Lateral plate mesoderm

Lateral plate mesoderm (or hypomere) is a type of mesoderm that is found at the periphery of the embryo.

Division into layers
It will split into two layers, the somatic layer/mesoderm and the splanchnic layer/mesoderm


 * The somatic layer forms the future body wall.
 * The splanchnic layer forms the circulatory system and future gut wall.

Spaces within the lateral plate are enclosed and forms the intraembryonic coelom.

It is formed by the secretion of BMP-4 by the ectoderm.

Serosal mesoderms
Lateral plate mesoderm gives rise to the serosal mesoderms.
 * forms a ventral layer associated with endoderm, the splanchnopleuric mesoderm. This forms the viscera and heart
 * forms a dorsal layer associated with ectoderm, the somatopleuric mesoderm. This forms the body wall lining and dermis.
 * Abdominal portion becomes contained in dorsal mesentery, part of the serosal mesoderm.
 * When the two layers form, a cardiogenic plate is visible. Later, this will form the myocardial primordium, which will contribute to the tubular heart.

Cavities
In the 4th week the coelom divides into pericardial, pleural and peritoneal cavities.
 * First partition: is the septum transversum.
 * This will be translocated later into the diaphragm and ventral mesentery.
 * Divides the coleom into primitive pericardial and peritoneal cavities
 * pleuropericardial folds appear on the lateral wall of primitive pericardial cavity, which will eventually cause a partition to form the pericardial and pleural cavities.
 * Communication between these partitions formed by the pericardioperitoneal canals. However, pleuroperitoneal membranes will grow to fuse with the septum transversarium to close off these canals.


 * At day 22, lung bud forms, remaining ensheathed in a splachnopleuric mesoderm