1 The roof of the mouth, which is formed by the hard and soft palates, separates the oral cavity from the nasal cavity. The vestibule is the area between the buccal mucosa and the outer surface of the teeth and gums. The oral cavity may be divided into the mouth and vestibule. (From Seidel HM, Ball JW, Dains JE, et al: Mosby’s guide to physical examination, ed 7, St. The turbinates help to increase the surface area for warming, filtering, and humidifying air.įIGURE 13-4 The anatomical structures of the oral cavity. Covered by vascular mucous membrane, the turbinates separate the nose into a superior meatus, medial meatus, and inferior meatus ( Figure 13-3). Three turbinate bones form the lateral walls of the nose. 6, 7 The adenoids lie on the posterior wall of the nasopharynx. This group of arteries and veins is called Kiesselbach’s plexus and is often responsible for epistaxis. A group of small fragile arteries and veins is located on the anterior superior portion of the septum. The cribriform plate that is part of the ethmoid bone on the roof of the nose houses the sensory endings of the olfactory nerve (i.e., cranial nerve I). Air enters the nose through the nostrils and passes posteriorly to the nasopharynx through one of the choanae, separated by one of three turbinate bones. The internal nose is divided into two anterior cavities, or vestibules, by the septum. (From Epstein O, Perkin GD, Cookson J, et al: Clinical examination, ed 4, Philadelphia, 2008, Mosby.) The most efficient and normal hearing pathway is through air conduction however, bone also conducts sound, by transmitting the vibrations of the skull directly to the vestibulocochlear nerve ( Box 13-1).įIGURE 13-2 The nose and nasal septum. Hearing is an interpretation of sound waves received via an air conduction path. Feedback from this movement is provided to the brain, assisting to maintain upright posture and balance. The vestibule is directly responsible for balance as the fluid in the semicircular canals shifts with head movement. The cochlea encodes the previous mechanical vibrations as electrical impulses that are then sent to the eighth cranial nerve (i.e., vestibulocochlear). The inner ear consists of the vestibule, semicircular canals, and cochlea. This passage opens briefly to equalize pressure within the inner ear that occurs with changes in atmospheric pressure caused by swallowing, sneezing, or yawning. The middle ear is connected to the nasopharynx by the eustachian tube. These bones transmit vibrations from the tympanic membrane mechanically to the inner ear, where the mechanical vibrations are changed to electrical signals. ![]() The translucent tympanic membrane permits visualization of the middle ear, which is an air-filled cavity in the temporal bone that contains the ossicles: the malleus, incus, and stapes. The external ear and the middle ear are separated by the tympanic membrane. (From Jarvis C: Physical examination & health assessment, ed 5, St. FIGURE 13-1 Anatomy of the ear, showing the external, middle, and inner ear.
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