes to decrease in bioavailability

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11
Q

What is the mechanism of action for androgen hormones?

A

Receptor is a ligand-activated transcription factor

Binds testosterone and DHT, but has higher affinity for DHT

Does NOT bind to DNA until the hormone is bound

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12
Q

What are the actions of androgens in the fetus?

A

Promote differentiation of the male reproductive tract and external genitals

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13
Q

What are the actions of androgens at puberty?

A

Growth and maturation of reproductive structures

Development of male secondary sexual characteristics

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14
Q

What are specific androgen actions?

A

Growth of hair and sebaceous glands

Enlargement of larynx and thickening of vocal cords

Behavioral effects

Erythropoietin

Promote bone growth and formation (conversion to estradiol)

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15
Q

What is the blood-testis barrier?

A

Tight junctions between adjacent Sertoli cells that limits the exchange of material between interstitial fluid and the lumen of the seminiferous tubules

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16
Q

What substances do Sertoli cells secrete?

A

Androgen Binding Protein

Estradiol

Glycoproteins (AMH, Inhibins, Activins)

17
Q

What is androgen binding protein and its function?

A

Secreted into the seminiferous tubules

Serve to keep testosterone levels elevated

Sertoli cell function can be assessed by measuring ABP production

18
Q

What is Anti-mullerian hormone?

A

Secreted by Sertoli cells, promotes the regression of mullerian ducts in male embryo

19
Q

What is Inhibin B?

A

Principal circulating inhibin in males

Plays important role in feedback regulation of FSH secretion

20
Q

What is the feedback loop involving FSH and inhibin B?

A

FSH and testosterone stimulate inhibin B production

Inhibin B feeds back to the pituitary where it blocks GnRH-stimulated FSH release

21
Q

What is the function of estradiol in sertoli cells?

A

Formed by the aromatization of androgens in response to FSH stimulation

22
Q

What is spermatogenesis?

A

Process that produces a continuous supply of functional germ cells in males

Begins at puberty

Requires functional sertoli cells and intact HPG axis

23
Q

What is the role of GnRH in spermatogenesis?

A

Delivery of GnRH in a pulsatile fashion is essential for appropriate FSH and LH

24
Q

What are the actions of FSH on Sertoli cells?

A

Promotes proiferation and differentiation

Maintains function

Promotes proliferation and development of spermatogonia

Stimulates release of ABP and Inhibin

25
Q

What pathway does FSH activate in Sertoli cells?

A

G-protein/cAMP pathway

26
Q

What is the role of LH in spermatogenesis?

A

LH is required

Indirect effects via stimulation of testosterone from Leydig cells

27
Q

How does testosterone act as a local regulator of spermatogenesis?

A

Activates genes in Sertoli cells

Works synergistically with FSH

28
Q

What is decapacitation?

A

While in the epididymis, spermatozoa are coated with substances that block the acrosomal reaction

SFIV Test 3 (14 decks)

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