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 ?
Expression of adiponectin and adiponectin receptors 1 (AdipoR1) and 2 (AdipoR2) in the porcine uterus during the oestrous cycle.
Determination of oestrous cycle of the rats by direct examination: how reliable?
The existence of a typical oestrous cycle in the guinea-pig - with a study of its histological and physiological changes.
2[alpha]] as well as its synthetic analogues induces luteolysis with concurrent decline in serum progesterone levels when injected between 5th and 16th day of the oestrous cycle (Hansel and Schechter 1972; Louis et al.
32) In a study of oestrous cycle in goats there was significant negative correlation between progesterone and globulin.
Immunohistochemical detection of receptors for oestrogen and progesterone in endometrial glands and stoma during the oestrous cycle in Nelore (Bos Taurus indicus) cows.
Ovulation rate and embryo survival in Damline ewes after treatment with bovine follicular fluid in the luteal phase of the oestrous cycle.
Thyroid Function of Friesian cows during the oestrous cycle and in conditions of ovarian abnormality.
Five each of pre-antral and antral follicles were selected in each phase of the oestrous cycle for measurement of the follicle, oocyte, and oocyte nucleus diameter.
Cell-specific localization of progesterone receptors in the bovine ovary at different stages of the oestrous cycle.
Valsala S, Karpagaganapathy P Effect of Mimosa pudica root powder on oestrous cycle and ovulation in cycling female albino rat, Rattus norvegicus.