Extraembryonic coelom
Encyclopedia
The extraembryonic coelom (or Chorionic cavity) is a portion of the conceptus
consisting of a cavity between Heuser's membrane
and the Trophoblast
.
During formation of the primitive yolk sac, some of the migrating Hypoblast
cells transdifferentiate into mesenchymal cells that fill the space between Heuser's membrane
and the Trophoblast
, forming the extraembryonic mesoderm
. As development progresses, small lacuna
e begin to form within the extraembryonic mesoderm
which become larger and form the extraembryonic coelom.
It divides the extraembryonic mesoderm
into two layers: extraembryonic splanchnopleuric mesoderm
, which lies adjacent to Heuser's membrane around the outside of the primitive yolk sac, and extraembryonic somatopleuric mesoderm
, which lies adjacent to the cytotrophoblast layer of the embryo.
The extraembryonic coelemic cavity is also called the chorionic cavity, and is enclosed by the chorionic plate, which is composed of an inner layer of somatopleuric mesoderm and an outer layer of trophoblast cells.
Conceptus
Conceptus denotes the embryo and its adnexa or associated membranes . The conceptus includes all structures that develop from the zygote, both embryonic and extraembryonic...
consisting of a cavity between Heuser's membrane
Heuser's membrane
Heuser's membrane is a short lived combination of hypoblast cells and extracellular matrix.At day 9-10, at the abembryonic pole, cells from the cytotrophoblast flatten to create a thin exocoelomic membrane known as Heuser’s Membrane. It surrounds the exocoelomic cavity.i.e...
and the Trophoblast
Trophoblast
Trophoblasts are cells forming the outer layer of a blastocyst, which provide nutrients to the embryo and develop into a large part of the placenta. They are formed during the first stage of pregnancy and are the first cells to differentiate from the fertilized egg...
.
During formation of the primitive yolk sac, some of the migrating Hypoblast
Hypoblast
The hypoblast is a tissue type that forms from the inner cell mass. It lies beneath the epiblast and consists of small cuboidal cells.Extraembryonic endoderm is derived from hypoblast.-External links:...
cells transdifferentiate into mesenchymal cells that fill the space between Heuser's membrane
Heuser's membrane
Heuser's membrane is a short lived combination of hypoblast cells and extracellular matrix.At day 9-10, at the abembryonic pole, cells from the cytotrophoblast flatten to create a thin exocoelomic membrane known as Heuser’s Membrane. It surrounds the exocoelomic cavity.i.e...
and the Trophoblast
Trophoblast
Trophoblasts are cells forming the outer layer of a blastocyst, which provide nutrients to the embryo and develop into a large part of the placenta. They are formed during the first stage of pregnancy and are the first cells to differentiate from the fertilized egg...
, forming the extraembryonic 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...
. As development progresses, small lacuna
Lacuna
Lacuna may refer to:* Lacuna , a missing section of text* Lacuna , an extended silence in a piece of music* Lacuna , a lexical gap in a language* Lacuna , the lack of a law or legal source addressing a situation...
e begin to form within the extraembryonic 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...
which become larger and form the extraembryonic coelom.
It divides the extraembryonic 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...
into two layers: extraembryonic splanchnopleuric 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...
, which lies adjacent to Heuser's membrane around the outside of the primitive yolk sac, and extraembryonic somatopleuric 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...
, which lies adjacent to the cytotrophoblast layer of the embryo.
The extraembryonic coelemic cavity is also called the chorionic cavity, and is enclosed by the chorionic plate, which is composed of an inner layer of somatopleuric mesoderm and an outer layer of trophoblast cells.
External links
- http://isc.temple.edu/marino/embryology/EMBI97/img015.GIF
- http://www.embryology.ch/anglais/hdisqueembry/triderm09.html
- http://sprojects.mmi.mcgill.ca/embryology/earlydev/week2/eemes&coel.html