Page 67 - 86 human physiology part-2

Chapter 15

body temperature. Temperature has to be lower than normal in order for spermatogenis (sperm
production) to take place.

A male can become sterile when testes have been exposed too often to high temperatures, such as
when frequently in a hot tub.

The two muscles that regulate the temperature of the testes are the dartos and cremaster muscles:

• Dartos Muscle

The dartos muscle is a layer of smooth muscle fibers in the subcutaneous tissue of the scrotum
(surrounding the scrotum). This muscle is responsible for wrinkling up the scrotum, in conditions of
cold weather, in order to maintain the correct temperature for spermatogenisis.

• Cremaster Muscle

The cremaster muscle is a thin strand of skeletal muscle associated with the testes and spermatic
cord. This muscle is a continuation of the internal oblique muscle of the abdominal wall, from which it
is derived. It is responsible for raising or lowering the testes to keep them at the correct temperature.
Because it is skeletal muscle, it can also be contracted voluntarily. Some males, such as athletes, have
the ability to consciously raise their scrotum up, to protect themselves against injury, while playing
sports. However, not all males have this ability.

Seminiferous Tubules

Each testis contains over 100 yards of tightly packed seminiferous tubules. Around 90% of the
weight of each testes consists of seminiferous tubules. The seminiferous tubules are the functional units
of the testis, where spermatogenisis takes place. Once the sperm are produced, they moved from the
seminiferous tubules into the rete testis for further maturation.

Interstitial Cells (Cells of Leydig)

In between the seminiferous tubules within the testes, are instititial cells, or, Cells of Leydig. They
are responsible for secreting the male sex hormones (i.e., testosterone).

Sertoli Cells

A Sertoli cell (a kind of sustentacular cell) is a 'nurse' cell of the testes which is part of a
seminiferous tubule.

It is activated by follicle-stimulating hormone, and has FSH-receptor on its membranes.

Its main function is to nurture the developing sperm cells through the stages of spermatogenesis.
Because of this, it has also been called the "mother cell." It provides both secretory and structural
support.

The junctions of Sertoli cells form the blood-testis barrier, a structure that partitions the interstitial
blood compartment of the testis from the adluminal compartment of the seminiferous tubules. Sertoli
cells control the entry and exit of nutrients, hormones and other chemicals into the tubules of the testis

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