Independent: Ovary

Question 1

FSH targets what cells?

LH targets what cells?

Answer 1

FSH - granulosa cells

LH - theca & granulosa

Question 2

Effects of FSH during the early follicular phase?

Answer 2

Acts on the primary follicle (NOT the primordial) to induce..

• Mitosis & cell proliferation
• FSH receptors
• Gap junction formation
• Aromatase to produce estradiol
• Inhibin B synthesis in granulosa cells
  
  • -> Stimulates androgen production by theca interna
  • -> Decrease FSH secretion

Question 3

Inhibin B is synthesized by ___ to do what?

Answer 3

Synthesized by granulosa cells to

Stimulates androgen production by theca interna

Decrease FSH secretion

Question 4

FSH in the late follicular phase (high estrogen)

Answer 4

Induces LH receptors on granulosa cells –> low progesterone production

Question 5

LH in the early vs late follicular phase

Answer 5

Note: the steps are cholesterol > progestins > androgen > estrogen

so in the late follicular phase, they just stop at progesterone

Question 6

Why does the peak of LH coincide with the drop in estrogen?

Answer 6

LH surge: High occupancy of LH receptor on theca cells blocks androgen precursors needed for estradiol synthesis

Question 7

When estradiol is high but not at its peak anymore, what does it do to FSH?

Answer 7

When it’s not at its peak anymore, estradiol facilitates the decline of FSH & LH.

So the process is:

1. Peak estrogen positive feedbacks FSH & LH
2. LH surge turns down estrogen
3. Lower lvl estrogen negative feedbacks FSH & LH

Question 8

Steroidogenesis in the ovary (estradiol)

Answer 8

1. Theca interna - LH stimulates androgen synthesis (androstendione & testosterone)
2. Granulosa cells - FSH stimulates
   
   1. inhibin B to stimulate androgen synthesis
   2. aromatase expression –> converts androgens to estradiol

Question 9

Explain estradiol synthesis according to this photo

Answer 9

LH in the theca interna stimulates androgen synthesis

Androgens enter the granulosa cells, where FSH-stimulated aromatase (CYP19) turns it into estradiol

Estradiol can then leave and go out the ovary

Question 10

How does LH stimulate androgen synthesis?

Answer 10

It stimulates side chain cleavage enzymes:

remember: the steps are cholesterol > progestins > androgen > estrogen

Question 11

Positive estradiol feedback leads to LH surge through what two ways?

Answer 11

• Increasing the pulse frq of GnRH
• Increases responsiveness of gonadotrophs to GnRH

Question 12

What does the LH surge do to the follicle?

Answer 12

• Oocyte completes first meiotic division –> secondary oocyte & 1st polar body
• Increase in progesterone production transforms granulosa cells into lutein cells
• Activation of proteolytic enzymes that degrade the follicular wall + formation of stigma (area through which Graafian follicle will burst thru)
• Oocyte with cumulus detaches from the wall of the follicle and floats in the liquor folliculi
• Rapid accumulation of fluid in antrum

Question 13

What cells make up the corpus luteum?

4 stages of corpus luteum development

Answer 13

Granulosa lutein cells from the granulosa cells

Theca lutein cells from the theca cells

This differentiation was caused by LH

Corpus luteum of cycle; menstruation; albicans; and pregnancy

Question 14

When does progesterone start rising? What cells are making it? What impact does it have on other hormones?

Answer 14

At the very end of the follicular phase, granulosa cells start producing progesterone

Then, in the luteal phase, they become lutein cells and start producing a ton of progesterone

Progesterone & inhibin A negative feedbacks the other hormones

Question 15

LH does what to the theca lutein cells and the granulosa lutein cells during the luteal phase?

Answer 15

Stimulates theca lutein cells to produce weak androgens

Stimulates granulosa lutein cells to produce progesterone & estradiol -> prep for fertilization and implantation

NOTE: androgens from theca lutein are still sent to granulosa lutein to become estradiol; but the progesterone is created right in the granulosa lutein cells.

Question 16

FSH during the luteal phase

Answer 16

Low FSH stimulates granulosa lutein cells to synthesize inhibin A

–> reduce FSH by negative feedback

Question 17

What is this and what is it producing?

Answer 17

Corpus luteum making lots of steroi dhormones

Question 18

What kind of cell is the black arrow pointing at in the folds of this corpus luteum?

