Neurocranium

From Wikipedia, the free encyclopedia
  (Redirected from Braincase)
Jump to: navigation, search
Neurocranium
Cranial bones en.svg
Neurocranium
Schädelbasis1.jpg
Details
Latin Neurocranium
Identifiers
Gray's p.128
Dorlands
/Elsevier
c_60/12264811
TA A02.1.00.007
FMA FMA:53672
Anatomical terms of bone

The skull can be divided into two parts: the neurocranium, which forms a protective case around the brain, and the splanchnocranium, which forms the skeleton of the face.[1]

In mammals, the neurocranium, braincase, brainpan, or brain-pan[2][3] is the back part of the skull and houses the brain. The interorbital region lies in front of the neurocranium.

In the human skull, the neurocranium includes the calvaria, or skullcap. The lower part of the skull is the splanchnocranium.

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.

The term "cranium" can be ambiguous in that it can refer to the neurocranium alone or to the whole skull (the neurocranium and the facial skeleton).

Structure[edit]

The size of the braincase is variable among mammals. The roof may contain ridges such as the temporal crests. Below the braincase is a complex of foramina (openings) and bones, including the foramen magnum which houses the neural spine. The auditory bullae, located in the same region, aid in hearing.[4]

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.

The neurocranium is divided into two portions:

(a) the membranous part, consisting of flat bones, which surround the brain as a vault; and

(b) the cartilaginous part, or chondrocranium, which forms bones of the base of the skull.[1]

Human neurocranial bones[edit]

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

The ossicles (three on each side) are usually not included when enumerating the bones of the neurocranium.[6] There may variably also be extra sutural bones present.

Neurocranium

Embryonic origins[edit]

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.

See also[edit]

References[edit]

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