SKELETAL SYSTEM

1
SKELETAL SYSTEM

• Part 1 Axial Skeleton
• (Skull)

2
THE SKULL

• Cranial Bones (fused by sutures) enclose/protect
  the brain provide attachments for muscles used
  in chewing/head movement
• Frontal bone forehead, roof of nasal cavity and
  orbits (eye sockets)
• Parietal bones side walls and roof of cranium
• Occipital bone back of skull, base of cranium
• Temporal bones side walls, floor of cranium (the
  temples)
• Sphenoid bone part of cranial base, sides of
  skull, floor and posterior portion of orbits
• Ethmoid bone part of roof/walls of nasal cavity
  part of orbital walls and cranial floor

3
Sutures

• Separate fused cranial bones
• Sagittal suture separates sides of parietal bone
• Coronal suture separates frontal bone from
  parietal/sphenoid bones
• Squamosal suture separates parietal and temporal
  bones
• Lambdoidal suture separates occipital bone from
  parietal/temporal bones

4
Frontal Bone

• Features
• Supraorbital foramina (sing. foramen) small
  openings above each orbit (supraorbital) blood
  vessels and nerves pass through it to access
  tissues of forehead
• Frontal sinuses located toward midline, deep to
  frontal bone and superior to orbits

5
Parietal Bones

• One curved plate on each side form the sides and
  roof of the cranium.
• Fused together _at_ midline along sagittal suture
  meet w/frontal bone along coronal suture.
• No special features

6
Occipital Bone

• Form back and bottom of the skull join
  w/parietal bones along lambdoidal suture
• Special features
• Foramen magnum large opening on lower surface
  nerve fibers from brain travel through it into
  vertebral canal, become part of spinal cord
• Occipital condyles large, rounded processes that
  articulate with the atlas (the most superior
  vertebra)
• External occipital protuberance the most
  posterior of the structures on the skull, at the
  base.

7
Temporal Bones

• Form parts of sides and base of cranium fused
  w/parietal bones along the squamosal suture
• Special features
• External auditory meatus an opening within the
  inferior part of the temporal bone that leads
  into the ear
• Internal ear structures
• Mandibular fossa one on each side below external
  auditory meatus depression that articulates with
  the mandible
• Mastoid process rounded projection below e.a.m.
  attachment site for some neck muscles
• Styloid process pointed projection below e.a.m.
  anchors tongue and pharynx muscles

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Other Structures to Know

• Inferior view of skull
• Foramen lacerum
• Foramen ovale
• Foramen spinosum
• Carotid canal
• Jugular foramen
• Stylomastoid foramen
• (first four found in sphenoid bone last two in
  temporal bone)

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• Facial bones vomer, ethmoid, sphenoid,
  zygomatic, maxilla, mandible
• -nasal septum separates the nasal cavity
  composed of vomer bone and perpendicular plate of
  ethmoid bone
• - other important structures in ethmoid bone
  crista galli, cribriform plate, olfactory
  foramina
• - important structure in sphenoid bone sella
  turcica (houses pituitary gland)

10

• Zygomatic arch (the cheekbone) is formed by the
  zygomatic process of the temporal bone
  (posterior) and the temporal process of the
  zygomatic bone (anterior).
• The mandible is the only movable bone in the
  skull. It contains the following structures
• mandibular condyle (articulates with the
  mandibular fossa on the temporal bone), ramus
  (flat area on the lateral edge), mental foramina
• - The maxilla forms the top of the mouth and most
  of the center of the face, as well as the nose
  all the way up to the nasal bone. It contains
  infraorbital foramina, one on each side.