Lecture 37: FEMALE REPRODUCTIVE SYSTEM 2 Flashcards
What is oogenesis?
Formation and development of the oocyte from oogonia
What does oogenesis require?
Mitosis and meiosis
What is produced before birth?
A lifetime supply of gametes
When does oogenesis occur?
It is initiated before birth and continues between puberty and menopause
How is oogenesis described?
Cyclic (1 ovulation every 28 days on average)
Where do oocytes develop?
Within an ovarian follicle (stationary) - 1 oocyte per follicle
What is in the gonad before birth?
oogonium (diploid, 2n=46)
What happens to the population of oogonia?
They increase by mitosis (stops before birth)
What do oogonia do?
Differentiate to form primary oocytes (diploid, 2n=46)
What are primary oocytes encased in?
Primordial follicle
What happens with many primary oocytes?
They undergo atresia
What do primary oocytes start?
Meiosis
When does meiosis halt?
At prophase 1 until puberty begins
How many oocytes do females have at puberty?
Approximately 300,000
What happens under GnRH influence?
A small number of follicles recruited each ovarian/menstrual cycle
What does only one oocyte do?
Complete development and ovulate (within the dominant follicle)
What does the primary oocyte complete?
Meiosis 1 to form a secondary oocyte and first polar body (both haploid, n=23)
What does the secondary oocyte start?
Meiosis 2
When does meiosis 2 halt?
At metaphase 2 which is suspended until fertilisation
When does meiosis 2 resume?
When the sperm penetrates the plasma membrane of the ovum at fertilisation
What happens if the secondary oocyte is not fertilised?
It will degenerate by atresia and therefore never complete meiosis
What does one primary oocyte form?
1 ova and 3 polar bodies will also form which under go atresia
What are the layers of the follicles?
Granulosa cells inside and theca cells outside
What do granules cells produce?
Inhibin
What happens in ovulation?
Oocyte and corona radiata released into peritoneal cavity
What are the female reproductive hormones?
GnRH, FSH, LH, estradiol, inhibit and progesterone
Where is GnRH released from?
The hypothalamus
What does GnRH do?
Stimulate the release of FSH and LH