Page 790 - Atlas of Histology with Functional Correlations

SECTION 1 Testis

The male reproductive system consists of a pair of testes, numerous excurrent

ducts, and accessory glands that produce secretions that are added to sperm to
form semen. The testis (plural, testes) contains spermatogenic stem cells that
continuously divide to produce new generations of cells that form spermatozoa,
or sperm. From the testes, the sperm move through excurrent ducts to the
epididymis for storage and maturation. During sexual excitation and ejaculation,

sperm leave the epididymis via the ductus (vas) deferens and exit the
reproductive system through the penile urethra.

The accessory glands—prostate gland, seminal vesicles, and bulbourethral
glands—of the male reproductive system are discussed and illustrated in detail in

Section 2.

SCROTUM

The testes are located outside the body cavity in the scrotum where the
temperature of the testes is about 2°C to 3°C lower than the normal body
temperature. This lower temperature is necessary for the normal functioning of

the testes and spermatogenesis, or sperm production. In addition to the external
location, perspiration and evaporation of sweat from the scrotal surface maintain
the testes in a cooler environment. However, this lower temperature is not
essential for hormone production by the testes.

Maintaining lower testicular temperature is also due to the arrangement of
blood vessels that supply the testes. Testicular arteries that descend into the
scrotum are surrounded by a plexus of veins that ascend from the testes and form
the pampiniform plexus. Blood returning from the testes in the pampiniform
plexus is cooler than the blood flowing in the arteries toward the testes. This

countercurrent heat-exchange mechanism cools the arterial blood before it
enters the testes and maintains a lower temperature in the testes.

TESTES

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