The axial skeleton is the part of the skeleton that consists axial and appendicular skeleton pdf the bones of the head and trunk of a vertebrate. The axial skeleton together with the appendicular skeleton form the complete skeleton. Another definition of axial skeleton is the bones including the vertebrae, sacrum, coccyx, ribs, and sternum.
View from both directions of a axial skeleton cut in half. Shows attachments to pelvis and does not show skull. From Sobotta’s atlas of human anatomy 1909.
Flat bones house the brain and other vital organs. The human axial skeleton consists of 80 different bones. It is the medial core of the body and connects the pelvis to the body, where the appendix skeleton attaches.
As the skeleton grows older the bones get weaker with the exception of the skull. The skull remains strong to protect the brain from injury. The human skull consists of the cranium and the facial bones. The cranium holds and protects the brain in a large space called the cranial vault.
In addition there are 14 facial bones which form the lower front part of the skull. Together the 22 bones that compose the skull form additional, smaller spaces besides the cranial vault, such as the cavities for the eyes, the internal ear, the nose, and the mouth. The most important facial bones include the jaw or mandible, the upper jaw or maxilla, the zygomatic or cheek bone, and the nasal bone.
Humans are born with separate plates which later fuse to allow flexibility as the skull passes through the pelvis and birth canal during birth. During development the eight separate plates of the immature bones fuse together into one single structure known as the Skull.
The only bone that remains separate from the rest of the skull is the mandible. The rib cage is composed of 12 pairs of ribs plus the sternum for a total of 25 separate bones. The rib cage functions as protection for the vital organs such as the heart and lungs.