lab 16: ovaries

oogenesis

production of ovum (gamete)

1. primordial follicles

• in clusters called egg nests

• contain primary oocyte surrounded by one layer of follicle cells

  • primary oocyte is suspended in meiosis I (DIPLOID)

2. primary follicle

• about 20 follicles ENLARGE every cycle

• granulosa cells form several layers around oocyte

• thecal cells form outermost layer of follicle

• granulosa and thecal cells secrete estrogen

• AFTER PUBERTY

zona pellucida

clear region that develops around oocyte during primary follicle stage

estrogen

stimulates growth of endometrium; vital for fertilization

3. secondary follicle

• wall of follicle becomes thicker

  • granulosa cells begin to secrete fluid that accumulates in pockets

4. tertiary follicle/graafian follicle

• one follicle fully matures

• pockets of fluid fuse to for single, fluid filled antrum

• oocyte projects into antrium

• protective layers of cells around oocyte is the corona radiata

  • oocyte completes meiosis I to form secondary oocyte that arrests in meiosis II; STILL DIPLOID AND ONLY COMPLETES MEIOSIS II IF FERTILIZED

5. ovulation

• tertiary follicle ruptures

• secondary oocyte and corona radiata are expelled into pelvic cavity

• enter uterine tube

• secondary oocyte will complete meiosis II only if it’s fertilized

tunica albuginea

dense connective tissue layer underlying germinal epithelium

germinal epithelium

• outer covering of ovary

  • continuous with visceral peritoneum

6. corpus luteum

• after ovulation, remaining follicle cells undergo physical and chemical transformation

  • secretes primarily progesterone and lesser amount of estrogen (maintains thick endometrium)

7. corpus albicans

• scar tissue

• remnants of corpus luteum if fertilization does not occur in about 10 days

• maintains wall of endometrium