The<unk>  (or cartilaginous neurocranium) is the primitive cartilaginous skeletal structure of the fetal skull that grows to envelop the rapidly growing embryonic brain. The<unk>  in different species can vary greatly, but in general it is made up of five components, the sphenoids, the mesethmoid, the occipitals, the optic capsules and the nasal capsules. In humans, the<unk>  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<unk>  is succeeded by the bony skull, some components do persist into adulthood. In cartilaginous fishes (e.g. sharks and rays) and agnathans (e.g. lampreys and hagfish), the<unk>  persists throughout life. Embryologically, the<unk>  represents the basal cranial structure, and lays the base for the formation of the endocranium.
Chondrocranium
Neuromatrix
Ranula
Microgyrus
Tapetum lucidum
Livedo racemosa
Neurosphere
Glia limitans