11.3 The Ovarian Cycle Flashcards
(24 cards)
What is the ovarian cycle?
The regular series of events that take place within an ovary of a non-pregnant female, associated with the maturation of an egg.
What events are associated with the ovarian cycle?
- Development of follicles in the ovary
- Formation of the corpus luteum
What is the corpus luteum?
The temporary endocrine gland that forms in the ovary after the release of an egg.
What is the length of the ovarian cycle?
An average of about 28 days but it ranges from 20-40 days
What happens to some of a female’s primary follicles during puberty?
When a female matures sexually at puberty, some of the primary follicles which contain a primary oocyte undergo further development.
What happens to the hormones during the first half of the ovarian cycle?
The levels of follicle-stimulating hormone and luteinising hormone slowly increase, prompting growth/maturation of follicles over 10-14 day period.
What is the first step a developing follicle goes through?
Cells forming the wall of the primary follicle begin to enlarge and divide, creating a layer of cells around the developing oocyte.
What is the second step a developing follicle goes through?
Secretions from these cells create a fluid-filled space that gradually forces the oocyte to the edge of the follicle.
- Secondary follicle
What is the third step a developing follicle goes through?
As more fluid accumulates within the follicle, it continues to enlarge and gradually moves towards the surface of the ovary.
What is the fourth step a developing follicle goes through?
On reaching the surface, it produces a bulge that looks like a swollen blister on the surface of the ovary
- Mature/Graffian Follicle
What is a secondary follicle?
A previously dormant follicle that has begun to develop.
What is a mature follicle?
A fluid-filled structure in the ovary; it contains an immature egg and its surrounding tissues; aka Graafian follicle
What happens to the other secondary follicles during each ovarian cycle?
Break down to be reabsorbed into the ovary. As the follicles grow, they release oestrogen, and a low level of progesterone.
What happens to the follicles and hormones on day 14 of the ovarian cycle?
- The level of oestrogen is high enough to stimulate a spike in LH and FSH.
- The surge in LH causes the ovulation of the most mature follicle, while the other follicles degenerate, releasing less oestrogen.
What happens to the mature follicle during ovulation?
It bursts and expels the oocyte.
What is the role of cilia in the uterine tube?
Beating cilia within the funnel create a current that sweeps the egg into the uterine tube.
What happens to the ruptured follicle during ovulation?
It collapses and the blood within forms a clot
What happens to the blood clot during ovulation?
The clot is gradually absorbed by the remaining follicle cells, which enlarge and change colour to form a cream-coloured body, the corpus luteum
What is the role of the corpus luteum?
- It secretes oestrogen and progesterone
- It inhibits the release of FSH and LF to prevent other follicles developing
What happens to the corpus luteum if fertilisation hasn’t occured?
The corpus luteum reaches its maximum development about 8 to 10 days after ovulation.
It then begins to degenerate into a fibrous mass of scar tissue, the corpus albicans
What is the corpus albicans?
A fibrous mass of scar tissue left on the ovary after the corpus luteum degenerates.
What happens to the corpus luteum during egg fertilisation and pregnancy?
It continues to develop and the ovarian cycles cease
What is the human chorionic gonadotropin (HCG)?
A hormone produced by the developing placenta in a pregnant woman
- Maintains the corpus luteum
When does the corpus luteum degenerate?
Once the placenta is able to secrete oestrogens and progesterone
- Degenerate is slow and C.L is still present in the ovary at childbirth
