Seminiferous tubules,
Epididymis,
Interstitial cells
The testes are paired organs wrapped in a tough
connective tissue sheath called the tunica albuginea. They are
surrounded by the scrotal sac, which keeps the testes on the
exterior of the body cavity, where the temperature is somewhat
cooler. The testes are the site of spermatozoa production and
this process must occur at about 35 degrees C. The scrotal sac
is lined with a layer of muscle called the dartos muscle. It is
composed of smooth muscle fibers that contract when the testes
are cold, thus bringing them closer to the body. When the
environment around the testes is warm, the dartos muscles relax
and the testes descend from the body, thus becoming cooler.
Extensions of the tunica albuginea enter the
testis, dividing it into a number of lobes, each of which houses
one to four highly coiled seminiferous tubules, the
sperm-forming factories. The seminiferous tubules of each lobe
converge to empty the sperm into the epididymis, located on the
exterior aspect of the testis. Lying between the seminiferous
tubules and softly padded with connective tissue are the interstitial
cells, which produce testosterone, the hormonal product of
the testis.
Observe a slide of the testes in cross section (Figure
10.4).
Numerous tubules are seen in cross section. These are the
seminiferous tubules. The gametes or spermatozoa are produced in
seminiferous tubules in the testis.
Find the clusters of cells that frequently
appear as triangles in between the tubules. These are called
interstitial cells. They produce the male sex hormone,
testosterone. Examine the seminiferous tubules under high
magnification. You should be able to see the outer row of cells
called the spermatogonia. These cells reproduce by mitosis to
produce primary spermatocytes. The primary spermatocytes undergo
meiosis, or reduction division, to eventually produce the sex
cells. The primary spermatocytes divide to form secondary
spermatocytes which are found closer to the lumen. The secondary
spermatocytes become spermatids. Spermatids lose their remaining
cytoplasm and mature into spermatozoa. Sertoli cells assist in
the movement of the primary spermatocytes.
