21 - Gamete Manufacture, Ovarian and uterine cycles Flashcards
What stage are primary oocytes held in
prophase of meiosis 1
What is the follicular phase
where the ovum and surrounding cells (the follicle) develop up to the point of ovulation
- length is variable
What is the luteal phase
where the remaining cells of the follicle hang around and secrete hormones (mainly progesterone)
- prepares the lining of the uterus and endometrium for a fertilized ovum (zygote)
How is the antrum formed
granulosa cells secrete follicular fluid –> antrum
What is the corona radiata
granulosa cells around the oocyte
Describe the negative pituitary regulation of the ovarian cycle
Stimulus: low estrogen in the blood
Receptor and control centre: hypothalamus detects low estrogen levels
Effector:
1. GnRH released from the hypothalamus
2. LH and FSH released from the pituitary –> follicle growth
3. LH stimulates production of estrogens which inhibit GnRH, LH, and FSH release
Describe the positive pituitary regulation of the ovarian cycle
Continued estrogen production stimulates GnRH, LH and FSH release
LH surges causing the follicle to rupture and the ovum to be released
Describe uterine histology
- endometrium - stratum basalis and stratum functionalis
- myometrium - smooth muscle
- serosa - visceral peritoneum
What is the purpose of the menstural cycle/uterine cycle
to prepare the lining of the uterus for the fertilized egg to implant
What are the layers of the endometrium
stratum functionalis (outest)
stratum basalis
myometrium
Which part of the endometrium is shed
stratum functionalis
What does the stratum functionalis growth do
proliferation of the stroma and growth and elongation of the endometrial glands – glands will produce material that will provide nutrition for the zygote (fertilized egg)
What are the phases of the uterine cycle
menstural phase
proliferation phase
secretory phase
What happens in the mentural phase
Shedding of the inner lining of the uterus, known as the endometrium – loss of cells in blood
Estrogen and progesterone levels are low
- Shedding of the endometrium triggered by a decrease in hormone levels
What happens in the proliferation phase
rapid growth and thickening of the endometrium under the influence of rising estrogen levels
estrogen:
- stimulates the proliferation of endometrial cells
- blood vessel formation
- development of glandular structures within the endometrium
Prepares the uterus for potential implantation of a fertilized egg by creating a thick, vascularized lining.
What happens in the secretory phase
secretion of progesterone from the corpus luteum
Progesterone (& some estrogen):
- acts on the endometrium to further thicken and vascularize it (preparing it for potential implantation of a fertilized egg)
If fertilization and implantation do not occur, the corpus luteum regresses –> decline in progesterone levels and triggering the onset of menstruation
What triggers ovulation
surge in estrogen –> LH surge
Surge in LH and some FSH –> stimulate the final maturation and release of the egg from the ovary
In which phase is estrogen most secreted
proliferative and secretory phase
In which phase is progesterone most secreted
secretory phase
what stops the degeneration of the corpus luteum
implanting zygote and the placenta releases human chorionic gonadotropin (hCG)
What does human chorionic gonadotropin do
acts like LH and stimulates the corpus luteum to produce lots of progesterone and a little estrogen
What does the progesterone released from the corpus luteum do
inhibits uterine contractions and prevents disintegration of the stratum functionalis that preceeded menstural flow
What are the parts of the sperm
acrosome
nucleus
midpiece
flagellum
What does the acrosome do
sperm head
contains digestive enzymes for penetrating the zona pellucida
