estrus cycle

estrus cycle

Etymology: Gk, oistros, gadfly, kyklos, circle

the periodic changes in the female body that occur under the influence of sex hormones.

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cycle

a succession or recurring series of events.

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cardiac cycle

a complete cardiac movement, or heartbeat, including systole, diastole, and the intervening pause.

The cycle includes eight separate phases: (1) isovolumetric contraction; (2) maximum ejection; (3) reduced ejection; (4) protodiastole (onset of ventricular relaxation); (5) isovolumetric relaxation; (6) rapid flow; (7) diastasis (onset of atrial contraction); (8) atrial systole.

cell cycle

the cycle of biochemical and morphological events occurring in a dividing cell population; it consists of the S phase, occurring toward the end of interphase, in which DNA is synthesized; the G₂ phase, for gap 2, the interval between S and M; the M phase, for mitosis, consisting of the four phases of mitosis; and the G₁ phase, which lasts from the end of M until the start of S phase of the next cycle. Fully differentiated cells are nondividing and are said to be in G₀.

Cell cycle. By permission from Booth DM, Small Animal Clinical Pharmacology and Therapeutics, Saunders, 2000

citric acid cycle

see tricarboxylic acid cycle.

estrus cycle

see estrous cycle.

Krebs cycle

see tricarboxylic acid cycle.

ovarian cycle

the sequence of physiological changes in the ovary involved in ovulation. See also ovulation and reproduction.

reproductive cycle

the cycle of physiological changes in the reproductive organs, from the time of fertilization of the ovum through gestation and parturition. See also reproduction.

sex cycle, sexual cycle

1. the physiological changes recurring regularly in the reproductive organs of female mammals when pregnancy does not supervene.

2. the period of sexual reproduction in an organism that also reproduces asexually.

tricarboxylic acid cycle

see tricarboxylic acid cycle.

urea cycle

a cyclic series of reactions that produce urea, a major route for removal of the ammonia produced in the metabolism of amino acids in the liver and kidney. See also urea.