Skull Bones

• Function of Cranial Bones

  formed by cranial + facial bones, 22 in all

  the cranial bones enclose + protect the fragile brain + furnish attachment sites for head + neck muscles
• Function of Facial Bones

  form the framework of the face

  contain cavities for the special sense organs of sight, taste + smell

  provide openings for air + food passage

  secure the teeth

  anchor the facial muscles of expression
• Sutures in the Skull

  most skull bones r flat bones

  except for the mandible, which is connected to the rest of skull by freely movable joints, all bones of the adult skull r firmly united by interlocking joints = sutures

  the suture lines have a saw-toothed appearance
• Major Skull Sutures

  the major skull sutures, the coronal, sagittal, squamous + lambdiod sutures connect cranial bones

  most other skull sutures connect facial bones + r named according to the bones they connect
• Cranial Bones

  8 cranial bones - 2 temporal bones + 2 parietal bones

  A) frontal bone

  B) parietal bone

  C) sphenoid bone

  D) temporal bone

  E) occipital bone

  F) ethmoid bone

  
• Skull Geography

  w the lower jaw removed, the skull = lopsided, hollow, bony sphere

  the facial bones form its anterior aspect + the cranium forms the rest of the skull
• Divisions of the Skull

  the cranium can be divided into a vault + base
• Cranial Vault

  cranial vault = forms the superior, lateral + posterior aspects of the skull, as well as the forehead

  
• Cranial Base

  cranial base forms the skull's inferior aspect

  internally, prominent bony ridges divide the base into 3 distinct fossae - anterior, middle + posterior cranial fossae

  the brain sits snugly in these cranial fossae, completey encolsed by the cranial vault

  
• Cranial Cavity

  the space enclosed by the cranial vault + cranial base = cranial cavity + is occupied by the brain
• Skull Cavities

  in addition to the large cranial cavity, the skull has many smaller cavities

  thse inc the middle + internal ear cavities, nasal cavity + the orbits, which house the eyeballs

  several skull bones contain air-filled sinuses, which lighten the skull
• Openings of the Skull

  the skull has approx 85 named openings (foramina, canals, fissures, etc.)

  the most important of these provide passageways for the spinal cord, the major bood vessels serving the brain + the 12 pairs of cranial nerves that transmit info to + from the brain
• Cranium

  the eight cranial bones r the paired parietal + temporal bones + unpaired frontal, occipital, sphenoid + ethmoid bones

  cos its superior aspect is curved, the cranium is self-bracing

  this allows the bones to be thin + like an egshell, the cranium is remarlably strong for its weight
• Frontal Bone

  the shell shaped frontal bone forms the anterior cranium

  it articulates posteriorly w the paired parietal bones via the prominent coronal suture
• Frontal Bone - Forehead

  the most anterior part of the frontal bone is the vertical squamous part = forehead

  = ends inferiorly at the supraorbital margins, the thickened superior margins of the orbits that lie under the eye-brows

  
• Parietal Bones

  the 2 large parietal bones r curved, rectangular bones that form most of the superior + lateral aspects of the skull

  form the bulk of the cranial vault

  the 4 largest sutures occur where the parietal bones articulate w other cranial bones
• Parietal Bones & Major Sutures

  coronal suture - where the parietal bones meet the frontal bone anteriorly

  sagittal suture - where the parietal bones meet superiorly at the cranial midline

  lambdoid suture - where the parietal bones meet the occipital bone posteriorly

  squamous suture - where a parietal + temporal bone meet on the lateral aspect of the skull

  
• Occipital Bone

  the occipital bone forms most of the skull's psterior wall + base

  it articulates anteriorly w the paired parietal + temporal bones via the lambodid + occipitomastoid sutures

  the basilar part of the occipital bone (located nearest the base of the skull) also joins w the sphenoid bone in the cranial base

  
• Temporal Bones

  the 2 temporal bones r best viewed on the lateral skull surface

  they lie inerior to the parietal bones + meet them at the squamous sutures

  they form the inferior + lateral aspects of the skull + parts of the cranial base
• Sphenoid Bone

  the bat-shaped sphenoid bone spans the width of the middle cranial fossa

  sphenoid = keystone bone of the cranium cos it forms a central wedge that ties the cranial bones together

  it also articulates w all of the other cranial bones

  
• Ethmoid Bone

  like the temporal + sphenoid bones, the delicate ethmoid bone has a complex shape

  lying between the sphenoid + nasal bones of the face, it is the most deeply situated bone of the skull

  it forms most of the bony area between the nasal cavity + orbits