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Germ cells produce gametes and are the only cells that can undergo meiosis as well as mitosis. Somatic cells are all the other cells that form the building blocks of the body and they only divide by mitosis. The lineage of germ cells is called the germline. Germ cell specification begins during cleavage in many animals or in the epiblast during ...
Human embryonic development or human embryogenesis is the development and formation of the human embryo. It is characterised by the processes of cell division and cellular differentiation of the embryo that occurs during the early stages of development. In biological terms, the development of the human body entails growth from a one-celled ...
Contents. Germline. In biology and genetics, the germline is the population of a multicellular organism 's cells that develop into germ cells. In other words, they are the cells that form gametes (eggs and sperm), which can come together to form a zygote. They differentiate in the gonads from primordial germ cells into gametogonia, which ...
The bilaminar embryonic disc, bilaminar blastoderm or embryonic disc is the distinct two-layered structure of cells formed in an embryo. In the development of the human embryo this takes place by day eight. It is formed when the inner cell mass, also known as the embryoblast, forms a bilaminar disc of two layers, an upper layer called the ...
A germ layer is a primary layer of cells that forms during embryonic development. [ 1 ] The three germ layers in vertebrates are particularly pronounced; however, all eumetazoans (animals that are sister taxa to the sponges) produce two or three primary germ layers.
Primordial germ cells are among the first lineages that are established in development [1] and they are the precursors for gametes. [2] It is thought that the process of primordial germ cell migration itself has been conserved rather than the specific mechanisms within it, as chemoattraction and repulsion seem to have been borrowed from blood cells, neurones, and the mesoderm. [1]
Cleavage in most animals segregates cells containing germ plasm from other cells. The germ plasm effectively turns off gene expression to render the genome of the cell inert. Cells expressing germ plasm become primordial germ cells (PGCs) which will then give rise to the gametes. The germ line development in mammals, on the other hand, occurs ...
Normal oogonia in human ovaries are spherical or ovoid in shape and are found amongst neighboring somatic cells and oocytes at different phases of development. Oogonia can be distinguished from neighboring somatic cells, under an electron microscope, by observing their nuclei. Oogonial nuclei contain randomly dispersed fibrillar and granular ...