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# Bones and Features of the Skull ## 8.2 Bones and Features of the Skull We will begin our examination of the skeleton by discussing its most complex structure, the skull. The skull is made up of 22 bones. Here we describe the anatomy and landmarks of the skull, the sutures (a type of fibrous join...

# Bones and Features of the Skull ## 8.2 Bones and Features of the Skull We will begin our examination of the skeleton by discussing its most complex structure, the skull. The skull is made up of 22 bones. Here we describe the anatomy and landmarks of the skull, the sutures (a type of fibrous joint; see section 9.2) that connect the bones of the cranium, and the specialized features of the orbital and nasal complexes and paranasal sinuses. ### 8.2a General Anatomy of the Skull **Learning Objective:** * Distinguish between the cranial and the facial bones. The skull is composed of both cranial and facial bones. **Cranial bones** form the rounded cranium (kranë-um; kranion=skull), which completely surrounds and encloses the brain. The cranium consists of eight bones that form a roof and a base. The roof of the cranium, called the **calvaria** (kal-vä're-ä), is composed of the superior part of the frontal bone, the parietal bones, and a small part of the occipital bone. The base of the cranium is composed of portions of the frontal, ethmoid, sphenoid, occipital, and temporal bones. Some skulls Osteologists (scientists who study bones) define the cranium as the entire skull minus the mandible. In this text, we use the **cranium** to denote the bones that directly surround the brain only. **Facial bones** form the face. They also protect the entrances to the digestive and respiratory systems. Touch your cheeks, your jaws, and the bridge of your nose: these bones are facial bones. The facial bones give shape and individuality to the face, form part of the orbit and nasal cavities, support the teeth, and provide for the attachment of muscles involved in facial expression and mastication (chewing). There are 14 facial bones, including the paired zygomatic bones, lacrimal bones, nasal bones, inferior nasal conchae, palatine bones, maxillae, and unpaired vomer and mandible. The skull contains several prominent cavities. The largest is the **cranial cavity** (or endocranium) that encloses, protects, and supports the brain. (The volume of an adult cranial cavity ranges from approximately 1300 to 1500 cubic centimeters, which is about 50 fluid ounces.) The skull also forms and has several smaller cavities, including the **orbits** (eye sockets), the **oral cavity**, the **nasal cavity**, and the **paranasal sinuses**. **Learning Objectives:** * Identify the locations of cranial and facial bones in various views of the skull * Identify and describe the individual skull bones and the major features found on each bone. * Compare and contrast the locations and contents of three cranial fossae. To best understand the complex nature of the skull, first examine the skull as a whole and learn which bones are best seen from a particular view.