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Reproduction . Male Reproductive Physiology . The major organ involved in maintaining male reproductive function is the testis. A normal functioning testicle is required for 1)the production of mature sperm 2)and the synthesis of the major male reproductive hormone testosterone. .

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Reproduction

Reproduction


Reproduction

Male Reproductive Physiology

The major organ involved in maintaining male reproductive function is the testis. A normal functioning testicle is required for

1)the production of mature sperm

2)and the synthesis of the major male reproductive hormone testosterone.


Reproduction

The Male Reproductive System

Physiological functions of major components-


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Section of human testis.

Seminiferous epithelium

* Blood–Testis Barrier

* Spermatogenesis


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Interaction between the Sertoli and

Leydigcells.


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Hypothalamic-pituitary-gonadal axis in the male

Hypothalamus

GnRH

Anterior Pituitary

LH and FSH

Testes

Testosterone


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Gonadotropin Releasing Hormone (GnRH)

  • 10 AA peptide

  • Released in median eminence of hypothalamus

  • Secreted for a few minutes every 1-3 hours

    • Pulsatile (frequency and amplitude)


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And Others

Negative feedback

Stress

Sleep/wake cycle

Hormones

Temperature

Hypothalamus

GnRH RELEASE

Change in amplitude

Change in frequency


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Gonadotroph

GnRH

Vesicles containing LH/FSH

Also  LH and FSH synthesis

PKC

IP3 & DAG

Release of LH/FSH via exocytosis

Ca2+


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Leydig Cell

LH

Increased testosterone production

cAMP

Via PKA

cholesterol

DNA transcription

testosterone


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Sertoli Cell

FSH

cAMP

Via PKA

Inhibin

Aromatase

ABP

Growth Factors

DNA transcription


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At the target tissues

*Synthesis

Testosterone

*Release

*in the bloodstream

Dihydrotestosterone

(5 alpha reductase)

Modulation of gene expression

proteins


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Physiological Action of Testosterone and Associated Androgens.

An androgen is a substance that stimulates the growth of the male reproductive tract and development of secondary sex characteristics. It is important to realize that androgens affect most other tissues as well.


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Penis and scrotum

hCG

Accessory Organs

Testosterone

Testicular descent

Female suppression

Fetal testes


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Reproductive

Organs

Spermatogenesis

Testosterone

(Adult)

Long bone fusion

Secondary

Sexual

Characteristics

Sex Drive


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Body Hair and

Baldness

Deep voice

Secondary

Sexual

Characteristics

Acne

Protein formation

Muscle

development

Bone size and

strength


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Hypothalamus

Some testosterone converted into estrogens

GnRH

Anterior Pituitary

FSH

LH

Leydig

cell

Sertoli Cell

Testosterone

Inhibin


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Formation of the Ejaculate and the Role of the Accessory Organs

As the sperm passes through the epididymus it matures (due to dihydrotestosterone), and becomes more concentrated (fluid reabsorption).

The sperm is then stored in the epididymus and vas deferens waiting for ejaculation.

Sperm can remain viable here for up to 60 days as nutrition is supplied and inhibitory factors decrease their energy use.

On ejaculation the sperm (and fluid) passes through the vas deferens, ejaculatory ducts and finally through the urethra. During this passage the fluid content is increased due to secretions from the accessory organs


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Epididymus

vas deferens

10%

Sperm

storage

Seminal vesicles

Sperm, fructose, prostaglandins, clotting precursors

60%

Prostate gland

30%

+ alkalization, semen clotters

And unclotters


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The male sex act

•The male must have an erection and ejaculate in order to complete the sex act.

PSYCHOLOGICAL

AND/OR PHYSICAL

STIMULI

Parasympathetic

Activity

Sympathetic

Activity

Via NO and/or ACh

Vasodilation

Erection


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Ejaculation

  • Emission

    • Genital duct / accessory organ contraction (sympathetic stimulation)

    • Vas deferens, prostate, seminal vesicles

    • Mix with mucus in urethra producing semen

  • Expulsion

    • Semen expelled by rhythmic skeletal muscle contraction at base of penis


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Hypogonadism

  • Non-functional testes in fetus

    • Lead to development of female sex organs

  • Loss of testes pre-puberty

    • Maintain infantile sex organs and characteristics

    • Bones less strong but longer

    • Maybe taller than other men


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(cont)

  • Loss of testes post-puberty

    • Slight decrease in size of sexual organs

    • Slight increase in voice pitch

    • Loss of bone and protein build up

    • Slight loss of sexual desire

    • Less easy for erection

    • Ejaculation rarely occurs


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Infertility

  • Sperm count

    • Should have ~ 120 million sperm / ml of semen

    • If below 20 million / ml are said to be infertile

  • Sperm morphology and motility

    • Abnormal shape of sperm

    • Lack of motility

Impotence

This is the inability to produce or maintain an erection. In most cases it is due to problems with blood flow.


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An 8 year old boy visited his pediatrician, and his mother reported that he was in good health until about two weeks ago. He describes that his initial symptoms include a mild bifrontalheadache, which has become progressively worse. During the last few days, he developed nausea and bouts of occasional projectile vomiting accompanying the headaches. Furthermore, he recently noticed that he has tremendous difficulty when walking down the stairs from his bedroom to the kitchen and reported difficulties in

sleeping. No family history of abnormal development or mental retardation exists. He has two perfectly healthy younger brothers.

General Examination:

This 8 year boy presents with pronounced pubic hair growth, a low pitched voice, enlarged genitalia, and acne on his forehead. Cardiac and respiratory examinations were unremarkable.

Neurological Examination:

Patient is alert and oriented x 3. No receptive or expressive aphasias were noted. Pupillary light reflex was intact bilaterally. Both the left and right optic discs appeared more pale than normal. Downward gaze (while the eyes were adducted) was impaired bilaterally.


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