Lecture 22 - The Ovarian (and Uterine) Cycle

Question 1

List the internal and external genitalia of the female reproductive system

Answer 1

Internal:
- Ovaries (gonads)
- Uterine (Fallopian) ducts
- Uterus
- Vagina

External:
- Mons pubis
- Clitoris
- Labia

Question 2

Ovaries function

Answer 2

Make the ova (gametes)

Question 3

Uterine tubes and uterus function

Answer 3

Uterine tube - site of fertilization

Uterus - site of embryonic and fetal development

Question 4

Clitoris and vagina function

Answer 4

Clitoris - erectile tissue; responsible for pleasurable sensation associated with the sexual response

Vagina - responsible for receiving sperm (and for pleasurable sensations associated with the sexual response). Also acts as the birth canal

Question 5

How are ovaries developed?

Answer 5

They develop from a bipotential gonad during the embryonic period and are not attached to the Fallopian tube

Question 6

Describe the structure of a mature ovary (complex organ)

Answer 6

The ovary is surrounded by an outer epithelium (germinal epithelium) and a dense connective tissue layer (tunica albuginea)

Blood is supplied through the ovarian hilum to the medulla

Oocytes develop within follicles in the ovarian cortex

Question 7

How are oocytes formed and what surrounds them?

Answer 7

Oogonia/oocytes are formed from germ cells w/in ovarian follicles, surrounded by 2 follicular layers:

Granulosa cells (support/nurse cells) - inner layer
Theca/thecal cells (steroid-secreting cells) - outer layer

Question 8

True or False? Oogenesis produces 4 oocytes from each oogonium

Answer 8

False - it only forms a single oocyte from each oogonium (stem cell). Involves mitosis and meiosis

Question 9

What are polar bodies?

Answer 9

They are the other 2-3 daughter cells of the primary oocyte that are non-functional cells

Question 10

What is oogenesis?

Answer 10

Begins during embryonic development and continues during the ovarian cycle. It is not fully complete until fertilization

It occurs in parallel with development and growth of the follicle surrounding an individual oocyte

Question 11

What is an ovum and when is it formed?

Answer 11

An ovum is a fully mature oocyte that has completed meiosis and it is the stage that only occurs AFTER the oocyte goes through fertilization by sperm

Question 12

Describe the stages and process of oogensis in terms of its timepoints of mitosis and meiosis

Answer 12

1. Mitosis of oogonium will be completed by month 5 of in utero development
2. Meiosis I will be stimulated every menstrual cycle after puberty (will be monthly). Meiosis I will occur for ~14 days
3. Meiosis II will be stimulated to occur by sperm entering the cell cytoplasm and will last for ~hours

Question 13

How is the corpus luteum formed?

Answer 13

At ovulation, the follicle ruptures, releasing the secondary oocyte. The follicular granulosa cells are converted into corpus luteum

Question 14

What happens when follicles don’t complete the process of ovulation?

Answer 14

The follicles become atretic during luteal phase of the cycle. This means that the atretic follicle is non-functional and its oocyte cannot be reactivated

Ovarian atresia is an ongoing process throughout reproductive lifespan, leading to loss of fertility

Question 15

How does the HPG axis control oogenesis and ovarian hormonal secretions?

Answer 15

1. Inhibin provides negative feedback for FSH secretion
2. Estrogens have a primary role in feedback control of LH secretion (low levels of estrogen: negative feedbackl; high levels: pos. feed)
3. Progesterone has a primary role in negative feedback of GnRH secretion (while progesterone is high, GnRH is low)

Question 16

What does Follicle stimulating hormone (FSH) stimulate?

Answer 16

• Follicle proliferation
• Secretion of aromatase by granulosa cells
• Secretion of the regulatory hormone inhibin

Question 17

What does Luteinizing hormone (LH) stimulate?

Answer 17

• Meiosis, ovulation, and corpus luteum formation
• Secretion of testosterone by thecal cells
• Secretion of progesterone by the corpus luteum

Question 18

How do oral contraceptive pills work?

Answer 18

They use synthetic forms of estrogen and/or progesterone to suppress ovulation through negative feedback

Question 19

Describe ovulation

Answer 19

Releases a mature secondary oocyte from its follicle into the peritoneal cavity. These released oocytes enter the uterine (Fallopian) tube and are moved towards the uterus

Question 20

What is the uterus and what are the layers associated with it?

Answer 20

A hollow organ with a thick, muscular wall and a glandular lining that can grow and shrink

Perimetrium - protective membrane
Myometrium - smooth muscle
Endometrium - secretory membrane

Question 21

What is the endometrium? And what are the different layers?

Answer 21

It’s a tissue membrane which contains 2 layers of tissue and 2 different types of arteries

Functional layer and basal layer - these are different parts of the stroma with different functions

Question 22

What does the functional layer of the endometrium do?

Answer 22

It changes across the uterine (menstrual) cycle and is shed during the menstrual phase

Question 23

True or False? The ovarian and uterine cycles are in sync and are coordinated by ovarian and steroid hormones

Answer 23

True - specifically, estrogen for proliferation, and progesterone for maintenance and secretion

Question 24

How does the ANS and SNS play a role in the female sexual response?

Answer 24

An orgasms consists of the:
- SNS: rhythmic activation of several pelvic floor muscles
- ANS: activation of smooth muscle in the uterus and vagina

The arousal ANS involves the engorgement of erectile tissue and lubricating secretions from vaginal glands

*Both parasympathetic and sympathetic divisions are necessary for female arousal responses