Reproductive cycle Flashcards
what is the reproductive cycles purpose
Providing females with repetitive opportunities to become pregnant. This is achieved through two types of cycles, the estrus and menstrual cycle
nthe estrus cycle has three types, name em
polyestrus, monoestrus, seasonal
define polyestrus
female has a recurring cycle consistently throughout the year
defeine seaonal estrus
estrus occurs only during a specific season
define monoestrus
occurs only once per year, they are typically for about a week (heat). in bitches
the estrus cycle has two major phases, what are they (phases defined by the dominant hormone)
folliclular phase and luteal phase
what is the follicular phase
20% of cycle, is the period from the regression of the corpus luteum to ovulation. (growth of the dominant follicle) - primary hormone is estradiol and it inclues proestrus and oestrus
what is the luteal phase
Phase is the period of ovulation until the corpora lutea regression. - The primary hormone is progesterone. And it include the metestrus and diestrus.
the menstral cycle is defined by:
Sloughing of the endometrium to the exterior (menstruation
No define segments of sexual recepritory
The timeline is define by menses (menstruation) not ovulation
it has two phases, follicular and luteal
what is anoestrus
period of which cyclicity stops, occurs during pregnancy or malnourishment
what is Lordosis
standing position, when the female is ready to mate she arches her back
what is true/ apparent annoestrus
True anestrus - insufficient hormonal stimuli to cause cyclicity
Apparent anestrus - failure to detect or recognise estrus in the animal
what is amenorrhea
Amenorrhea - extended time without cyclicity in women of reproductive age,
list the four stages of the oestrus cycle and what they achive
Proestus - ‘priming’ prepares for ovulation
oestrus - when the female allows ovulation
metestrus - transition from estrogen dominance to progesterone dominance.
diestrus - maximum luteal function
decribe the key event of proestrus
Progesterone declines after luteolysis and the hormone production favours estrogen. This transition is caused by the gonadotropins FSH and LH.
During this period follicles are recruited for ovulation and the body prepares for estrus.
describe the key events of oestrus
Visible behavioural symptoms like sexual receptivity and mating. (standing estrus, lordosis)
Estradiol is the dominant hormone during this cycle as it induces the behavioural change but also causes physiological changes.
describe the key events of metestrus
At the beginning estrogen and progesterone are relatively low.
Newly ovulated follicle undergoes cellular and structural remodeling which results in the formation of an intraovarian endocrine gland (corpus luteum), this transition is called luteinization.
describe the key events of diestrus
Longest phase and when the progesterone levels are high due to the corpus luteum being highly functional.
Ends when corpus luteum is destroyed
The progesterone promotes the uterus to prepare for an embryo in the endometrium.
what are the possible causes of anoestrus
pregnancy
lactation
offspring presence
season
stress
pathology
nutrional
Discuss the mechanism by which photoperiod is translated into a physiologic signal in the short/long day breeder;
The photoperiod is important for the estrus cycle, which for seasonally polyestrus animals can control the initiation and continuation of the estrus cycle.
describe lactational anoestrus
Influenced by suckling, more than 2 daily causes anestrus.
Stimulation of the mammary gland causes inhibition of the GnRH which results in basal LH levels and causes anestrus
describe nutritional anoestrus
Characterized by absence of GnRH from the hypothalamus due to absence of gonadotropin secretion and inactive ovaries.
In primiparous females (first time birthers) bad nutrition will prolong lactation estrus
what is menopause
anestrus
Caused by the depletion of supplied follicles
