Male Reproductive anatomy and physiology�

Self reading

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Objectives

On completion of this part, the student will be able to:

• Define each vocabulary and term listed
• Identify the male reproductive organs
• Explain the menstrual and ovarian cycles
• List the functions of the male hormone testosterone

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Male reproductive system

External structure

1. Scrotum
2. Testes
3. penis

Internal structure

1. Epididymis
2. Vas deferens (ductus deferens)
3. Seminal vesicles
4. Ejaculatory ducts
5. Prostate gland
6. Bulbouretheral gland
7. Urethera

Scrotum

• Rugated, skin-covered, muscular pouch

Function

1. To support the testes
2. Help regulate the temperature of sperm

Testes

• Two ovoid glands (feel firm, smooth), 2-3 cm wide, lie in the scrotum
• Descend into the scrotal sac by 34^th-38^th wks gestation
• Encased by protective white fibrous capsule
• Composed of number of lobules
• Lobules: contain
• Interstitial cells ( Leydig’s cells): produce testosterone hormone
• Seminiferous tubule: produce spermatozoa (need lower temperature than the body 1F°)

Penis

• Composed of 3 cylindrical masses of erectile tissue (2 corpus cavernosa, 1 corpus spongiosum)
• Urethra passes through these layers
• Blood supply: penile and branch of pudendal arteries
• Stimulates by parasympathetic nerve innervation

Glans: bulging, sensitive ridge tissue at the distal end

Prepuce: a retractable casing of skin protect the glans

Internal structure�Epididymis

• A tightly coiled narrow tube, 20ft long
• Sperm: took 12-20 days to travel the epididymis and they are immature and not mobile
• 5 % of the semen

Function:

1. Conducting sperm from the testis to the vas deferens
2. Store some sperm
3. Produce alkaline fluid that surrounds sperm

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Vas deferens (Ductus deferens)

• Hollow tube surrounded by arteries and veins and protected by a thick fibrous tissue (spermatic cord)
• Sperm mature in vas deferens but not mobile

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• Function:
• Carries sperm through the inguinal canal to the seminal vesicles and ejaculatory ducts

Seminal vesicles

• 2 convoluted poutches
• Located lower, posterior to bladder
• Empty into the urethera
• Sperm become motile by the secretion of it
• 30% of the semen

Function:

1. Secrete a viscous portion of the semen (alkaline, and has a high content of sugar, protein, prostaglandins)

Ejaculatory ducts

• 2 ducts pass through the prostate gland and join the seminal vesicles to the urethra

Prostate gland

• Chestnut size gland that lies below the bladder
• Urethra passes through the centre of it
• 60% of the semen

Function:

1. Secrets a thin alkaline fluid that help sperm mobility

Bulbourethral (Cowper’s) glands

• Lie beside the prostate gland
• Empty into the urethra
• 5% of the semen

Funcion:

Secretes alkaline fluid to decrease the acidity of the urethra

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Urethra

• Hollow tube
• Passing from the bladder through the prostate gland to the glans of the penis
• 18-20 cm long
• Lined with mucous membrane

The sperm

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• Each sperm cell has three parts: a head, middle piece, and tail.
• An acrosome at the head tip produces enzymes that help penetrate the female ovum (egg). The middle piece contains mitochondria, structures that provide energy for the sperm.
• The mitochondria are tightly spiraled around the flagellum (tail), which moves the sperm toward the ovum.
• An ejaculation (ejection of sperm from the penis) has 300 to 500 million sperm.

Role of testosterone at puberty

In male:

1. Further development of the external and internal reproductive structure
2. Appearance of pubic, axillary, and facial hair
3. Laryngeal enlargement
4. Maturation of spermatozoa
5. Closure of growth of long bones

In female:

1. Influence enlargement of the labia majora, clitoris
2. Formation of axillary and pubic hair