Triploblasty
Encyclopedia
Triploblasty is a condition of the blastula
in which there are three primary germ layer
s: the ectoderm
, mesoderm
, and endoderm
. The germ layers form during gastrulation
of the blastula
. Additionally, the term may refer to any ovum in which the blastoderm
splits into three layers.
All higher and intermediate animals (from flat worms to humans), arise from a triploblastic ovum. Triploblastic organisms are organisms which develop from such an ovum. Generally speaking, triploblastic organisms belong to the Bilateria
subregnum. Triploblastic organisms generally possess bilateral symmetry, which is where the clade Bilateria
takes its name.
Simpler animals qualified as diploblastic
, such as cnidaria
(which include jellyfish, corals and hydra), possess two germ layers. Even simpler animals such as sponges
within the formally termed Porifera phylum contain no true tissues.
Blastula
The blastula is a hollow sphere of cells formed during an early stage of embryonic development in animals . The blastula is created when the zygote undergoes the cell division process known as cleavage. The blastula is preceded by the morula and is followed by the gastrula in the developmental...
in which there are three primary germ layer
Germ layer
A germ layer, occasionally referred to as a germinal epithelium, is a group of cells, formed during animal embryogenesis. Germ layers are particularly pronounced in the vertebrates; however, all animals more complex than sponges produce two or three primary tissue layers...
s: the ectoderm
Ectoderm
The "ectoderm" is one of the three primary germ cell layers in the very early embryo. The other two layers are the mesoderm and endoderm , with the ectoderm as the most exterior layer...
, mesoderm
Mesoderm
In all bilaterian animals, the mesoderm is one of the three primary germ cell layers in the very early embryo. The other two layers are the ectoderm and endoderm , with the mesoderm as the middle layer between them.The mesoderm forms mesenchyme , mesothelium, non-epithelial blood corpuscles and...
, and endoderm
Endoderm
Endoderm is one of the three primary germ cell layers in the very early embryo. The other two layers are the ectoderm and mesoderm , with the endoderm as the intermost layer...
. The germ layers form during gastrulation
Gastrulation
Gastrulation is a phase early in the embryonic development of most animals, during which the single-layered blastula is reorganized into a trilaminar structure known as the gastrula. These three germ layers are known as the ectoderm, mesoderm, and endoderm.Gastrulation takes place after cleavage...
of the blastula
Blastula
The blastula is a hollow sphere of cells formed during an early stage of embryonic development in animals . The blastula is created when the zygote undergoes the cell division process known as cleavage. The blastula is preceded by the morula and is followed by the gastrula in the developmental...
. Additionally, the term may refer to any ovum in which the blastoderm
Blastoderm
-In amniotes:A blastoderm is the layer of cells formed at one pole of macrolecithal eggs such as the yolky egg of birds. The yolk prevents the division from taking place through the egg, resulting in meroblastic cleavage during the many cleavage divisions...
splits into three layers.
All higher and intermediate animals (from flat worms to humans), arise from a triploblastic ovum. Triploblastic organisms are organisms which develop from such an ovum. Generally speaking, triploblastic organisms belong to the Bilateria
Bilateria
The bilateria are all animals having a bilateral symmetry, i.e. they have a front and a back end, as well as an upside and downside. Radially symmetrical animals like jellyfish have a topside and downside, but no front and back...
subregnum. Triploblastic organisms generally possess bilateral symmetry, which is where the clade Bilateria
Bilateria
The bilateria are all animals having a bilateral symmetry, i.e. they have a front and a back end, as well as an upside and downside. Radially symmetrical animals like jellyfish have a topside and downside, but no front and back...
takes its name.
Simpler animals qualified as diploblastic
Diploblasty
Diploblasty is a condition of the blastula in which there are two primary germ layers: the ectoderm and endoderm.Diploblastic organisms are organisms which develop from such a blastula, and include cnidaria and ctenophora, formerly grouped together in the phylum Coelenterata, but later...
, such as cnidaria
Cnidaria
Cnidaria is a phylum containing over 9,000 species of animals found exclusively in aquatic and mostly marine environments. Their distinguishing feature is cnidocytes, specialized cells that they use mainly for capturing prey. Their bodies consist of mesoglea, a non-living jelly-like substance,...
(which include jellyfish, corals and hydra), possess two germ layers. Even simpler animals such as sponges
Sea sponge
Sponges are animals of the phylum Porifera . Their bodies consist of jelly-like mesohyl sandwiched between two thin layers of cells. While all animals have unspecialized cells that can transform into specialized cells, sponges are unique in having some specialized cells, but can also have...
within the formally termed Porifera phylum contain no true tissues.