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Pharynx

life science Maturity 9-11 Next article →

The pharynx is a vital structure located in the throat. It sits behind the mouth and the nasal cavity. It is positioned above the esophagus and the trachea. The esophagus is the tube that carries food to the stomach. The trachea is the tube that carries air to the lungs. In humans, the pharynx serves two major roles. It is part of the digestive system for moving food. It is also part of the respiratory system's conducting zone. This zone filters, warms, and moistens air before it reaches the lungs.

Blausen 0872 UpperRespiratorySystem
Blausen 0872 UpperRespiratorySystem

To manage these two jobs, the human pharynx is divided into three distinct sections. The first section is the nasopharynx. It extends from the base of the skull to the soft palate. This area contains the adenoids, which are lymphoid tissue structures. The second section is the oropharynx. It lies behind the oral cavity and extends from the uvula to the hyoid bone. The third section is the laryngopharynx, also known as the hypopharynx. This is the lowest part of the throat. It connects the common pathway to the separate respiratory and digestive routes.

Torus tubarius dissection
Torus tubarius dissection

The pharynx operates through a precise mechanical process to ensure safety. Because food and air share this space, the body must prevent mistakes. A flap of cartilage called the epiglottis acts as a gate. When you swallow, the epiglottis closes over the glottis. This prevents aspiration, which is when food enters the airway. During this process, food has the "right of way." This means the air passage temporarily stops so food can pass safely. The pharynx uses two layers of muscles to shape its lumen, or internal space. These include an inner layer of longitudinal muscles and an outer layer of pharyngeal constrictor muscles.

Specific anatomical features exist within each of these three sections. In the nasopharynx, the auditory tube opens to connect the middle ear to the throat. This tube helps equalize barometric pressure in the ear with the outside atmosphere. The oropharynx contains the palatine tonsils located between the palatoglossal and palatopharyngeal arches. It is also home to certain microbes. The HACEK organisms are part of the normal oropharyngeal flora. These organisms grow slowly and prefer carbon dioxide. In the laryngopharynx, the area includes the pyriform sinus and the postcricoid area. This section is controlled by the pharyngeal plexus and the recurrent laryngeal nerve.

Biological history and development show how important this structure is. All vertebrates possess a pharynx for feeding and breathing. During development, the pharynx arises from six or more outpocketings called pharyngeal arches. These arches eventually form many parts of the skeletal and muscular systems. The vertebrate pharynx is unique because it uses neural crest cells to create endoskeletal support. This evolutionary foundation is seen even in simpler creatures. For example, invertebrates like tardigrades and annelids also have a pharynx. Even the nematode worm uses a muscular pharynx as a food pump.

There are many surprising ways animals use the pharynx. Some fish, such as the moray eel, have pharyngeal jaws. These are a second set of jaws located inside the throat. When a moray eel captures prey with its oral jaws, the pharyngeal jaws move forward. They bite down on the prey to grip it tightly. Then, they retract to pull the food down into the esophagus. This allows the eel to swallow effectively. In humans, the pharynx also helps with speech. It acts as a resonating chamber during phonation and helps articulate pharyngeal consonants.

Understanding the pharynx is important for medicine. Inflammation of this area is called pharyngitis, which causes painful swelling.

Pharyngitis
Pharyngitis

Doctors also study the Waldeyer's tonsillar ring. This is an annular arrangement of lymphoid tissue in the nasopharynx and oropharynx. This ring is believed to prevent microorganisms from invading the respiratory and alimentary systems. It acts as a defense mechanism for the body. Additionally, the vagus nerve connects the pharynx to the ear. This connection can cause referred ear pain during pharyngeal cancer. It even triggers the ear-cough reflex when the ear canal is stimulated.

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File:Blausen 0872 UpperRespiratorySystem.png
Blausen 0872 UpperRespiratorySystem.png
File:Torus tubarius dissection.jpg
Torus tubarius dissection.jpg
File:Pharyngitis.jpg
Pharyngitis.jpg
File:Pharyngeal jaws of moray eels.svg
Pharyngeal jaws of moray eels.svg
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