FIGURE 3.

Paracrine angiocrine signalling promotes Meckel’s cartilage proliferation to drive jaw growth during development. Jaw bone formation is preceded by the initial formation of the arrowhead-shaped Meckel’s cartilage, which acts as a scaffold for the mandible bone to later ossify around. This size and shape of Meckel’s cartilage therefore dictates the shape of the jaw bone later in development. Meckel’s cartilage lies in close apposition with the mandibular artery, which releases angiocrine IGF1 to act in a paracrine manner on IGF1R on Meckel’s chondrocytes, inducing their proliferation and promoting appropriate jaw lengthening prior to bone ossification. Since ossification of the mandible bone occurs around the already formed mandibular artery, foramen (holes) are present in mature jaw bone which allow passage of the artery and continued blood flow through the bone.