Male Reproductive Physiology Flashcards by Tosin Ibrahim

The pulsatile secretion of what hormone initiates puberty?

GnRH

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GnRH drives the pulsatile secretion of what hormones? What are these hormones responsible for?

FSH and LH -secondary sex characteristics

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During the adult reproductive period, is LH or FSH secreted more?

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What is the function of the testes?

1) Spermatogenesis 2) Testosterone secretion

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What is the function of the epididymis?

Primary location for maturation and storage of sperm

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What is the function of the vas deferens?

-Storage for sperm -Secrete rich fluid

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What is the function of the sminal vesicle?

Secretes fluid that aids in the motility of sperm and penetration –> becomes semen -prostaglandins helps semen react with female cervix -helps ejaculated sperm into fallopian tube and uterus

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What is the function of the prostate gland?

Secrete solution that gives the semen an alkaline pH to survive in the acidity in female vagina

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What two type of cells are found in the seminiferous tubules? What are their functions?

Sertoli cells: produce sperm and forms barrier between testes and bloodstream Leydig cells: produce testosterone

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Where are spermatogonia and spermatozoa found?

Spermatogonia (immature sperm): periphery Spermatozoa (mature sperm): lumen of tubule

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What are the androgens secreted by testes

Testosterone (most abundant)

Dihyrotestosterone (DHT)

Androstenedione

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What cells synthesize and secrete Testosterone

Leydig Cells

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In the lumen of the seminiferous tubules, how is testosterone concentrated?

Testosterone is bound to androgen-binding protein (ABP) -ABP secreted by sertoli cells

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What converts androstenedione to testosterone?

17β-hydroxysteroid dehydrogenase

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What is the active form of testosterone in some tissue

Dihydrotestosterone (DHT)

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What converts testosterone to dihydrotestosterone (DHT)?

5α-reductase

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In circulation, what is testosterone bound to?

Sex hormone binding globulin (SHBG)

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What is the first step in testosterone production?

Cholesterol –> Pregnenolone -RATE LIMITING STEP

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Where is estrogen produced in the males & how?

1) Sertoli Cells: Testosterone –> Estradiol via aromatase
2) Larger amounts formed in other tissues of the body, especially adipose tissue

What stimulates the conversion of cholesterol into pregnenolone?

Leutinizing Hormone (LH). Leydig cells has receptor for LH which promotes synthesis in two ways:

Increasing P450scc enzyme (desmolase) affinity for cholesterol
Stimulates synthesis of desmolase

The androgen receptor complex is a ____ receptor.

Nuclear receptor

What is DHT responsible for?

External male genitalia differentiation (penis, scrotum & prostate)
Male hair distribution
Sebaceous gland activity
Growth of prostate

What might happen if there is a deficiency of 5α-reductase?

Lack of dihydrotestosterone (DHT) leading to ambiguous external genitalia

What is cryptorchidism?

Lack of descent of testes due to absence of testosterone

What is testosterone responsible for?

- Increased muscle mass - Pubertal growth spurt - Closure of the epiphyseal plates - Growth of the penis & seminal vesicles - Deepening of the voice - Spermatogenesis - Libido

What is benign prostatic hyperplasia?

Prostate gland enlargement leading to increased urinary frequency, urinary urgency, nocturia, difficulty initiating and maintaining a urinary stream, etc. - Less concentration of DHT in prostatic tissue - Increased DHT receptors on prostate

What stimulates Sertoli cells & what do Sertoli cells do once stimulated?

**FSH** Stimulates Sertoli cells to secretes ABP into seminiferous tubules (increase testosterone concentration)

What inhibits Sertoli cells?

Inhibin which inhibits FSH

Describe the process of spermatogenesis.

**Phase 1 (Mitotic divisions):** Spermatogonium --\> primary spermatocytes (diploid 4N) **Phase 2 (Meiotic divisions):** Primary spermatocyte --\> Secondary spermatocytes (haploid 2N) --\> Spermatids (haploid 1N) **Phase 3 (Spermiogenesis):** Spermatids mature into Spermatozoa

Identify the hormones that stimulate spermatogenesis ## Footnote 1. Stimulates Leydig cells to secrete testosterone 2. Stimulate Sertoli cells to nurse and form sperm 3. Controls background metabolic functions of the testes 4. Essential for growth & division of testicular cells, which is beginning of sperm formation 5. Formed from testosterone by Sertoli cells when they are stimulated by FSH.

1. LH 2. FSH 3. GH 4. Testosterone 5. Estrogen

In the epididymis, how does the sperm mature?

- Becomes more motile - Decapacitation to prevent acrosomal reaction before contact egg - Act as storage site for mature sperm for several months - Will spend a month

What structure secretes a mucoid material containig nutrients as well as prostaglandins & fibrinogen which aid in fertilization

Seminal vesicles

What structure secretes a slightly alkaine thick, milky fluid containing Ca²⁺ and other substances that helps with pH adjustments

Prostate gland

What secretion is composed of fluid & sperm from the vas deferens, seminal vesicles, prostate & bulbouretheral gland that has a pH of 7.5

Semen

What three erectile bodies make up the penis?

2 corpora cavernosa & 1 corpus spongiosum

During an erection, what do the parasympathetic nerves stimulate?

Innervate vascular smooth muscle of helicine arteries --\> NO released --\> relaxation of smooth muscle --\> vasodilation --\> penis is engorged and erect, reducing venous drainage --\> somatic stimulation increases contraction of muscle, further promoting an erection

During an erection, what does the sympathetic control do?

Movement of semen from epididymis to ejaculatory duct & closing internal sphincter of bladder

What causes ejaculation?

Rhythmic contraction of bulbospongiosus and ischiocavernosus muscles at base of penis -innervated by somatic motor nerves

When sperm enters the female tract, what happens to the sperm?

Capacitation of sperm - loss of inhibitory factors - more permeable to calcium, increasing motility

What is male hypogonadism

A condition in which the body doesn't produce enough of the hormone that plays a key role in masculine growth and development during puberty (testosterone) or enough sperm or both

Distinguish between primary and secondary hypogonadism

**Primary:** Decreased T, Increased LH **Secondary:** Decreased T & Decreased or normal LH

What is Kallman's syndrome?

GnRh neurons fail to migrate to the hypothalamus leading to delayed or absent puberty & loss of smell

What is Klinefelter's syndrome (Seminiferous tubular dysgenesis)?

47, XXY genotype * Phenotypically male because of presence of Y chromosome * At puberty, increased gonadotropins fails to induce normal testicular growth & spermatogenesis. * Androgen production is usually low but gonadotropins are elevated, thereby indicating primary hypogonadism. * Seminiferous tubules are largely destroyed, resulting in infertile

What is the effect and classification of male hypogonadism that occurs due to testicular dysfunction. Give an example.

**Example** - Klinefelter's Syndrome **Effect** - Decreased testosterone secretion **Classification** - Primary hypogonadism

What is the effect and classification of male hypogonadism that occurs due to pituitary dysfunction dysfunction. Give an example.

**Cause:** Tumor **Effect:** Decreases LH & FSH secretion **Classification:** Secondary hypogonadism

What is the effect and classification of male hypogonadism that occurs due to hypothalamic dysfunction. Give an example.

Cause: Tumor Effect: Decreases LH & FSH secretion Classification: Secondary hypogonadism

What is hyperprolactinemia

Increased levels of prolactin supresses FSH & secretion