Lecture 50: Female Reproductive Physiology Flashcards
how does spermatogenesis contrast with oogenesis
- spermatogenesis occurs daily; new sperm made every day
- maturation of oocytes from primitive progenitor cells begins even before birth
describe the genetic material of primary oocyte
- 2n + 2n (double the genetic material)
- considered diploid as chromosomes paired
describe the genetic material of secondary oocyte
- n + n (double genetic material)
- considered haploid as chromosomes unpaired
outline the process of oogenesis
- maturation of oocytes from primitive progenitor cells begins before birth
- initially oogonia undergo mitotic division to multiply numbers of potential oocytes
- first meiotic division before birth to form primary oocytes
- all division then stops until puberty
- at this point, 1st meiotic division complete giving 2 distinct cells
- one is haploid cell rich in cytoplasm and nutrient –> secondary oocyte
- haploid cell w/ unpaired chromosomes but 2x genetic material of final gamete
- second smaller cell is polar body
what hormone stimulates follicles
follicle stimulating hormone
describe follicular phase of ovarian cycle
- day 1-14 but can be shorter
- oocytes contained in follicles
- most basic being primordial follicles
- consist of primary oocyte surrounded by single layer of granulosa cells, sitting upon CT basal lamina
- granulosa cells multiply and create layer of mucopolysaccharide around ovum, called zona pellucida
- layer of cells outside basal lamina differentiates to form theca cells
- start of each ovarian cycle, several primordial cells enlarge and cavity (antrum) is visible filled w/ follicular fluid prod by granulosa cells
- only 1 of these follicles develops further becoming dominant
- remaining follicle (Graafian or astral follicle) enlarges
- theca cells differentiate into theca interna and theca externa
- at around 14 days, follicle so large it distorts ovary surface
- fluid accumulation in follicle and proteolytic enzyme activity combine to allow follicle rupture
- ovum released
describe the luteal phase of ovarian cycle
- day 14-28
- after rupture, follicle fills w/ blood –> corpus haemorrhagicum
- many women get ovulatory pain due to little irritation from some of the blood in peritoneum
- granulosa and theca cells swell up –> rich in yellow fatty deposits
- blood vessels infiltrate follicle (attracted by vascular endothelium growth factor; VEGF)
- now called corpus luteum (yellow body) facilitating important endocrine function
- if no fertilisation, corpus luteum degenerates after 10 days
- precipitates breakdown of uterine wall (menses)
describe hormonal control during ovarian cycle
- at start of cycle, gonadotropin releasing hormone (GnRH) secreted by hypothalamus
- causes release of follicle stimulating hormone (FSH) and luteinising hormone (LH) from ant. pit.
- these hormones start cycle by stimulating primordial follicle development
- FSH encourages cell division and oestrogen secretion by granulosa cells
- LH functioning in formation of luteal body later in cycle
- LH also has role in early part of cycle stimulating androgen prod by theca cells
- androgens diffuse into granulosa cells
- converted into oestrogens
- rising conc of oestrogen inhibits gonadotropins
- after day 10 oestrogen levels actually stimulate LH secretion
- giving rise to dramatic surge day 14 which stimulates ovulation
- corpus luteum takes over hormone prod
- produces oestrogen and progesterone
- level of these hormones -vely feedback on FSH and LH
- day 22-24 corpus luteum undergoes atresia (degeneration) causing rapid falling off in hormone levels
- this removes -ve feedback on GnRH –> levels rise again, cycle repeats
what is the role of follicle stimulating hormone (FSH) in ovarian cycle
FSH encourages cell division and oestrogen secretion
what is the role of luteinising hormone (LH) in ovarian cycle
- LH functioning in formation of luteal body later in cycle
- LH also has role in early part of cycle stimulating androgen prod by theca cells
what inhibits gonadotropins
rising conc of oestrogens
what is one of the most important functions of female specific hormones
- proliferation and maintenance of endometrial lining of uterus
- so that at time of ovum release, it can serve to nourish developing embryo
what is the predominant hormone after ovulation
progesterone
what is the role of progesterone after ovulation
maintenance of uterine lining
what are the two layers of uterine endometrium
stratum functionalis and stratum basalis
