Compare and contrast spermatogenesis and oogenesis
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Spermatogenesis
• The entire process, starting with the spermatogonial cell and ending with sperm, takes about 64 days.
• The process begins at puberty and continues into old age.
• The spermatogonia have been dormant in the seminiferous tubules since the fetal period. These begin to increase in number at puberty by mitosis. They will grow and undergo gradual changes that transform them into primary spermatocytes, the largest germ cells in the tubules.
Oogenesis
• This maturation process begins before birth, but it is not completed until after puberty.
• During early fetal life, oogonia proliferate by mitotic division. All oogonia enlarge to form primary oocytes before birth. No more will be made after birth.
• Before birth occurs, the primary oocytes begin the first meiotic division. The completion does not occur until after puberty. The primary oocytes are suspended in prophase until puberty (OMI)
• After puberty, a primary oocyte will complete the first meiotic division. The division of the cytoplasm is unequal. The secondary oocyte receives the most cytoplasm and the first polar body receives hardly any. The first polar body is a small, nonfunctional cell that soon degenerates.
• At ovulation, the nucleus of a secondary oocyte begins the second meiotic division, and progresses only to metaphase 2, when division is arrested. If a sperm penetrates the secondary oocyte, the second meiotic division is completed, and most cytoplasm is again retained by one cell, the oocyte. The oocyte is mature when the second polar body is extruded. The mature oocyte is commonly referred to as the mature ovum.
• The entire process, starting with the spermatogonial cell and ending with sperm, takes about 64 days.
• The process begins at puberty and continues into old age.
• The spermatogonia have been dormant in the seminiferous tubules since the fetal period. These begin to increase in number at puberty by mitosis. They will grow and undergo gradual changes that transform them into primary spermatocytes, the largest germ cells in the tubules.
Oogenesis
• This maturation process begins before birth, but it is not completed until after puberty.
• During early fetal life, oogonia proliferate by mitotic division. All oogonia enlarge to form primary oocytes before birth. No more will be made after birth.
• Before birth occurs, the primary oocytes begin the first meiotic division. The completion does not occur until after puberty. The primary oocytes are suspended in prophase until puberty (OMI)
• After puberty, a primary oocyte will complete the first meiotic division. The division of the cytoplasm is unequal. The secondary oocyte receives the most cytoplasm and the first polar body receives hardly any. The first polar body is a small, nonfunctional cell that soon degenerates.
• At ovulation, the nucleus of a secondary oocyte begins the second meiotic division, and progresses only to metaphase 2, when division is arrested. If a sperm penetrates the secondary oocyte, the second meiotic division is completed, and most cytoplasm is again retained by one cell, the oocyte. The oocyte is mature when the second polar body is extruded. The mature oocyte is commonly referred to as the mature ovum.
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