Otolaryngology The medical specialty that studies the anatomy and physiology of the ears, nose, mouth, and throat (ENT) and uses diagnostic tests, medical and surgical procedures, and drugs to treat ENT diseases.
Figure 16-1 Ears, nose, and throat (ENT) system
Anatomy and Physiology The ears, nose, and throat (ENT) system is contained entirely in the head and neck. The head contains the external and internal structures of the ears, nose, and mouth, and the internal structures of the sinuses. The neck contains the internal structures of the pharynx and larynx.
Anatomy and Physiology (cont’d) The ENT system shares some structures with the gastrointestinal system and the respiratory system, so it serves as a passageway for both food and air. The ENT system also contains lymphoid tissue that functions as part of the immune response. The body’s senses of hearing and smell are also part of the ENT system.
Anatomy of the ENT System External Ear – Known as the auricle or pinna – The helix is the outer rim of tissue and cartilage that forms a C and ends at the ear-lobe. – The external auditory meatus is the opening that leads into the external auditory canal (EAC).
Figure 16-2 External ear
Anatomy of the ENT System (cont’d) External Ear (cont’d) – The canal has glands that secrete cerumen, a waxy, sticky substance that traps dirt and has an antibiotic action against microorganisms that enter the canal. – At the end of the canal is the tympanic membrane (TM), or eardrum, a thin dividing wall between the external ear and the middle ear.
Figure 16-3 Tympanic membrane Pearson Education/PH College
Anatomy of the ENT System (cont’d) External Ear (cont’d) – The mastoid process is a bony projection of the temporal bone that lies just behind the external ear and contains tiny cavities filled with air.
Anatomy of the ENT System (cont’d) Middle Ear – The middle ear is a hollow area inside the temporal bone of the skull. – It contains three tiny bones: the malleus, incus, and stapes, collectively known as the ossicles. – It is connected to the nasopharynx by the eustachian tube.
Anatomy of the ENT System (cont’d) Middle Ear – The eustachian tube allows air pressure in the middle ear to equalize with air pressure in the throat and outside of the body.
Figure 16-4 Structures of the middle ear and inner ear
Anatomy of the ENT System (cont’d) Inner Ear – Contains three fluid-filled structures: Vestibule Semicircular canals Cochlea
Anatomy of the ENT System (cont’d) Vestibule is the entrance area to the inner ear. One end of the vestibule becomes the three semicircular canals. The other end of the vestibule becomes the coiled cochlea.
Anatomy of the ENT System External Nose and Mouth – The external nose is supported by the nasal bone, which forms the bridge of the nose and the dorsum. – At the nasal tip, the nasal bone becomes cartilage. – The nares are the external openings, or nostrils; the flared cartilage on each side of the nostril is a nasal ala.
Figure 16-5 External nose, mouth, and neck
Anatomy of the ENT System (cont’d) External Nose and Mouth (cont’d) – The lips, cheeks, and chin are supported by the maxilla (upper jawbone) and mandible (lower jawbone). – The nasolabial fold is the crease in the cheek that goes from the nose to the corner of the mouth. – The philtrum is the vertical groove above the upper lip. – The chin is also known as the mentum.
Anatomy of the ENT System (cont’d) Sinuses – A sinus is a hollow cavity within a bone that is lined with a mucous membrane. – Four pairs of sinuses: frontal, maxillary, ethmoid, and sphenoid. – As a group, these are also known as the paranasal sinuses.
Figure 16-6 Sinuses
Anatomy of the ENT System (cont’d) Nasal Cavity – The nasal cavitiy is formed by the ethmoid bone of the cranium and by the maxilla of the upper jaw. – The nasal septum is a vertical wall of cartilage that divides the nasal cavity into right and left sides. – In the posterior nasal cavity, this cartilage becomes the ethmoid bone of the cranium.
Figure 16-7 Structures of the internal nose, mouth, and throat
Anatomy of the ENT System (cont’d) Nasal Cavity – Along the nasal cavity walls are three long, bony projections − the superior, middle, and inferior turbinates, or nasal conchae. – The turbinates divide and slow down inhaled air and give it warmth and moisture. – The nasal cavity is lined with nasal mucosa, a mucous membrane that continuously produces mucus.
Anatomy of the ENT System (cont’d) Oral Cavity – Contains the tongue, hard palate, soft palate and uvula, teeth, and salivary glands – Lined with the oral mucosa that is known as buccal mucosa in the cheek area
Anatomy of the ENT System (cont’d) Oral Cavity – The hard palate or roof of the mouth divides the oral cavity from the nasal cavity and is made up of 3 different cranial bones: the maxilla at the front of the mouth, the palatine bone, and the vomer bone at the back of the mouth. – Submental lymph nodes in the tissue under the chin contain lymphocytes and macrophages that attack bacteria and viruses.
Anatomy of the ENT System (cont’d) Pharynx – Divided into three areas: the nasopharynx, the oropharynx, and the laryngopharynx. – The eustachian tubes open into the nasopharynx. – The roof and walls of the nasopharynx contain the pharyngeal tonsil, a collection of lymphoid tissue commonly known as the adenoids.
Anatomy of the ENT System (cont’d) Pharynx (cont’d) – The nasopharynx becomes the oropharynx or middle portion of the throat, which contains the palatine tonsils. – The laryngopharynx contains the lingual tonsils on either side of the base of the tongue.
Anatomy of the ENT System (cont’d) Pharynx (cont’d) – The tonsils and adenoids are part of the lymphatic system, and they function in the immune response; they contain lymphocytes and macrophages that attack bacteria and viruses in the tissues around the oral cavity.
Figure 16-8 Pharynx
Anatomy of the ENT System (cont’d) Larynx (cont’d) – Pharynx divides into two parts: the larynx leads to the trachea and the esophagus leads to the stomach. – The larynx, or voice box, is a short, triangular structure. – Is surrounded by two thick rings of cartilage that can be clearly seen at the front of the neck as the laryngeal prominence (Adam’s apple)
Anatomy of the ENT System (cont’d) Larynx (cont’d) – At the superior end of the larynx is the epiglottis; in the middle of the larynx are the glottis, ligaments, and the vocal cords. – When you swallow, the larynx moves superiorly and closes against the epiglottis to keep food from entering the lungs. – Remains open during breathing, speaking, or singing to allow air to pass over the vocal cords.
Anatomy of the ENT System (cont’d) Larynx (cont’d) – Muscles in the larynx relax or tighten the vocal cords to lower or raise the pitch. – Surface layer of each vocal cord vibrates, producing sound waves that travel through the vocal cords and past the soft palate, tongue, and lips, all of which shape the sound waves into words.
Physiology of the Sense of Hearing The external ear captures sound waves. The tympanic membranes move the malleus, the incus, and then the stapes. The stapes transmits this mechanical motion to the oval window, which causes inner ear fluid on the other side of the oval window to move.
Physiology of the Sense of Hearing (cont’d) The vibration is transmitted to the cochlea. Tiny hair cells detect the loudness and pitch of the sound and send this sensory information as nerve impulses through the cochlear branch of the vestibulocochlear nerve to the medulla oblongata in the brainstem. From there, the impulses are relayed to the auditory cortex in the brain.