Paraxial mesoderm

Paraxial mesoderm
Transverse section of a chick embryo of forty-five hours’ incubation. * Chordamesoderm: yellow, at notochord. * Paraxial mesoderm: red, at somite. * Intermediate mesoderm: purple, near Wolffian duct. * Lateral plate mesoderm: purple, near "Somatic mesoderm" and "Splanchic mesoderm".
Chick embryo of thirty-three hours’ incubation, viewed from the dorsal aspect. (Paraxial mesoderm labeled at left.)
Gray's	subject #6 50
Carnegie stage	9
Gives rise to	somitomere, head mesoderm
Dorlands/Elsevier	m_11/12527037

Paraxial mesoderm is the area of mesoderm that forms just lateral to the neural tube on both sides.

It gives rise to the somitomeres/somites and mesoderm of the branchial arches.

• Somites form the vertebral column dermis and skeletal 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 straited 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.

External links

• Overview at nih.gov
• Diagram and overview at mcgill.ca
• Diagram at lww.com

This article was originally based on an entry from a public domain edition of Gray's Anatomy. As such, some of the information contained herein may be outdated. Please edit the article if this is the case, and feel free to remove this notice when it is no longer relevant.

Human development of embryo and development of fetus (some dates are approximate - see Carnegie stages and a timeline)
Week 1	Zygote - Morula - Blastula (Blastomere) - Blastocyst - Inner cell mass
Week 2	Bilaminar disc (Hypoblast, Epiblast)
Week 3 (Trilaminar embryo, germ layers)	Archenteron/Primitive streak (Primitive pit, Primitive knot/Blastopore, Primitive groove) - Gastrula/Gastrulation Ectoderm: Surface ectoderm - Neuroectoderm - Somatopleure Endoderm: Splanchnopleure Mesoderm: Chorda- - Paraxial (Somite/Somitomere/Sclerotome/Myotome/ Dermatome) - Intermediate - Lateral plate (Intraembryonic coelom, Splanchnopleure/Somatopleure)
Extraembryonic/uterus	Trophoblast (Cytotrophoblast, Syncytiotrophoblast) Blastocoele - Yolk sack/exocoelomic cavity - Heuser's membrane - Extraembryonic coelom - Vitelline duct Umbilical cord (Umbilical artery, Umbilical vein, Wharton's jelly) - Allantois Placenta - Decidua (Decidual cells) - Chorionic villi/Intervillous space - Gestational sac (Amnion/Amniotic sac/Amniotic cavity, Chorion)
Histogenesis and organogenesis	Limb development: Limb bud - Apical ectodermal ridge/AER