Mammal, testis (Gross, Low)

Structure List Head of epididymis Body of epididymis Tail of epididymis Ductus deferens Testis

TESTIS. Seminiferous tubules form the mass of the testes and are the sites of spermatogenesis. Each lobule consists of seminiferous tubules which unite and form straight tubules (tubuli recti). Straight tubules join the rete testis in the mediastinum. Several efferent ducts (efferent ductules) leave the rete to join the head of the epididymis. Seminiferous tubules are composed of a thick layer of spermatogenic cells (most numerous) and sustentacular (Sertoli) cells which rest on a basement membrane. The spermatogenic cells--spermatogonia, primary spermatocytes, secondary spermatocytes, spermatids and spermatozoa--represent different cell stages in spermatogenesis. The outlines of sustentacular cells are not distinct. Maturing spermatozoa are found embedded, head first, in the sustentacular cells, which provide mechanical support, protection and possibly nutrition for the developing spermatozoa.