MALE REPRODUCTIVE PHYSIOLOGY

Dr. Amel Eassawi

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OBJECTIVES Describe the physiological functions of the major

components of the male reproductive system.  Explain how the secretions of FSH and LH are

regulated in the male and describe the actions of these hormones.

Describe spermatogenesis and the role of Sertoli cells, Leydig cells. 

Explain the hormonal control of spermatogenesis and describe the effects of androgens on the male accessory sex organs. 

Discuss the mechanisms of erection and ejaculation. Discuss the various factors that affect male fertility.

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MALE REPRODICTION SYSTEM

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MALE REPRODUCTIVE SYSTEM

Primary Sex Organs: Testes

Functional Compartments:A. Seminiferous Tubules :

Exocrine Function (spermatogenesis)

B. Interstitial Tissue: Endocrine Function: Leydig cells (interstitial cells). Androgen Secretion (mainly testerone)

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TESTICULAR MORPHOLOGY

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Male Reproductive SYSTEM

Testosterone – Steroid hormone.– Synthesized from the cholesterol precursor in

the Leydig cells and also from the androstenedione secreted by the adrenal cortex.

– Testosterone secretion rate is 4-9mg/dL in normal adults and very small amount is secreted in women.

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TESTOSTERONE BASED ACTIVITIES

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TESTOSTERONE IN MALES

Effect of Testosterone

1. Effects before Birth1. Masculinizes the reproductive

tract and external genitalia.2. Promotes descent of the testes

into the scrotum

2. Effects on Sex-Specific Tissues after Birth

Puberty

Adulthood

1. Enlargement and maturation of gonads.

2. Development of secondary sexual characteristics.

3. Essential for spermatogenesis.4. Growth and maturation of the

reproductive tract.5. Maintains the reproductive tract

throughout adulthood

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TESTOSTERONE IN MALES

Effect of Testosterone

3. Other Reproduction-Related Effects

1. Develops the sex drive at pubert.2. Controls gonadotropin hormone

secretion by negative feedback

4. Effects on Secondary Sexual Characteristics

1. Induces the male pattern of hair growth (e.g., beard).

2. A deep voice because of thickening of the vocal folds.

3. Thick skin.4. Promotes muscle growth

responsible for the male body configuration.( as a result of protein-anabolic affect)

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TESTOSTERONE IN MALES

Effect of Testosterone5. Non reproductive Actions 1. Exerts a protein anabolic

(synthesis) effect.2. Promotes bone growth at puberty3. Closes the epiphyseal plates

after being converted to estrogen by aromatase.

4. Stimulates oil secretion by sebaceous glands (results in development of acne).

5. May induce aggressive behavior

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ESTROGEN IN MALES

Small amount produce by adrenal cortex

A portion of the testosterone secreted by the testes is converted to estrogen outside the testes by the enzyme aromatase, which is widely distributed but most abundant in adipose tissue

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SPERMATOGENESIS

1. Complex process by which diploid primordial germ cells (spermatogonia) are converted into motile haploid spermatozoa (sperm).2. It takes 64 days for development of mature sperm from spermatogonium (several hundred million sperm may reach maturity daily)

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SPERMATOGENESIS

Spermatogenesis: Spermatids to Sperm

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SPERMATOGENESIS

Spermatozoa:Consists of four parts• Head

• Consists primarily of the nucleus (contains DNA)

• Acrosome• containing hydrolytic enzymes that

allow the sperm to penetrate and enter the egg

• Midpiece• Area where mitochondria are

concentrated • Tail

• Provides mobility for spermatozoa

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FUNCTIONS OF SERTOLI CELLS

1. Form blood-testes barrier.2. Provide nourishment and phagocytic function.3. Secrete seminiferous tubule fluid which flushes

released sperm from tubule into epididymis.4. Secrete androgen-binding protein.5. Site of action for testosterone & FSH to control

spermatogenesis6. Release inhibin, acts in negative-feedback

fashion to regulate FSH secretion7. Released mullerian inhibiting factor ( fetal

development).

