The brain of the fetus is surrounded by a membranous capsule which is continuous with a similar capsule surrounding the spinal cord. Chondrification begins in the base, but ossification begins in the calvaria (supraorbital portion) before the chondrifying process has progressed very far. Bones which are formed in membrane are the frontal, parietal, squamous temporals, the greater wings of the sphenoid (except their roots) and the occipital above the nuchal lines. Centers appear for these bones about the 7th week. In general, the older basal portion of the skull is preformed in cartilage, but the facial and the roofing bones are formed intramembranously.
KeywordsFrontal Sinus Condyloid Process Cribriform Plate Middle Meningeal Artery Jugular Foramen
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