Female Repro Phys Flashcards
What is the cortex of the ovary made of? Histology?
Densely cellular stroma
Ovarian follicles reside within stroma
Follicles contain primary oocyte surrounded by follicle cells
Covered by simple epithelium
What are the stages of ovarian follicle?
Resting primordial follicle
Growing preantral (primary and secondary) follicle
Growing antral (tertiary) follicle
Dominant (preovulatory, graafian) follicle
Dominant follicle within periovulatory period
Corpus luteum
Atretic follicles (degenerate before maturity)
Describe primordial follicle
Primary oocyte with surrounding single layer of pregranulosa cells
Describe primary oocyte
Arrested in diplotene stage of prophase I
What is the endocrine function of the primordial follicle?
No ovarian steroid hormone
Release paracrine factors
Follicles stimulate oocyte growth by release of kit ligand (stem cell factor)
Kit ligand binds to c-KIT receptor
Describe primary follicle
Has larger primary oocyte than in primordial follicle
Has cuboidal granulosa cells
Describe secondary follicle
Primary oocyte
Multilayered cuboidal granulosa cells
Thecal cells outside of basement layer (stromal cells differenitated after paracrine signals from granulosa cells)
Formation of capillaries
Movement from outer cortex to inner cortex
Describe gamete in preantral follicles (primary & secondary follicles)
Oocyte does not complete meiosis I
Grows and produces and secretes proteins
Initiates secretion of extracellular matrix glycoproteins (ZP1, ZP2, ZP3) that form zona pellucida
Describe endocrine function of granulosa cells in primary/secondary follicles
Express FSH receptor but are dependent on oocyte factors to grow
Do not produce ovarian hormones yet
Describe endocrine function of thecal cells during primary/secondary follicle
Androstenedione production is absent or minimal at this stage
Describe antral follicles (Graafian)
Granulosa epithelium increases layers
Fluid-filled antrum appears
Granulosa cells divide into mural granulosa cells (stratum granulosum) and cumulus cells (cumulus oophorus or corona radiata)
Dependent on FSH
Describe mural granulosa cells (stratum granulosum)
Form outer wall of follicle
Close to outerlying thecal layers
Become highly steroidogenic
Remain in ovary after ovulation to differentiate into corpus luteum
Describe cumulus cells (cumulus oophorus or corona radiata)
Inner cells surrounding oocyte Innermost layer (relative to oocyte) maintains gap and adhesion junctions with oocyte During ovulation, cumulus cells are released from ovary with oocyte Crucial for ability of fimbriated end of oviduct to grab and move oocyte along length of oviduct to site of fertillization
Describe gamete in antral (Graafian) follicle
Oocyte gains meiotic competence but still maintains meiotic arrest until LH surge
Elevated cAMP maintains arrest
Describe endocrine function of thecal cells in antral (Graafian) cells
Produce significant amounts of androstenedione and testosterone (less extent)
Describe endocrine function of mural granulosa cells
Proliferation stimulated by FSH
FSH also induces expression of CYP19-aromatase
Granulosa cells secrete inhibin
Describe the effects of low levels of estrogen and inhibin on FSH secretion
Exert negative feedback
Contributes to selection of follicle with most FSH-responsive cells
Describe dominant follicle
Out of 20 recruited large antral follicles, largest follicle with most FSH receptors
Becomes preovulatory follicle
Describe gamete of dominant follicle
Oocyte grows at slower late
Arrested in meiosis I
Stalk of cumulus cells attaching them to granulosa cells becomes thin
Describe endocrine function of thecal cells in dominant follicle
Express LH receptors and produce androgens
LH stimulate production of steroidogenic enzymes (3betaHSD, CYP17, CYP11A1), LDL receptors
Androstenedione and testosterone released and diffused to mural granulosa cells or vasculature
Describe endocrine function mural granulosa cells in dominant follicle
High number of FSH receptors
FSH upregulates aromatase gene expression and activity (aromatase converts androstenedione to estrone and testosterone to estradiol-17beta)
Express isoforms of 17betaHSD which drives steroidogenesis toward production of estradiol-17beta
FSH also induces expression inhibin B
FSH also induces expression of LH receptors, so cells still have high levels of CYP19 (aromatase) in face of declining FSH levels
Respond to LH surge
Describe luteinization
Culminates in formation of a corpus luteum, which is capable of producing large amounts of progesterone, along with estrogen, within a few days after ovulation
Describe major structural changes associated with LH surge
Induces release of inflammatory cytokines and hydrolytic enzymes from theca and granulosa cells. These breakdown follicle wall, tunica albuginea, and surface epithelium near stigma (bulge that forms when follicle presses against wall of ovary)
Cumulus cells detach from granulosa cells, and oocyte is freed within antral cavity
Basal lamina of granulosa cells is enzymatically degraded, so blood vessels and theca cells can push into granulosa cells