The head and face are made up of the cranial vault and facial bones. The cranial vault, or skull, is composed of several bones: one frontal, two sphenoid, two parietal, two temporal, and one occipital (Figure 2-1). Of these, the strongest is the occipital bone, and the weakest are the temporal bones. The frontal bone forms the forehead, and the temporal and sphenoid bones form the anterolateral walls of the skull, or the temples of the head. The parietal bones form the top and posterolateral portions of the skull, and the occipital bones form the posterior portion of the skull. The cranial vault reaches 90% of its ultimate size by age 5.

In addition to the cranial vault bones, there are 14 facial bones. These bones develop more slowly than the cranial bones, reaching only 60% of their ultimate size by age 6. The facial skeleton is composed of the mandible, which forms the lower jaw; the maxilla, which forms the upper jaw on each side; the nasal bones, which form the bridge of the nose; and the palatine, lacrimal, zygomatic, and ethmoid bones, which form the remainder of the face. It is the zygomatic bone that gives the cheek its prominence. The sphenoid bones also form part of the orbital cavity. The facial skull has several cavities for the eyes (orbital), nose (nasal), and mouth (oral), as well as spaces for nerves and blood vessels to penetrate the bony structure. Weight is saved in the skull area by the addition of sinus cavities (Figure 2-2).

The muscles of the head and face are controlled primarily by the 12 cranial nerves. The cranial nerves and their chief functions are shown in Table 2-1. The cranial nerves generally contain both sensory and motor fibers. However, some cranial nerves are strictly sensory (olfactory and optic), whereas others are strictly motor (oculomotor, trochlear, and hypoglossal).

The external eye is composed of the eyelids (upper and lower), conjunctiva (a transparent membrane covering the cornea, iris, pupil, lens, and sclera), lacrimal gland, eye muscles, and bony skull orbit (Figure 2-3). Muscles of the eye, their actions, and their nerve supply are shown in Table 2-2. The muscles and movements of the eye are shown in Figure 2-4. To produce some of the actions, the various muscles of the eye must work in concert. The eyelids protect the eye from foreign bodies, distribute tears over the surface of the eye, and limit the amount of light entering the eye. The conjunctiva is a thin membrane covering the majority of the anterior surface of the eye. It helps to protect the eye from foreign bodies and desiccation (drying up). The lacrimal gland provides tears, which keep the eye moist (Figure 2-5). The eye itself is made up of the sclera, cornea, and iris as well as the lens and retina (Figure 2-6). The sclera is the dense white portion of the eye that physically supports the internal structures. The cornea is very sensitive to pain (e.g., the extreme pain that accompanies corneal abrasion) and separates the watery fluid of the anterior chamber of the eye from the external environment. It permits transmission of light through the lens to the retina. The iris is a circular, contractile muscular disc that controls the amount of light entering the eye and contains pigmented cells that give color to the eye. The lens is a crystalline structure located immediately behind the iris that permits images from varied distances to be focused on the retina. It is primarily the lens and its supporting ligaments that separate the eye into chambers: the anterior chamber (aqueous humor) and the posterior chamber (vitreous humor). Finally, the retina is the primary sensory structure of the eye that transforms light impulses into electrical impulses that are then transmitted by the optic nerve to the brain, which interprets the impulses as the objects seen.

The external ear consists of cartilage covered with skin. Its primary purpose is to direct sound and to protect the external auditory meatus, through which sound is transmitted to the eardrum. The external ear, which is sometimes called the pinna, auricle, or trumpet, consists of the helix and lobule around the outside and the triangular fossa, antihelix, concha, tragus (a cartilaginous projection anterior to external auditory meatus), and antitragus on the inside (Figure 2-7). The middle ear structures consist of the tympanic membrane, or eardrum, which vibrates when sound hits it and sends vibrations through the ossicles—called the malleus (hammer), incus (anvil), and stapes (stirrup)—to the cochlea. The cochlea, which is part of the inner ear, transmits the sound waves to the vestibulocochlear nerve (cranial nerve VIII), which transmits electrical impulses to the brain for interpretation. The semicircular canals, the other part of the inner ear, play a significant role in maintaining balance.

The external nose, like the external ear, consists primarily of cartilage covered with skin. However, its proximal portion contains bone covered with skin. Figure 2-8 shows the bone and cartilage makeup of the nose. The floor of the nose consists of the hard and soft palates and forms the roof of the mouth (Figure 2-9). Cartilage and the nasal, frontal, ethmoid, and sphenoid bones form the roof of the nose. The frontal and maxillary bones form the nasal bridge. Three bony structures called turbinates (superior, middle, and inferior) form the lateral aspects of the nose, which increase the surface area of the nose and thereby warm, humidify, and filter more of the inspired air. The nose is divided into two chambers (vestibules) by a septum. These chambers are lined with a mucous membrane containing hairs that collect debris and other foreign substances from the inspired air. The cribriform plate of the ethmoid bone contains the sensory fibers of the olfactory nerve (cranial nerve I) for smell.

In addition to the questions listed under Patient History in Chapter 1, the examiner should obtain the following information from the patient who has sustained an injury to the head or the face: