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As the fetal hypothalamus matures, activation of the hypothalamic–pituitary–adrenal (HPA) axis initiates labor through two hormonal mechanisms. The end pathway of both mechanisms lead to contractions in the myometrium, a mechanical cause of placental separation, which is due to the sheer force and contractile and involutive changes that occur within the uterus, distorting the placentome.
Prophase I in meiosis is the most complex iteration of prophase that occurs in both plant cells and animal cells. [3] To ensure pairing of homologous chromosomes and recombination of genetic material occurs properly, there are cellular checkpoints in place.
It occurs in the stage of meiotic prophase I [2] in ootidogenesis. It starts late in fetal life [ 2 ] and is terminated shortly before ovulation by the LH surge. [ 3 ] Thus, although the majority of oocytes are produced in female fetuses before birth, these pre-eggs remain arrested in the dictyate stage until puberty commences and the cells ...
Three types of cell division: binary fission (taking place in prokaryotes), mitosis and meiosis (taking place in eukaryotes).. When cells are ready to divide, because cell size is big enough or because they receive the appropriate stimulus, [20] they activate the mechanism to enter into the cell cycle, and they duplicate most organelles during S (synthesis) phase, including their centrosome.
The synaptonemal complex is a tripartite structure consisting of two parallel lateral regions and a central element. This "tripartite structure" is seen during the pachytene stage of the first meiotic prophase, both in males and in females during gametogenesis.
Prometaphase is the phase of mitosis following prophase and preceding metaphase in eukaryotic somatic cells. In prometaphase, the nuclear membrane breaks apart into numerous "membrane vesicles," and the chromosomes inside form protein structures called kinetochores. [1]
Prolonged labor is the inability of a woman to proceed with childbirth upon going into labor. [1] Prolonged labor typically lasts over 20 hours for first time mothers, and over 14 hours for women that have already had children. [1] Failure to progress can take place during two different phases; the latent phase and active phase of labor. [1]
During telophase, the effects of prophase and prometaphase (the nucleolus and nuclear membrane disintegrating) are reversed. As chromosomes reach the cell poles, a nuclear envelope is re-assembled around each set of chromatids , the nucleoli reappear, and chromosomes begin to decondense back into the expanded chromatin that is present during ...