Male Reproductive Physiology Flashcards by Kolbie Chancellor

Describe the Gonadotropin secretion over the lifetime

Fetus: small increase
Childhood: Low and constant
Puberty: Starts to increase
Adult life: PULSATILE
Old age: slow increase

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How is puberty initiated by GnRH?

GnRH is secreted in a pulsatile manner

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Pulsatile secretion of GnRH drives the pulsatile secretion of?

FSH and LH

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What do FSH and LH stimulate secretions of?

Steroid sex hormones - Testosterone and Estradiol

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Increased levels of steroid sex hormones (Testosterone and Estradiol) result in the appearance of what at puberty?

Secondary sex characteristics at puberty

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_______ secretion rate of GnRH is necessary for reproductive function and puberty

Pulsatile

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If a constant GnRH analogue is administered, what occurs?

NO puberty or reproductive function will be initiated!

– must be pulsatile

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Main function of the Testes?

Spermatogenesis

Testosterone secretion

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Why is the scrotum a lower temperature?

It is necessary for spermatogenesis within the testes

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Where are sperm matured and stored?

Epididymis

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The vas deferens ____ can also serve as a sperm storage site

Ampulla

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Adult testis are ______ seminiferous tubules and _____ CT with leydig cells

80%

20%

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Main function of the sertoli cells

Provide nutrients to differentiating sperm and create the blood-testis barrier

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Main function of leydig cells

Synthesis and secretion of testosterone

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3 main androgens secreted from testes?

Testosterone (main one)
DHT
Androstenedione

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Where is the majority of Testosterone converted to DHT?

Peripheral tissues

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What enzyme in the testes can convert Androstenedione to Testosterone?

17beta - hydroxysteroid dehydrogenase

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What enzyme in testes and in peripheral tissues can convert Testosterone to DHT (dihydrotestosterone)?

5alpha - reductase

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DHT binds to the androgen receptor in target tissues with a _____ affinity than testosterone?

Higher

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What can the circulating testosterone be bound to in the blood?

Free
Albumin
SHBG (sex hormone binding globulin)

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What binds to circulating testosterone in the blood the majority of the time?

SHBG

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The most biologically important form of testosterone is bound to?

Nothing - free

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DHT is important for what changes associated with puberty?

External male genitalia

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If there is a 5alpha - reductase deficiency, what can become ambiguous?

External male genitalia due to low levels of DHT

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What are the 2 sources for male estrogen?

Sertoli cells in seminiferous tubules | Adipose tissue

Estrogen can potentially have a role in what for males?

Spermatogenesis because sperm cells express an estrogen receptor

______ forms 80% of all male estrogen

Adipose tissue

Testosterone is converted to Estradiol with what enzyme?

Aromatase (CYP19)

Rate limiting step in testosterone synthesis?

Cholesterol --> Pregnenolone using the Desmolase enzyme

What is the main steriodogenic cell in the testes and why?

Leydig cells because they can synthesize and store cholesterol (precursor for testosterone)

What hormone acts on leydig cells to control their rate of testosterone synthesis?

3 main actions of DHT

1. External male genitalia formation 2. Male hair distribution and its loss 3. Prostate growth

Potential treatment for male pattern hair loss?

5alpha-reductase inhibitors to stop the formation of excess DHT

Benign Prostatic Hyperplasia (BPH)

Excessive urination, difficulty urinating, urinary urgency and dribbling - majority of males over 80 have this

Describe DHT levels in males with BPH

NOT HIGHER than a regular male - normal levels

What may men with BPH have more of?

DHT receptors which will cause a larger enlargement of the prostate that compresses the prostatic urethra

LH binds to what cell?

Leydig cell

From the leydig cell, where can testosterone go?

Circulation or Sertoli cell (seminiferous tubule)

FSH binds to what cell?

Sertoli cell

What 3 products (besides mature sperm) can sertoli cells produce in response to FSH?