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TESTICULAR CELL INTERACTIONS

• Sertoli cell products estradiol, inhibin, activin and other proteins modulate leydig cell activity

• Sertoli cell products modulate germ cell function

• Leydig cell testosterone modulate peritubular & Sertoli cell function

• Peritubular cell products influence Sertoli cell activity

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LOCATION AND FUNCTIONS OF THE COMPONENTS OF THE MALE REPRODUCTIVE SYSTEM

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MALE SEXUAL PERFORMANCE

Erection

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MALE SEXUAL PERFORMANCE

Mechanism of Penile Erection– Relaxation of trabecular smooth muscle leading to

increased blood flow into cavernosal sinousoids– Engorged corpora cavernosa presses venules

against tunica albuginea restricting venous outflow.

Regulation of penile erection (smooth muscle tone)– Proerectile factors: parasympathetic input,

intracellular Ca+2, PGE1, NO, smooth muscle sensitivity to Ca+2

– Antierection factors: sympathetic input intracellular Ca+2, NE, smooth muscle sensitivity to Ca+2

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MALE SEXUAL PERFORMANCE

Components of the Male Sex Act1. Erection Hardening of the

normally flaccid penis to permit its entry into the vagina

Parasympathetic induced vasodilatation of the penile artioles and mechanical compression of the veins.

2. EjaculationA. Emission phase

B. Expulsion phase

Emptying of semen into urethra.

Forceful expulsion of semen from penis.

Sympathetic induced contraction of the smooth muscles of the walls ducts and accessory sex glands.Motor neuron induced contraction of the skeletal muscles at the base of the penis.

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HUMAN SEXUAL RESPONSE CYCLE PHASES

Phases include excitement, plateau, orgasm and resolutionThe resolution time for men is longer resulting in an increased

refractory period to further stimulation

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MALE SEXUAL PERFORMANCE

Erectile dysfunction or Impotence:

Failure to achieve or maintain an erection suitable for sexual intercourse. Affect 50% of men between 40 and 70 years old. May be due to:

1. Psychological factors.2. Physical factors.

A. Nerve damageB. Medication that interfere with autonomic function C. Problem with blood flow to the penis.

Sildenafil (Vigra): prescribed to treat erectile dysfunction. It does not produce an erection but it amplifies and prolongs an erectile response triggered by usual means of stimulation.

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GYNECOMASTIADefined as presence of any palpable breast tissue in men.

Due to increase in estrogen-androgen ratio.

Three classes physiological, pathological and idiopathic.

Three time period(Birth, Puberty, Old Age).

Pysiological

The breast enlargement of newborns, the transient gynecomastia of adolescence and breast development of aging men, which cannot be associated with a pathological condition are considered to be physiological.

Pathological

1. Hypogonadism (Klinefelters).

2. Chronic liver diseases (cirrhosis, hepatitis).

3. Thyrotoxicosis.

4. Neoplasia.

5. Drugs (estrogen, testosterone)

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ABNORMALITIES OF TESTICULAR FUNCTION

1. Cryptorchidism:

descent of testes is incomplete, testes remain in the abdomen. Occurs in neonatal life.

1. Bilateral: Impaired Testosterone secretion and spermatogenesis.

2. Unilateral :Normal Testosterone and impaired spermatogenesis.

2. Male hypogonadism:

Clinical picture depends on whether testicular deficiency develops before or after puberty.

causes:– Testicular disease (Hypergonadotrophic Hypogonadism)– Disorder of hypothalamus or pituitary (Hypergonadotrophic

Hypogonadism)

3. Androgen secreting tumors :

Leydig cell tumors (a rare condition) leads to precocious pseudopuberty in prepubertal boys.

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REFERENCES

Human physiology, Lauralee Sherwood, seventh edition.

Text book physiology by Guyton &Hall,11th edition.

Text book of physiology by Linda .s Contanzo, third edition.

Physiology by Berne and Levy, sixth edition.