oestrous cycle


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Related to oestrous cycle: menstrual cycle

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

or

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).

References in periodicals archive ?
Lower doses of DC seed extract (3-100 mg/kg BW) arrested the oestrous cycle and prolonged diestrus, while higher doses (150-250 mg/kg BW) prolonged the oestrous stage of the cycle.
These results demonstrate that DC seed affects the oestrous cycle in rodents, likely through interaction with oestrogen receptors.
Modification of the oestrous cycle of the mouse by external stimuli associated with the male.
Influence of level of nutrition and season on the oestrous cycle rhythm and on fertility in buffaloes.
Follicular waves during the oestrous cycle in Nili-Ravi buffaloes undergoing spontaneous and PGF2alpha-induced luteolysis.
The criteria for selecting the studies were (i) oestrous cycle, (ii) buffalo (iii) steroid and protein hormones and (iv) radioimmunoassay.
To the best of our knowledge and belief, this is the first study to report the meta-analysis of hormonal profiles of oestrous cycle in buffalo.
Regulation of dominant follicle turnover during the oestrous cycle in cows.
Secretion of inhibin A and follicular dynamics throughout the oestrous cycle in sheep with and without the Booroola gene (FecB).
Taken together, these observations imply that number of follicles that develop during oestrous cycle may play an important role in regulation of fertility.
Peripheral plasma progesterone concentration of cows during puberty, oestrous cycles, pregnancy and lactation, and the effects of under-nutrition or exogenous oxytocin on progesterone concentration.