Spermatogenesis Reproductive System > Physiology > Physiology
CORRECTION: Spermatogonia 1A remains as stem cell population, NOT Spermatogonia 1B, as depicted in the diagram and narration.
SPERMATOGENESIS
• 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
1 / 3 - 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
2 / 3 • 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.
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