Oogenesis Flashcards
What is oogenesis?
Process of ovum formation in ovary
How are ova originate as?
- Produced from immature oocytes (primary follicles that develop before birth)
What is oogonia also referred to?
Primary follicles
What happens during oogenesis?
- Primordial oogonium undergoes mitosis before birth
- Oogonium enters meiosis & frozen in prophase 1 (primary oocyte)
- Primary oocytes enter resting phase until just before ovulation
- 1 oocyte chosen for ovulation will complete meiosis 1
- 2 cellular products formed (secondary oocyte & polar body)
- Polar body degenerates
- Secondary oocyte freezes in metaphase of meiosis 2
- This freezing point is only released post-fertilisation
- Meiosis 2 is completed with genetic material from sperm
What is a primary follicle (oogonium)?
Germ cell surrounded by a cluster of granulosa cells
What is the function of FSH?
Stimulates primary oocytes to form enlarged primary oocytes (Follicle stimulating hormone)
What is the zona pellucida important for?
Sperm binding + penetration
What happens to the primary follicle as it completes meiosis 1?
Produces 2 haploid cells:
- Large secondary follicle
- Smaller first polar body
What is an antrum?
A cavity that forms when fluid collects between granulosa cells + separates them
What are Graafian follicles?
Mature follicles on ovary surface
What do the granulosa cells secrete?
Oestrogen
What hormones stimulate the follicle to rupture?
LH + FSH
What does monotocous mean?
One ovum per oestrus period
E.g. humans, cows, etc.
What does polytocous mean?
Many ova per cycle
E.g. pigs, rabbits, mice, etc.
How is the corpus luteum formed?
- Once ovum is released, ruptured follicle fills with blood
- Granulosa cells proliferate + gradually replace clotted blood with lateral cells rich in lipid
- Ruptured follicle is transformed into corpus luteum
