Lecture 8 - Paraxial Mesoderm

What does dorsal part of somite differentiate into??

Dorsal part develops into dermamyotome by the signals Wnts and BMP.

What does ventral part of somite differentiate into??

Sclerotome by Shh and noggin

Dorsal Root

• Sensory neurons

• Nucleus is in dorsal root ganglion of spinal chord

Ventral Root

• Motor neurons with nucleus in white matter of spinal chord.

epidermis is formed from

ectoderm

dermis is formed from

mesoderm

to form the vertebral column

8 cervical somites split and resegment to form 7 cervical vertebrae each originating from two partial sclerotomes

Pax 3

Indicate Muscle Expansion

Layers of Somite Differentiation

Sclerotome → Dermamyotome → Dermatome and Myotome - Epimere & Hypomere

Resegmentation of Sclerotome

• split into cranial and caudal and bind to adjacent halves to join myotome to neural tube via spinal nerves

What forms ribs

• Vertebrae elongate

• Costovertebral joints develop seperating ribs from vertebrae.

Long bone development

endochondrial ossification (cartilage phase)

Skull formation

membraneous ossification: bone forms directly from the mesenchyme. characterized by bone spicules radiating outwards

Craniosyntosis

Outgrowth depending on sutures that do not close.

Hox

• Tells hindbrain which part of neural tube to form

Pharyngeal Arches

Medial nasal process → Intermaxillary Process → Philtrum