The lateral plate mesoderm is the

mesoderm The mesoderm is the middle layer of the three germ layers that develops during gastrulation in the very early development of the embryo of most animals. The outer layer is the ectoderm, and the inner layer is the endoderm.Langman's Medical Emb ...

that is found at the periphery of the

embryo An embryo is an initial stage of development of a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male spe ...

. It is to the side of the

paraxial mesoderm Paraxial mesoderm, also known as presomitic or somitic mesoderm is the area of mesoderm in the neurulating embryo that flanks and forms simultaneously with the neural tube. The cells of this region give rise to somites, blocks of tissue running ...

, and further to the axial mesoderm. The lateral plate mesoderm is separated from the paraxial mesoderm by a narrow region of intermediate mesoderm. The mesoderm is the middle layer of the three germ layers, between the outer ectoderm and inner endoderm. During the third week of embryonic development the lateral plate mesoderm splits into two layers forming the

intraembryonic coelom In the development of the human embryo the intraembryonic coelom (or somatic coelom) is a portion of the conceptus forming in the mesoderm during the third week of development. During the third week of development, the lateral plate mesoderm split ...

. The outer layer of lateral plate mesoderm adheres to the ectoderm to become the somatic or parietal layer known as the

somatopleure In the anatomy of an embryo, the somatopleure is a structure created during embryogenesis when the lateral plate mesoderm splits into two layers. The outer (or somatic) layer becomes applied to the inner surface of the ectoderm, and with it (part ...

. The inner layer adheres to the endoderm to become the splanchnic or visceral layer known as the splanchnopleure.

Development

The lateral plate mesoderm will split into two layers, the

somatopleuric mesenchyme In the anatomy of an embryo, the somatopleure is a structure created during embryogenesis when the lateral plate mesoderm splits into two layers. The outer (or somatic) layer becomes applied to the inner surface of the ectoderm, and with it (part ...

, and the

splanchnopleuric mesenchyme In the anatomy of an embryo, the splanchnopleuric mesenchyme is a structure created during embryogenesis when the lateral mesodermal germ layer splits into two layers. The inner (or splanchnic) layer adheres to the endoderm, and with it forms ...

. * The ''somatopleuric layer'' forms the future body wall. * The ''splanchnopleuric layer'' forms the

circulatory system The blood circulatory system is a system of organs that includes the heart, blood vessels, and blood which is circulated throughout the entire body of a human or other vertebrate. It includes the cardiovascular system, or vascular system, tha ...

. Spaces within the lateral plate are enclosed and forms the

. It is formed by the secretion of

BMP-4 Bone morphogenetic protein 4 is a protein that in humans is encoded by ''BMP4'' gene. BMP4 is found on chromosome 14q22-q23. BMP4 is a member of the bone morphogenetic protein family which is part of the transforming growth factor-beta superfam ...

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 The mesentery is an organ that attaches the intestines to the posterior abdominal wall in humans and is formed by the double fold of peritoneum. It helps in storing fat and allowing blood vessels, lymphatics, and nerves to supply the intestin ...

, 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 The peritoneum is the serous membrane forming the lining of the abdominal cavity or coelom in amniotes and some invertebrates, such as annelids. It covers most of the intra-abdominal (or coelomic) organs, and is composed of a layer of meso ...

cavities. ::* First partition: is the

septum transversum The septum transversum is a thick mass of cranial mesenchyme, formed in the embryo, that gives rise to parts of the thoracic diaphragm and the ventral mesentery of the foregut in the developed human being and other mammals. Origins The septum ...

. :::*This will be translocated later into the diaphragm and ventral mesentery. :::*Divides the coelom 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 transversum to close off these canals. * At day 22,

lung buds The lung bud sometimes referred to as the respiratory bud forms from the respiratory diverticulum, an embryological endodermal structure that develops into the respiratory tract organs such as the larynx, trachea, bronchi and lungs. It arises from ...

form, remaining ensheathed in a splanchnopleuric mesoderm

Limb development

Cells from the lateral plate mesoderm and the myotome migrate to the limb field and proliferate to create the limb bud. The lateral plate cells produce the cartilaginous and skeletal portions of the limb while the myotome cells produce the muscle components. The lateral plate mesodermal cells secrete a fibroblast growth factor (FGF7 and FGF10, presumably) to induce the overlying ectoderm to form an important organizing structure called the apical ectodermal ridge (AER).The AER reciprocatively secretes FGF8 and FGF4 which maintains the FGF10 signal and induces proliferation in the mesoderm. The position of FGF10 expression is regulated by Wnt8c in the hindlimb and Wnt2b in the forelimb. The forelimb and the hindlimb are specified by their position along the anterior/posterior axis and possibly by two T-box containing transcription factors: Tbx5 and Tbx4, respectively.

Additional images

File:Gray31.png, Model of human embryo 1.3 mm. long. (Splanchic mesoderm labeled at left, somatic mesoderm at top right

References

External links

* {{DEFAULTSORT:Lateral Plate Mesoderm Embryology of urogenital system Mesoderm