6.2 Review of Anatomy and Physiology of the Respiratory System
6.2 Review of Anatomy and Physiology of the Respiratory System
This section will review the anatomy and physiology of the respiratory system. Common disorders affecting these anatomic structures are also introduced. See Figure 6.1[1] for an illustration of the major structures of the respiratory system.
Nose, Nasal Cavity, and Sinuses
The upper respiratory system refers to the nose, nasal cavities, sinuses, pharynx, and larynx. See Figure 6.2[2] for an illustration of anatomic structures of the upper respiratory system. An upper respiratory infection (URI) refers to a viral infection of one or more of these structures.
The entrance and exit for the respiratory system are through the nose. The nostrils are the opening to the nose, also referred to as nares. The nares and nasal cavities are lined with mucous membranes, containing sebaceous glands and hair follicles that serve to prevent the passage of large debris, such as dirt, through the nasal cavity. Rhinorrhagia refers to bleeding from the nose, also called epistaxis. Rhinitis refers to inflammation of the nasal mucosa.
The nares open into the nasal cavity, which is separated into left and right sections by the nasal septum. The floor of the nasal cavity is composed of the hard palate and the soft palate. The nasal cavities are lined with mucous membranes that produce mucus, a substance created for lubrication and protection. Rhinorrhea, commonly referred to as a “runny nose,” is a medical term for excess mucus production by the nasal cavities.
Adjacent to the nasal cavity are the sinuses that serve to warm and humidify incoming air. There are four sinuses named for their adjacent bones: frontal sinus, maxillary sinus, sphenoidal sinus, and ethmoidal sinus. Air moves from the nasal cavities and sinuses into the pharynx. Sinusitis refers to inflammation of the sinus cavities.[3]
Pharynx
The pharynx, commonly known as the throat, is divided into three major regions: the nasopharynx, the oropharynx, and the laryngopharynx. See Figure 6.3[4] for an illustration of the regions of the pharynx.[5]
At the top of the nasopharynx is the pharyngeal tonsil, also called adenoid. The function of the pharyngeal tonsil is to trap and destroy invading pathogens that enter the airway during inhalation. Pharyngitis is inflammation of the pharynx, and tonsillitis is inflammation of the tonsils.[6]
The soft palate and a bulbous structure called the uvula swing upward during swallowing to close off the nasopharynx to prevent ingested materials from entering the nasal cavity. Eustachian tubes connect the middle ear cavities with the nasopharynx. This connection is why upper respiratory infections often lead to ear infections.[7]
The oropharynx is bordered superiorly by the nasopharynx and anteriorly by the oral cavity. The oropharynx contains two distinct sets of tonsils called the palatine tonsils and lingual tonsils that also trap and destroy pathogens entering the body through the oral or nasal cavities. Adenoids