Hypopharynx

👉The hypopharynx is interposed between the oropharynx superiorly and the upper esophagus inferiorly, with the larynx located anteriorly.

👉In the adult, the hypopharynx extends from the hyoid bone (fourth cervical vertebrae) above to below the cricopharyngeus muscle, around the lower border of the cricoid cartilage (sixth cervical vertebrae).

👉The cervical esophagus extends from the lower border of the cricoid cartilage into the thorax.

👉The hypopharynx includes the posterior pharyngeal wall, the piriform fossae or sinuses, and the post cricoid area or space.

👉Anatomical description based on the AJCC/UICC:

1. Pharyngo-esophageal junction (postcricoid area) extends from the level of the arytenoid cartilages and connecting folds to the inferior border of the cricoid cartilage (C6), thus forming the anterior wall of the hypopharynx.

2. Piriform sinus extends from the pharyngoepiglottic fold to the upper end of the esophagus.

– The piriform sinus is bounded laterally by the thyroid cartilage and medially by the hypopharyngeal surface of the aryepiglottic fold, and the arytenoid and cricoid cartilages.

👉Posterior pharyngeal wall extends from the superior level of the hyoid bone (or floor of the valleculae) to the level of the inferior border of the cricoid cartilage and from the apex of the piriform sinus to the other.

👉The wall of the hypopharynx is composed of four layers:

1. An inner mucosal lining of stratified squamous epithelium over a loose stroma.

2. A fibrous layer of the pharyngeal aponeurosis.

3. A muscular layer formed by the inferior pharyngeal constrictor muscle and, in the upper part by the distal portion of the middle pharyngeal constrictor muscle.

– The most distal fibres of the inferior pharyngeal constrictor muscle condense into the cricopharyngeus muscle

– Just proximal to this muscle on the posterior wall is an area of relative weakness known as Killian’s dehiscence.

4. An outer layer of fascia that derives from the buccopharyngeal fascia.

👉The piriform sinus is divided into a superior or membranous part, and an inferior or cartilaginous part.

1. The thyrohyoid membrane bounds the superior aspect of the piriform sinus laterally, through which passes the internal branch of the superior laryngeal nerve.

– Sensory innervation of this area synapses with the jugular ganglion, along with sensory nerves of the external auditory canal (Arnold’s nerve), which accounts for the referred otalgia frequently encountered with the patient presenting with tumors of the piriform sinus.

2.The lower portion of the piriform sinus is bounded by the ala of the thyroid cartilage.

👉The terminal branches of the recurrent laryngeal nerve pass through the fibres of the cricopharyngeus muscle and the posterior cricoarytenoid muscle of the larynx.

👉Motor and sensory innervation of the hypopharynx occurs via the pharyngeal plexus, which is formed by branches of the cranial nerves IX and X.

👉The arterial supply arises from branches of the superior thyroid arteries along with collateral vessels from the lingual and ascending pharyngeal arteries.

👉Lymphatic drainage of the hypopharynx terminate in lymph nodes along the jugular vein (levels II, III and IV) and appear to a lesser extent in the nodes along the spinal accessory nerve (level V) and even less frequently in the submandibular area (level Ib).

👉Significant lymphatic drainage occurs from the posterior pharyngeal wall and drains to the retropharyngeal lymph nodes.

👉Lymphatics from the inferior part of the piriform sinus, the postcricoid area and the upper esophagus often drain to the nodes along the recurrent laryngeal nerves to the paratracheal lymph nodes (level VI).

#Arrangoiz #HeadandNeckSurgeon #CancerSurgeon #SurgicalOncologist #HeadandNeckCancer

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