Two sets of bones comprise the skull: cranial bones and facial bones. The cranial bones have two functions. First of all, they protect and enclose the brain. Second, they provide the site for which the head muscles can attach. The facial bones provide the framework for the face and mouth. All bones comprising the skull are attached to each other via immovable joints, except for the mandible which is attached to the skull via a freely movable joint.
There are eight cranial bones which make up the cranium. These bones are remarkable thin and can be compared to an eggshell in the way that they are self-bracing. The forehead is formed by the frontal bone which also forms the upper half of the eye sockets. Two parietal bones comprise the sides of the skull. Named so because they are above the parietal area of the brain, the parietal bones form the bulk of the cranium. Temporal bones lie inferior to the parietal bones on both sides of the skull. The occipital bone, also named for the part of the brain it covers, forms the posterior of the skull. The sphenoid bone encloses the rest of the cranial cavity. It lies behind the eye sockets anterior to the temporal bones and posterior to the frontal bone.
The face is comprised of roughly seven bones. The sides of the eye sockets are formed by the Zygomatic bones. The rest of the sockets are formed by the Maxilla which is two bones that are fused together. The upper teeth are attached to the inferior of the Maxilla. The jaw is formed by the mandible where the lower teeth reside on the superior surface.
The spinal column is formed by 26 bones that are connected to each other in such a way that results in a flexible, curved spine. At the base of the column is the sacrum. The sacrum is comprised of 5 vertebrae that have been fused. Below the sacrum is the coccyx which is made of 4 fused vertebrae. The spinal column is divided into 3 parts. The cervical vertebrae are the first 7 vertebrae down from the skull. The next 12 are the thoracic vertebrae. The thoracic vertebrae are followed by the lumbar vertebrae which are the last 5 vertebrae.
Anterior to the spinal column is the sternum and the rib cage. There are 12 pairs of ribs. The first 7 pairs are true ribs, that is they are attached directly to the sternum. The rest are false ribs, meaning that they attach to the sternum indirectly or not at all in the case of the two pairs of floating ribs. The ribs are attached to the sternum by cartilage. At the inferior end of the sternum is the xiphoid. This serves as an attachment point for the diaphragm.
Two bones comprise the shoulder girdle. They are the clavicle and the scapula. It should be noted that there are two shoulder girdles, one on each side. The clavicle mainly acts as a brace that holds the scapulae and the arms up and away from the ribs. The scapulae lie on the posterior side of the rib cage. The scapula connects the upper arm to the rest of the body. The scapulae are only attached to the rest of the body by the clavicle. This helps for us to be able to raise our hands by allowing the scapula to slip forward and back.
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