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The Estrous Cycle: Terminology and Basic Concepts - Coggle Diagram
The Estrous Cycle: Terminology and Basic Concepts
Estrus Stage
Most recognizable stage of the estrus cycle because it shows visible behavioral symptoms
Sexual receptivity and mating are some of these behavioral symptoms
Gradual progression, and female is not sexually receptive at first
As the female gets closer to sexual receptive, she will shows increased locomotion, phonation (vocal expression), nervousness and attempts to mount other animals
Standing estrus: females willingness to accept the male mating
Estradiol is the dominant hormone here
Proestrus Stage
Begins when progesterone declines as a result of luteolysis (destruction of the corpus luteum) and terminates at the onset of estrus
This stage lasts from 2 to 5 days depending on species
The gonadotrophins FSH and LH are the primary hormones here
Metestrus Stage
Period between ovulation and the formation of functional corpora lutea
Both estrogen and progesterone are relatively low in this stage
The newly ovulated follicle undergoes cellular and structural remodeling resulting in the formation of an intraovarian endocrine gland called the corpus luteum
Called luteinization
Progesterone secretion is detectable soon after ovulation
Diestrus Stage
Longest stage of the estrous cycle and encompasses the period of time when the corpus luteum is fully functional and progesterone production is high
Ends when the corpus luteum is destroyed (luteolysis)
Usually lasts 10 to 14 days, and it is directly related to the length of time that the corpus luteum remains functional
Females during this stage do not display sexual receptivity
Overall estrus cycle
Consist of a series of predictable reproductive events
Provide females with repeated opportunities to copulate and become pregnant
Sexual receptivity and copulation are the primary behavioral events that occur during estrus
Two major phases: follicular and luteal phase
Follicular phase: period from the regression of corpora lutea to ovulation
Luteal phase: period of ovulation until corpora lutea regression
Primary dominant ovarian structures are the corpora lutea and the primary reproductive hormone is progesterone
Anestrus Stage
Condition when the female does not exhibit regular estrous cycles
Ovaries are relatively inactive and neither ovulatory follicles nor functional corpora lutea are present
Result of insufficient GnRH release from the hypothalamus to stimulate and maintain gonadotrophin secretion
Many different types of anestrus
Seasonal anestrus
Developed as a way of preventing females from conceiving during periods of the year when survival of the developing embryo and the neonate would be low
Chances are reduced significantly with high temperatures and high humidity
Photoperiod: seasonal breeders normally make the transition from the cyclic state to the anestrus state and back again in an annual basis
Lactational anestrus