Histology Flashcards
(74 cards)
How to find the cortex in an ovary
It is generally where the follicles are hanging out. the boundary between cortex and medulla is indistinct.
Why do ovary cross sections look so different
Depends on stage of cycle, age of ovary, and species
Follicles consist of…
an oocyte, which is then encapsulated by one or more layers of cells.
Primordial follicle
The follicles that the woman is born with. All that she will ever have. Must migrate to cortex and be encapsulated or they will die before the woman is born. This process is not cyclical and not hormone-dependent. Consist of the oocyte with single layer of flattened follicular cells (these are the ones that must be present in order for the cell to survive). Primordial follicle that is encapsulated with follicular cells will be arrested in first meiotic division. Once they migrate to the cortex, they will be surrounded by stromal cells.
Progression from primary follicle to secondary follicle to Graffian follicle.
Form sexual maturity until menopause Hormone-dependent (GnRH)
Stromal cells
Accumulate around the edge of primordial follicle after it migrates to the cortex; Become theca cells;
Secondary oocyte
After the oocyte has been ovulated.
Primary follicle
A primary oocyte within a primary follicle. Cells around the oocyte are now cuboidal and they’re called granulosa cells. There is a now a basal lamina/membrane that separates granulosa cells from the stromal vasculature. So the oocyte is also separated., therefore the developing follicle is avascular and must depend on diffusion of nutrients from surrounding stromal cells. Next, the granulosa cells undergo multiple divisions to make multiple layers called the zona (stratum) granulosa. This is the first sign of follicular recruitment. Stromal cells differentiate into 2 layers: Theca intern (work w granulosa cells to prod estrogen) and Theca externa (will develop into smooth muscle cells that will help with ovulation of the oocyte later on). Zona pellucida develops between granulosa cells and oocyte. Helps send signals and nutrient to the oocyte.
When are the cyclical stages of follicle development?
Froms sexual maturity to menopause. Three phases: follicular, ovulation, luteal phase. Lasts 12-14 days.
Zona pellucida
- develops in the primary follicle between granulosa cells and oocyte. Helps send signals and nutrient to the oocyte. - key role in fertilization. Acrosome reaction when a sperm penetrates the oocyte membrane, resulting in spillage of proteases that crosslink with proteins in zona to trap sperm and close the barrier. –> prevents polyspermy, which is embryonic lethal
Development of the secondary follicle
- Antrum begins to form - fluid-filled cavity in a hole of lost granulosa cells, that is important for follicular growth, maturation, ovulation
Mature graafian follicle
Marked by the development of a full antrum, pushing oocyte off the one side of the follicle. The oocyte and surrounding zona pellucida and surrounding corona radiata cellsa will ovulate from the graafian follicle, leaving behind the corpus luteum.
zona granulosa
the granulosa cells that are pushed the periphery of the graafian follicle by the antrum
cumulus oophorus
granulosa cells dividing the antrum into a horseshoe and bridging the corona radiata and the zona granulosa
corona radiate
the granulosa cells between the oocyte and the antrum
theca interna cells
next to the granulosa cells and involved in hormone production
theca externa cells
smooth muscle cells that are important for assisting ovulation
What is ovulated from the graafian follicle?
oocyte + surrounding zona pellucida + corona radiata
what happens to the corpus luteum after ovulation?
the antrum fills with blood, which clots. Zona granulosa cells become granulosa lutein cells; theca interna cells become theca lutein cells - both of these now produce progesterone to maintain the uterine lining until implantation.
Potential fates of corpus luteum
- Corpus luteum of pregnancy - if fertilization is successful. Enlarges. hCG from embryo tells corpus luteum to continue secreting progesterone (& estrogen). Becomes corpus albicans of pregnancy. 2. Corpus luteum of menstruation - pumps progesterone for about 12 days. Becomes the corpus albicans at end of cycle.
Estrogen secreted from follicle stimulates…
endometrial proliferation and at first inhibits FSH and LH.
Estrogen peak stimulates…
LH surge, which triggers ovulation.
corpus luteum changes hormone profile to produce….
progesterone. Estrogen is still there, but the progrestone is responsible for maintaining uterine lining and expansion of glands and arteries in the lining. It also suppresses LH and FSH.
Why is development of glands in the uterus important?
Glands produce glycogen. Glycogen is an early nutrient source for the implanting oocyte. There is not yet a placenta to get nutrients form mum.
