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The hypopharynx is the most inferior and longest of the 3 segments of the pharynx. It extends from the level of the tip of the epiglottis superiorly to the lower border of the cricoid cartilage inferiorly. It is divided into 3 regions, namely the pyriform sinuses, posterior pharyngeal wall, and the post-cricoid area.The pyriform sinuses are pyramidal shaped areas with the base situated superiorly and the apex inferiorly. The superior extent is the oropharynx and glossoepiglottic folds. The anterolateral border is the medial surface of the thyroid cartilage and the anteromedial border is the lateral surface of the cricoid/arytenoid cartilages. The sinuses are bounded posteriorly by the lateral and posterior pharyngeal walls. The inferior extent is to the laryngeal ventricles. f
The post-cricoid area is the posterior surface of the arytenoid and cricoid cartilages.
The posterior pharyngeal wall extends from a level at the tip of the epiglottis to the a level at the lower extent of the cricoid cartilage. It meets the posterior oropharyngeal wall superiorly and meets the posterior wall of the esophagus inferiorly.
The hypopharyngeal wall is made up of mucosa, pharyngobasilar fascia, constrictor musculature, buccopharyngeal fascia (in a lumen to external direction).
The mucosa is stratified squamous epithelium. The pharyngobasilar fascia is more developed in the nasopharynx and is less so as it approaches the hypophayrnx. External to the pharyngobasilar fascia is the musculature composed of the middle and inferior constrictors.
The constrictors are innervated by the laryngeal nerves as well as the pharyngeal plexus. The middle constrictor takes its origin from the lesser/greater cornua of the hyoid bone and the inferior constrictor originates from the oblique line of the thyroid cartilage as they both insert into the midline pharyngeal raphe. The lower fibers of the inferior constrictors blend into the cricopharyngeus muscle.
The buccopharyngeal fascia is a thin layer covering the external aspect of the constrictor muscles. There are gaps between the constrictors as they overlap one another.
The glossopharyngeal nerve, styloid ligament, stylopharyngeus muscle, and the lingual artery traverse the gap between the superior and middle constrictor muscles. The area between the middle and inferior constrictors is not a true gap since the thyrohyoid membrane closes this area. However, the superior laryngeal artery and vein, as well as the internal laryngeal nerve traverse this area. The inferior laryngeal artery and vein and the recurrent laryngeal nerve traverse the space between the inferior constrictor and the esophagus.
The esophagus extends from the lower extent of the hypopharynx (inferior cricoid) superiorly down to the gastro-esophageal junction. The cervical esophagus is that portion of the esophagus above the suprasternal notch.
The esophageal wall is made up of the mucosa, submucosa, and muscle. The mucosa is composed of stratified squamous epithelium and a deeper scant muscular layer, the muscularis mucosa. Nerves and blood vessels traverse a loose connective tissue layer, the submucosa. The outermost layer is the muscular layer made up of an inner circular and an outer longitudinal muscles.
The lymphatic drainage systems for both the hypopharynx and the esophagus are richly supplied. The superior drainage is into the superior and middle jugular nodes, and the inferior drainage is into the lower jugular nodes as well as the paratracheal nodes. The cervical esophagus also drains into the mediastinal nodes.
The hypopharynx is involved in the third phase of swallowing (pharyngeal phase) as the food bolus is propelled by pharyngeal peristalsis into the cervical esophagus. Once the food bolus is received by the cervical esophagus, it is propelled by muscular contractions into the stomach. In this way, both the hypopharynx and the esophagus serve as dynamic conduits for food passage.
Czerny performed the first recorded pharyngoesophageal reconstruction in 1877 and Mikulicz performed the first successful cervical esophageal reconstruction in 1886. Both used local cervical skin flaps for reconstruction, as it was the earliest method of reconstruction of defects in this area. Multiple techniques of reconstruction have emerged from the turn of the century until the present.
Wookey in the early 1940's came up with the standard reconstruction technique of the time by using the anterior neck skin in a staged procedure to form a neo-hypopharynx/esophagus conduit. The technique involved creating a pharyngostoma and esophagostoma initially, followed by tubing the anterior cervical skin at a later stage to form a conduit from the pharynx to the esophagus. The raw area remaining was then covered by a split thickness skin graft (STSG). Various modifications have evolved, but they only alter the method of covering the remaining raw area after tubing the anterior cervical skin.
Tissue transposition techniques were then popularized by the advent of the deltopectoral flap of Bakamjian in the 1960's. This flap however was supplanted by the myocutaneous flaps in the late 1970's. Aryian and Theogaraj in the late 1970's and early 1980's reported using pectoralis major myocutaneous flaps for the reconstruction of hypopharyngeal/cervical esophageal defects.
Abdominal visceral transposition techniques evolved in the 1960's and 1970's to reconstruct defects in this area and include gastric pull-up by Ong and Lee, as well as revascularized autografts of hollow segments (such as free jejunum by Huguier et al) and colon transposition by Keling and Vuillet.
Most recently, fasciocutaneous free flaps have been developed for reconstruction. Harii in 1985 reported use of a tubed radial forearm free flap for reconstruction in this area. Subsequently, lateral thigh and scapular fasciocutaneous free flaps have also been developed.
The ideal reconstructive technique to reconstruct defects resulting from resection of the hypopharynx and cervical esophagus should restore normal anatomy, provide normal breathing without a tracheostomy, allow normal dynamic swallowing without aspiration, and participate in normal speech. Unfortunately, no such technique currently exists, but should shoot for:
The various techniques are compared based on a literature review, and the data shown in the following table: