• Spermatogenesis comprises cell division and differentiation processes that produce sperm cells.
• Takes place in the seminiferous tubules of the testes.
• Requires sustentacular cell stimulation from FSH and testosterone (discussed in detail, elsewhere).
• Takes approximately 64 days.

STAGES:

Spermatocytogenesis

• Mitotic divisions create spermatocytes.
• Meiotic divisions create spermatids.

Spermiogensis

• Spermatids differentiate to become sperm (aka, spermatozoa).

Spermination

• Occurs when the sperm disassociate from the sustentacular cell and enter the lumen of the seminiferous tubule.
• From here, sperm cells travel to the epididymis for storage and maturation.

CELL DIVISIONS:

Spermatogonium

• Primordial stem cells from which the sperms originate.
• Undergoes mitosis and creates two cell types:
  • A replication of itself
  • Another that is committed to passing through spermatogenesis = a spermatocyte.

Primary spermatocyte

• Primary spermatocyte undergoes meiosis I to create two daughter cells: secondary spermatocytes

Secondary spermatocytes

• Undergo meiosis II, which produces spermatids.
  This concludes the spermatocytogenesis phase of spermatogenesis.

Spermatids

• Undergo spermiogenesis to form immature sperm; during this time, the cells develop but no longer divide.

Early sperm

• Enveloped in the cytoplasmic processes of the sustentacular cells.
• Have tails, which extend towards the lumen.
• Cytoplasm is concentrated towards one end, the head.
• Are released via spermination into the lumen of the seminiferous tubule.

Maturation:

• Full maturation and motility are not achieved until after ejaculation.
• Uterine tubule fluids within the female reproductive tract triggers capacitation (further maturation), which prepares the sperm for fertilization.

ANATOMY OF A SPERM CELL:

Head

• Comprises the cell nucleus covered by the acrosome; the acrosome contains enzymes that facilitate joining of sperm and ovum at fertilization.

Midpiece

• Comprises mitochondria, which provide the energy for sperm motility.

Tail

• Produces flagellar movements (“back and forth” movements) that enable the sperm to “swim” upon ejaculation.

Clinical Correlation:

• Sperm cells must be able to move through the female reproductive tract for conception to occur; if they cannot, a man may be infertile despite normal sperm count.
• Poor motility may stem from stress, excessive heat, drug effects, and dietary inefficiencies.