Flashcards on Craniofacial Embryology and Developmental Malformations
Craniofacial Embryology & Malformations: Student Guide
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Skull development
13 cards
Card 1
Question: What are the two main portions of the neurocranium involved in skull development and how do they form?
Answer: The cartilaginous neurocranium (basicranium) forms ventrally via endochondral ossification; the membranous neurocranium (cranial vault) forms dorsally
Card 2
Question: Which bones are included in the basicranium and what is their embryonic origin?
Answer: The basicranium includes the sphenoid, ethmoid, mastoid and petrous parts of the temporal bone, and the base of the occipital bone; these derive from
Card 3
Question: Through which process do basicranial bones form and what is the defining feature of that process?
Answer: They form by endochondral ossification, where a cartilaginous template (anlage) is established first and then replaced by bone via vascular invasion.
Card 4
Question: Which skeletal elements associated with the basicranium retain a cartilaginous fate?
Answer: Parachordal cartilage, hypophyseal cartilages, ala orbitalis and temporalis (sphenoid-associated), trabeculae cranii (ethmoid-associated), and the per
Card 5
Question: Which bones comprise the membranous neurocranium (cranial vault) in skull development?
Answer: Seven bones: paired frontal, paired squamosal, paired parietal, and the occipital bone.
Card 6
Question: What is the embryonic origin of the membranous neurocranium and how does it ossify?
Answer: It is derived from cranial neural crest and forms mostly by intramembranous ossification, where mesenchymal cells condense and directly differentiate
Card 7
Question: How does intramembranous ossification proceed histologically in the membranous neurocranium?
Answer: Neural crest–derived mesenchymal cells secrete a collagenous matrix that mineralizes; ossification begins separately in each bone and expands radially
Card 8
Question: What is unique about the ossification of the occipital bone?
Answer: The occipital bone is composite: its inferior part forms by endochondral ossification, while its superior part forms by intramembranous ossification.
Card 9
Question: Which cranial sutures are primary in humans and what bones do they separate?
Answer: Frontal suture (between frontal bones); sagittal suture (between parietal bones); coronal suture (between frontal and parietal bones); lambdoid suture
Card 10
Question: What are fontanelles and which two are most well known?
Answer: Fontanelles are 'soft spots' present prior to suture fusion. The anterior fontanelle (between coronal, sagittal, and interfrontal sutures) and the pos