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orthodontic isw.pptx - FACIAL DEVELOPMENT IN PRENATAL...

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FACIAL DEVELOPMENT IN PRENATALONTOGENYDONE BY: HALA AL TAMIMI
In 2 planes: Rostrocaudalaxis and Lateral axis.• After the formation ofhead fold, the developingbrain and the pericardiumform two prominentbulging on the ventralaspect of the embryo
During the third week of development an oro- pharyngeal membraneis first seen at the site of the future face, between primordium of theheart and the rapidly enlarging primordium of the brainComposed of ectoderm externally and endoderm internally ,ultimately breakdown during the fourth week in order to form theopening between the future oral cavity and foregutWhile tissues around it expand rapidly, the oropharyngealmembrane’s non proliferating cells are gradually pulled apartbecause they cannot fill the expanding area
PHARYNGEAL ARCHESRod-like thickenings of mesoderm in the foregut.At first 6 arches. 5th arch disappear, only 5 remains.The ventral ends of the arches of the right and left sides meet atthe middle line in the floor of the pharynx.They bring about elongation of the region between thestomatodeum and the pericardium forming neck.In the interval between any two adjoining arches, endodermextends outwards to form a series of pouches. They are calledendodermal or pharyngeal pouches.
DEVELOPMENT OF HEADFormation of the head is definedby the migration of neural crestcells that arise from therhombomeres, segments of theforming hindbrain which willgive rise to differentiatedneurons
DEVELOPMENT OF THE SKULLThe skeleton of the head is the skull,can be divided into 2 main partscalvaria and the facial skeletonConsist of 28 bones, calvaria andface are composed of 14 bones eachThe skull cap develops byintramembranous ossification, base ofthe skull in contrast ossifies by intra-cartilagenous ossification

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