Skull

From ArticleWorld

The skull is a somewhat hollow bony structure that forms the head, part of the face and houses the brain of humans and other higher animals. While it appears to be one single bone, the skull is actually made of 28 bones in the adult human. All of these bones, except one, are fused together in childhood, forming what are called suture lines.

Anatomy

The bulk of the skull itself is called the neurocranium. Made up of 8 fused bones, the neurocranium houses the brain itself. These are the paired temporal bones, and the frontal bones, along with the occipital bone, the frontal bone, the ethmoid bone and the sphenoid bone. Fourteen bones together form the splanchnocranium or the facial bones. Inside each temporal bone are the six tiny ear bones or ossicles. The mandible is the only articulated bone in the skull. It forms the lower jaw. These mainly fused bones began as 45 separate bones in a newborn that gradually grow and fuse over time.

The skull is very complex, with exit points or foramina for important blood vessels and for the twelve cranial nerves that supply nerves to the head must exit. A large foramen magnum is at the base of the skull and is where the lower part of the brain and the beginning of the spinal cord exit the neurocranium.

Function

The skull protects the brain from injury and, through its many foramina, allow for the blood supply to serve the outside of the skull and the face. Nerves for the face and head, including those that are specifically for vision and hearing, must exit the skull to reach the outside.

Muscles attached to the skull, including the mandible, allow for chewing, facial expressions, the opening and closing of the eyes and the movement of the neck. The cranium itself has only a pair of occipitalis muscles in the back and is otherwise covered by a sheet of connective tissue called the galea aponeurotica.

Special functions of the skull are the housing of the eyes for vision, the mouth for taste, the nose for the sense of smell and the ears for hearing. The function of the eyes, ears, nose and mouth are intimately connected to the brain and its activity.

Conditions

The skull or facial bones can be fractured as a result of injury. A skull fracture in the absence of any brain injury is not particularly dangerous; however, most skull fractures cause internal brain injury as well. Certain genetic diseases can cause abnormalities of the facial features, such as a cleft palate or Crouzon’s Disease. An infant with anencephaly is born without a formed skull or a completely developed brain. In adults, one can develop temporomandibular joint syndrome due to inflammation of the joint that connects the mandible to the rest of the skull.