MALE REPRODUCTIVE SYSTEM

Functions:

1. Produce and maintain sperm2. Transport sperm to the female

reproductive tract3. Secrete male hormones

Testes• Primary sex organs• Located in the scrotum• Contain interstitial cells that make

hormones• Contains spermatogenic cells

(cells that make sperm)

Testes

• 1 to 2 months before birth the testes descend from kidney area into the scrotum (triggered by release of testosterone)

• If testes do not descend, they fail to produce sperm due to high abdominal temp (called cryptorchidism)

Epididymis

• Tightly coiled thread-like tube about 6 meters long

• Support the sperm as they mature

Vas Deferens

• Conveys sperm from testes to ejaculatory duct

• This is the tube that is cut when

men have a vasectomy

Seminal Vesicle

• Secretes alkaline fluid that has nutrients and prostaglandins which stimulate muscle contraction in the female to move the sperm to the egg

• Adds liquid volume to seminal fluid about 60% of volume.

Prostate gland

• Surrounds beginning of the urethra and secretes a thin, milky fluid which is alkaline (neutralizes acidic build up of waste from sperm and environment of vagina)

• enhances motility of sperm

Prostate enlargement

• Gland is small in boys and grows to adult size 2 years into puberty

• Gland quits growing until age 50 when it begins to grow again

• In about ½ of men it grows until it presses on the urethra

Prostate enlargement

• Pressure causes a frequent need to urinate b/c bladder doesn’t empty completely

• Risk factors for enlargement include: fatty diet or vasectomy

• Diagnostic tests include rectal exam, PSA levels

Bulbourethral Glands

• Fluid is released in response to sexual stimulation to lubricate the end of the penis for intercourse

Penis

• Conveys urine and semen outside of the body

Semen• Consists of sperm and secretions from

the seminal vesicles, prostate gland, and bulbourethral glands

• Slightly basic (7.5)• 2-6 milliliters are released with 120

million sperm/milliliter• 240 – 720 million

Hormones in the male

• The hypothalamus secretes GnRH (gonadotropin releasing hormone) – targets the pituitary – stimulates pituitary to release FSH and LH.

Hormones in the male• Pituitary secretes 2 male sex

hormones – LH and FSH• LH ( lutenizing hormone) –

promotes the development of the interstitial cells that secrete male sex hormones

• FSH ( follicle-stimulating hormone) – along with testosterone it stimulates spermatogenesis

Male sex hormones

Testosterone

• most abundant androgen (male sex hormone)

• Secretion begins during fetal development, then ceases during childhood

• Between the ages of 13-15 the production of testosterone increases tremendously (puberty) as signaled by the pituitary gland

Functions of testosterone

• In the fetus it stimulates the development of the male reproductive organs and causes the testes to descend into the scrotum

• During puberty it causes the enlargement of the testes and the development of the secondary sex characteristics in males

Male secondary sex characteristics

• Increased growth of body hair• Thickening of the vocal cords which

causes the voice to deepen• Increased muscle growth, broadening

of shoulders, and narrowing of waist

Spermatogenesis

• During embryonic development, hormones stimulate spermatogonia (sperm stem cells) to undergo mitosis

• Some of the resulting cells become primary spermatocytes (46 X) and some become supporting cells (help sustain developing sperm cells)

Spermatogenesis (cont)

• At puberty, each primary spermatocyte undergoes meiosis to make two secondary spermatocytes (23 X)

• Each sec. spermatocyte divides to create 2 spermatids (23 X) which mature into sperm cells

• Each primary cell that undergoes meiosis will make 4 sperm cells.