Anatomy, Physiology and Immunology of the Pharynx

Anatomy, Physiology and Immunology
of the Pharynx :

The pharynx is a tubular, fibromuscular space extending from the skull base to the inlet of the esophagus (upper esophageal sphincter). Anatomically and clinically, the pharynx consists of a nasal part (nasopharynx), an oral part (oropharynx), and a laryngeal part (hypopharynx). The entire pharynx is bounded externally by several muscle systems, which perform diversefunctions and are continuous distally with the muscles of the esophageal wall.
The primary function of the pharynx and esophagus is to coordinate the act of swallowing, which is regulated by a complex interaction of various cranial nerves and peripheral muscular and connective-tissue structures located in the oral cavity, pharynx, and esophagus. The pharynx also contains the tonsillar ring, a series of lymphoepithelial organs that are important in the immune response to infection. Finally, portions of the pharynx function as a variable resonance chamber for modulating vocal sounds.

Nasopharynx, Oropharynx,
andHypopharynx

Anatomical Extent

Nasopharynx: This highest part of the pharynx extends from the bony skull base to an imaginary horizontal line at the level of the velum . It communicates with the nasal cavity via the choanae and with the middle ear via the orifice of the Eustachian tube. The nasopharynx is bounded superiorly by the floor of the sphenoid sinus and pharyngeal roof. Also in this region is the pharyngeal tonsil, which forms part of the tonsillar ring .Medial to the Eustachian tube orifice, the tubal cartilage forms a projecting lip called the torustubarius. The concavity behind it is termed the pharyngeal recess (Rosenmullerfossa) . The nasopharynx is bounded posteriorly by the curve of the first cervical vertebra, with its overlying prevertebral cervical fascia and prevertebralmusculature.

Oropharynx: The oral cavity communicates via the faucial isthmus with the oropharynx, which extends inferiorly from the lower boundary of the nasopharynx to the upper margin of the epiglottis . It is bounded anteriorly by the tongue base and lingual tonsil and posteriorly by the second and third cervical vertebrae with their prevertebral fascia. It is bounded laterally by the faucialpillars , which flank the palatine tonsils.

Hypopharynx: The lowest pharyngeal segment is the hypopharynx, which extends from the superior border of the epiglottis to the inferior border of the cricoid cartilage plate of the larynx , where it joins with the esophagus. Lying posterior to the hypopharynx
are the third through sixth cervical vertebrae. Its anterior wall is formed by the back of the larynx, which protrudes into the hypopharynx and forms two lateral mucosal pouches (piriform sinuses), which rejoin at the level of the esophageal inlet.