Cranial bone

Cranial Bones
Details
System	Skeletal system
Identifiers
Latin	Ossa cranii
TA98
TH	{{#property:P1694}}
TE	{{#property:P1693}}
FMA	{{#property:P1402}}
Anatomical terminology

The cranial bones are the bones that form the skull, which encloses and protects the brain. The human skull is typically composed of eight cranial bones and fourteen facial bones. The cranial bones provide structural support for the head and serve as an attachment point for various muscles and ligaments. They also contain cavities that house the organs of sight, hearing, and smell.

Structure

The cranial bones include:

• Frontal bone – located at the front of the skull, forming the forehead and the upper part of the eye sockets.
• Parietal bones (2) – located on the sides of the skull, these bones are involved in forming the roof and sides of the skull.
• Temporal bones (2) – situated at the lower sides of the skull, these bones are involved in forming the base of the skull and contain structures essential for hearing.
• Occipital bone – found at the back and base of the skull, this bone contains the foramen magnum, through which the spinal cord passes.
• Sphenoid bone – located at the base of the skull, this bone is shaped like a butterfly and spans the width of the skull.
• Ethmoid bone – a light, spongy bone located at the roof of the nasal cavity and forming part of the orbits of the eyes.

Development

Cranial bones develop through a process known as intramembranous ossification, where connective tissue is transformed directly into bone. This is different from most other bones in the body, which are formed through endochondral ossification, a process where cartilage is first formed and then gradually replaced by bone tissue.

Function

The primary function of the cranial bones is to protect the brain from injury. They also provide attachment points for the muscles of the head and neck, which are essential for movements such as chewing, facial expressions, and head movement. Additionally, the cranial bones support the structures of the face and contribute to the individual's overall facial appearance.

Clinical significance

Damage to the cranial bones can lead to serious conditions such as cranial fractures, which may affect the brain and other structures enclosed by the skull. Conditions like craniosynostosis, where the cranial sutures close prematurely, can also affect the shape and functionality of the skull.

See also

• Skull
• Bone
• Human skeleton
• Facial bones