Anatomy pharynx

• Pharynx


  Wide muscular tube, about 12 cm long, situated behind the nose, mouth and larynx

  
• Pharynx


  • Superiorly it extends till the base of the skull
  • Inferiorly it continues as esophagus at the level of 6th cervical vertebra
  • Upper part is wide and lower part is narrow
  • Located anterior to upper 6 cervical vertebrae

  
• Communications of pharynx


  • Anteriorly with nasal cavity, oral cavity and larynx
  • On each side with middle ear through auditory tube

  
• Parts of pharynx

  • Nasopharynx – nasal part
  • Oropharynx – oral part
  • Laryngopharynx – laryngeal part

  
• Nasopharynx (nasal part)


  • Upper most part of pharynx situated behind the nose and above the soft palate
  • Respiratory in function – lined by ciliated columnar epithelium
  • Anteriorly it communicates with nasal cavity through posterior nasal apertures (choanae)
  • Inferiorly it extends till the lower border of soft palate and communicates with oropharynx through pharyngeal isthmus
  • Supplied by the branches of maxillary nerve

  
• Boundaries of nasopharynx

  • Roof
  • Floor
  • Posterior wall
  • 2 lateral walls
• Roof of nasopharynx


  • Contains body of sphenoid bone and basilar part of occipital bone
  • Contains pharyngeal tonsil (collection of lymphoid tissue) – adenoids

  
• Floor of nasopharynx


  • Mobile and formed by the soft palate
  • Has pharyngeal isthmus - communicates with oropharynx
• Lateral wall of nasopharynx

  • Opening of auditory tube – connects the nasopharynx to the middle ear cavity
  • Tubal elevation - formed by the cartilage of auditory tube (also contains tubal tonsil – lymphoid aggregation)
  • Salpingopharyngeal fold – begins from the posterior end of tubal elevation (contains salpingopharyngeus muscle)
  • Pharyngeal recess (fossa of Rosenmuller) – groove situated behind the tubal elevation and salpingopharyngeal fold
  • Salpingopalatine fold – mucosal fold extending from the anterior end of tubal elevation to the soft palate
  • Fold of levator palati – triangular elevation below the opening of auditory tube (formed by the levator palati muscle)

  
• Oropharynx (oral part)


  • Middle part of pharynx, located behind the oral cavity
  • Extent - lower border of soft palate to upper border of epiglottis
  • Above it communicates with nasopharynx through pharyngeal isthmus
  • Anteriorly it communicates with oral cavity through oropharyngeal isthmus
  • Below it is continuous with laryngopharynx at the upper border of epiglottis
  • It lies in front of 2nd (axis) and 3rd cervical vertebrae
  • Supplied by - glossopharyngeal nerve

  
• Structures in lateral wall of oropharynx

  • Palatoglossal fold or arch (produced by palatoglossus muscle)
  • Palatopharyngeal fold or arch (produced by palatopharyngeus muscle)
  • Palatine tonsil (collection of lymphoid follicles located between the arches)

  
• Laryngopharynx (laryngeal part)


  • Is the lower part of pharynx, situated behind the larynx
  • It is situated in front of 3rd, 4th, 5th and 6th cervical vertebrae
  • Extends from the upper border of epiglottis to 6th cervical vertebra (lower border of cricoid cartilage)
  • Continues inferiorly as esophagus
  • Supplied by the branches of vagus nerve

  
• Anterior wall of laryngopharynx

  • Presents inlet of larynx in the upper part and cricoid and arytenoid cartilages of larynx in the lower part
  • Piriform fossa (small depression on either side of inlet of larynx)

  
• Piriform fossa


  • Lateral boundary is formed by the thyrohyoid membrane and lamina of thyroid cartilage
  • Medial boundary is formed by the aryepiglottic fold (which separates it from the inlet of larynx)
  • Internal laryngeal nerve and superior laryngeal vessels - deep to the mucous membrane
  • Ingested food particles such as fish bone may get impacted in the fossa. If care is not taken while removing the foreign particle, internal laryngeal nerve may be injured causing loss of sensations from the upper part of larynx which leads to loss of protective cough reflex

  
• Pharyngeal (Waldeyer's) lymphatic ring


  • Formed by - palatine, tubal, lingual and pharyngeal tonsils
  • Incomplete circular band of lymphoid tissue around the superior part of the pharynx
  • Anteroinferior part of the ring - lingual tonsil
  • Lateral parts of the ring - palatine and tubal tonsils
  • Posterior and superior parts of the ring - pharyngeal tonsil
  • Acts as a first line of defense against microbes that enters the body via the nasal and oral routes
• Layers of pharyngeal wall

  • Mucosa
  • Submucosa
  • Pharyngobasilar fascia – thin sheet of connective tissue, forms pharyngeal raphe on the posterior aspect
  • Muscular coat – containing
  • Inner longitudinal layer – made up of stylopharyngeus, salpingopharyngeus and palatopharyngeus muscles
  • Outer circular layer – made up of 3 pharyngeal constrictors
  • Buccopharyngeal fascia (connective tissue layer)
• Muscles of pharynx


  • Superior, middle and inferior constrictor muscles
  • Palatopharyngeus muscle
  • Stylopharyngeus muscle
  • Salpingopharyngeus muscle
• Pharyngeal constrictor muscles


  • Situated at the outer part of pharynx

  Constrictors contract involuntarily so that contraction takes place sequentially from the superior to the inferior end of the pharynx, propelling food into the esophagus

  
• Other pharyngeal muscles


  • Palatopharyngeus, stylopharyngeus and salpingopharyngeus muscles are located at the inner part of pharynx

  These elevate the larynx and shorten the pharynx during swallowing and speaking

  
• Nerve supply to pharyngeal muscles

  Stylopharyngeus - glossopharyngeal nerve

  All other muscles of pharynx - pharyngeal branch of vagus nerve via pharyngeal plexus of nerves (inferior constrictor also supplied by external and recurrent laryngeal nerves)
• Gaps in pharyngeal musculature

  • The levator palati, auditory tube, and ascending palatine artery - between superior constrictor and the skull

  Stylopharyngeus muscle and glossopharyngeal nerve - between the superior and middle constrictors

  Internal laryngeal nerve and superior laryngeal artery and vein - between the middle and inferior constrictors

  Recurrent laryngeal nerve and inferior laryngeal artery pass through a gap inferior to the inferior constrictor
• Killian's dehiscence


  Potential gap which exists between 2 parts of inferior constrictor muscle – thyropharyngeus and cricopharyngeus

  Seen as a dimple in the mucosa at this region

  Pharyngeal diverticulum may develop through this weak area in case of neuromuscular incoordination i.e. if cricopharyngeus fails to relax following contraction of thyropharyngeus part

  
• Nerve supply of pharynx

  Pharynx is supplied by pharyngeal plexus of nerves formed by the pharyngeal branches of glossopharyngeal, vagus and superior cervical sympathetic ganglion

  Pharyngeal plexuses are located on the middle constrictor

  
• Arterial supply of pharynx

  • Ascending pharyngeal artery of external carotid artery

  Ascending palatine and tonsillar arteries of facial artery

  Palatine, pharyngeal branches of maxillary artery
• Venous drainage of pharynx

  Veins of pharynx terminate at the internal jugular vein and facial vein
• Lymphatic drainage of pharynx

  Retropharyngeal and deep cervical lymph nodes