female reproductive system 1/2 Flashcards
follicular phase of menstrual cycle
Begins with menstrual bleeding (menstruation), which marks the first day. Bleeding occurs after estrogen and progesterone levels decrease at the end of the previous cycle. This decrease causes the top layers of thickened lining of the uterus (endometrium) to break down/be shed.
About this time, FSH increases slightly, stimulating the development of several follicles in the ovaries. Each follicle contains an egg. Later, as FSH decreases, only one follicle continues to develop and produces estrogen .
in period, bleeding occurs after _______ levels ______
why?
estrogen and progesterone; decrease
this causes thickened endometrium to be shed
what stimulates the development of several follicles in the ovary in the follicular phase?
FSH slightly increases
ovulatory phase
second phase
begins with a surge in LH and FSH. LH stimulates egg release (ovulation), which usually occurs 16 to 32 hours after the surge begins. Estrogen peaks during the surge, and progesterone starts to increase.
luteal phase
third phase
LH and FSH decrease.
ruptured follicle forms a corpus luteum, which produces progesterone.
During most of this phase, the estrogen level is high. Progesterone and estrogen cause the uterus lining to thicken, preparing for possible fertilization.
If the egg is not fertilized, the corpus luteum degenerates and no longer produces progesterone, estrogen decreases, the top layers of the lining are shed, and menstrual bleeding occurs (the start of a new menstrual cycle).
surface epithelium of the ovary?
simple cuboidal mesothelium (germinal epithelium)
gonads arise from these 3 different sources:
Yolk sac (oocytes)
Coelomic epithelium (follicle cells)
Intermediate mesoderm
when des oogenesis begin?
4th fetal month
primordial germ cells are connected by ____ and proliferate by ____
intercellular bridges
mitosis
oogenesis by 5th fetal month
- oogonia stop undergoing mitosis; begin but DO NOT complete meiosis; enter state of dormancy. Primordial follicles form
at birth all oocytes are arrested in…
temporal? physical?
prophase of meiosis 1
they are in primordial follicles
pool of oocytes is ____ early in life
fixed
oogenesis and rate of atresia
- About 7 million oocytes at 5 months gestation
- Oocytes die and follicles degenerate:
- Oogonia not surrounded by follicular cells die
- Majority oocytes die in utero
- 700,000 to 2 million oocytes remain in ovaries at birth
- About 400,000 oocytes remain in ovaries at puberty
primordial ovarian follicle
- Cells quiescent, dormant
- Junctions between oocyte and follicle cells
- Follicle cells are squamous and sitting on a basement membrane
growing ovarian follicle
-
Zona pellucida
- Glycoprotein shell
- maintains sperm binding; also induces the acrosome reaction
- Zp is pierced by microvilli of oocyte and the filipodia follicular cells
- Contacted by gap junctions
-
Granulosa cells – secrete estrogen!
- Rest on a basement membrane
- Blood vessels do not pierce the basement membrane
vesicular ovarian follicle
- Fluid filled cavities form
- Fluid in cavities contains: hormones, growth factors, ions, proteoglycans, and oocyte maturation inhibitor
- Ovarian stroma is organized into:
- Theca interna – secretes androgen (estrogen precursor)
- Theca externa
mature graafian follicle
progression of follicle stages
primordial –> growing –> vesicular –> mature/graafian
puberty and the cyclic recruitment of follicles depends on….
FSH