Neurocranium

Neurocranium
The eight bones that form the human neurocranium.
The eight cranial bones. (Facial bones are shown in semi-transparent.)   Yellow: Frontal bone (1)   Blue: Parietal bone (2)   Purple: Sphenoid bone (1)   Orange: Temporal bone (2)   Green: Occipital bone (1)   Red: Ethmoid bone (1)
Details
Identifiers
Latin	Neurocranium
Dorlands /Elsevier	c_60/12264811
TA	A02.1.00.007
FMA	53672
Anatomical terms of bone [edit on Wikidata]

In mammals, the neurocranium, also known as the braincase, brainpan, or brain-pan^[1][2] is the upper and back part of the skull.

The skull can be divided into two parts: the neurocranium, which forms a protective case around the brain, and the facial skeleton, which forms the skeleton of the face.^[3]

In the human skull, the neurocranium includes the calvaria, or skullcap. The lower part of the skull is the facial skeleton also known as the splanchnocranium.

Structure

The neurocranium is divided into two portions:

• the membranous part, consisting of flat bones, which surround the brain; and
• the cartilaginous part, or chondrocranium, which forms bones of the base of the skull.^[3]

In humans, the neurocranium is usually considered to include the following eight bones:

• 1 ethmoid bone
• 1 frontal bone^[4]
• 1 occipital bone
• 2 parietal bones
• 1 sphenoid bone
• 2 temporal bones

The ossicles (three on each side) are usually not included as bones of the neurocranium.^[5] There may variably also be extra sutural bones present.

Below the neurocranium is a complex of openings (foramina) and bones, including the foramen magnum which houses the neural spine. The auditory bullae, located in the same region, aid in hearing.^[6]

The size of the neurocranium is variable among mammals. The roof may contain ridges such as the temporal crests.

Development

The neurocranium arises from paraxial mesoderm. There is also some contribution of ectomesenchyme. In Chondrichthyes and other cartilaginous vertebrates this portion of the cranium does not ossify; it is not replaced via endochondral ossification.

Other animals

The neurocranium is formed by the endocranium, the lower portions of the cranial vault, and the skull roof. These are not fused in fishes, and a proper neurocranium is only found in land vertebrates.

Evolutionarily, the human neurocranium has expanded from comprising the back part of the mammalian skull to being also the upper part: during the evolutionary expansion of the brain, the neurocranium has overgrown the splanchnocranium. The upper-frontmost part of the cranium also houses the evolutionarily newest part of the human brain, the frontal lobes.

Additional images

• 

  Animation without left parietal bone, showing cranial cavity and inner surface of base of skull.

• 

  Inner surface of base of skull.

• 

  Neurocranium (labeled as "Brain case") and facial bones.

See also

*Cranial cavity

References

1. "Brainpan - Medical Definition and More from Merriam-Webster". Merriam-Webster/Medical.
2. Nyiszli, Miklos (2011). Auschwitz: A Doctor's Eyewitness Account. New York: Arcade Publishing.
3. Sadler, Thomas W. (February 2009). Langman's Medical Embryology. Lippincott Williams & Wilkins. p. 173. ISBN 0781790697.
4. In small children, the frontal bone is still separated into two parts, by the frontal suture, which normally closes during postnatal development.
5. but if they are included, the neurocranium will then have to be said to consist of fourteen bones
6. Elbroch, M. 2006. Animal skulls: A guide to North American species. Stackpole Books, pp. 20–22. ISBN 978-0-8117-3309-0