Seminiferous Tubules

The seminiferous tubules are the site of spermatogenesis. The epithelium is composed of supporting Sertoli cells and spermatogenic cells.

Sertoli cells

Sertoli cells are irregular columnar cells that extend from the basal lamina to the lumen and provide structural organization to the tubule.

■ They synthesize testicular androgen-binding protein, which helps to maintain the high androgen levels within the seminiferous tubules. The androgen is necessary for spermatogenesis.

• They provide the blood—testis barrier. Tight junctions between adjacent Sertoli cells divide the seminiferous tubules into a basal compartment (containing spermatogonia) and an adluminal compartment (containing spermatocytes and spermatids).

Spermatogenic cells

Spermatogenic cells are the germ cells located between the Sertoli cells. They consist of spermatogonia, primary and secondary spermatocytes, spermatids, and spermatozoa (see Embryology section).

Spermatozoa

There are approximately 60,000 spermatozoa per cubic millimeter of seminal fluid, or 200 to 600 million in a single ejaculation (Figures 1-9-2 and 1-9-3).

The mature spermatozoa consist of a head and a tail.

• The head of the spermatozoon is pear-shaped, and chromatin is enclosed within the nuclear envelope. Covering the apex of the nucleus is the acrosome.

« The tail of the spermatozoon consists primarily of microtubules for the flagellum and mitochondria for energy.

Spermatozoa

Secondary

Spermatids

Spermatogonium

Basement membrane

Leydig cell

Figure 1-9-1. Seminiferous Tubule Diagram

Spermatozoa

Secondary

Primary spermatocyte

Tight junction

Spermatids

Spermatogonium

Basement membrane

Connective tissue

Leydig cell

Figure 1-9-1. Seminiferous Tubule Diagram

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