| Chondrocranium | |
| Latin: | chondrocranium |
The chondrocranium (or cartilaginous neurocranium) is the primitive cartilaginous skeletal structure of the fetal skull that grows to envelop the rapidly growing embryonic brain.[1]
The chondrocranium in different species can vary greatly, but in general it is made up of four components, the sphenoids, occipitals, otic capsules, and nasal capsules.[2]
In humans, the chondrocranium begins forming at 28 days from mesenchymal condensations and is fully formed between week 7 and 9 of fetal development. While the majority of the chondrocranium is succeeded by the bony skull, some components do persist into adulthood.[1] In cartilaginous fishes (e.g. sharks and rays) and agnathans (e.g. lampreys and hagfish), the chondrocranium persists throughout life.[3] Embryologically, the chondrocranium represents the basal cranial structure, and lays the base for the formation of the endocranium.[4]
The portion of the chondrocranium that is associated with the notochord is termed the chordal chondrocranium and is formed from mesodermally-derived mesenchyme. The more rostral portion of the chondrocranium that lie anterior to the notochord constitutes the prechordal chondrocranium, and is derived primarily from neural crest-derived mesenchyme.