ON TESTIS AND EPlDlDYMlS OF RATS - Pondicherry University ...

layers, an outer layer of visceral peritoneum, the tunica vaginalis, the tunica albuginea
proper and on the inside the tunica vasculosa. Posteriorly funica albuginea is
thickened and projects into the parenchyma of testis to form mediastenum, a
honeycomb-like structure, which provides a passageway linking seminiferous tubules
with efferent ductules and epididymis.
Testis is made up of seminiferous tubules where the spermatozoa are formed.
Senliniferous tubules owe their cylindrical shape to multiple layers of cellular and
extracellular elements collectively known as the lamina propria. tunica propria, or
peritubular tissue. Seminiferous tubules are two ended. convoluted loops with both
ends opening into rete testis, through which sperm and fluid produced by the tubules
pass on their way to excurrent duct systems. There are 30 tubules in rat testis (Dym.
1976) with a diameter between 50 and 100 pm (Setchell, 1970; Wing and
Christensen. 1982). Within the seminiferous tubules germ cells and somatic Sertoli
cells make up the seminiferous epithelium, a complex stratified arrangement of germ
cells. supported by tall columnar Sertoli cells. which rest upon the basement
membrane and extend apically toward the lumen of the tubule (de Kretser er rrl.
1995).
Germ cells are highly synchronized in their proliferation and development to
lorm a distinct cellular associations, establishing a precisely coordinated 'cycle of the
seminiferous epithelium', believed to be regulated in part by Sertoli cells which do
not divide in adult testis (de Kretser cr ul.. 1998; Orth. 1982). Walls of' the
seminiferous tubules are composed of four layers of non-cellular materials surrounded
by a layer of smooth muscle-like or myoid cells which are responsible for peristaltic
movements of the tubules (Clermont, 1958). Interstitial tissue between seminiferous
tubules is composed of clusters of Leydig cells, mesenchymal cells. macrophages.
occasional mast cells, blood and lymph vessels (for review, see Johnson el al, 1999).
The interstitial tissue is mainly composed of Leydig cells, which are the site of
testicular steroidogenesis. Leydig cells have an abundance of smooth endoplasmic
reticulum, many mitochondria with tubular cristae. Golgi complex, centrioles,