Lecture 16: Gametogenesis Flashcards
(34 cards)
When does oogenesis begin?
In fetal development
What is used to perform mitosis in females?
oogonium
In between Mitosis and Meiosis I, what do you call the gamete?
oocyte
What is special about Meiosis in oogenesis?
It stops at Prophase I and only resumes during a monthly menstrual/ovulation cycle, and pauses at Metaphase II until fertilization. One of the cells from Meiosis I is a large cell, called a secondary oocyte, but the others are small, called polar bodies, and are destroyed.
What are the groups that help and promote oogenesis called?
Follicles.
Approximately how many primary oocytes are chosen each cycle to continue Meiosis?
Five
Does a primary follicle stop developing and support the other follicle?
Yes
How many cell layers form around the oocyte and what do they do?
-Two layers and they eventually guide the oocyte to the edge of the ovary, this process is called ovulation.
What does the remaining cells of the oocyte become?
They become a hormone secreting structure that remain in the ovaries, which is called corpus luteum.
What is the cervix?
An opening from the uterus that can stretch large to let a baby through.
What is the size of a uterus and what is it composed of?
About the size of a fist, composed of a thick muscular wall that can stretch a lot.
What is the thickening of the lining of the uterus called? and what causes it?
It is called the endometrium, and its caused by hormones.
Where does the oocyte go after ovulation?
Moves along the fallopian tubes, waiting to be fertilized.
What does the corpus luteum signal after ovulation?
It signals to the uterus to prepare and provide proper nutrients to prepare for a fertilized oocyte.
How long does the corpus luteum last for?
A few weeks, after that, it stops supporting the uterine layers, and menstruation begins. Unless, a fertilized egg arrives to the uterus.
How many phases are involved in the uterine cycle? name them.
- 4 phases
- Follicular phase, ovulation, luteal phase and menstruation.
What happens in the follicular phase?
Follicles release estrogen, which causes the uterine wall to thicken.
What happens in ovulation?
The follicle ruptures and develops into a corpus luteum, and progesterone is produced.
What happens in the luteal phase?
Progesterone and estrogen are released from the corpus luteum which thickens the endometrium.
What happens in menstruation?
Endometrium is sloughed away when the corpus luteum degenerates, and a new cycle begins.
List the hormone regulation in a female?
- Hypothalamus -> GnRH -> pituitary gland -> FSH -> blood
- FSH -> ovary -> follicles develop
- Dominant follicle -> estrogen -> stimulate endometrium growth and inhibits the pituitary gland (stops FSH production.
- Estrogen -> pituitary gland -> LH -> ovulation (formation of corpus luteum
- Corpus luteum -> progesterone -> developed endometrium and inhibits pituitary gland
Describe the pituitary hormone levels in all phases of the uterine cycle?
- Follicular phase: FSH levels are initially high before being inhibited by estrogen production.
- Ovulation: huge spike of LH levels triggers ovulation.
- Luteal phase: rising level of estrogen and progesterone inhibits FSH and LH
- Menstruation: When the corpus luteum degenerates, estrogen and progesterone levels fall and FSH levels rise.
Describe the ovarian hormone levels in all phases of the uterine cycle?
- Follicular phase: Estrogen levels rise as estrogen is produces by developing follicles.
- Ovulation: Estrogen levels drops.
- Luteal phase: Progesterone levels rise with the development of the corpus luteum.
- Menstruation: corpus luteum degenerates, estrogen and progesterone levels fall.
Describe the ovarian cycle.
- Follicular phase: FSH causes follicle to mature and produce estrogen.
- Ovulation: an LH surge causes ovulation
- Luteal phase: ruptured follicles form a corpus luteum and secrete progesterone (and some estrogen)
- Menstruation: Corpus luteum degenerates, new ovarian cycle begins.
