Estrous Cycle

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estrous cycle

[′es·trəs ‚sī·kəl]
The physiological changes that take place between periods of estrus in the female mammal.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Estrous Cycle


the aggregate of regularly-recurring changes in the reproductive system of female mammals. Characteristic synchronous changes in the entire female body and especially in the fallopian tubes, uterus, and vagina are governed by the rhythmic processes occurring in the ovaries (the development of the follicles, ovulation, and the formation of the corpus luteum). Each phase of the estrous cycle corresponds to certain changes in the mucous membrane of the vagina and in the cellular composition of the vagina.

The estrous cycle lasts 4–5 days in rats and mice, 16–17 days in guinea pigs, 21 days in cows, and 19–23 days in horses. The estrous cycle in rodents is conventionally divided into four stages—diestrus (the quiescent period), proestrus (preparation for estrus), estrus (heat), and metestrus (the luteal phase following estrus). During diestrus, which accounts for approximately one-half of the length of the entire estrous cycle, a smear shows a predominance of mucus and leukocytes. During proestrus, which lasts approximately 12 hours, the smear consists almost entirely of epithelial cells sloughed from the vaginal wall. During estrus, which lasts approximately 27 hours, the smear contains only squamous epithelial cells (anuclear, cornified cells). Animals normally mate only at the beginning of estrus. Metestrus lasts approximately six hours; during this stage the smear shows some leukocytes among the mass of squamous cells. Primates have a menstrual cycle.

The estrous cycle is observed only in animals with normally functioning ovaries. After neutering, diestrus sets in, and the other stages of the estrous cycle do not occur.


Eskin, I. A. Osnovy fiziologii endokrinnykh zhelez, 2nd ed. Moscow, 1975.


The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
The slides were then observed and analysed for the assessment of each cell type and phase of the oestrous cycle and the digital images were obtained with the aid of the Olympus BX51 system microscope and the Olympus DP71 microscope digital camera.
[74] indicates the modulatory effect of adiponectin on the porcine ovarian cells during the luteal phase of the oestrous cycle. The researchers observed that adiponectin influences the number of genes, including steroidogenic enzymes, genes responsible for prostaglandin synthesis, or genes responsible for vascularization, which suggests the important role of this adipokine in the regulation of CL growth and activity (Figure 1).
Laloraya, "Histochemical study of superoxide dismutase in the ovary of the rat during the oestrous cycle," Journal of Reproduction and Fertility, vol.
Five-day stimulation covers a dioestrus and a round of the oestrous cycle. As for the group treated with the Baixiangdan capsule, Baixiangdan was intragastrically administered to animals at 0900 hours each day and lasted for 5 days when modelling stimulation was in progress.
The existence of a typical oestrous cycle in the guinea-pig - with a study of its histological and physiological changes.
(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.
As regards BCM, to date, there is no satisfactory classification to categorize the different crystallization patterns that can be observed during the oestrous cycle, and specifically in the oestrus stage.
Follicular population during the oestrous cycle in Nili-Ravi buffaloes undergoing spontaneous and PGF2a induced luteolysis.
Increase in ovulation rate after treatment of ewes with bovine follicular fluid in the luteal phase of the oestrous cycle. J.
In studies performed on female rats, it has been indicated that AAS applications cause disorders in oestrous cycle and delay the beginning of puberty by affecting FSH synthesis as same as LH synthesis in male rats (Gerez et al 2005, Mobini Far et al 2007).