This process starts occurring at puberty, prior to which spermatogonia are present only in seminiferous tubules.

Physiology

Spermatogonia are joined by intercellular bridges. The cells are, therefore, in continuity with respect to cytoplasm – i.e. a true syncytium. This allows for synchronised differentiation: all progeny of any one spermatogonium develop at the same rate. [In contrast, stem cells are not joined by intercellular bridges.] Once they reach the stage of spermatozoa, and the cytoplasmic bridging has been lost, they are released into the seminiferous tubule.

Cells undergo cytological changes in the Spermiogenesis phase leading to the formation of a spermatozoon. These changes include:

1. Formation of autosome
2. Development of flagellum
3. Condensation of chromatin and changes in shape/size of nucleus
4. Loss of excess cytoplasm

Histopathology

Pseudostratified columnar epithelium

• Tall columnar cells with cilia
• Cuboidal cells with microvilli (absorb fluid to concentrate sperm)
• Basal cells

Epithelium is surrounded by smooth muscle which becomes progressively thicker toward the epididymis, helping to promulgate the sperm. Between two and 20 efferent ducts drain into the epididymis.

Epididymis

A pseudostratified columnar epithelium consists here of two primary cell types:

• Principal Cells are columnar at the head and have transitioned to be cuboidal at the tail of the epididymis. They have microvilli (could be classified as stereocilia) for increased absorption to store and concentrate sperm before ejaculation.
• Spermatozoa mature and gain motility while in the epididymis. This is a testosterone-dependent process. The epithelium is surrounded by a thin lamina propria and smooth muscle in the tail (used more for storage) while at the head and body the muscle is more developed, for squeezing.

Ductus Deferens

1. Pseudostratified epithelium: columnar cells with stereocilia (long microvilli)
2. Lamina propria: contains numerous elastic fibres
3. 2-3 muscle layers

The ductus ends where the prostatic urethra begins. Its terminal end is enlarged (ampulla) to accommodate sex-gland secretions. These accessory sex glands, which function to maintain the spermatozoa, secrete a fructose-rich mix before ejaculation to help supply the team of spermatozoa with energy and for genital tract lubrication: they include the paired seminal vesicles; the paired bulbourethral glands; and the unpaired prostate.