control of reproduction in the female Flashcards
when does puberty start?
It has many definitions:
age at the first heat
age at the first ovulation
what is the Oestrous cycle?
the series of recurring reproductive events - controlled by reproductive hormones
what is the oestrus phase in the oestrous cycle?
the period of sexual receptivity, also known as heat
what are the different types of cyclicity ?
polyoestrus
seasonally polyoestrus
monoestrus
what does polyoestrus mean?
regular oestrous cycles throughout the year
what does seasonally polyoestrus mean?
regular oestrous cycles in certain seasons of the year
what does monoestrus mean?
one oestrous cycle in certain seasons of the year
what does anoestrus mean?
it is the period without cyclicity
when can anoestrus occur?
seasonally
during gestation
during lactation
what is the oestrous cycle split into?
oestrus:
sexually receptive
oestrogen (E2)
dioestrus:
not sexually receptive
progesterone (P4)
how long does each oestrous cycle last?
cow, sow, mare = 21 days
ewe = 17 days
queen = 20 - 40 days variable
when does the oestrus part of the oestrous cycle begin?
cow and sow = day 20
ewe = day 16
mare = day 18
what are the 2 phases of the oestrous cycle?
follicular
luteal
what is the follicular phase?
occurs after luteolysis
follicle development
hormones involved = FSH + LH = increase oestrogen
in the oestrus phase
what is the luteal phase?
after ovulation
active corpus luteum
hormones involved = P4
during dioestrus phase
what are the physiological changes in the oestrous cycle?
endocrine
genital tract
what are the behavioural changes during the oestrous cycle?
oestrus vs dioestrus
what is responsible for endocrine system changes?
hypothalamic-pituitary-gonadal axis
what is the hypothalamus responsible for in the hypothalamic-pituitary-gonadal axis?
secreting gonadotropin-releasing hormone (GnRH)
what is the pituitary gland responsible for in the hypothalamic-pituitary-gonadal axis?
follicle-stimulating hormone (FSH)
luteinising hormone (LH)
what is the ovary responsible for in the hypothalamic-pituitary-gonadal axis?
oestrogens (oestradiol 17B)
progesterone
what is the uterus responsible for in the hypothalamic-pituitary-gonadal axis?
prostaglandin F2a (PGF2a)
prostaglandin E2 (PGFE2)
how does the pineal gland effect endocrine changes?
detects changes in daylight
produces melatonin during hours of darkness
Short days (autumn/ winter) = high melatonin
Long days (spring/ summer) = low melatonin
what occurs during short days?
short days = high melatonin - feeds back to hypothalamus
long day breeders = inhibits HPG axis
short day breeders = excites HPG axis
causing increase in GnRH
what occurs during long days?
long days = low melatonin - feeds back to the hypothalamus
long day breeders = excites HPG axis
causing an increase in GnRH
short day breeders = inhibits HPG axis
what is the gonadotropin-releasing hormone ( GnRH) responsible for?
acts on the anterior pituitary, causing physiological effects
small amount of GnRH goes to the central nervous system:
causing a behavioural effect
secreted from the hypothalamus
what is the episodic release of GnRH and reproductive hormone?
during tonic (basal) secretions:
small pulses
frequent and consistent (hours)
causing low oestrogen in a negative feedback loop and high progesterone
during the preovulatory surge:
low progesterone and high oestrogen in a positive feedback loop.
what is the purpose of FSH?
drives follicle development
controlled by GnRH = increase FSH
progesterone = decrease FSH
acts on granulosa cells
what is the purpose of LH?
drives follicle development and oestrogen secretion
cause theca cell activity
causes ovulation and subsequent CL formation
controlled by:
increase GnRH = increase LH
increase oestrogen = increase LH
progesterone = decrease in LH
what occurs prior to ovulaiton?
increase in GnRH
decrease in progesterone
increase in oestrogen
1 large LH pre-ovulatory peak
oestrus ends a day after ovulation
what causes ovulation?
most mammals experience a short peak
the mare experiences a prolonged peak
peak = day after ovulation
oestrus ends 2 days after ovulation (D2)
purpose of oestrogen ( oestradiol) (E2)
drives oestrus
control increase of FSH and LH
positive feedback to increase LH
negative feedback to decrease FSH
secreted by large follicles
purpose of progesterone?
acts to prepare for pregnancy
therefore inhibits the HPG axis
reduces LH and FSH
if pregnant, then CL and P4 remain
it plateaus during the luteal phase to allow the oestrus phase.
what occurs if the woman is not pregnant?
there will be a reduction in progesterone
the removal will result in an increase in FSH
causing the oestrogen to increase at the start of the next oestrus phase
LH will then increase to induce ovulation
to knock out the corpus luteum need a luteolytic agent - PGF2a.
what is the purpose of prostaglandin F2a (PGF2a)
causes luteolysis at the corpus luteum
ends the luteal phase
reduces progesterone
ends inhibition of the HPG axis
allows ovulation and the oestrus phase to occur
when does the prostaglandin increase?
21D cycle = D14/15
17D cycle = D13
what are the changes that occur during dioestrus?
prepare for implantation and pregnancy
protect
what are the changes that occur during oestrus?
allow passage of penis
encourage the movement of sperm to ovulated ova/ovum
what occurs during the dioestrus phase, under the influence of progesterone?
the cervix is tight, white and dry
the uterine wall is thickened
epithelium proliferates, cuboidal
increase in endometrial gland activity = fluid in uterus
increase tone
what are the genital tract changes?
vulva swells, reddening
the cervix becomes loose, red/pink/ moist
the uterus gets thinner walls
epithelial cells columnar
reduced endometrial gland activity = no fluid in the uterus
flacci
myometrial contractions
what are the behavioural changes?
dioestrus = hostility to male
oestrus:
increased locomotion
docility
acceptance of male
urination stance
raised tail
mounting activity
mare = lengthening and eversion of vulva clitoris winking
quee = lordosis and vocalisation
