Term
| The inner layer of thecal cells, the theca interna, contains abundant smooth ER to accomodate what? |
|
Definition
|
|
Term
| What is the purpose of the basement membrane in early follicle development? |
|
Definition
| Seperates the oocyte and granulosa cells from the highly vascularized thecal cells; serves as a vascular barrier |
|
|
Term
| What is the name of the emcompassing granulosa cells of the ripe preovulatory follicle? |
|
Definition
|
|
Term
| During the luteal phase, what do granulosa and thecal cells differentiate into? |
|
Definition
|
|
Term
| When does the corpus luteum regress? What is it replaced with? |
|
Definition
The corpus luteum regresses after 2 weeks
It is replaced with fibrous tissue and is called the corpus albicans |
|
|
Term
| What are the primary ovarian steroid hormones synthesized in the thecal and granulosa cells and the corpus luteum? |
|
Definition
| Progesterone and the estrogens 17B-estradiol and estrone |
|
|
Term
| What is the rate limiting step in steroid biosyntheis? |
|
Definition
Conversion of C27 cholestrol to C21 pregnenolone by the cholestrol side chain cleavage
This occurs in mitochondria |
|
|
Term
| Where does the conversion of progestogens to androgens to estrogens take place? |
|
Definition
|
|
Term
| What causes the androgens androstenedione and testosterone to be converted into estrone or 17B-estradiol? |
|
Definition
|
|
Term
Where is estrone converted to estriol?
What is more potent: estrone, 17B-estradiol, or estriol? |
|
Definition
Estrone is converted to estriol in the liver
Potency: 17B-estradiol > estrone > estriol |
|
|
Term
| Most estrogens circulate bound to what? |
|
Definition
Albumin
Most estrogens are not bound to sex steroid-binding globulin (SSBG) because they have a lower affinity for SSBG than androgens; estrogens actually have a higher affinity for SSBG than albumin |
|
|
Term
| Where are estrogens degraded? |
|
Definition
|
|
Term
| What is the primary physiologically active androgen in women? |
|
Definition
|
|
Term
| Where are androgens produced? |
|
Definition
Ovaries and the adrenals
Dehydroepiandrosterone - adrenals
Androstenedione - ovary and adrenals
Testosterone - ovary, adrenals, and conversion from other steroids in the peripheral tissues |
|
|
Term
| What is most testosterone in circulation bound to? |
|
Definition
|
|
Term
| What is progesterone secreted by? |
|
Definition
| The corpus luteum and adrenals |
|
|
Term
| In circulation, what is progesterone bound to? |
|
Definition
| Albumin (low affinity) or corticosteroid binding globulin (high affinity) |
|
|
Term
| Where are relaxin and inhibin produced and what are their functions? |
|
Definition
Relaxin - produced by the corpus luteum; relaxes the myometrium in humans
Inhibin - produced by granulosa cells during the preovulatory period; inhibits FSH secretion |
|
|
Term
| True or False: Follicle development can procede to the preantral stage without the pituitary |
|
Definition
True
Beyond the antral stage, FSH and LH are required; FSH and LH are required for ovulation, luteinization, and steroid hormone formation by the follicle and corpus lutem |
|
|
Term
| Where are FSH receptors expressed in women? What does their stimulation cause? |
|
Definition
FSH receptors are only expressed on the granulosa cells in the ovary
FSH causes the granulosa cells to proliferate and secrete estrogen; FSH stimulates the synthesis of the aromatase complex in granulosa cells, which converts the androgens produced by thecal cells into estrogens |
|
|
Term
| Where are LH receptors found in women? What do they cause? |
|
Definition
LH receptors before antrum formation are only expressed on theca interna and stromal cells
LH stimulates the synthesis and secretion of steroids; LH can cause the hypertrophy of stromal cells
LH stimulates the synthesis of androstenedione and testosterone in thecal cells |
|
|
Term
| How does estradiol affect granulosa cells? |
|
Definition
Estradiol stimulates granulosa cell and possibly theca interna cell proliferation; it increases granulosa cell responsiveness to FSH, by increasing the expression of FSH receptors - this is a positive feedback mechanism
As the follicle matures, it becomes more sensitive to FSH and concomitantly has a greater capacity for producing estradiol; estradiol increases its own production |
|
|
Term
| Where is gonadotropin releasing hormone (GnRH) produced? What does it control? |
|
Definition
GnRH is released by the neurons of the arcuate nuclei and medial preoptic area of the hypothalamus
FSH and LH are controlled by GnRH |
|
|
Term
| What surges 16 hours before ovulation? |
|
Definition
LH
A modest increase in FSH also occurs |
|
|
Term
| What stimulates the development of the corpus luteum? |
|
Definition
LH
Causes proliferation and differentiation of the granulosa and thecal cells from the ruptured follicle into luteal cells; LH stimulates the secretion of quantities of progesterone and some estrogen by the corpus luteum |
|
|
Term
| What happens to the corpus luteum if there is no signal that an ovum has been fertilized (in regards to LH and FSH interactions)? |
|
Definition
| The combined presence of estrogen with elevated progesterone inhibits GnRH release from the hypothalamus; this, in turn, diminishes LH and FSH secretion from the pituitary; the corpus luteum becomes less sensitive to LH and regresses about one week after ovulation |
|
|
