Mesoderm

Chordamesoderm

Forms notochord → nucleus pulposus

Paraxial Mesoderm

Forms somites → muscle, dermis, vertebrae

Sclerotome

Forms vertebrae and ribs

Dermomyotome

Forms dermis and muscle

Intermediate Mesoderm

Forms kidneys and gonads

Lateral Plate Mesoderm

Forms circulatory system and body cavity

Somatic Mesoderm

Forms body wall and limb bones

Splanchnic Mesoderm

Forms heart and blood vessels

BMP Gradient

High BMP → lateral plate; low BMP → paraxial

Hox Genes

Control anterior-posterior identity

Clock-Wavefront Model

FGF gradient + Notch oscillations → somite formation

Kidney Development

Ureteric bud + metanephric mesenchyme interaction

GDNF

Induces ureteric bud growth

Heart Fields

First = left ventricle; Second = right ventricle + atria

Intramembranous Ossification

Direct bone formation

Endochondral Ossification

Bone from cartilage template

Osteoblasts

Build bone

Osteoclasts

Break down bone