Reproductive System
Male
Chapter 24
Function
• Gonads (testes and ovaries) – produce
gametes (sperm and oocytes).
• Gonads secrete hormones that regulate
formation of sex cells and maintain gender
specific sex characteristics.
• Glands, external genitalia, and ducts are
used in transporting and storing gametes.
• Uterus supports the life of developing
offspring until birth.
Scrotum – sac that hangs from the root of the penis and consists of
loose skin and superficial fascia. It supports the paired tests
Dartos muscle – (smooth muscle), found in the vertical septum that divides the
scrotum and continues into the subcutaneous tissue up to the abdominal wall.
Dartos muscle – acts to regulate the temperature of the scrotum by contracting to
wrinkle the scrotal skin which reduces the surface area available for heat loss.
Temperature regulation is important for optimal spermatogenesis.
Dartos muscle – Production and survival of sperm is dependent on a 3°C lower temp.
than body temp.
Cremaster muscle – covers the testes. Also aids in raising and lowering the
testes. Continuous with the internal obliques.
Testes – paired oval glands (4cm long, 3cm dia. on avg.). Each
covered by a tough fibrous capsule.
Develop in abdomen of fetus and descend about month 7.
Seminiferous tubules – thin dividers of C.T. divide the testes into about 250
lobules, each containing 1-3 coiled tubules (70 cm).
Tubules contain specialized stratified epithelium and spermatogenic cells.
Interstitial cells (Leydig cells) – cells that are in spaces between seminiferous
tubules. Responsible for secretion of testosterone.
Testosterone is the most important androgen (stimulating male characteristic
development) or male sex hormone.
Cells undergo a reduction and
maturation in a process called
spermatogenesis.
Cells ultimately released into
lumen of seminiferous tubule.
Approx. 300 million sperm are
produced each day.
Development cycle of sperm is
approximately 60-75 days.
Male Hormone Development
1. hypothalamus secretes gonadotropin
releasing hormone (GRH)
2. stimulates pituitary to release leutenizing
hormone (LH) and follicle stimulating
hormone (FSH).
3. LH triggers leydig cells to produce testosterone
4. FSH stimulates spermatogenesis
5. Testosterone converted to dihydrotestosterone
(DHT) in some tissues, a potent androgen.
hypothalamus
GRH
pituitary
Androgen functions:
LH
FSH
1. stimulates male repro. organs before birth
2. further development, enlargement of male
sex organs, and secondary masculine
characteristics.
leydig
Cell
T
sertoli
cell
3. aids in spermatogenesis and libido.
4. promotes aggressiveness and increase
BMR.
tissues
spermatogenesis
Epididymis – posterior border of testes. Storage of mature sperm occurs here
up to one month.
Vas deferens (ductus deferens) – widening of epididymis duct.
Vas deferens It ascends the medial side of
each teste, penetrates the
inginual canal, enters the
pelvic cavity, loops over the
ureter, and posterior to the
bladder, where it joins the
ejaculatory duct located in the
prostate gland.
Seminal vesicle – A structure in the male that is about 5 centimeters (2 inches) long
and is located behind the bladder and above the prostate gland. The seminal vesicles
contribute fluid to the ejaculate.
Fluid makes up about 60% of semen volume and contains acid neutralizers, sugars,
coagulating enzyme and prostaglandans.
Ejaculatory duct – formed by the union of the vas deferens and seminal vesicles.
Prostate Gland – Inferior to bladder and surrounds urethra.
Contributes about 25% of semen volume which contains proteolytic enzymes and
citrate.
Bulbourethral glands (Cowper’s gland) – paired glands inferior to prostate. Opens
into spongy urethra.
During sexual arousal it adds lubricant (mucous) to urethra.
Penis – cylindrical organ that transports
urine and semen to the external
environment.
Body of penis contains 3 cylindrical
masses, each contains erectile tissue
permeated by blood sinuses.
Distal end of corpora cavernosa is
enlarged into the structure glans penis,
which contains sensory nerve endings
associated w/ sexual pleasure.
Covering of the glans in an uncircumcised
penis is the prepuce (foreskin).
Corpus spongiosum – single, smaller
cylindrical mass that contains the spongy
urethra.
Vasectomy - a surgical procedure
designed to make a man sterile by
cutting or blocking both the right
and left vas deferens, the tubes
through which sperm pass into the
ejaculate.
Castration: Removal of the sex
glands, usually used to indicate
removal of the male testicles.
Removes effects of testosterone.