![]() ![]() This epithelium contains afferent fibers from the olfactory nerves (cranial nerve I) that communicate through the cribriform plate of the ethmoid bone to the adjacent olfactory bulb. The olfactory epithelium occupies the apical third of the nasal cavity. The mucosa can be divided into respiratory and olfactory areas because it not only lines the tracts followed by respired air but also covers the cells that act as the receptors for smell. The nasal cavities are lined with mucous membranes that are continuous with those of the pharynx. Such obstruction can lead to middle ear pathology. Eustachian drainage can become obstructed when the inferior concha or adenoid tonsils become inflamed. It extends to within approximately 2 cm of the middle of the anterior naris, and its posterior tip lies approximately 1 cm in front of the pharyngeal orifice of the eustachian tube. The inferior concha, which lies along the lower part of the lateral wall of the nasal cavity, is in the pathway of airflow in the nose, and it is the one most commonly injured during nasal intubation. The superior concha is by far the smallest of the three, and the middle concha extends forward much farther than the superior concha. The conchae overlie the superior, middle, and inferior meatus, which contain the openings to the paranasal sinuses. The conchae are scroll-shaped prominences projecting from the lateral walls and have their free margins directed downward and inward. This obstruction may be life threatening in the obligate nose-breathing newborn. They open into the nasopharynx by the posterior nares (also known as choanae) and are bordered medially by the nasal septum and laterally by three turbinates arranged one above the other.Ĭhoanal atresia is a birth defect characterized by obstruction of the posterior nasal airway. The nasal fossae usually communicate freely with the paranasal air sinuses (frontal, ethmoid, maxillary, and sphenoid). ![]() The septum is formed by the ethmoid and vomer bones superiorly and the vomeronasal and nasal septal cartilages inferiorly. The fossae are separated from each other by the nasal septum, which also separates the two nostrils. The anterior portion of the external nose, the vestibule, expands above and behind into triangular spaces, or fossae. Intranasal infections can produce intracranial infection via vascular connections, as discussed later in this section. Prolonged nasotracheal intubation is associated with obstruction of the nasal sinuses, sinus infection, and fever. The tube should not be directed upward into the turbinates but rather along the floor of the nose formed by the superior aspect of the palatine bone, which forms the hard palate of the mouth directly below the nose. The floor of the nose is at a level higher than the opening of the nostril therefore, during nasal intubation, the apex of the nose should be elevated superiorly with gentle pressure while the tube is inserted parallel to the roof of the mouth. ![]() In its lower half, it has sebaceous glands and coarse hairs, which serve to filter incoming air. The vestibule is lined with cutaneous epithelium. Each nostril opening (anterior naris) leads directly into the vestibule, which is the forwardly expanded portion of the nasal cavity. The cartilage around the entrance to the nostrils that can flare during heavy breathing is called the alar cartilage or ala nasae (“nasal wings”). The external nose is only a small part of the nasal air passageway, the major portion of which lies directly behind the nose and includes three scroll-shaped turbinate bones, also called the nasal conchae. Air passing through the nose is filtered, heated to body temperature, and humidified. ![]() Inhaled air enters the body through the nose or mouth. These functions are all discussed in this chapter. Indeed, the visual hallmark of an anesthetist is frequently a stethoscope earpiece pinned to the scrub top a device that places each patient breath at the forefront of the anesthetist’s consciousness.īesides the basic functions of the respiratory system, which include extracting oxygen (O 2) from the atmosphere and delivering it to the blood while excreting carbon dioxide (CO 2), the respiratory system functions in the processes of maintaining acid-base balance, phonation, pulmonary defense, and metabolism (synthesis and breakdown of bioactive materials). This is not surprising considering that they administer oxygen to the majority of patients, administer inhaled anesthetics down a cascade of concentration gradients through the lungs, provide artificial ventilation for many patients under general anesthesia, and monitor and interpret blood gas analysis, capnography, and oximetry. Anesthetists are known as the airway experts, but they are also expected to possess an excellent command of the entire respiratory system. Knowledge of the respiratory system is essential to the practice of anesthesia. ![]()
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