Search results
Results from the WOW.Com Content Network
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 ...
The average age of a girl's first period is 12 to 13 (12.5 years in the United States, [6] 12.72 in Canada, [7] 12.9 in the UK [8]) but, in postmenarchal girls, about 80% of the cycles are anovulatory in the first year after menarche, which declines to 50% in the third year, and to 10% by the sixth. [9]
When experiencing menarche, the blood flow (colloquially described as having one's "period") can vary from a slow and spotty discharge to a consistent blood flow for 3–7 days. The color of the blood ranges from bright red to brown in color; this is normal. Periods may be light or heavy. [15]
This is an accepted version of this page This is the latest accepted revision, reviewed on 16 February 2025. Cell division producing haploid gametes For the figure of speech, see Meiosis (figure of speech). For the process whereby cell nuclei divide to produce two copies of themselves, see Mitosis. For excessive constriction of the pupils, see Miosis. For the parasitic infestation, see Myiasis ...
Development of the human body is the process of growth to maturity.The process begins with fertilization, where an egg released from the ovary of a female is penetrated by a sperm cell from a male.
The normal period of gestation (pregnancy) is about nine months or 36 weeks. The germinal stage refers to the time from fertilization through the development of the early embryo until implantation is completed in the uterus. The germinal stage takes around 10 days. [1] During this stage, the zygote divides in a process called cleavage.
Mitosis is the normal process in eukaryotes for cell division; duplicating chromosomes and segregating one of the two copies into each of the two daughter cells, in contrast with meiosis. The mitosis theory states that meiosis evolved from mitosis. [ 9 ]
Steps of the cell cycle. The restriction point occurs between the G 1 and S phases of interphase.. The restriction point (R), also known as the Start or G 1 /S checkpoint, is a cell cycle checkpoint in the G 1 phase of the animal cell cycle at which the cell becomes "committed" to the cell cycle, and after which extracellular signals are no longer required to stimulate proliferation. [1]