The walls of the nasal cavity are uneven. There are three mucous covered projections that stick out into the nasal cavity. These lobes are known as conchae. These projections help increase the area that the mucosa can affect. The nasal cavity is separated from the oral cavity by a palate of bone. Anteriorly, where the palate is supported lies the hard plate. The unsupported area of the palate houses the soft plate.
The nasal cavity is surrounded by the paranasal sinuses. These sinuses are located in the maxillary, ethmoid, sphenoid, and frontal bones. The sinus chambers help lighten the weight of the skull. The sinus chambers also act as resonance chambers for vocalization. The sinus cavities also secrete mucous for the nasal cavity.
The pharynx is the muscular passageway that provides a means of transportation for air and food. The pharynx, also known as the throat, is about 13 cm. long.
Air enters the pharynx through its superior portion, the nasopharynx. Air then descends from the nasopharynx to the oropharynx, to the laryngopharynx. From the laryngopharynx air enters the larynx. Food travels the same way, through the nasopharynx to the laryngopharynx, but instead of entering the larynx, it enters the esophagus. Since the auditory tubes from the ear open into the nasopharynx, the mucosae of each regoin are continuos. Since the mucosae is continuos ear infections may proceed after a sore throat. Tonsils, clusters of lymphatic tissue, are also found in the pharynx. The pharyngeal tonsils, also called the adenoids, are found in the nasopharynx. The palatine tonsils are located in the oropharynx. The lingual tonsils are located at the base of the tongue.
The larynx, also known as the voice box, routes food and air to its proper destination. The larynx is made up of eight hyaline cartilages and a flap of elastic cartilage, the epiglottis. The epiglottis' job is to prevent food from entering the superior opening of the larynx, and traveling down the trachea. Breathing opens the epiglottis and allows free passage of air to the lungs. The larynx is pulled in an upward direction while swallowing, causing the epiglottis to " tip " and close over the opening of the larynx. When the epiglottis is closed, it forces food to be pushed down the esophagus. If something beside air enters the larynx, a cough occurs. A coughs' purpose is to repel any foreign substance, beside air, from entering the trachea. The mucous membrane of the larynx form the vocal folds. When expelled by air, the vocal folds vibrate. This vibration allows human's the ability of speech. The glottis is the thin passageway between the vocal folds. The largest of the hyaline cartilages is the thyroid cartilage. The thyroid cartilage, also called the Adams apple, protrudes anteriorliy.
The trachea, also called the windpipe, is about 10-12 cm. The trachea's walls are covered with ciliated mucousa. The cilia are always beating in the opposite direction of the incoming air. The cilia also send dust pathogens up the trachea so that it may be swallowed and digested.
The trachea is quite rigid due to the fact that its walls are made up of c-shaped hyaline cartilage. The open part of the rings allow the esophagus to expand when one swallows a large amount of food. The opposite ends keep the trachea open.
|[Index] [Systems] [Credits] [Feedback] [Other]|