Skull

• Skull


  Composed of several bones united at immobile joints called sutures (except mandible united with skull by the mobile temporomandibular joint)

  
• Functions of skull

  • Protects the brain, meninges, and cerebral vasculature
  • Supports the soft tissues of the face
  • Fuses to house the orbits, nasal, and oral cavities
• Bones of the cranium (neurocranium)

  • Frontal bone
  • Occipital bone
  • Sphenoid bone
  • Ethmoid bone
  • Temporal bones
  • Parietal bones

  
• Bones of the face (viscerocranium)

  • Zygomatic bones
  • Maxillae
  • Nasal bones
  • Lacrimal bones
  • Palatine bones
  • Inferior conchae
  • Vomer
  • Mandible

  
• Cranial sutures


  Fibrous joints that allow slight movement of bones during labor and allow the skull to grow as the baby's brain grows, but they fuse completely around the age of 20 and become immovable

  
• Main sutures in the skull

  • Coronal suture
  • Sagittal suture
  • Lambdoid suture
  • Squamous suture
• Metopic suture (Frontal Suture)


  Vertical joint that separates the two frontal bones at birth

  
• Lambda


  Point of convergence of sagittal and lambdoid suture
• Bregma


  Point of convergence of sagittal and coronal sutures
• Pterion


  Point of convergence of sutures between the frontal, sphenoid, parietal, and temporal bones

  
• Asterion


  Point of convergence of sutures between occipital bone, temporal bone, and parietal bone

  
• Bones of the skull

  • Frontal
  • Parietal
  • Temporal
  • Occipital
  • Mandible
  • Maxilla
  • Zygoma
  • Nasal
  • Ethmoid

  
• Frontal bone


  • Located in the forehead region, creates curvature of forehead, participates in the formation of the roof of orbital cavity & floor of anterior cranial fossa

  
• Articulations of frontal bone

  • Lacrimal bone
  • Nasal bone
  • Ethmoid bone
  • Maxilla
  • Zygomatic bone
  • Sphenoid bone
  • Parietal bones

  
• Landmarks of frontal bone (external surface)

  • Supraorbital margin
  • Supraciliary arch
  • Glabella
  • Supraorbital notch or supraorbital foramina
  • Zygomatic processes
  • Maxillary processes
  • Frontal air sinuses
  • Orbital plates
  • Lacrimal fossa

  
• Landmarks of frontal bone (internal surface)

  • Frontal crest
  • Foramen cecum

  
• Parietal bones


  • Form sides and roof of the cranium (bulk of calvaria)

  
• Articulations of parietal bones

  • Sagittal suture
  • Lambdoid suture
  • Coronal suture
  • Sphenoid bone
  • Squamous suture
• Landmarks of parietal bones (external surface)

  • Parietal foramina
  • Superior and inferior temporal lines
  • Parietal eminence

  
• Landmarks of parietal bones (internal surface)

  • Grooves for middle meningeal artery
  • Groove for superior sagittal sinus
  • Granular foveolae

  
• Temporal bones


  • Contribute lower lateral walls of skull, contain middle and inner portions of the ear

  
• Parts of temporal bone

  • Squamous
  • Tympanic
  • Mastoid
  • Zygomatic process
  • Petrous

  
• Landmarks of temporal bone

  • External auditory meatus
  • Mastoid process
  • Internal auditory meatus
  • Carotid canal
  • Styloid process
  • Mandibular fossa
• Occipital bone


  • Single triangular bone which articulates with sphenoid, parietal, temporal bones and with the 1st cervical vertebra

  
• Parts of occipital bone

  • Basilar part
  • Condylar parts
  • Squamous part

  
• Landmarks of occipital bone (internal surface)

  • Internal occipital protuberance
  • Internal occipital crest
  • Groove for transverse venous sinus
  • Groove for superior sagittal sinus

  
• Landmarks of occipital bone (external surface)

  • Foramen magnum
  • Occipital condyles
  • Condylar fossa and canal
  • Hypoglossal canal

  
• Occipital bone


  Bone that forms the posterior part of the cranium

  
• Parts of the occipital bone

  1. Basilar part

  2. Condylar parts

  3. Squamous part

  
• Basilar part


  • Lies anterior to foramen magnum
  • Contains clivus
  • Contains pharyngeal tubercle
• Condylar parts


  • Lie lateral to foramen magnum
  • Contains occipital condyles
  • Contains condylar fossa and canal
  • Contains hypoglossal canal
• Squamous part


  • Largest part
  • Contains external and internal surfaces
• Internal surface landmarks


  • Internal occipital protuberance
  • Internal occipital crest
  • Groove for transverse venous sinus
  • Groove for superior sagittal sinus
• External surface landmarks


  • External occipital protuberance (Inion)
  • Supreme, superior and inferior nuchal lines
  • External occipital crest
• Occipital bone is a complex bone referred to as "wasp bone or butterfly bone" and it is a keystone of cranial floor because it articulates with all cranial bones

  
• Sphenoid bone


  • Greater wings
  • Lesser wings
  • Two pterygoid processes
  • Body containing sphenoidal air sinuses
• Landmarks of sphenoid bone

  • Chiasmatic groove
  • Sella turcica
  • Anterior and posterior clinoid processes

  
• Sella turcica


  Saddle-shaped depression where pituitary gland is located
• Ethmoid bone


  • Contributes to formation of orbit, nasal cavity, nasal septum and floor of anterior cranial fossa
  • Contains cribriform plate, crista galli, perpendicular plate, and ethmoidal labyrinths

  
• Zygomatic bone


  • Articulated with frontal, sphenoid, temporal and maxillary bones
  • Has frontal, temporal and maxillary processes
  • Has zygomaticoorbital, zygomaticofacial and zygomaticotemporal foramina