Lecture 22 - The Ovarian (and Uterine) Cycle Flashcards
List the internal and external genitalia of the female reproductive system
Internal:
- Ovaries (gonads)
- Uterine (Fallopian) ducts
- Uterus
- Vagina
External:
- Mons pubis
- Clitoris
- Labia
Ovaries function
Make the ova (gametes)
Uterine tubes and uterus function
Uterine tube - site of fertilization
Uterus - site of embryonic and fetal development
Clitoris and vagina function
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
How are ovaries developed?
They develop from a bipotential gonad during the embryonic period and are not attached to the Fallopian tube
Describe the structure of a mature ovary (complex organ)
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
How are oocytes formed and what surrounds them?
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
True or False? Oogenesis produces 4 oocytes from each oogonium
False - it only forms a single oocyte from each oogonium (stem cell). Involves mitosis and meiosis
What are polar bodies?
They are the other 2-3 daughter cells of the primary oocyte that are non-functional cells
What is oogenesis?
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
What is an ovum and when is it formed?
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
Describe the stages and process of oogensis in terms of its timepoints of mitosis and meiosis
- Mitosis of oogonium will be completed by month 5 of in utero development
- Meiosis I will be stimulated every menstrual cycle after puberty (will be monthly). Meiosis I will occur for ~14 days
- Meiosis II will be stimulated to occur by sperm entering the cell cytoplasm and will last for ~hours
How is the corpus luteum formed?
At ovulation, the follicle ruptures, releasing the secondary oocyte. The follicular granulosa cells are converted into corpus luteum
What happens when follicles don’t complete the process of ovulation?
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
How does the HPG axis control oogenesis and ovarian hormonal secretions?
- Inhibin provides negative feedback for FSH secretion
- Estrogens have a primary role in feedback control of LH secretion (low levels of estrogen: negative feedbackl; high levels: pos. feed)
- Progesterone has a primary role in negative feedback of GnRH secretion (while progesterone is high, GnRH is low)
What does Follicle stimulating hormone (FSH) stimulate?
- Follicle proliferation
- Secretion of aromatase by granulosa cells
- Secretion of the regulatory hormone inhibin
What does Luteinizing hormone (LH) stimulate?
- Meiosis, ovulation, and corpus luteum formation
- Secretion of testosterone by thecal cells
- Secretion of progesterone by the corpus luteum
How do oral contraceptive pills work?
They use synthetic forms of estrogen and/or progesterone to suppress ovulation through negative feedback
Describe ovulation
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
What is the uterus and what are the layers associated with it?
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
What is the endometrium? And what are the different layers?
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
What does the functional layer of the endometrium do?
It changes across the uterine (menstrual) cycle and is shed during the menstrual phase
True or False? The ovarian and uterine cycles are in sync and are coordinated by ovarian and steroid hormones
True - specifically, estrogen for proliferation, and progesterone for maintenance and secretion
How does the ANS and SNS play a role in the female sexual response?
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
