PHIS 206 Lecture Notes - Lecture 34: Oogenesis, Oogonium, Spermatogenesis
2 May 2018
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Lecture 34: Reproduction II
Oogenesis
• Replication of germ cell (oogonium) occurs completely before birth. All the eggs a
woman ever has, she had when she was born
• Every cycle, one primary oocyte is developed and expands. When it divides (just before
ovulation), it does so unevenly, generating a large secondary oocyte.
• Engineered Wastefulness
o If fertilized, the oocyte divides again, now with appropriate genetic content.
o Polar bodies are small, unviable cell division products.
o Their purpose is provide extra cellular machinery to the eventual ovum.
• Cells split in smarter way
Spermatogenesis versus Oogenesis
• Differences
o Spermatogenesis is continuous from puberty onward.
o Oogenesis has a pre-birth phase, and advances step-wise after puberty and with
possible fertilization.
o Before puberty eggs are lost through a unproductive cycle.
Female Reproductive Cycle
• Female Reproductive Cycle has two phases:
o Ovarian Cycle → Ovary develops a follicle in which an egg prepared to be
released (ovulation) for possible fertilization.
▪ Ovary then aids (via hormonal secretion) in preparation and maintenance
of uterus for implantation
o Uterine (Menstrual Cycle) → In response to hormones from ovary, the
endometrium of the uterus thickens, vascularizes, and prepares for implantation of
fertilized ovum.
▪ Without fertilization, the uterus sheds the developed tissue, then repairs
itself for the next cycle
All cycles together
• Synchronization
o Cycles line up with onset of menses
• Involvement
o Hormones from pituitary regulate ovarian hormone release which cause uterine
changes
Ovarian Cycle
• Follicular Phase
o Follicle within ovary develops for purpose of permitting proper ovulation. Follicle
also secretes estrogen for uterine preparation and control of ovulation.
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Document Summary
Lecture 34: reproduction ii: replication of germ cell (oogonium) occurs completely before birth. All the eggs a woman ever has, she had when she was born: every cycle, one primary oocyte is developed and expands. When it divides (just before ovulation), it does so unevenly, generating a large secondary oocyte: engineered wastefulness. If fertilized, the oocyte divides again, now with appropriate genetic content: polar bodies are small, unviable cell division products, their purpose is provide extra cellular machinery to the eventual ovum, cells split in smarter way. Spermatogenesis versus oogenesis: differences, spermatogenesis is continuous from puberty onward, oogenesis has a pre-birth phase, and advances step-wise after puberty and with possible fertilization, before puberty eggs are lost through a unproductive cycle. All cycles together: synchronization, cycles line up with onset of menses. Involvement: hormones from pituitary regulate ovarian hormone release which cause uterine changes. Ovarian cycle: follicular phase, follicle within ovary develops for purpose of permitting proper ovulation.
