estrous cycle

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a succession or recurring series of events.
cardiac cycle a complete cardiac movement, or heart beat, including systole, diastole, and the intervening pause.
Cardiac cycle. From Applegate, 2000.
cell cycle the cycle of biochemical and morphological events occurring in a reproducing cell population; it consists of the S phase, occurring toward the end of interphase, in which DNA is synthesized; the G2 phase, a relatively quiescent period; the M phase, consisting of the four phases of mitosis; and the G1 phase of interphase, which lasts until the S phase of the next cycle.
citric acid cycle tricarboxylic acid cycle.
estrous cycle the recurring periods of estrus in adult females of most mammalian species and the correlated changes in the reproductive tract from one period to another.
hair cycle the successive phases of the production and then loss of hair, consisting of anagen, catagen, and telogen.
menstrual cycle see menstrual cycle.
ovarian cycle the sequence of physiologic changes in the ovary involved in ovulation; see also ovulation and reproduction.
reproductive cycle the cycle of physiologic changes in the reproductive organs, from the time of fertilization of the ovum through gestation and childbirth; see also reproduction.
sex cycle (sexual cycle)
1. the physiologic changes that recur regularly in the reproductive organs of nonpregnant female mammals.
2. the period of sexual reproduction in an organism that also reproduces asexually.
tricarboxylic acid cycle the cyclic metabolic mechanism by which the complete oxidation of the acetyl portion of acetyl-coenzyme A is effected; the process is the chief source of mammalian energy, during which carbon chains of sugars, fatty acids, and amino acids are metabolized to yield carbon dioxide, water, and high-energy phosphate bonds. Called also citric acid cycle, Krebs cycle, and TCA cycle.
 Central pathways of metabolism: How the body produces energy from the energy-containing nutrients using the tricarboxylic acid cycle. From Davis and Sherer, 1994.
urea cycle a cyclic series of reactions that produce urea; it is a major route for removal of the ammonia produced in the metabolism of amino acids in the liver and kidney.

es·trous cy·cle

the series of physiologic uterine, ovarian, and other changes that occur in higher animals, consisting of proestrus, estrus, postestrus, and anestrus or diestrus.

estrous cycle

The recurrent set of physiological and behavioral changes that take place from one period of estrus to another.

es·trous cy·cle

(es'trŭs sī'kĕl)
The series of cyclic uterine, ovarian, and other changes that occur in higher animals.
Synonym(s): oestrous cycle.

oestrous cycle


estrous cycle

a reproductive cycle caused by the cyclic production of gonadotrophic hormones by the PITUITARY GLAND. It occurs in adult female mammals and is only complete when pregnancy does not occur. It lasts from 5 to 60 days, dependent on species.

Initially, follicle growth occurs in the ovary as a result of FOLLICLE-STIMULATING HORMONE being secreted by the anterior pituitary This results in increased OESTROGEN production and a thickening of the uterus lining. The build-up of oestrogen results in positive feed-back, causing the anterior pituitary to produce LUTEINIZING HORMONE which in turn brings about ovulation with the formation of a CORPUS LUTEUM, development of the uterine glands, secretion of PROGESTERONE by the corpus luteum (which inhibits FSH production) and a consequent decrease in oestrogen production. Fertilization may occur at this stage and if it does so, pregnancy results. If not, there is a regression of the corpus luteum and a feedback to the anterior pituitary to produce FSH as progesterone decreases. New follicles are formed, the lining of the uterus thins, menstruation (see MENSTRUAL CYCLE occurs in human females and some other primates, and there is a cessation of progesterone secretion and a continued decrease of oestrogen. The cycle then begins again as new follicles grow. Only during the initial period of the cycle, during which ovulation takes place, will the female of most mammalian species copulate (the period of ‘heat'or oestrus).


pertaining to or emanating from estrus.

estrous cycle
one of the two types of reproductive cycles, the other is the menstrual cycle of humans and primates. Regularly occurring periods during which the female is sexually active and receptive, estrus, separated by periods in which there is no sexual receptivity. This period is divided, on the basis of ovarian activity into metestrus (early corpus luteum development), diestrus (mature corpus luteum) and pro-estrus (period of follicle development). The details of estral activity are summarized in Table 17.
References in periodicals archive ?
In June 2007, the crabs were collected at random with local crab traps (made by local people, not size selective, personal communication) close to the mating season (Song et al.
The following predictions were tested: (1) Testosterone levels in high-ranking males would be higher than in low-ranking males both in the mating season and non-mating seasons, (2) Copulatory behaviors would be positively correlated with fecal testosterone levels in both the mating and non-mating season, independent of social rank.
During the mating season, information was collected on the monthly average maximum temperature in degrees Celsius (T) and air relative humidity (RH), to find the maximum THI (THImax), and the minimum monthly temperature and relative humidity to obtain the minimum THI (THImin) through the model defined by Thom (1959):
Dunn said spring is the mating season for woodcocks, which are most active at dusk.
The animals spend their lives apart, keeping to their own enclosures and coming together only for the brief mating season.
For ten years the British Trust for Ornithology has chosen St Valentine's Week to encourage all who own nest boxes to give them a spring clean ready for the mating season.
As the mating season begins, gentoo penguins have been stealing pebbles from rival nests to line their own breeding ground.
They also do it to mark their territories for mating season.
Females collected in the nonmating months were significantly smaller than females collected during all of the mating season months except for the late mating season of year 1 (Tukey HSD, P < 0.
Inspired by the prairie chicken during mating season, the male dances to win the female.
The activity levels of wild ungulates increases when the mating season approaches (Berger, 1992), and the intensity of ano-genital sniffing, agonistic behaviour and tail rubbing, related to sexual activities, increased to a peak in October during the non-mating season.
This is prime mating season for the humpbacks as they stay in warmer tropical waters until September before returning to Antarctic waters.