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The embryonic disc begins flat and round, but eventually elongates to have a wider cephalic part and narrow-shaped caudal end. [10] At the beginning, the primitive line extends in cephalic direction and 18 days after fertilization returns caudally until it disappears.
A neural groove (future spinal cord) forms over the notochord with a brain bulge at one end. Neuromeres appear. (day 18 of fertilization. [1]) Somites, the divisions of the future vertebra, form. (day 20 of fertilization. [1]) Primitive heart tube is forming. Vasculature begins to develop in embryonic disc. (day 20 of fertilization. [1])
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 resulting zygote develops through mitosis and cell differentiation , and the resulting embryo then implants in the uterus , where the embryo continues development through a fetal stage until birth .
Synapses do not begin to form until week 17. [11] Neural connections between the sensory cortex and thalamus develop as early as 24 weeks' gestational age, but the first evidence of their function does not occur until around 30 weeks, when minimal consciousness, dreaming, and the ability to feel pain emerges. [12]
In animals, fertilization begins the process of embryonic development with the creation of a zygote, a single cell resulting from the fusion of gametes (e.g. egg and sperm). [5] The development of a zygote into a multicellular embryo proceeds through a series of recognizable stages, often divided into cleavage, blastula, gastrulation, and ...
In embryology, Carnegie stages are a standardized system of 23 stages used to provide a unified developmental chronology of the vertebrate embryo.. The stages are delineated through the development of structures, not by size or the number of days of development, and so the chronology can vary between species, and to a certain extent between embryos.
When does life begin? Luke Kelley is the pastor Christ Community EFC. This article originally appeared on Ashland Times Gazette: Column: Personhood is the biggest detail in abortion debate.
The question of embryology is discussed among a number of early Christian writers, largely in terms of theological questions such as whether the fetus has value and/or when it begins to have value. (Although a number of Christian authors continued the classical discussions on the description of the development of the embryo, such as Jacob of ...