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The luteal phase is characterized by changes to hormone levels, such as an increase in progesterone and estrogen levels, decrease in gonadotropins such as follicle-stimulating hormone (FSH) and luteinizing hormone (LH), changes to the endometrial lining to promote implantation of the fertilized egg, and development of the corpus luteum. In the ...
Each cycle occurs in phases based on events either in the ovary (ovarian cycle) or in the uterus (uterine cycle). The ovarian cycle consists of the follicular phase, ovulation, and the luteal phase; the uterine cycle consists of the menstrual, proliferative and secretory phases. Day one of the menstrual cycle is the first day of the period ...
Follicular phase diagram of hormones and their origins Follicle-stimulating hormone (FSH) is secreted by the anterior pituitary gland (Figure 2). FSH secretion begins to rise in the last few days of the previous menstrual cycle, [ 3 ] and is the highest and most important during the first week of the follicular phase [ 4 ] (Figure 1).
A woman’s monthly cycle has four parts: menstrual, follicular, ovulation and luteal phases. The ovaries make eggs, and the area around the developing egg is called the follicle.
Ovulation occurs about midway through the menstrual cycle, after the follicular phase, and is followed by the luteal phase.Note that ovulation is characterized by a sharp spike in levels of luteinizing hormone (LH) and follicle-stimulating hormone (FSH), resulting from the peak of estrogen levels during the follicular phase.
There are theories of continuous recruitment of antral follicles, theories of a single recruitment episode at the end of the luteal phase, and more recently there has been evidence for a recruitment model marked by 2 - 3 waves of follicle recruitment and development during the menstrual cycle (only one of which is actually an ovulatory wave). [6]
In the early follicular phase, uterine contractions in the non-pregnant woman occur 1–2 times per minute and last 10–15 seconds with a low intensity of usually 30 mmHg or less. This sub-endometrial layer is rich in estrogen and progesterone receptors. [3] The frequency of contractions increases to 3–4 per minute towards ovulation.
While the normal human menstrual cycle typically lasts 4 weeks (28 days, range 24–35 days) and consists of a follicular phase, ovulation, and a luteal phase followed by either menstruation or pregnancy, the anovulatory cycle has cycle lengths of varying degrees.