Respiratory Anatomy

The pharynx is a component of the digestive system that lies posterior to the nasal cavity, oral cavity, and larynx. The pharynx can be divided into the oropharynx, nasopharynx, and laryngopharynx. Pharyngeal muscles play an integral role in vital processes such as breathing, swallowing, and speaking. The muscles of the pharynx receive innervation from the vagus and glossopharyngeal nerve to propel food from the oral cavity into the esophagus.

The nose is the human body's primary organ of smell and functions as part of the upper respiratory system. The nose may be best known for inhaling oxygen and exhaling carbon dioxide, but it also contributes to other important functions, such as tasting. The anatomy of the nose can be divided into the external nose and the nasal cavity. There are 12 cranial bones that contribute to the structure of the nose's walls and nasal conchae.

The 4 pair of paranasal sinuses include the maxillary, ethmoid, sphenoid, and frontal sinuses. The sinuses are a group of air-filled cavities located within the facial and cranial skeleton; all are connected to the main nasal cavity and nasopharynx. Functions include contributing to voice resonance, reducing the skull weight to facilitate an upright head position, conditioning (warming and humidifying) inhaled air, and maximizing the surface of the nasal mucosa.

The larynx, also commonly called the voice box, is a cylindrical space located in the neck at the level of the C3–C6 vertebrae. The larynx is continuous superiorly with the oropharynx and inferiorly with the trachea. This structure is made up of 9 cartilages that are connected by membranes, ligaments, and muscles and that house the vocal cords. The major structures forming the framework of the larynx are the thyroid cartilage, cricoid cartilage, and epiglottis. The larynx serves to produce sound (phonation), conducts air to the trachea, and prevents large molecules from reaching the lungs.

The trachea is a tubular structure that forms part of the lower respiratory tract. The trachea is continuous superiorly with the larynx and inferiorly becomes the bronchial tree within the lungs. The trachea consists of a support frame of 16–20 semicircular, or C-shaped, rings made out of hyaline cartilage and reinforced by collagenous connective tissue. The posterior wall of the trachea is free of cartilage. In this area, the paries membranaceus forms a plate out of smooth tracheal muscle and connective tissue and forms the border to the dorsally running esophagus.

Lungs are the main organs of the respiratory system. Lungs are paired viscera located in the thoracic cavity and are composed of spongy tissue. The primary function of the lungs is to oxygenate blood and eliminate CO2. To perform this function, the lungs need to be able to capture as much O2 as possible, a task that is easily achieved owing to their elastic morphology. Each lung is enclosed within the visceral pleura and completely fills 1 of the non-symmetrical pleural cavities, which are situated on the left and right sides of the mediastinum. The lungs encase the bronchial tree and are divided functionally and anatomically into lobes.