The human head contains the skull, a complex bony structure that serves as both a protective shell and a support framework. This structure, part of the body’s axial skeleton, houses the brain and provides scaffolding for the facial features and sensory organs. The skull is composed of various flat and irregular bones joined together, creating a robust enclosure that protects the central nervous system and enables functions like sight and chewing. The total number of bones counted in this region depends on the specific anatomical definition used.
The Definitive Count
The standard count for the human skull is twenty-two separate bones, which is the generally accepted figure in anatomy. These twenty-two bones are traditionally divided into two groups: the eight bones that form the cranium (neurocranium) and the fourteen bones that make up the facial skeleton (viscerocranium). This division distinguishes the structure surrounding the brain from the structure forming the face. The majority of these bones are connected by fibrous, immovable joints called sutures, with the exception of the lower jaw.
Bones of the Cranium
The eight bones of the cranium (neurocranium) form the protective vault around the brain, safeguarding the tissue from external trauma. Four of these bones are unpaired:
- Frontal bone
- Occipital bone
- Sphenoid bone
- Ethmoid bone
The remaining four cranial bones consist of two paired sets: the two parietal bones and the two temporal bones. The parietal bones form the top and side walls of the skull, while the temporal bones are situated on the sides near the ears. These eight bones interlock firmly through jagged connections called sutures, which are synarthrodial joints that prevent movement in adults. These sutures remain unfused in infants, allowing the brain to grow, but they gradually ossify over time.
Bones of the Face
The facial skeleton (viscerocranium) is composed of fourteen bones that define the contours of the face and support the sensory apparatus. These bones provide the structure for the eye orbits, the nasal and oral cavities, and the jaw.
The facial bones include:
- Two maxillae, which form the upper jaw and anchor the upper teeth.
- Two zygomatic bones, commonly known as the cheekbones.
- Two nasal bones, forming the bridge of the nose.
- Two lacrimal bones, which contribute to the tear ducts near the inner eye.
- Two palatine bones, forming the posterior part of the hard palate.
- Two inferior nasal conchae, which help humidify and warm inhaled air within the nasal cavity.
The only unpaired facial bones are the vomer, which forms the lower part of the nasal septum, and the mandible (lower jawbone). The mandible is the only movable bone of the entire skull, articulating at the temporomandibular joint to allow for chewing and speech.
The Often-Excluded Bones
While the standard skull count is twenty-two, the total number of bones in the head region is often cited as twenty-nine due to the inclusion of associated bones. This includes the six tiny auditory ossicles of the middle ear: the malleus, incus, and stapes. These three pairs of bones are the smallest in the human body.
The ossicles are located within the temporal bone and transmit sound vibrations from the eardrum to the inner ear. The higher count also includes the single hyoid bone, a U-shaped structure situated in the anterior neck beneath the lower jaw. The hyoid is unique because it does not directly articulate with any other bone. These seven bones are typically excluded from the skull count because they are either embedded within a skull bone or lack a direct joint connection to the main structure.