Although the cranium—the largest section of the skull—might appear to be one solid bone, there are actually 22 bones that encase the brain. Twenty-one of those pieces are fused together by sutures, which are nearly rigid, fibrous joints found only in the skull. Similar connective fibers are found in teeth and the spine.
These sutures give the appearance of cracks or fissures. These are easiest to see on the side of the head where the temporal bone meets the parietal bone, and in the back where the occipital bone adjoins the temporal and parietal bones.
The skull consists of the cranium and the mandible, or jawbone. It is the semi-circular bone at the bottom of the skull and attached to the cranium at the jaw. The mandible is responsible for the up and down motion of the jaw.
The mandible also holds the bottom row of teeth; the maxilla holds the upper row. Mammals, including humans, develop two sets of teeth during their lives.
The shape and structure of human teeth serve many purposes. As most humans are omnivores (eat both plants and animals), their teeth must perform many functions to ensure proper chewing of food. The thin incisors and pointed canines help rip and tear meat, and the premolars and molars help grind down substances so they are easy to swallow.
Because teeth play a role in the way your body receives nutrients, proper tooth care is important. Common tooth ailments include:
- Plaque and buildup: Accumulation of mouth bacteria that can lead to cavities
- Cavities: Areas of decay that develop in the teeth
- Gingivitis: Irritation of the gum line that can result in tooth loss
The skull also provides housing for the eye and optic nerve. This portion of the skull is called an orbit, but it is more commonly known as the eye socket. Seven separate bones make up the eye socket:
- Frontal bone
- Lacrimal bone
- Ethmoid bone
- Zygomatic bone
- Maxillary bone
- Palatine bone
- Sphenoid bone
The eye is protected from the hard edges of the bone by fat tissue, which makes movement of the eye smooth. Nerves, blood vessels, ligaments, and other important tissues occupy the rest of the orbit.