a succession or recurring series of events.
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.
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.
the sequence of physiologic changes in the ovary involved in ovulation; see also ovulation
the cycle of physiologic changes in the reproductive organs, from the time of fertilization of the ovum through gestation and childbirth; see also reproduction
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.
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.
the regularly recurring physiologic changes in the endometrium
that culminate in its shedding (menstruation
). Menstrual cycles vary in length, with the average being about 28 days. The length of time of menstrual flow is also variable, with an average of about 5 days. Women menstruate from puberty
, except during pregnancy. The first 14 days of the cycle are called the follicular phase;
containing an ovum
is developing in one of the ovaries
. It begins as the menstrual flow ceases; the lining of the uterus is stimulated by estrogen
and begins to increase in thickness to prepare for the possibility of reproduction
. On the twelfth or thirteenth day of the cycle, the ovulatory phase
begins with a surge in levels of luteinizing hormone
and follicle-stimulating hormone
then takes place and the ovary
discharges the ovum
. The ruptured follicle is transformed into a yellowish material called the corpus luteum
; the luteal phase
begins as the corpus luteum
. Progesterone acts on the endometrium
, building up tissues with an enriched supply of blood to nourish the future embryo. If fertilization
do not take place, the estrogen
level in the blood falls, the endometrium
is no longer stimulated, and the uterus again becomes thinner. Blood circulation slows, blood vessels contract, and the menstrual phase
begins; unused tissue breaks down into the bloody discharge known as menstruation
. The cycle then starts again.
Average 28-day menstrual cycle. The cycle begins when hormones from the pituitary gland stimulate the development of an egg in a follicle inside one of the ovaries. About the fourteenth day, ovulation occurs: The follicle bursts, and the egg is discharged from the ovary. If the egg is not fertilized, the cycle ends in menstruation on the twenty-eighth day. If the egg is fertilized, pregnancy begins.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.
men·stru·al cy·cle (men'strū-ăl sī'kĕl)
The period in which an oocyte or ovum matures, is ovulated, and enters the uterine lumen through the uterine tube; ovarian hormonal secretions effect endometrial changes such that, if fertilization occurs, nidation will be possible; in the absence of fertilization, ovarian secretions wane, the endometrium sloughs, and menstruation begins; this cycle lasts an average of 28 days, with day 1 of the cycle designated as that day on which menstrual flow begins.
Medical Dictionary for the Health Professions and Nursing © Farlex 2012
PHASES OF THE MENSTRUAL CYCLE
The periodically recurrent series of changes occurring in the uterus and associated sex organs (ovaries, cervix, and vagina) associated with menstruation and the intermenstrual period. The human cycle averages 28 days in length, measured from the beginning of menstruation. The menstrual cycle is, however, quite variable in length, even in the same person from month to month. Variations in the length of the cycle are due principally to variation in the length of the proliferative phase. See: illustration
The menstrual cycle is divided into four phases characterized by histological changes that take place in the uterine endometrium. They are:
Proliferative Phase: Following blood loss from the endometrium, the uterine epithelium is restored to normal; the endometrium becomes thicker and more vascular; the glands elongate. During this period, the ovarian follicle is maturing and secreting estrogens; with the estrogen stimulation, the endometrium hypertrophies, thickening and becoming more vascular, and the glands elongate. The phase is terminated by the rupture of the follicle and the liberation of the ovum at about 14 days before the next menstrual period begins. Fertilization of the ovum is most likely to occur in the days immediately following ovulation.
Luteal or Secretory Phase: After releasing the ovum, the corpus luteum secretes progesterone. With the progesterone stimulation, the endometrium becomes even thicker; the glands become more tortuous and produce an abundant secretion containing glycogen. The coiled arteries make their appearance; the endometrium becomes edematous; the stroma becomes compact. During this period, the corpus luteum in an ovary is developing and secreting progesterone. This phase lasts 10 to 14 days.
Premenstrual or Ischemic Phase: If pregnancy has not occurred, the coiled arteries constrict and the endometrium becomes anemic and shrinks a day or two before menstruation. The corpus luteum of the ovary begins involution. This phase lasts about 2 days and is terminated by the opening up of constricted arteries, the breaking off of small patches of endometrium, and the beginning of menstruation with the flow of menstrual fluid.
Menstruation: The functional layer of the endometrium is shed.
The menstrual cycle is altered by pregnancy, the use of contraception, intercurrent illnesses, diet, and exercise.
Medical Dictionary, © 2009 Farlex and Partners
A hormonally regulated series of monthly events that occur during the reproductive years of the human female to ensure that the proper internal environment exists for fertilization, implantation, and development of a baby. Each month, a mature egg is released from the follicle of an ovary. If an egg is released, fertilized, and implanted, the lining of the uterus continues to build. If fertilization and/or implantation does not occur, the egg and all of the excess uterine lining are shed from the body during menstruation.
Gale Encyclopedia of Medicine. Copyright 2008 The Gale Group, Inc. All rights reserved.
men·stru·al cy·cle (men'strū-ăl sī'kĕl)
The period in which an oocyte matures, is ovulated, and enters the uterine lumen through the uterine tube; ovarian hormonal secretions effect endometrial changes such that, if fertilization occurs, nidation will be possible; in the absence of fertilization, ovarian secretions wane, the endometrium sloughs, and menstruation begins; this cycle lasts an average of 28 days, with day 1 of the cycle designated as that day on which menstrual flow begins.
Medical Dictionary for the Dental Professions © Farlex 2012
Patient discussion about menstrual cycle
Q. is it normal to get a nausous feeling around the time i would start my menstrual cycle?
A. Yes, it is absolutely normal to feel nausea before and during menstrual cycle. The shift in hormonal levels can cause also headaches, mood changes, feeling of bloating and other common symptoms.
Q. can you get poly-cystic ovarian syndrome when you still have your menstrual cycle?
A. polycystic ovarian syndrome is when the egg does not come out- so i guess there is no menstrual that month. but as far as i know it's not every month that an egg decides to stay at home after 18... i guess you can check up more exact at this site:More discussions about menstrual cycle
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