Page 136 - Clinical Anatomy

ECA2 7/18/06 6:43 PM Page 121

The male genital organs 121

Lymph drainage
The lymphatic drainage of the testis obeys the usual rule; it accompanies
the venous drainage and thus passes to the para-aortic lymph nodes at
the level of the renal vessels. Free communication occurs between the lym-
phatics on either side; there is also a plentiful anastomosis with the para-
aortic intrathoracic nodes and, in turn, with the cervical nodes, so that
spread of malignant disease from the testis to the nodes at the root of the
neck is not rare.

Nerve supply
T10 sympathetic fibres via the renal and aortic plexus. These convey affer-
ent (pain) fibres—hence referred pain from the testis to the loin.

Structure

The testis is divided into 200–300 lobules each containing one to three semi-
niferous tubules. Each tubule is some 2 feet (62cm) in length when teased
out, and is thus obviously coiled and convoluted to pack away within the
testis. The tubules anastomose posteriorly into a plexus termed the rete
testis from which about a dozen fine efferent ducts arise, pierce the tunica
albuginea at the upper part of the testis and pass into the head of the epi-
didymis, which is actually formed by these efferent ducts coiled within it.
The efferent ducts fuse to form a considerably convoluted single tube
which constitutes the body and tail of the epididymis; unravelled, it is the
length of a cricket pitch.

Development of the testis
This is important and is the key to several features which are of clinical
interest.
The testis arises from a germinal ridge of mesoderm in the posterior
wall of the abdomen just medial to the mesonephros (Fig. 85), and links up
with the epididymis and vas, which differentiate from the mesonephric
duct. As the testis enlarges, it also undergoes a caudal migration according
to the following timetable:
3rd month (of fetal life) reaches the iliac fossa;
7th month traverses the inguinal canal;
8th month reaches the external ring;
9th month descends into the scrotum.
Amesenchymal strand, the gubernaculum testis, extends from the caudal
end of the developing testis along the course of its descent to blend into the
scrotal fascia. The exact role of this structure in the descent of the testis is
not known; theories are that it acts as a guide (gubernaculum = rudder) or
that its swelling dilates the inguinal canal and scrotum.
In the third fetal month, a prolongation of the peritoneal cavity invades
the gubernacular mesenchyme and projects into the scrotum as the