Reproduction Cyclicity Flashcards
what is puberty followed by in females
reproductive cyclicity
Estrus (heat)
characterized by endocrine changes, behavioural changes, sexual receptivity and physical and structural changes in the reproductive tract
whcih species undergo Polyestrus
cow, cat, pig, rodent
what species undergo seasonally polyestrus
long day breeder: mare
short day breeder: sheep
what does seasonally polyestrus mean
clusters of estrous cycles during a certain peiod of the year
what does monoestrus mean
one cycle per year
what species are monoestrus
dog, wolf, fox, bear
what does polyestrous mean
uniform distribution of estrous cycles throughout the year
what are the 4 stages of the estrous cucle of the cow
proestrus
estrus
metestrus
diestrus
what stages of the estrous cycle are considered the follicular phase? what kind of follicle persists
follicular phase = proestrus and estrus
- follicle is predominant
what 2 stages of estrous are considered the luteal phase. what type of follicle is predominant
luteal phase = metestrus and diestrus. CL is predominant
what is the predominant hormone at ovulation
estrogen
what are some physical changes in the reproductive tract during estrus
- increased blood flow
- increased edema of tissues (external genetalia)
- mucus secretion from cervix and caudal vagina
-elevated urine tone due to smooth muscle contraction
-growth of uterine glands - hyperemia
what effects does the LH surge have on the oocyte
promotes maturation of oocyte (progression of meiosis) prior to ovulation, induces breakdown of cytoplasmic processes allowing oocyte to resume meiosis
- primary oocyte arrested at meiotic prophase completes its first meiotic division under the influence of LH
what is the cardinal sign of estrus in a cow
standing estrus: cow allows mating or stands in a characteristic mating posture to be mounted by herd mates
Proestrus
2-5 days immediately preceding behavioural estrus, ovulatory follicles develop, secretes E2
Estrus
shortest stage, period of sexual receptivity and maximum e2 secretion
Metestrus
period of CL development and beginning of P4 secretion
what day does the CL become fully functional
Day 5 (day 0 = day of estrus)
Diestrus
presence of fully functional CL, ends with luteolysis
in mammals, what is the ovulated egg (what stage is it arrested in, and what kind of oocyte)
secondary oocyte with nucleus arrested at metaphase II
when does the ovulated egg in a mammal progress past metaphase II
when sperm makes contact with its cytoplasm
How does LH have an effect on follicular pressure
LH surge will to an increase in production of PGE2 (a prostaglandin). –> promotes histamine production –> increase blood flow to ovary –> increased hydrostatic pressure in follicle –> increase follicular pressure
what effect does PGF2 alpha have on ovulation
induse contractions of ovarian smooth muscle –> increase follicular pressure
also induce release of lysosomal enzymes from granulosa cells of the follicular wall –> follicular wall weakening
following the LH surge, what begins to synthesize P4
theca internal cells
increased progesterone levels following an LH surge results in what to make the follicular wall even weaker
production of collagenases in theca internal –> break down collagen fibers and connective tissue of the tunica albuginea
what is a stigma
avascular region that develops on the follicular wall which ruptures and releaases the oocyte and follicular fluid
after ovulation, what does the remaining follicular structure become
corpus leuteum
histologically, what 2 types of cells are contained within the CL
theca and granulosa cells
what is the corpus luteum
a transient endocrine gland
thecca cells become _____ in the CL
small luteal cells
granulosa cells become ____ in the CL and contain _____ and ____ (2 hormones)
granulosa cells become large luteal cells in the CL and contain relaxin and oxytosin
small luteal cells and large luteal cells both produce
P4
what are 4 luteotropic agents
LH, prolactin, eCG, hCG
when does the CL stop increasing in size
in the middle of the cycle
through what mechanisms does the CL increase in size
hypertrophy of large luteal cells (formerly granulosa)
hyperplasia of small luteal cells (formerly theca)
what are 3 target organisms of P4
- hypothalamus
- mammary gland
- uterus (myometrium and endometrium)
what is the mechanism for P4 synthesis in the corpus luteum
- LH activates protein kinases
- Internalization of LDL-Cholesterol-
receptor - Release of cholesterol esters from its
receptors - Release of cholesterol from
cholesterol esters - Conversion of cholesterol to
pregnenolone in the mitochondria - Conversion of PREG to P4 in the
cytoplasm
what is luteolysis
regression of the CL, usually towards the end of diestrus
what effect does the uterus have on luteolysis
the uterus synthesizes prostaglandin F2 alpha which is a luteolytic factor. if you remove the uterus or the ipsilateral horn that is producing the CL, the CL will persist for longer (aka wont get destroyed)
what is the mechanism that ensures PGF2a from the uterus exerts its luteolytic activity on CL without being diluted
counter current exchange and passive diffusion between the uterine venous blood and ovarian arterial blood
which species does not have counter current exchange of PGF2a from the uterus to the ovary
horses, PGF2a reaches ovary through systemic circulation
lyteolysis is characterized by a dramatic drop in which hormone
p4
what hormones control luteolysis
P4, oxytocin, and PGF2a
what 2 hormones are important for the synthesis of oxytocin receptors in the uterus
P4 and E2
why is the expression of oxytocin receptors in the uterus important
oxytocin secreted by the CL must act on uterine endometrium for the synthesis of PGF2a in a pusatile manner
what stimulates the growth of a cohort of factors. what do these growing follicles effect
high FSH, Low LH
- produces small amounts of E2 and inhibin, both inhibitory to the pituitary
under what conditions do selected follicles grow
Low FSH, moderate LH, moderiate inhibin
how many selected follicles become dominant
1 or 2
what are the 3 phases of decelopment for a dominant follicle
- growth, stasis and regression and ovulation
what does the dominant follicle produce
estradiol to threshold levels –> in absence of p4, this will induce surge of GnRH from surge center with codominant surge of LH –> ovulation
what hormone determines wether the dominant follicle will undergo atresia or ovulation
P4
