Book 4 - Self Instructional Manual for Cancer Registrars - SEER ...

AXIALSKELETONThere are a total of eighty bones in the axial skeleton. It is composed of the skull (29 bones), thethorax (25 bones) and the vertebral column (26 bones).Bones of the Skull. The skull is the skeleton of the face and head. These bones protect the brainand related structures. The skull is composed of 29 bones, 8 forming the cranium, 14 forming thebones of the face, 6 forming the small bones in the middle ear, and 1 hyoid bone.Cranial bones. The cranial bones are the frontal, occipital, sphenoid, ethmoid, 2 temporal, and2 parietal bones. They are joined together by suturae 1 and are immovable.• The frontal bone is located at the front of the skull. It contains the frontal sinuses and formsthe upper rim of the orbit.• The occipital bone makes up the framework of the lower, posterior part of the skull.• The sphenoid bone houses the pituitary gland in a depression in its upper surface, the sellaturcica, and forms a part of the roof of the nose with its undersurface. It contains thesphenoidal sinuses.• The ethmoid bone is a light, spongy bone located at the base of the cranium, between theorbits, and at the roof of the nose. It contains the ethmoid air cells (sinuses).• The temporal bones (2 bones) form part of the sides and part of the base of the skull.• The parietal bones (2 bones) form the roof and upper part of the sides of the cranium.Figure 63. CRANIAL BONESPtrtet.l . '_ '_ /Llbcr tm_to==lpl,.t ', : :i.lsuturae--fibrous joints in which the apposed bony surfaces are so closely united by a very thinlayer of fibrous connective tissue that no movement can occur.359