Session 4- The Menstrual Cycle Flashcards
How does the hypothalamus-pituitary-gonadal axis differ in males and females
Males
- continuous gamete production required
- levels of hormones are maintained at a steady state
Females
- periodic gamete production
- tract needs to prepare for implantation
- waiting phase in case implantation occurs
- cyclical hormone changes
Average length of mentrual cycle
28 days
What is the purpose o the ovarian cycle
Preparation of the gamete for release
What are the two phases of ovarian cycle
Follicular phase- early and late
Luteal phase
Ovarian cycle- early follicular phase - 0-5
No ovarian hormone production
Granulosa cells secrete activin- stimulates FSH ONLY
-increased FSH production and receptors on granulosa cells
-reduced production of androgens by theca cells- less oestrogen
THIS STIMULATES FOLLICLE GROWTH
Outcome of early follicular phase
Stimulate follicle growth
Theca interna appears
Enhanced aromatase function-> folllicle now capable of enhanced oestrigen production
Dominant follicle granulosa cells switch to produce inhibin which cause FSH to decrease which allows LH to increase
Late follicular phase
Days 5-14
Dominant follicle granulosa cell produce oestrogen and inhibin
Oestrogen
- increase FSH receptors on follicle
- LH receptors on granulosa cells- prep for ovulation
Inhibin
-decrease FSH production and help LH to increase theca cell androgen production
Ovulatory phase
Day 14
Oestrogen continues to rise independently of FSH
High levels of oestrogen exert positive feedback on hypothalamus and ant pituitary which causes a surge in LH production
Ovulation occur
Ovulation
Meiosis 1 completes
Meiosis 2 begun but not completed yet
Mature oocyte travels through the capsule of the ovary not the Fallopian tube
Luteal phase
Follicle is luteinised -Corpus luteum
Secrets oestrogen and progesterone in large quantiles
Inhibin also secreted so another follicle doesnt develop
Oestrogen and progesterone exert negative feedback on LH
FSH levels remain low
What hormone causes proliferative epithelium to develop
Oestrogen
What hormone causes secretory epithelium to develop
Progesterone and oestrogen
What layers is the uterus mae up of
Endometrium- stroma and epithelium
Myometrium
Perimetrium
What layers is the endometrium made up of
Functional layer- responsive to hormone shed in menstruation
Basal layer- develops into new functional layer
Early proliferative phase of uterine cycle
Sparse glands, straight
Late proliferative stage of uterine cycle
Thicker functional layer, glands coiled
Secretory phase of uterine cycle
Endometrial thickness of maximum very coiled glands
Coiled arterioles
What happens at the end of menstrual cycle if no fertilisation
Corpus luteum -> corpus albicans if no fertilisation
Dramatic fall in oestrogen, progesterone and inhibin as corpus luteum is gone
No negative feedback so sow rising FSH
End of menstrual cycle- if fertilisation occurs
Syncytiotrophoblast produces hCG
Extends lifespan of corpus luteum-> before placenta forms
What is teh normal duration of teh cycle
21 - 35 days
Variegation is due to length of follicular phase
When is oestrogen mostly used
Follicular phase
-Thickening of endometrium Fallopian tube function Growth and motility of myometrium
Thin alkaline cervical mucus Vaginal changes Changes in Skin, hair, metabolism
When is progesterone mostly used
Luteal phase
-Further thickening of endometrium (secretory)
Thickening of myometrium and reduction of motility
Thick, acidic cervical mucus Development of breast tissue Increased body temperature Metabolic changes Electrolyte changes
what triggers ovulation
LH
LH surge
