Trilaminar embryo
Encyclopedia
A trilaminar embryo is an early stage in the development of triploblastic organisms, which include humans and many other animals.
It is an embryo which exists as three different germ layer
s - the ectoderm
, the mesoderm
and the endoderm
. These layers are arranged on top of each other like a stack of paper, giving rise to the name trilaminar, or "three-layered".
It arises early in the third week, after gastrulation
.
It is an embryo which exists as three different 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...
, the 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 the 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...
. These layers are arranged on top of each other like a stack of paper, giving rise to the name trilaminar, or "three-layered".
It arises early in the third week, after 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...
.