Mandible Development, Lecture notes of Oral Biology

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Development of

Mandible

Dr. Kanza Nawadat

BDS, MSc.

Derivatives of the 1 st Pharyngeal Arch

Anatomy of the Mandible

Anatomy of the Mandible

Why study mandible? Healthy mandible

Body of Mandible

• (^) The cartilage of the first arch (Meckel’s cartilage) has a close positional relationship to the developing mandible but makes NO CONTRIBUTION to it.
• 6 th^ week of development Meckel’s cartilage extends as a solid hyaline, cartilaginous rod surrounded by a fibrocellular capsule extends form the developing ear region to the midline of the fused mandibular processes the two cartilages of each side do not meet at the midline but are separated by a thin band of mesenchyme

Photomicrograph of a coronal section through an embryo showing the general pattern of intramembranous bone deposition associated with formation of the mandible. The relationship among nerve, cartilage, and tooth germ is evident. Arrowheads indicate the future directions of bone growth to form the neural canal and lateral and medial alveolar plates

During the 6th^ week of embryonic development a condensation of mesenchyme occurs on the lateral aspect of Meckel’s cartilage in the angle formed by the division of the inferior alveolar nerve into its incisive and mental branches at the 7 th^ week Intramembranous ossification begins in this condensation, forming the first bone of the mandible From this center of ossification bone formation spreads rapidly in both anterior and posterior directions Anteriorly the ossification spreads towards the midline and posteriorly it spreads towards the point of division of the mandibular nerve into its branches

New bone formation spreads anteriorly along the lateral aspects of Meckel’s cartilage forming a trough The trough consists of lateral and medial plates that unite beneath the incisive nerve This trough of bone extends to the midline, coming into approximation with the trough in the adjoining mandibular process The trough coverts into a canal as bone forms over the nerve joining the medial and lateral plates The 2 separate centers of ossification remain separated at the mandibular symphysis until shortly after birth

Ramus of Mandible

• (^) The ramus of mandible develops by a rapid spread of

ossification posteriorly into the mesenchyme of the first

arch turning away from the Meckel’s cartilage

• (^) This point of divergence is marked by Lingula in the adult

mandible the point at which the inferior alveolar nerve

enters the body of the mandible

• (^) By 10th^ week rudimentary mandible is formed almost

entirely by membranous ossification with little or no direct

involvement of Meckel’s cartilage