Gametogenesis Flashcards
What is a follicle?
An Ovarian structure that enables the ovary to fulfill its dual function
What is folliculogenesis?
Formation of the graafian follicle
What is follicle turnover?
Frequent emergence of new follicles
What is ovulation?
Release of oocyte from the graafian follicle
What are the seven events during follicular growth?
- Recruitment of follicles
- Selection of dominant follicle(s) and atresia of the remaining
- Nuclear maturation of oocyte
- Cytoplasmic maturation of oocyte
- Steroid synthesis
- Stigma formation
- Release of egg
What happens during the Recruitment of follicles during follicle growth?
cohort of follicles are selected
What is the Recruitment of follicles during follicle growth dependent on? how does it get it?
FSH - Theca interna has FSH receptors
What happens during the Selection of dominant follicle phase of follicle growth?
- LH receptors are developed in the granulosa cells
- remaining follicles undergo atresia
- steroidogenesis of estradiol
What happens during the Nuclear Maturation phase of follicle growth?
- Meiotic arrest until an LH surge is reached (stopped in prophase 1)
- Meiotic resumption until metaphase 2 where it stops again
What happens during the Cytoplasmic Maturation phase of follicle growth?
- Granulosa cells around the oocyte begin to loosen
- mRNA, proteins, substrates, and nutrients that are required to achieve oocyte and embryonic development accumulate
What happens during prophase 1?
Chromosomes pair
What happens during metaphase 1?
Paired chromosomes migrate to center due to centrioles
What happens during anaphase 1?
Chromosome pairs are separated and pulled to opposite ends of the cell
What happens during telophase 1?
Cell divides
What happens during prophase 2?
Centrioles duplicate and cell gets ready for another division
What happens during metaphase 2?
Chromosomes line up in the middle of the cell
What happens during anaphase 2?
Chromosomes as pulled apart and pulled to opposide sides of the cell
What happens during telophase 2?
Cell divides and each becomes haploid
What does the zona pellucida which surrounds the ovum do?
Help protect the ovum from being bombarded by many sperm at once. (prevents sperm from reaching egg easily)
Which steroids are produced and where during the steroid synthesis of follicular growth?
- Cholesterol is transported to the ovarian follicle -> High density lipoproteins and low density lipoproteins
- Testosterone synthesis by theca interna (controlled by LH)
- Estradiol synthesis by granulosa cells (Controlled by FSH)
What happens during the stigma formation of follicular growth?
- The apical wall becomes thin (weaker)
- Becomes avascular (further weakens)
- Ruptures at ovulation
What happens during the release of egg or ovum during follicular growth?
- Cumulus-oophorus complex loosens
- Prostaglandin causes uterine contractions + vascular contractions
- Ovum is expelled and picked up by the oviduct
Which hormones are produced in great quantity during ovulation?
- GnRH and LH
What is the biochemical composition of Follicular fluid?
- Steroids and glycoproteins secreted by cells of the follicle wall and serum exudate.
- Enzymes, prostaglandins and gonadotropins