1. Aromatase (testosterone --> estradiol) 2. ABP (androgen binding protein, binds testosterone in the lumen of the sertoli cells) 3. Inhibin (inhibits more FSH release)

What intracellular pathway is activated with LH or FSH bind to either leydig cells or sertoli cells?

cAMP - protein kinase A pathway

ABP action

Androgen binding protein - Binds testosterone in the lumen of the seminiferous tubule to provide local testosterone source for developing spermatogonia

Aromatase action

Testosterone converted to estradiol

Inhibin action

Inhibits more FSH release from the anterior pituitary

3 phases of spermatogenesis?

1. Mitotic phase 2. Meiotic phase 3. Spermiogenesis

Mitosis takes spermatogonia to?

Type A and Type B spermatogonia each with 2N DNA

Meiosis 1 takes Type B spermatogonia (2N) to?

``` Primary spermatocytes (4N) and then to Secondary spermatocytes (2N) ```

Meiosis 2 takes secondary spermatocytes (2N) to?

4 spermatids (1N)

Spermiogenesis takes spermatids to?

Spermatozoa

Where in the mature sperm is there mitochondria?

Middle piece

Residual body of the sperm is phagocytized by?

Sertoli cells

What is necessary for early division of sperm and without it, spermatogenesis will not occur?

Growth hormone

Sertoli cells need ____ to form sperm

FSH

Leydig cells need _____ to form testosterone

What steroid hormones are essential for spermatogenesis?

Testosterone (leydig) and Estrogen (sertoli)

What does exogenous administration of androgens cause?

(-) feedback on pituitary to release less LH/FSH which DECREASES spermatogenesis

Job of seminal vesicals

Secrete nutrients, fructose and prostaglandins for sperm

What do prostaglandins do from the seminal vesical?

- make female mucous less thick so sperm can travel | - reverse peristaltic contractions in the female to move sperm from the uterus to the uterine tubes

Job of prostate gland

Secrete alkaline fluid to help neutralize acidic environment of vagina

Semen is composed of sperm and fluid from?

Vas deferens Seminal vesicals Prostate gland Bulbourethral glands

What is the final pH of semen?

7.5

Less than _____ sperm = infertile

20 million

During flaccid state, blood flow to erectile tissue is?

Minimal

What is the main innervation during erection?

Parasympathetics

During erection, parasympathetic nerves cause the helicine arteries to release?

NO - nitric oxide

Helicine arteries supply?

Cavernous spaces

Once the helicine arteries release NO, what happens?

Guanylyl cyclase Increased cGMP Decreased calcium = Relaxation of smooth muscle in the helicine arteries and blood can flow into cavernous spaces

Emission

Movement of semen from epididymis, vas deferens, seminal vesicals and prostate gland to ejaculatory duct

During emission, what is the main innervation?

Sympathetic

During emission, sympathetic control causes what 2 things?

1. Peristaltic contractions of vas deferens | 2. Closure of internal sphincter of bladder

Why is it important to close the internal sphincter of bladder during emission and with what surgery can the internal sphincter of the bladder be damaged?

To prevent retrograde ejaculation into the bladder | - Prostatectomy can damage this sphincter and cause retrograde ejaculation into the bladder

Ejaculation

Propulsion of semen out of male urethra

Contractions of what muscles cause ejaculation?

Bulbospongiosus | Ischiocavernosus

Ambiguity of external genitalia - testosterone age deficiency?

Early gestation

Inadequate testicular descent - testosterone age deficiency?

Late gestation

Poor secondary sexual development - testosterone age deficiency?

Puberty

Decreased libido, Decreased hair growth, and erectile dysfunction - testosterone age deficiency

Post-puberty

Kallman's syndrome

GnRH neurons fail to migrate to hypothalamus during development

Symptoms of Kallman's syndrome

Delayed or absent puberty and altered sense of smell

Klinefelter syndrome

47, XXY | - Phenotypically male but at puberty failure to induce normal testicular growth and spermatogenesis

Primary hypogonadism

Decreased testosterone | - klinefelter

Secondary hypogonadism

Decreased testosterone | Decreased LH/FSH

Tertiary hypogonadism

Decreased testosterone Decreased LH/FSH Decreased GnRH - Kallman

Hyperprolactinemia inhibits?

FSH and LH secretion

Andropause

Gonadal sensitivity to LH and FSH decreases as you age which causes increased levels of LH and FSH and less androgen production

Male Reproductive Physiology Flashcards

(85 cards)