Learning Objectives
By the end of this section, you will be able to:
- List and identify the bones of the cranium and facial skull
- Locate the major suture lines of the skull
- Identify the paranasal sinuses and their location
- Identify the bones and structures that form the nasal septum and locate the hyoid bone
The skull is the skeletal structure of the head that supports the face and protects the brain. It is subdivided into the facial bones and the cranium, or cranial vault (Figure 7.3.1). The facial bones underlie the facial structures, form the nasal cavity, enclose the eyeballs, and support the teeth of the upper and lower jaws. The rounded cranium surrounds and protects the brain and houses the middle and inner ear structures.
In the adult, the skull consists of 22 individual bones, 21 of which are immobile and united into a single unit. The 22nd bone is the mandible (lower jaw), which is the only moveable bone of the skull.
External Website
Watch this video to view a rotating and exploded skull, with color-coded bones. Which bone (yellow) is centrally located and joins with most of the other bones of the skull?
Anterior View of Skull
The anterior skull consists of the facial bones and provides the bony support for the eyes, teeth and structures of the face and provides openings for eating and breathing. This view of the skull is dominated by the openings of the orbits and the nasal cavity. Also seen are the upper and lower jaws, with their respective teeth (Figure 7.3.2).
The orbit is the bony socket that houses the eyeball and muscles that move the eyeball or open the upper eyelid and provides for passage for sensory nerves.
Inside the nasal area of the skull, the nasal cavity is divided into halves by the nasal septum. The upper portion of the nasal septum is formed by the perpendicular plate of the ethmoid bone and the lower portion is the vomer bone. When looking into the nasal cavity from the front of the skull, two bony plates are seen projecting from each lateral wall. making up the nasal concha, which is part of the ethmoid bone.
Lateral View of Skull
On the lateral side of the cranium, above the level of the zygomatic arch, is a shallow space called the temporal fossa. Arising from the temporal fossa and passing deep to the zygomatic arch is another muscle that acts on the mandible during chewing, the temporalis.
Bones of the Cranium
The cranium contains and protects the brain. The interior space that is almost completely occupied by the brain is called the cranial cavity. This cavity is bounded superiorly by the rounded top of the skull, which is called the calvaria (skullcap), and the lateral and posterior sides of the skull. The bones that form the top and sides of the cranium are usually referred to as the “flat” bones of the skull.
The floor of the brain case is referred to as the base of the skull or cranial floor. This is a complex area that varies in depth and has numerous openings for the passage of cranial nerves, bl