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Immediately after meiosis I, the haploid secondary oocyte initiates meiosis II. However, this process is also halted at the metaphase II stage until fertilization , if such should ever occur. If the egg is not fertilized, it is disintegrated and released ( menstruation ) and the secondary oocyte does not complete meiosis II (and does not become ...
Oocyte (or ovum/egg) activation is a series of processes that occur in the oocyte during fertilization.. Sperm entry causes calcium release into the oocyte. In mammals, this is caused by the introduction of phospholipase C isoform zeta (PLCζ) from the sperm cytoplasm. [1]
Nine-week-old human embryo from an ectopic pregnancy. Organogenesis is the development of the organs that begins during the third to eighth week, and continues until birth. Sometimes full development, as in the lungs, continues after birth. Different organs take part in the development of the many organ systems of the body.
Development before birth, including gametogenesis, embryogenesis, and fetal development, is the process of body development from the gametes are formed to eventually combine into a zygote to when the fully developed organism exits the uterus. Epigenetic processes are vital to fetal development due to the need to differentiate from a single cell ...
After birth, the fundus contracts downward into the pelvis one centimeter each day. After two weeks the uterus will have contracted and return into the pelvis. [ 9 ] The sensation and strength of postpartum uterine contractions can be stronger in women who have previously delivered a child or children.
During pregnancy the plasma volume increases by 40-50% and the red blood cell volume increases only by 20–30%. [22] These changes occur mostly in the second trimester and prior to 32 weeks gestation. [24] Due to dilution, the net result is a decrease in hematocrit or hemoglobin, which are measures of red blood cell concentration.
This, in turn, may be altering family (and birth order) dynamics—and not in a bad way. First, a quick look at the data: Between 1967 and 2017, the spacing between sibling births only increased ...
The average time to birth has been estimated to be 268 days (38 weeks and two days) from ovulation, with a standard deviation of 10 days or coefficient of variation of 3.7%. [32] Fertilization age is sometimes used postnatally (after birth) as well to estimate various risk factors.