Fertilization is a process of fusion between male sperm and female oocyte. it takes place within the Fallopian tube of a female reproductive system. As soon as the nuclei of the oocyte and sperm fuses with each other a zygote is formed. The zygote undergoes a series of cell divisional stages and turns in to a 2 cell then 4 and then 8 cell mass. Through continued cell division the zygote turns into a morulla, blastula and then blastocyst. The blastocyst contains two types of cells, the embryoblast and trophoblast. The embryoblast will become the future baby and the trophoblast will form the supporting tissues of the baby. The blastocyst will implant in the uterine wall and this implanted blastocyst is now called the embryo.
The embryoblast of the blastocyst will convert into two layers of cells called the epiblast and the hypoblast. These two layers together is called the bilaminar disc. The bilaminar disc will convet into a trilamilar disc by forming an additional layer in-between the epiblast and hypoblast. This third layer originates from the epiblastic layer. The three germ layers now formed together is called a trilaminar disc. The trilaminar disc is composed of the ectoderm, mesoderm and endoderm.The trilaminar disc will fold rostrocranially and laterally .
Neuralation or neural tube formation originates from the superficial layer of the ectoderm. Under the influence of the underlying notochord a longitudinal thickening appears on the ectodermal layer just above the notochord forming the neural plate. The central area of the neural plate depresses downwards while its sides raising upwards , the central depressed point is called the neural groove while the raised sides are called the neural folds. The neural folds grows towards each other until they meet and forms the neural tube. Some cells will detach from the neural tube during neurulation process called the neural crest cells.
Video (diagrams+editing) & Voiceover:
Dr.Maryam Kazman
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#fertilizaton #implantation #neurulation #blastula #blastocyst #embryogenesis #trophoblast #epiblast #hypoblast #bilaminardisc #ectoderm #notochord #mesoderm #endoderm #trilaminardisc #gastrulation #neurulation #neuraltubeformation #neuralcrestcells #zygote #morulla
Негізгі бет What is Fertilization, Gastrulation and Neurulation - Overview
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