Female Reproductive Physiology Flashcards
Trace the steps followed by a primordial germ cell through the process of meiosis and oogenesis and compare with spermatogenesis.
Like spermatogenesis, oogenesis is a meiotic process that begins during embryonic development and culminates in the formation of a single haploid oocyte and “three” polar bodies.
1. primordial germ cells develop form the germinal epithelium of the indifferent gonad early in embryonic development and migrate to future ovaries to become oogonia
2. oogonia are surrounded by a single layer of nongerminal granulosa cells. this complex is called primordial follicle. Ovum is now a primary oocyte.
3. the primary oocyte begins the process of meiosis, but arrests during prophase I. Beginning at puberty, one of these primary oocytes will complete the first stage of meiosis to become: •A Secondary Oocyte + Polar body
4. Secondary oocytes complete the second half of meiosis to become ootids and polar bodies.
5. Fertilization occurs at the second metaphase stage of oogenesis:
•Therefore, an immature egg is fertilized.
•Meiosis is not completed unless fertilization occurs.
Describe the time intervals of the ovarian phases based on a 28-day cycle
Days 5-14 -> follicular growth
Day 14 -> ovulation
Days 14-23 -> development of corpus luteum
Days 24-28 -> regression of corpus luteum
Describe the time intervals of the uterine phases based on a 28-day cycle.
Days 1-5 -> Menstruation
Days 4-14 -> Proliferation
Days 14-28 -> Secretion
Describe the relationship between the release of anterior pituitary hormones and ovarian hormones in relation to the phases of the menstrual cycle.
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Describe the interactions between the granulosa and theca cells in estrogen production and relate to LH and FSH
Theca:
•The theca interna:
•Cells become epithelioid and develop the ability to secrete estrogen and progesterone.
•The theca externa:
•Will become the protective capsule of the developing follicle.
Granulosa cells:
•Secrete a follicular fluid containing a high concentration of estrogen
•This causes an antrum to appear.
Describe the role of enzymes and hormones postulated to be involved in ovulation.
Hypothalamic releasing hormone: gonadotropin releasing hormone (GnRH): •Increases much less drastically than the other two sources. It is secreted in short pulses averaging once every 90 minutes, as occurs in males.
Anterior pituitary sex hormones: FSH, LH •Almost no secretion throughout childhood. •Small glycoproteins with MW of about 30,000. •Combine with highly specific receptors in ovarian target cell membranes. •Signal transduction involves cAMP second messenger system in most instances leading to formation of protein kinase and multiple phosphorylations.
Ovarian hormones: estrogen and progesterone •Primordial follicles are surrounded by single layers of granulosa cells. •Throughout childhood these cells: •Provide nourishment for the ovum •Secrete oocyte maturation-inhibiting factor that keeps ovum suspended in its primordial state.
Describe changes that occur in the uterus during each phase of the menstrual cycle
Proliferative stage:
•Estrogen phase: Occurs before ovulation
•Most of the endometrium has been desquamated at beginning of phase.
•The only epithelial cells left are those in the deeper portions of the glands and crypts.
•Estrogen causes stromal and epithelial cells to rapidly proliferate.
•Endometrial surface is re-epithelialized within 4-7 days after the beginning of menstruation.
•There is progressive thickening of the endometrium due to increasing number of stromal cells and growth of endometrial glands.
•Endometrial glands, especially in cervical region, secrete a thin, stringy mucous.
Secretory stage:
•Progesterone phase: Progesterone and estrogen are secreted in large quantities by corpus luteum.
•Progesterone causes marked swelling and secretory development of the endometrium.
•Glands increase in tortuosity.
•Excess of secretory substances accumulates in glandular epithelial cells.
•Results are a highly secretory endometrium that contains large amounts of stored nutrients.
•These uterine secretions (“uterine milk”) provide nourishment for the early dividing ovum.
Menstruation:
•If ovum is not fertilized, corpus luteum suddenly involutes about 2 days before the end of the cycle and decreases secretion level.
•Reduction in estrogens and progesterones (especially progesterone) causes menstruation.
•Decreased stimulation of endometrial cells is followed by involution of endometrium itself.
•24 hours before the beginning of the onset of menstruation, tortuous blood vessels leading to the mucosal layers become vasospastic, leading to necrosis of the endometrium
Describe the effects of estrogen on various structures and physiological pathways.
Uterus and External Organs: minimal at birth until puberty when levels increase 20- fold. secondary characteristics appear. vaginal epi becomes stratified. uterus bigger and glands apper.
Fallopian tubes: increase in ciliated cells.
Breasts: initiation of female breast character
Skeleton: stimulate bone growth. in old age, deficiency=bone deterioration
Protein deposition: slight increase in total body pt (but not as much as testo)
^ metabolism and fat deposition (not as high meta as testo)
hair production slightly
skin: soft texture, thickens, vasculated
electrolyte balance: Na and H2O retention – think: surge o estrogen during pregnancy and water retention
Describe the effects of progesterone on various structures and physiological pathways.
Secretory changes in uterus: promotes during cycle to prepare uterus to hold ovum, decreases premature contractions
fallopian tubes: secretions by tubes
breast development: dev of lobules and alveoli of breasts
