The skull has two parts: the cranium, which encloses the brain, and the facial bones. All its bones except the mandible are joined by immovable joints.
The cranium
The frontal, two parietal, two temporal and the occipital bones form the vault, with the sphenoid and ethmoid in the base. The temporal bone is thin, and the middle meningeal artery runs just inside it.
The skull base
The base has openings (foramina) for the spinal cord, blood vessels and cranial nerves. The largest, the foramen magnum, is where the brainstem joins the spinal cord.
Facial bones
The maxillae, zygomatic bones, nasal bones and mandible shape the face. The mandible is the only movable skull bone, hinged at the temporomandibular joint.
Sutures and fontanelles
In infants, the bones are separated by sutures and soft spots called fontanelles, which let the head mold during birth and the brain grow. The posterior fontanelle closes in the first months and the anterior one by 12 to 18 months.
At the bedside
A blow to the temple can tear the middle meningeal artery and cause an epidural hematoma, so watch for a falling level of consciousness. Signs of a skull base fracture include bruising behind the ear (Battle sign), bruising around the eyes (raccoon eyes) and clear fluid from the nose or ear.
Related guides
Written by Making Synapses. Topic reference: OpenStax, Anatomy and Physiology 2e (no text adapted).