MALE REPRODUCTIVE SYSTEM
Essentials of Histology
Consisting of the Testis, ducts epididymus, genital ducts, accessory glands and penis.
TESTIS
The Testis
develop early in embryonic life on the dorsal wall of the abdominal cavity,
they later descend into the scrotum, that provides an environment a few
degrees lower in temperature (comparing with the abdominal cavity) that
is a necessary condition for spermatogenesis . Besides the production
of sperm, the cells located in the interstice among the seminiferous tubule,
the Leydig cells are responsible for the production of male sex hormone,
testosterone.
Surrounding each Testis is possible
to observe a layer of connective tissue, called Tunica albuginea.
A external layer derived from the peritoneum called Tunica vaginalis, forms
a serous cavity enveloping the anterior and lateral surfaces of the testis.
Beginning in the Tunica
albuginea, thin fibrous partitions, called the septula testis, divide the
testis into about 250 compartments, the lobuli testis. Each lobule contains
from 1 to 4 seminiferous tubules, where the spermatogenesis take place.
SEMINIFEROUS TUBULES
The seminiferous
tubules are lined by a very complex stratified epithelium, containing spermatogenic
cells and supporting cells. The spermatogenic cells include several morphologically
distinguishable types: spermatogonia, primary spermatocytes, secondary
spermatocytes, spermatides and spermatozoa, and the supporting cells are
called Sertoli cells. The tubules present approximately 0.2 mm of diameter
and 30-70 cm length. The cells from the seminiferous epithelium are surrounded
by a intesticium and supported by a lamina propria. The seminiferous tubules
form short straight tubuli recti that converge on the rete testis and from
there to a number of ductuli efferentes and finally to the ductus epididymidis.
The Sertoli
cells provide nutritional and mechanical support to the germ cells. The
spermatogenesis is the process that encompass the transformation of a spermatogonia,
a 2N (diploid) cell into a mature haploid, fast swimming cell, the spermatozoa.
The spermatogonia undergo successive mitotical divisions to ensure the
normal number of mother cells, and a small group originate a modified spermatogonia
(type B) that go throw the meiosis process. These cells originate large
round cells, the primary spermatocytes, that enter prophase of the fist
meiotic division. With the end of the first meiotic division, the spermatocytes
I, originate two spermatocytes II, that in the end of the second meiotic
division produce 4 round haploid cells, the spermatid. By a process known
as Spermiogenesis the spermatids go throw a series of shape and morphological
transformations and originates the spermatozoa. During this process the
cell forms a nuclear cap, filled with enzymes, known as acrosomal cap,
organize a flagellum and a mitochondrial sheath and loose the exceeding
cytoplasm and cytoplasmic structures as a residual body, which is later
digested by the Sertoli cells.
The mature
spermatozoon has a head consisting of condensed nucleus and a tail that
provides the motility necessary to transport the sperm to the site of fertilization.
DUCTUS EPIDIDYMIDIS
This structure
is formed by a long convoluted ductus, with about 7.5cm long. The epididymidis
is the site of accumulation, maturation and storage of spermatozoa. During
the 3 - 5 days that the spermatozoa are in transit through the epididymidis
they acquire motility and the capacity to fertilize ova. The ductus is
lined by a pseudostratified columnar epithelium with stereocilia. External
to the epithelium there is a layer of contractile cells.
DUCTUS DEFERENS
In the transition
from the ductus epididymidis to the ductus deferens, the lumen widens and
the wall thickens. The epithelium and the lamina propria form longitudinal
folds. The height of the pseudostratified epithelium is lower comparing
to the epididymidis and the muscular coat consist of a inner and outer
layers of longitudinal smooth muscle and a intermediate layer of circular
muscle. Surrounding the muscle layer is a an adventitial layer of connective
tissue.
ACCESSORY GLANDS
Seminal Vesicle - Are a pair of diverging saccular structures. They are composed of pseudostratified epithelium consisting of low columnar or cuboidal cells. A layer of smooth muscle and a capsule of connective tissue compose the wall of these Glands.
Prostate - This gland presents a dense capsule of connective tissue that extends into the stroma. Both capsule and stroma contain smooth muscle, as well as, fibroblast and collagen. Actually the Prostate is formed by several tubuloacinar glands. The epithelium is usually simple or pseudostratified columnar, but can be reduced to low cuboidal cells.
Bulbourethral Glands - The paired glands are tubuloalveolar type, and present from cuboidal to low columnar epithelium. They are embedded in the muscle of the urogenital diaphragm and present a abundant connective tissue with collagen and elastic fibers, and also fibers of smooth and striated muscle.
THE PENIS
The penis is formed of three cylindrical bodies made up cavernous erectile tissue, namely the two corpora cavernosa and the unpaired corpus spongiosum. The erectile tissue is a sponge-like system of irregularly vascular spaces fed by arteries and drained by veins. The three bodies are surrounded by a thick, fibrous capsule, the tunica albuginea. The corpus spongiosum surrounds the urethra.
