two cell theory part 2 Flashcards
at what stage are gametes at birth
primary oocyte (in primordial follicle)
what are the 3 follicle cell types
1.oocytes
2. granulosa cells (follicular)
3. thecal cells
what is the progression of follicle maturation in initial recruitment (preantral phase)
oogonia -> primordial -> primary -> secondaryw
what is the progression of follicle maturation in cyclic recruitment (antral phase)
tertiary -> preovulatory
what hormone is cyclic recruitment dependent on
FSH
what does the primordial follicle contain
-primary oocytes arrested in prophase I of meiosis
-oocytes surrounded by flattened granulosa cells
how is the primary follicle changed
-oocyte enlarges
-layer of granulosa cells gets larger, cuboid, then starts to divide
-zona pellucida appears
-first see FSH receptors
how is the secondary follicle changed
-granulosa cells continue to divide: 2-6 cell layers
-theca cells now present
what is the role of FSH
important to transition from secondary to tertiary follicles
are any hormones needed from the progression of primordial follicles to secondary follicles
no, FSH-independent
how does FSH affect granulosa cells
divide; more granulosa cells = bigger follicles
what does a tertiary follicle look like/contain
-presence of antrum
-late (large follicle): progress from primary oocyte to secondary oocyte
what stage is a gamete in a graafian follicle
secondary oocyte (what gets ovulated)
if an ovary-having individual has a reproductive window of 40 years, and only ovulates one oocyte per month, how many follicles do they lose?
12 x 40 = 480
what is atresia
-coordinated apoptosis
-as follicles mature, there are some that stop and whose cells undergo apoptosis
-can occur at any stage of follicular growth
what does inner theca cells respond to
-LH
-LH starts cAMP cascade
-major outcome: androstenedione
what does granulosa cells respond to
-respond to FSH by increasing cAMP levels
-have FSH receptors
where do we find aromatase
granulosa cells, inner theca cells, oocytes
does FSH cause aromatase expression
no in the example, shows that aromatase shows up in granulosa cells
but overall, FSH does drive up aromatase expression
how does aromatase get produced
-granulosa cells respond to FSH which causes cAMP cascade and leads to production of aromatase
-converts androstenedione from theca cells into estradiol
what causes LH receptor expression in granulosa cells
estradiol which expresses LH receptors
what is luteinization
FSH produces estradiol, increased estradiol causes granulosa cell production which expresses LH receptors and also makes progesterone production. they are now called luteal cells because they produce progesterone
what does the presence of LH receptors cause
leads to cascade that starts expression of enzymes that produce progesterone
why didn’t the granulosa cell make progesterone before it was stimulated by LH
they do not yet express the enzymes that convert cholesterol to progesterone
why didnt the granulosa cells start expressing LH receptors earlier
-don’t have many LH receptor expressing luteal cells earlier because not sufficient estrogen in circulation
-not enough estrogen because the major source of estradiol in the body comes from granulosa cells, stimulated by FSH
IHH (idiopathic hypogonadotropic hypogonadism)
-have significantly less sex steroids in circulation
-have smaller gonads
-do not hit puberty
-are infertile
