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Thus, a cycle may be short, totaling approximately 3 weeks. [21] Horses mate in spring and summer; autumn is a transition time, and anestrus occurs during winter. A feature of the fertility cycle of horses and other large herd animals is that it is usually affected by the seasons. The number of hours daily that light enters the eye of the ...
Menstrual cycle The menstrual cycle is a series of natural changes in hormone production and the structures of the uterus and ovaries of the female reproductive system that makes pregnancy possible. The ovarian cycle controls the production and release of eggs and the cyclic release of estrogen and progesterone. The uterine cycle governs the preparation and maintenance of the lining of the ...
Within each cycle, the time period during which the process is more active is called the acrophase. [4] When the process is less active, the cycle is in its bathyphase or trough phase. The particular moment of highest activity is the peak or maximum; the lowest point is the nadir. How high (or low) the process gets is measured by the amplitude.
The follicular phase (or proliferative phase) is the phase of the menstrual cycle during which the ovarian follicles mature. The follicular phase lasts from the beginning of menstruation to the start of ovulation. [12] [13] For ovulation to be successful, the ovum must be supported by the corona radiata and cumulus oophorous granulosa cells. [14]
For this reason, the human uterine lining becomes fully thickened during each cycle as a defense to trophoblast penetration of the endometrial wall, [23] regardless of whether an egg becomes fertilized or successfully implants in the uterus. This produces more unneeded material per cycle than in non-menstruating mammals, which may explain why ...
Diagram illustrating how the uterus lining builds up and breaks down during the menstrual cycle Menstruation (also known as a period, among other colloquial terms) is the regular discharge of blood and mucosal tissue from the inner lining of the uterus through the vagina. The menstrual cycle is characterized by the rise and fall of hormones. Menstruation is triggered by falling progesterone ...
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).
From the whole pool of follicles a woman is born with, only 0.1% of them will rise ovulation, whereas 99.9% will break down (in a process called follicular atresia). From birth, the ovaries of the human female contain many immature, primordial follicles. These follicles each contain a similarly immature primary oocyte.