the embryo from three germ layers during embryogenesis.
the embryo from three germ layers during embryogenesis.
when does the embryo from three germ layers?
during embryogenesis
within the field of developmental biology one goal is to understand how a particular cell (or embryo) develops into the final cell type (or organism), essentially how a cell's fate is determined. within an embryo, 4 processes play out at the cellular and tissue level to essentially create the final organism. these processes are cell proliferation, cell specialization, cell interaction and cell movement. each cell in the embryo receives and gives cues to its neighboring cells and retains a cell memory of its own cell proliferation history. almost all animals undergo a similar sequence of events during embryogenesis and have, at least at this developmental stage, the three germ layers and undergo gastrulation. while embryogenesis has been studied for more than a century, it was only recently (the past 15 years or so) that scientists discovered that a basic set of the same proteins and mrnas are involved in all of embryogenesis. this is one of the reasons that model systems such as the fly ("drosophila melanogaster"), the mouse (muridae), and the leech ("helobdella"), can all be used to study embryogenesis and developmental biology relevant to other animals, including humans. the fate map of the nematode ("caenorhabditis)" can be analyzed down to the cellular level. this is due to cell mixing during development. what continues to be discovered and investigated is how the basic set of proteins (and mrnas) are expressed differentially between cells types, temporally and spatially; and whether this is responsible for the vast diversity of organisms produced. this leads to one of the key questions of developmental biology of how is cell fate determined.
cell fate determination
unlike plant cells, animal cells have neither a cell wall nor chloroplasts. vacuoles, when present, are more in number and much smaller than those in the plant cell. the body tissues are composed of numerous types of cell, including those found in muscles, nerves and skin. each typically has a cell membrane formed of phospholipids, cytoplasm and a nucleus. all of the different cells of an animal are derived from the embryonic germ layers. those simpler invertebrates which are formed from two germ layers of ectoderm and endoderm are called diploblastic and the more developed animals whose structures and organs are formed from three germ layers are called triploblastic. all of a triploblastic animal's tissues and organs are derived from the three germ layers of the embryo, the ectoderm, mesoderm and endoderm.
anatomy