What are the three main subdivisions of intraembryonic mesoderm?

The intraembryonic mesoderm differentiates into three longitudinal columns: paraxial mesoderm (adjacent to the neural tube), intermediate mesoderm (between paraxial and lateral plate mesoderm), and lateral plate mesoderm (in the lateral most part of the embryonic disc).

What structures are formed from the paraxial mesoderm?

Paraxial mesoderm segments into somites, which subdivide into sclerotome (forms vertebrae and ribs), myotome (forms skeletal muscles), and dermatome (forms the dermis of the skin).

What does the intermediate mesoderm develop into?

Intermediate mesoderm primarily contributes to the urogenital system, forming structures such as kidneys, testes and ovaries, and parts of the genital ducts.

How does the lateral plate mesoderm split and what does it form?

Lateral plate mesoderm splits into two layers due to the intraembryonic celom: somatopleuric mesoderm (contributes to body wall structures) and splanchnopleuric mesoderm (contributes to walls of internal organs or viscera).

What are the subdivisions of the intraembryonic celom?

The intraembryonic celom is divided into the pericardial cavity (anterior region), pericardioperitoneal canals (connecting channels), and peritoneal cavity (limbs of the horseshoe-shaped celom).

What are somites and when do they appear in development?

Somites are blocks formed from segmented paraxial mesoderm, appearing in a cranio-caudal sequence starting around day 20 of embryonic development. By day 30, approximately 38 somites are present, correlating with embryo age.

What are the special derivatives of the lateral plate mesoderm?

Special derivatives include the septum transversum (forms the liver and central tendon of the diaphragm) and the epicardium (develops from splanchnopleuric mesoderm near the prochordal plate).

Intraembryonic Mesoderm – Paraxial, Intermediate, Lateral

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