PSL201 – Mar 11 – Endocrine 8 Female Reproductive System.docx

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11 Apr 2012
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PSL201 Mar 11 Endocrine 8: Female Reproductive System
The Female Reproductive System
3 general characteristics:
1. cyclic changes in activity: menstrual cycle which is accompanied by regular
periodic changes in the secretion of hypothalamic, anterior pituitary, and
ovarian hormones. The beginning of each cycle is marked by menstration
2. restricted periods of fertility: ovulation is a prerequisite for fertilization and
a female is only fertile for a few days that roughly coincide with ovulation
3. limited gamete production: ova develop from a fixed number of germ cells
Ova and Their Development
- the process is called oogenesis
- start as germ cells called oogonia (in fixed number and do not generate
more)
- begins in first 3 months of embryonic life, oogonia undergoe mitosis to yield
2-4 milli clones
- then differentiate into primary oocytes
- meiosis I begins but the stops (meiotic arrest) until just before ovulation
- at puberty one primary oocyte per month continues meiosis one to yield one
secondary oocyte and a first polar body
- only if the secondary oocyte is fertilized does meiosis II occur
o yields an ovum and a second polar body
- ovum contains 46 chromosomes (2n)
The Menstual Cycle
- sets the stage for fertilization and pregnancy
The Ovarian Cycle:
- two phases: the follicular phase (14 days) and the luteal phase (14 days)
- follicular phase is the start on menstruation and ends with ovulation
- the luteal phase is the rest of the menstrual cycle
The Follicular Phase:
- most follicles are in the primordial phase, but a small fraction begin to
develop independent of each other
- follicle cells proliferate into multiple layers around the oocyte and
differentiate into granulosa cells
- the primordial follicle is now a primary follicle
- granulosa cells secrete noncellualr material forming a membrane between
them and the oocyte called zona pellucida
- the oocyte is provided for through gap junctions between granulosa cells and
the oocyte
- follicles continue to develop and form a fluid filled cavity called an antrum
- the follicle is now called a secondary follicle (some follicles stop at this point)
- after about seven days one follicle (the dominant follicle) is selected to
develop to maturity
o remaining follicles undergo atresia and are lost
- follicular growth is stimulated by FSH and estrogens secreted by follicles
themselves
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