b. Scrotum.
(1) Description/information. The scrotum is a two-layered sac that looks like
an outpouching of the abdomen. This sac encloses the testes and the lower part of the
spermatic cords. Externally, the scrotum looks as though it is divided into two portions
by a ridge (the raphe). Internally, the scrotum is divided into two sacs by a septum,
each sac containing a single testis. There are smooth muscles in the walls of the
scrotum.
(2) Temperature regulation inside the scrotum. The smooth muscles in the
scrotum walls regulate the temperature in the testes where sperm are produced and
stored. These smooth muscles contract when it is cold, bringing the testes closer to the
warmth of the body. When it is hot, these same muscles relax, moving the testes away
from the body to be cooler. For sperm to be produced and survive, the temperature in
the testes must be lower than the temperature of the body. Since the scrotum is outside
the body, its internal temperature can be kept lower than the internal temperature of the
body. The temperature inside the scrotum is about 3F below body temperature.
1-8.
INTERNAL ORGANS
a. Testes. The testes are the primary organs of reproduction in the male. The
male testes correspond to the female ovaries.
(1) Description/information. The testes are located in the scrotum. They
are oval structures enclosed in a fibrous capsule. The testes are covered by a dense
layer of white fibrous tissue called the tunica albuginea. This tissue layer extends
inward and divides each testis into a series of internal compartments called lobules.
Each of the 200 to 300 lobules contains one to three tightly coiled tubules called the
seminiferous tubules.
(2) Functions. The seminiferous tubules produce sperm by a process called
spermatogenesis. As well as producing sperm, the testes produce the male hormone
testosterone. Interstitial cells within the testes produce this hormone, which is essential
for the development of the male secondary sex characteristics. If testosterone is not
produced in a male body, growth of hair on the face and body, deepening of the voice,
and an increase in skeletal mass do not occur. Also, sperm will not develop without
testosterone.
(3) Sperm. The seminiferous tubules produce sperm by a process called
spermatogenesis. Sperm can be defined as the reproductive cells of the male. Each
seminiferous tubule is packed with sperm in various stages of development. Beginning
at about puberty, a male produces about 300 million sperm cells each day. As a male
grows older, the production of sperm decreases. Males continue to produce sperm
throughout life.
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