Paraxial mesoderm
Encyclopedia
Paraxial mesoderm is the area of mesoderm
that forms just lateral to the neural tube
on both sides.
It differentiates rostrally into somatomeres and caudally into somite
s.
It gives rise to the somitomere
s/somite
s and mesoderm of the branchial arches.
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...
that forms just lateral to the neural tube
Neural tube
In the developing vertebrate, the neural tube is the embryo's precursor to the central nervous system, which comprises the brain and spinal cord...
on both sides.
It differentiates rostrally into somatomeres and caudally into somite
Somite
A somite is a division of the body of an animal. In vertebrates this is mainly discernible in the embryo stage; in arthropods it is a characteristic of a hypothetical ancestor.- In vertebrates :...
s.
It gives rise to the somitomere
Somitomere
In the developing vertebrate embryo, the somitomeres are loose masses of paraxial mesoderm derived cells that form along each side of the neural tube towards the end of the third gestational week...
s/somite
Somite
A somite is a division of the body of an animal. In vertebrates this is mainly discernible in the embryo stage; in arthropods it is a characteristic of a hypothetical ancestor.- In vertebrates :...
s and mesoderm of the branchial arches.
- Somites form the vertebral columnVertebral columnIn human anatomy, the vertebral column is a column usually consisting of 24 articulating vertebrae, and 9 fused vertebrae in the sacrum and the coccyx. It is situated in the dorsal aspect of the torso, separated by intervertebral discs...
, dermisDermisThe dermis is a layer of skin between the epidermis and subcutaneous tissues, and is composed of two layers, the papillary and reticular dermis...
and skeletal muscleSkeletal muscleSkeletal muscle is a form of striated muscle tissue existing under control of the somatic nervous system- i.e. it is voluntarily controlled. It is one of three major muscle types, the others being cardiac and smooth muscle... - Branchial arches will develop into facial muscle and cartilage, plus other structures.
- eventually differentiates into the axial skeleton, skeletal muscle, part of the dermis
- almost immediately as it is formed, somitomeres develop.
- starts with several pairs in the cranial region, and increasingly more proceed to develop towards the caudal region.
- The original seven pairs form the striated muscles of head and neck, which develop within the pharyngeal arches
- The other somitomeres develop further, to form discrete blocks called somites, starting at approximately 20 days.
