Skull

The human skull consists of approximately 30 bones, which can be anatomically divided into the cranial bones (neurocranium) and the facial bones (viscerocranium). The neurocranium consists of the frontal, the ethmoid, the sphenoid, the occipital, and the paired temporal and parietal bones. The cranial bones are connected by fibrous joints called sutures. The bones of the infant neurocranium are not fused but are instead connected by membranous gaps between the bone plates called fontanelles, which enable flexion of the skull to facilitate passage through the birth canal and accommodate the rapidly growing brain. The fontanelles, which comprise the anterior, posterior, and the paired mastoid and sphenoid fontanelles, close between the age of 2 months and 18 months. The viscerocranium consists of the unpaired mandible and vomer and the paired zygomatic bones, inferior nasal conchae, lacrimal bones, nasal bones, maxillary bones, and palatine bones. The temporomandibular joint connects the lower jaw to the temporal bone and enables movement for speech and mastication. The skull features numerous foramina through which pass the cranial nerves, the spinal cord, arteries, and veins.

Overview

• Protects the skull while permitting growth
• Provides bony architecture to major neurovascular and lymphatic structures

Gross anatomy

• Viscerocranium (facial bones)
  • Temple: zygomatic bones (frontal, sphenoidal, temporal, maxilla)
  • Nose
    • Lacrimal bones
    • Nasal bones
    • Inferior nasal conchae
    • Vomer (bone)
  • Jaw
    • Maxillae (upper jaw bones)
    • Mandible (lower jaw/jaw bone)
  • Mouth
    • Palatine bones
    • Hyoid bone
• Neurocranium (cranial bones)
  • Anterior
    • Frontal bone
    • Ethmoid bone
    • Sphenoid bone
  • Lateral
    • Parietal bones
    • Temporal bones
  • Posterior
    • Occipital bone

3D Anatomy

Adult skull

The calvaria (skullcap) comprises the superior portions of the frontal bone, the occipital bone, and the parietal bones.

Infant skull (fontanelles)

An infant's neurocranium consists of five separate bones (two frontal bones, two parietal bones, and one occipital bone) held together by connective tissue sutures. This allows for stretching and deformation of the skull to facilitate birth and accommodate the brain's growth at a faster rate than the surrounding bone. The larger areas of connective tissue that arise at the gaps between the bone plates are called “fontanelles”.

• Posterior fontanelle
• Anterior fontanelle
• Sphenoidal fontanelles (not pictured)
• Mastoid fontanelles (not pictured)

Superior surface of the base of the skull (cranial fossa)

Inferior surface of the base of the skull

3D Anatomy

Gross anatomy

Jaw

• Consists of the maxilla (upper jaw bone; composed of two maxillary bones fused at the intermaxillary suture) and the mandible (lower jaw bone), which are connected at the temporomandibular joints.
• The mental foramen: two openings in the mandible through which pass the mental nerves (from V₃)

Temporomandibular joints (TMJ)

• Associated structures
  • Bone
    • Joint head: head of mandible
    • Joint socket: mandibular fossa and articular tubercle of the temporal bone
  • Soft tissue
    • Articular disc
    • Stylomandibular ligament
    • Sphenomandibular ligament
• Associated conditions
  • Temporomandibular joint dysfunction
  • Lockjaw