The male reproductive system p .2

The male reproductive system 2
Seminiferous tubules
1. Overview
a. Seminiferous tubules are 30 to 70 cm long, with a diameter of 150 to 250 ?m.
b. They are enveloped by a fibrous connective tissue tunic composed of several layers of fibroblasts and extensive capillary beds.
c. They form tortuous pathways through the testicular lobules and then narrow into short, straight segments, the tubuli recti, which connect with the rete testis.
d. They are lined by a thick complex epithelium (seminiferous or germinal epithelium).
This epithelium consists of four to eight cell layers and contains spermatogenic cells, from which the germ cells eventually develop (spermatogenesis), and Sertoli cells, which have several functions.
2. Sertoli cells
a. Structure
(1) Sertoli cells have a pale, oval nucleus that displays frequent indentations; they are highly infolded and possess a large nucleolus.
(2) They have a well-developed smooth endoplasmic reticulum (SER), some rough endoplasmic reticulum (RER), an abundance of mitochondria and lysosomes, and an extensive Golgi complex.
b. Function
(1) Sertoli cells support, protect, and nourish the spermatogenic cells.
(2) They phagocytose excess cytoplasm discarded by