HPO axis and the menstrual cycle Flashcards
1
Q
what are the 3 physical cycles involved in the female reproductive cycle + female reproduction
A
- hypothalamic-pituitary-ovarian axis
- ovarian cycle
- uterine cycle
2
Q
what are the 2 phases in the ovarian cycle and what are they separated by
A
- the follicular phase - day 1 to 14
- ovulation
- the luteal phase - 15 to 28
3
Q
why may the ovarian cycle range from 21-35 days
A
follicular phase length may change
luteal phase stays at 14 days
4
Q
5 stages in the follicular phase
A
- primordial follicles become primary follicles
- the primary follicle matures into a secondary follicle, the zona pellucida + theca folliculi are formed
- cells of the theca produce oestrogens during the maturation process
- a fluid filled space around the oocyte develops + some granulosa cells develop into a corona radiata surrounding the oocyte
- the follicle is now a mature Graafian follicle, ready to release a secondary oocyte at ovulation
5
Q
what are the 4 stages in the ovulation
A
- ovulation occurs in alternative ovaries
- follicle ruptures and the secondary oocyte is expelled into the abdominal cavity
- the oocyte enters the fimbriated end of the fallopian tube
- one is released each ovulation
- follicular phase ends in ovulation
6
Q
what are the 6 phases in the luteal phase
A
- ruptured follicle caves in and fills with a blood clot
- granulosa + theca cells increase + form an endocrine structure = corpus luteum
- corpus luteum secretes progesterone + oestrogen and is essential for preparing for fertilisation + for maintaining a pregnancy (if it occurs)
- if fertilisation does not occur the corpus luteum degenerates after 12-14 days
- the area of the corpus luteum becomes scar tissue + is called the corpus albicans
- if fertilisation occurs, the corpus luteum continues to function to maintain pregnancy until the placental + foetal hormone production is sufficient
7
Q
what is the ovarian cycle controlled by
A
- gonadotropins
- hypothalamus
8
Q
how is gonadotropin released + the role of the hypothalamic pituitary axis
A
- small body neurons in arcuate nucleus + preoptic area of hypothalamus
- they release = gonadotropin releasing hormone (GnRH) +luteinising releasing hormone
- released in rhythmic pulses - 1 an hour
- secreted into medial eminence + hypophyseal portal system where GnRH binds to receptors on gonadotropic cells of anterior pituitary
- the gonadotropins produced by the anterior pituitary are - follicle-stimulating hormone (FSH) , luteinising hormone (LH)
- in the ovary, theca cell have LH receptors and granulosa cells have LH and FSH receptors , their activation stimulates initial follicular development and oocyte maturation
- oestrogens and progesterone are produced that control the menstrual cycle
- in response to FSH , granulosa cells produce inhibins that negatively feed back on FSH production from anterior pituitary
9
Q
what is the roles of oestrogens
A
- prepare female reproductive tract for fertilisation and implantation
- induces expression of progesterone receptors in target tissues
- required for corpus luteum to work
- tubal epithelium
- stimulates proliferation of epithelial lining
- secretes sugar rich fluid
- endometrium
- stimulates hyperplasia and hypertrophy of epithelial lining
- glands elongate and spiral arteries grow
- smooth muscle
- up regulates receptors for prostaglandins and oxytocin
- spontaneous activity increased
- cervix
- increases mucous volume
- decreases mucus viscosity
10
Q
what are the 3 phases of the uterine cycle
A
- proliferative
- secretory
- menstrual
11
Q
what is the role of the uterine cycle
A
- prepares the endometrium for possible implantation by the fertilised embryo
- changes occurring in the uterus as the endometrium responds to ovarian hormones
12
Q
what is the proliferative phase of the uterine cycle
A
- corresponds to the follicular phase of ovarian cycle
- starts at day 5
- where the basal layer of the endometrium remains
- oestrogen is released and this results in cell proliferation + regeneration of the stratum functionalis
- the proliferative phase ends with the maturation of the Graffian follicle and ovulation at day 14
- 2mm thick
- cervical mucus changes from thick plug to thin slippery mucus that can be penetrated by spermatozoa
13
Q
what is the secretory phase of the uterine cycle
A
- corresponds with the luteal phase of the ovarian cycle
- 14 days long
- endometrium is influenced by progesterone, enlarges glands, secrete glycogen to nourish embryo
- spinal arteries increase in size and become thick
- cervical mucus changes into a thick plug, blocking the cervical canal
- if fertilisation doesn’t occur the corpus luteum hormones decline which results in spinal artery spasm + endometrium degeneration due to deprivation of nutrients in endometrium degeneration due to deprivation of nutrients and autodigestion by lysosomes
- menstruation happens 24h after
14
Q
what is the menstrual phase of the uterine cycle
A
- spiral arteries ilate + bleed into necrotic stratum functionalis
- blood, other fluids, endometrial fragments
- 3-6 days
- clotting of menstrual blood flow is prevented by fibronolysins, ensuring the endometrium is expelled fully
- uterus contracts in response to prostaglandins
15
Q
what is dysmenorrhoea
A
dull achy cramps → intense pain
