Female Reproductive System I: The Ovaries

Question 1

List the 4 layers of the ovaries and briefly describe them

Answer 1

1) Germinal epithelium
- highly regenerative
- modified mesothelium
- simple cuboidal epithelium

2) Tunica albuginea
- dense, irregular CT
- rich in collagen & contains fibroblasts

3) Cortex
- follicles
- highly cellular CT stroma
- low vascularity except around highly developed follicles and in glandular tissue

4) Medulla
- loose CT
- contains blood and lymphatic vessels and nerves that enter the ovary hilus

Question 2

what are primary oocytes? What do they originate from?

Answer 2

Primordial germ cells differentiate into oogonia, which will proliferate and enter meiosis, arresting at prophase 1 becoming known as primary oocytes

Question 3

T/F: Oocyte and follicle formation occur only during fetal development

Answer 3

True

Question 4

Stromal cells around the primary oocyte reorganize to form?

Answer 4

follicular epithelium

Question 5

What are the 4 follicles we can need to identify and what are some characteristics associated with them?

Answer 5

1) Primordial follicle
- smallest
- first follicle stage
- central primary oocyte surrounded by follicular epithelium (simple squamous -low metabolic activity)

2) Unilaminar primary follicle
- follicular cells become cuboidal in shape (higher metabolic activity)
- as follicles grow, they move deeper into cortex

3) Multilaminar primary follicle
- follicular cells become stratified, cuboidal epithelium (granulosa)
- zona pellucida (thick, acellular glycorpotein) surrounds primary oocyte (aid in activation of sperm for fertilization)

4) Secondary (antral)
- oocyte has COMPLETED ITS growth
- granulosa cells continue to proliferate
- granulosa cells produce follicular liquid (antrum)

5) Graafian follicle
- aka mature/vesicular follicle
- usu. only 1 activated follicle reaches this stage
- follicular liquid accumulates dramatically enlarging follicle to a diameter of 2+ cm
- forms a bulge on ovary surface called stigma

Question 6

When does follicle activation occur? What triggers it?

Answer 6

Follicle activation occurs at the start of the 28 day menstrual cycle, triggered by FSH. FSH triggers granulosa cells to produce aromatase (androstenedione to estrogen). Estrogen will then promote follicular cell mitosis.

Question 7

Blood vessels do not penetrate follicles. All signals that get to the primary oocyte have to cross the basement membrane, the granulosa cells, and the zona pellucida. How does this occur?

Answer 7

Gap junctions btw granulosa cells promote transport & signaling within the follicle.

Also, granulosa cells have filopodia that can reach thru zona pellucida to contact microvilli on the oocyte, making gap junctions.

Question 8

As liquid accumulates in secondary follicle, the oocyte and granulosa cells are pushed to the periphery. Near the oocyte, the granulosa cells are bunched together forming a mound called? What is the name for the granulosa cells that directly surround the oocyte?

Answer 8

• cumulus oophorus = the mound of granulosa cells in which the oocyte is embedded
• corona radiata = granulosa cells that directly surround the occyte

Question 9

The stroma around developing follicles rearranges to form theca folliculi. Describe the 2 components of the theca folliculi.

Answer 9

1) Theca externa (outer layer)
- provides structural support
- SM cells, fibroblasts, collagen fibers
- blends w/ stroma

2) Theca interna (inner layer)
- secrete androsteneidone
- extensive smooth ER, large mitochondria, lipid droplets
- foamy looking cytoplasm
- becomes highly vascular to transport hormones

Question 10

Follicular/granulosa cells undergo apoptosis. What about the oocyte?

Answer 10

autolysis

Question 11

What is corpus fibrosum?

Answer 11

later stages of atresia, BM thickens & collapses into the follicular space, leaving a mostly acellular collagenous scar called corpus fibrosum

Question 12

What are interstitial glands?

Answer 12

Theca interna cells that continue to produce hormones after atresia so they are called intersitital glands b/c they are not associated with a follicle.

Question 13

What triggers ovulation?

Answer 13

the rupturing of a graafian follicle releases oocyte from ovary into peritoneal space is triggered by LH surge –> positive feedback of estrogen.

Question 14

When does the primary oocyte (arrested in prophase I since birth until puberty) finishes the first meiotic division?

Answer 14

A few hrs prior to ovulation, the primary oocyte of graffian follicle completes the first meiotic division. This oocyte will commence its 2nd meiotic division but not complete it unless fertilization occurs.

Question 15

What is the oocyte complex?

Answer 15

The granulosa cells forming corona radiata remain attached to zona pellucida surrounding the expelled secondary oocyte = oocyte complex

Question 16

What does the ovulated follicle give rise to?

Answer 16

corpus luteum is formed after ovulation when the follicle wall collapses into folds and the antrum is infiltrated w/ clotted blood and then CT

Question 17

What is LH’s effect on granulosa cells and theca cells after ovulation?

Answer 17

LH causes granulosa and theca interna cells to differentiate into steroid hormone-producing luteinized granulosa and luteinized theca cells.

Question 18

What gives corpus luteum its yellow hue?

Answer 18

Lipochrome pigment accumulation in luteinized GRANULOSA cells gives corpus luteum its yellow hue

Question 19

Explain what happens to the corpus luteum without fertilization

Answer 19

after 10-12 days, corpus luteum requires further hormone stimulation or undergoes luteolysis (apoptosis). Macrophages engulf remaining debris. A large scar of dense CT will form, known as corpus albicans. This will last several months. Loss of progesterone –> trigger menstruation.

Question 20

Explain what happens to corpus luteum in case of pregnancy.

Answer 20

trophoblast cells forming the outermost layer of implanting embyro secrete hCG which prevents corpus luteum from undergoing luteolysis. Progesterone levels are sustained.