Answer 18

Theca lutein cells just in the folds; everything else granulosa lutein

Question 19

Which are larger, theca or granulosa lutein cells?

Answer 19

Granulosa

Question 20

Why does LH fall in later luteal phase?

What does this do to the corpus luteum?

Answer 20

Negative feedback from progesterone decreasing GnRH pulse frq and downregulating GnRH receptors on gonadotrophs

This kills the corpus luteum –> corpus albicans

Question 21

What is the key feature to identify corpus albicans histologically?

Answer 21

No nuclei because the cells are dead

Question 22

Corpus luteum of pregnancy - how does it form and what does it do?

Answer 22

Forms when hCG from the implanting blastocyst rescues the corpus luteum; acts like LH

Continues progesterone & estrogen production to maintain the endometrial lining

Question 23

Question 24

Inhibin B vs Inhibin A

Answer 24

Inhibin B: from granulosa cells; suppresses FSH-secreting gonadotrophs; follicular phase

Inhibin A: from granulosa lutein cells; suppresses LH and FSH-secreting gonadotrophs; luteal phase

Question 25

In the follicular phase, LH causes cholesterol \> progesterone\>androgens in the theca cell, then the androgens go to the granulosa cell where FSH activates aromatase to turn it into estradiol (pictured). What happens in the luteal phase?

Answer 25

Same thing happens in the theca lutein cell (LH turns cholesterol\>androstenedione), and the granulosa lutein cells still turn that androstenedione into estradiol to release, but now the **granulosa lutein cells can also respond to LH**: Take up LDL \> cholesterol \> progesterone, but dont have the enzymes to turn that progesterone into androgens, so they send **progesterone directly** into the blood.

Question 26

Ovarian cyst

Answer 26

Non-neoplastic fluid-filled cavities that originate from unruptured Graafian follicles

Question 27

Polycystic ovary syndrome

Answer 27

**High androgens & LH** but **low FSH** --\> bilateral ovarian enlargement with multiple follicular cysts

Question 28

Ovarian tumors can originate from

Answer 28

surface epithelium, oocytes, follicular cells, or stromal cells

Question 29

Menopause (~50yo)

Answer 29

Cessation of menses; **follicles dont develop** in response to FSH/LH ## Footnote - \> **reduced estradiol, progesterone, and inhibin B** --\> loss of negative feedback on hypothalamus/pituitary - \> **high FSH & LH**

Question 30

Most menopausal symptoms (bone loss, hot flashes, increased coronary artery disease) are the result of what?

Answer 30

**Estrogen deficiency.** **Only low estrogen levels are produced in adipose tissues** from androgen precursors

Question 31

Function of the oviduct What are its regions?

Answer 31

* It's where the ovum discharges into * Provides proper environment for fertilization and development of preimplantation embryo * Conducts preimplantation emrbyo to the uterus **intramural part****, isthmus, ampulla, infundibulum, fimbria**

Question 32

Components of the oviduct wall

Answer 32

**Mucosa** * **Simple columnar epithelium** - cilitated cells & secretory cells * **Lamina propria** - highly cellular & vascular **Muscularis** - ​Inner circular, outer longitudinal smooth muscle **Serosa/adventitia** - blood vessels & loose ct

Question 34

Estrogen has what impact on the serosa and muscularis of the ampulla?

Answer 34

Question 35

What do the ciliated simple columnar cell do? What do the secretory / peg cells do?

Answer 35

Question 36

Name these cells in the blue vs the black brackets

Answer 36

Black= ciliated Blue = peg

Question 37

As you go from infundibulum to isthmus, what histological changes do u see?

Answer 37

Smaller lumen Less folds in the mucosa Thicker muscularis

Question 38

**Estradiol** on the epithelium, lamina propria, and muscularis of the oviduct

Answer 38

Question 39

Progesterone on the oviduct

Answer 39

Question 40

Fertilization occurs in what region of the oviduct?

Answer 40

Ampulla

Question 41

What happens during fertilization of the secondary oocyte?

Answer 41

* **Zona pellucida** has sperm receptors and will initiate the **acrosome reaction**: acrosomal enzymes digest a path thru the zona pellucida * **Cortical reaction:** egg releases granules to ZP inpenetrable to sperm (prevents polyspermia) * Entry of sperm nucleus triggers completion of second meiotic division --\> mature ovum & second polar body * Nuclei of ovum and sperm fuse to form a zygote