Hypopharynx

«The hypopharynx or laryngopharynx forms the most inferior portion of the pharynx, being the continuation of the oropharynx superiorly and both the larynx and esophagus inferiorly. The hypopharynx begins as the continuation of the oropharynx at the pharyngoepiglottic fold (which is at the level of the hyoid bone) superiorly, and extends inferiorly to the level of the inferior aspect of the cricoid cartilage, where it continues as the cervical esophagus. It is a mucosa-lined, muscular tube with its posterolateral walls formed by the inferior constrictor muscle and anterior wall by laryngeal cartilages. It forms part of the pharyngeal mucosal space.

The  boundaries are:

• anteriorly: post-cricoid mucosa, posterior cricoarytenoid muscle;
• posteriorly: mucosal wall, middle and inferior constrictor muscles;
• superiorly: hyoid bone, glossoepiglottic and pharyngoepiglottic folds;
• inferiorly: cricoid cartilage, cricopharyngeus muscle.

Three subsites of the hypopharynx are described, being pertinent to localize where squamous cell carcinoma arises:

• pyriform sinus;
• posterior wall;
• post-cricoid region/pharyngo-esophageal junction: forms the anterior wall [1].»

«Embryologically, the larynx interjects into the hypopharynx anteriorly and is therefore considered a separate structure. Hypopharyngeal cancers are often named for their location, including pyriform sinus, lateral pharyngeal wall, posterior pharyngeal wall, or post-cricoid pharynx [2].»

Illustration of the pharynx:

Source: Commons.wikimedia.org. (n.d.). File:2411 Pharynx.jpg - Wikimedia Commons. [online] Available at: https://commons.wikimedia.org/wiki/File:2411_Pharynx.jpg [Accessed 21 Mar. 2019].

«The hypopharynx is the longest of the 3 segments of the pharynx. It is wide superiorly and progressively narrows toward the level of the cricopharyngeal muscle. It is bounded anteriorly by the posterior face of the cricoid cartilage. The parts of the hypopharynx that lie partly to each side of the larynx form the pyriform sinuses or fossae [2].»

Source: [2].

Source: [2].

Bibliographic references:
[1] Deng, F. and Knipe, H. (2018). Hypopharynx | Radiology Reference Article | Radiopaedia.org. [online] Radiopaedia.org. Available at: https://radiopaedia.org/articles/hypopharynx [Accessed 21 Mar. 2019].

[2] Quon, H. and Goldenberg, D. (2017). Hypopharyngeal Cancer: Overview, Clinical Presentation, Etiology and Risk Factors. [online] Emedicine.medscape.com. Available at: https://emedicine.medscape.com/article/1375268-overview [Accessed 21 Mar. 2019].