The blastula (from Greek βλαστός, meaning "sprout") is a hollow sphere of cells, referred to as blastomeres, surrounding an inner fluid-filled cavity called the blastocoele formed during an early stage of embryonic development in animals. Embryo development begins with a sperm fertilizing an egg to become a zygote which undergoes many cleavages to develop into a ball of cells called a morula. Only when the blastocoel is formed does the early embryo become a blastula. The blastula precedes the formation of the gastrula in which the germ layers of the embryo form. A common feature of a vertebrate blastula is that it consists of a layer of blastomeres, known as the blastoderm, which surrounds the blastocoel. In mammals, blastulation leads to the formation of the blastocyst, instead of the blastula. The blastocyst contains an embryoblast (or inner cell mass) that will eventually give rise to the definitive structures of the fetus, and the trophoblast, which goes on to form the extraembryonic tissues. During the blastula stage of developoment, a significant amount of activity occurs within the early embryo to establish cell polarity, axis formation, and regulate gene expression. In amphibians, the mid blastula transition (MBT) is a crucial step in development during which the maternal mRNA is degraded and control over development is passed to the embryo. Many of the interactions between blastomeres are dependent on cadherin expression, particularly E-cadherin in mammals and EP-cadherin in amphibians. The study of the blastula and of cell specification has many implications on the field of stem cell research as well as the continued improvement of fertility treatments. Embryonic stem cells are a field which, though controversial, have tremendous potential for treating disease. In Xenopus, blastula behave as pluripotent stem cells which can migrate down several pathways, depending on signaling. By manipulating the signaling factors, various tissues can be formed. This potential can be instrumental in [regenerative medicine] for disease and injury cases. In vitro fertilisation involves implantation of a blastula into a mother’s uterus. Blastula cell implantation could potentially serve to eliminate infertility.
Dorlands prefix
b_14
Dorlands suffix
12188083
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