Physiology - Gender, Family & Culture Flashcards
What does the HPO axis control
Female reproduction
What is the menstrual cycle
Ovarian and uterine cycle together
The hormonal cycle tightly regulated to
Select ovarian follicle for ovulation
Prepare endometrium for implantation of fertilized follicle
Duration of ovarian cycle
28 days
Duration of follicular phase
Incl ovulation
1 -1 4
Duration of luteal phase
Days 15-28
What can cause changes in duration of ovarian cycle
The follicular phase, duration of the luteal phase remains unchanged
The follicular phase
FSH increases and causes primordial follicles become primary follicles
1’ follicles –> 2’ follicles, the theca folliculi are formed
Each follicle contains an egg but only one fully matures
What hormone is released during follicular phase
Oestrogen by cells of the thecca
Where does ovulation occur
Alternate ovaries
Ovulation phase
FSH and LH are high
The follicle ruptures and the 2’ oocyte is expelled into the abdominal cavity
The oocyte enters the fimbriated end of the fallopian tube
Luteal phase
FSH and LH decrease and oestrogen and progesterone rise
The ruptured follicle caves in and fills with a blood clot
Corpus luteum forms
Corpus luteum
Endocrine structure formed by granulosa and theca cells
What does the corpus luteum secrete
Progesterone and oestrogen
What is the corpus luteum essential in
Preparing for fertilization and for maintaining a pregnancy should it occur
What happens if fertilisation does not occur during the luteal phase
The corpus luteum degenerates after 12-14 days due to decreasing levels of FSH and LH
The area of the corpus luteum becomes scar tissue (corpus albicans)
What happens if fertilisation occurs during the luteal phase
The corpus luteum continues to function to maintain pregnancy until placental and fetal hormone production is sufficient
When is the concentration of LH, FSH and oestrogen the highest
Just before ovulation
When is the concentration of progesterone the highest
Days 20-26
Hormones secreted by hypothalamus
GnRH
Hormones secreted by pituitary gland
FSH and LH
Hormones secreted by ovary
Oestrogen and progesterone
What is the uterine cycle
Changes occurring in the uterus as the endometrium responds to ovarian hormones
Corresponds to the ovarian cycle
What does the uterine cycle prepare the endometrium for
Possible implantation by the fertilized embryo
Phases of uterine cycle
Proliferative
Secretory
Menstrual
Proliferative phase
Corresponds to the follicular phase of the ovarian cycle
Starts ~day 5 when bleeding ceases
The release of oestrogen results in cell proliferation & regeneration of the stratum functionalis
Cervical mucus in proliferative phase
Changes from a thick plug, blocking the cervix to profuse amounts of thick slippery mucus that can be penetrated by spermatozoa
Secretory phase
Corresponds with the luteal phase of the ovarian cycle
14 days in duration
The endometrium prepared by oestrogen is now influenced by progesterone
Cervical mucus in secretory phase
Changes to a thick plug, blocking the cervical canal and protecting the embryo
Menstrual phase of uterine cycle
The spiral arteries in the endometrium dilate and bleed into the necrotic stratum functionalis and this lasts 3- 6 days
What causes the uterus to contract during menstruation
Prostaglandins
Body temperature variation during menstruation
Fall corresponding with the LH surge ~24hrs priors to ovulation
Progesterone secreted by the corpus luteum results in a rise in metabolic rate & temp by 0.5 degrees
This rise persists until menstruation
Altered pathology of HPO axis and menstruation
Abnormal uterine bleeding Endometriosis Infertility Endocrinopathies Genetic causes Iatrogenic Age and weight impact
Endocrinopathies causing altered pathology
Hypothyroidism
Genetic causes of altered pathology
Turner syndrome (complete or partial X chromosome deletion)
Iatrogenic causes of altered pathology
Impact of chemo
How does moderate oestrogen levels impact the menstrual cycle
Exert negative feedback on the HPO axis
How does high oestrogen levels (in the absence of progesterone) impact the menstrual cycle
+vely feedback on HPO axis
How does oestrogen levels in the presence of progesterone impact the menstrual cycle
-vely feedback on HPO axis
Inhibin
Produced by granulosa cells
Selectively inhibits FSH at the anterior pituitary
