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Pharynx - Lecture Notes Flashcards (Fill in the Blank)

Introduction

  • The pharynx (Latin throat) is a conical fibromuscular tube behind the nose, mouth, and larynx; part of the digestive system and the respiratory conducting zone.
  • Functions: conduit for air (nasopharynx, laryngopharynx) and food (oropharynx); aids pharyngeal phase of deglutition; part of vocal tract for speech; houses taste buds; provides local immunity.
  • Extends from the base of the skull to the inferior border of the cricoid cartilage at C_6. Anterior wall is incomplete, communicating with the nasal cavity, oral cavity, and larynx.
  • Three parts from superior to inferior: nasopharynx, oropharynx, laryngopharynx.

Extent and Boundaries

  • Extent: cranial base to inferior border of cricoid cartilage anteriorly; inferiorly continuous with the esophagus at the level of C_6; posteriorly separated from cervical vertebral bodies by prevertebral fascia.
  • Length: 12-14\ \text{cm}; width: widest part 3.5\ \text{cm}; narrowest part at pharyngoesophageal junction \approx 1.5\ \text{cm}.
  • Boundaries:
    • Superior: base of skull (posterior part of sphenoid body and basilar occipital bone) in front of pharyngeal tubercle.
    • Inferior: continuous with esophagus at C_6.
    • Posterior: separated from vertebral bodies by prevertebral fascia.
    • Anterior: communicates with nasal cavity, oral cavity, and larynx.

Parts of Pharynx

  • Nasopharynx
  • Oropharynx
  • Laryngopharynx

Nasopharynx

  • Upper portion from base of skull to the upper surface of soft palate (level of C_1).
  • Communicates with nose via two choanae; respiratory function: conditions inspired air, passes to larynx.
  • nasopharyngeal isthmus: space between soft palate and posterior pharyngeal wall where nasopharynx joins the oral pharynx; soft palate elevates to meet posterior wall during swallowing (Passavant ridge).
  • Epithelium: respiratory epithelium (pseudostratified ciliated columnar with goblet cells).
  • Key features: opening of auditory tube, pharyngeal recesses (Rosenmüller), pharyngeal tonsil (adenoids).
  • Pharyngeal recess walls are rigid/non-collapsible to keep air passage patent.

Nasopharynx - Details

  • Opening of auditory tube lies in lateral wall ~1.25 cm behind inferior concha; bounded by tubal elevations containing tubal (pharyngeal) tonsil.
  • Folds: salpingopharyngeal fold (with salpingopharyngeus) and salpingopalatine fold (with levator veli palatini).
  • Pharyngeal recess (fossa of Rosenmüller): deep depression behind tubal elevation; clinically important as a potential route for perforation; walls non-collapsible.
  • Pharyngeal tonsil: lymphoid tissue in roof/posterior nasopharynx; atrophy after puberty; enlargement = adenoids (nasal obstruction, mouth breathing, nasal voice, risk to middle ear).

Waldeyer’s Ring

  • Annular lymphoid tissue around the oropharynx.
  • Components: right and left palatine tonsils; pharyngeal tonsil (nasopharyngeal); tubal tonsil (in fossa Rosenmüller); lingual tonsil (posterior dorsum of tongue).

Oropharynx

  • Middle part of pharynx; from base of soft palate to upper border of the epiglottis (roughly at the level of the body of the C3 vertebra).
  • Function: digestive role; participates in both voluntary and involuntary phases of deglutition.
  • Boundaries: superior—soft palate; inferior—base of tongue; anterior—isthmus of Fauces; lateral—palatoglossal and palatopharyngeal arches with palatine tonsils between.
  • Features:
    • Lingual tonsil on dorsum of tongue.
    • Epiglottis and epiglottic folds (glossopharyngeal relations).
    • Palatine tonsil between arches; glossopharyngeal sensory involvement.

Laryngopharynx (Hypopharynx)

  • Distal pharyngeal portion from the upper border of the epiglottis to the level of the cricoid cartilage (C6) where it becomes continuous with the esophagus.
  • Anterior wall: laryngeal inlet in the upper part; inferiorly contains the aryepiglottic folds.
  • Lateral wall: piriform fossae/recesses (one on each side of the laryngeal inlet); clinically important for foreign bodies.
  • Clinically relevant closure: pharyngoesophageal junction; Killian’s dehiscence location.
  • Below the inlet, the anterior wall includes the arytenoids and cricoid lamina covered by mucosa; posterior wall formed by the constrictors.

Piriform Fossa (Fossa)/Recess

  • Small depressions on either side of the laryngeal inlet; formed by bulging of larynx into the laryngopharynx.
  • Boundaries: medially by aryepiglottic fold and quadrangular membrane; laterally by mucosa over thyroid lamina and thyrohyoid membrane.
  • Internal laryngeal nerve and superior laryngeal vessels pierce thyrohyoid membrane.
  • Clinically important: risk of injury during endoscopic procedures; contents include branches of the pharyngeal plexus.

Structure of Pharynx / Pharyngeal Wall

  • Four layers (inner to outer):
    • Mucous membrane (mucous coat)
    • Pharyngobasilar fascia (pharyngeal aponeurosis)
    • Muscular coat (pharyngeal muscles)
    • Buccopharyngeal fascia (loose areolar tissue)
  • Mucosa:
    • Nasopharynx: respiratory epithelium (ciliated columnar) continuous with nasal cavity.
    • Oropharynx/Laryngopharynx: non-keratinized stratified squamous epithelium.
    • Rich in elastic tissue; contains pharyngeal, tubal, palatine, and lingual tonsils.
  • Pharyngobasilar fascia (pharyngeal aponeurosis): fibrous layer thickest near skull base; attaches to basiocciput, petrous temporal bone, auditory tube region, and pterygoid plates; forms pharyngeal raphe posteriorly.
  • Muscular coat: outer circular layer (three constrictors) + inner longitudinal layer (stylopharyngeus, salpingopharyngeus, palatopharyngeus).
  • Buccopharyngeal fascia: covers the outer surface of constrictors; blends with pharyngobasilar fascia above; contains pharyngeal venous and nerve plexuses between fascia and muscles.

Pharyngeal Muscles

  • Superior constrictor (outer): attaches to pterygomandibular raphe, mandible, pterygoid plates, pharyngobasilar fascia; inserts into pharyngeal raphe and tubercle.
  • Middle constrictor: from hyoid and stylohyoid region; inserts into pharyngeal raphe; anterior gap with inferior constrictor closed by thyrohyoid membrane.
  • Inferior constrictor (thyropharyngeus and cricopharyngeus parts): forms sphincter at the cricopharyngeal region; cricopharyngeus continuous with esophageal muscular coat; Killian’s dehiscence between thyropharyngeus and cricopharyngeus.
  • Longitudinal muscles: stylopharyngeus (CN IX) elevates pharynx/larynx; salpingopharyngeus (from pharyngotympanic tube) elevates pharynx; palatopharyngeus (from soft palate) shortens/widens pharynx during swallowing.
  • Nerve supply: pharyngeal muscles receive motor fibers from the pharyngeal plexus (CN X via vagus and CN XI via accessory) except stylopharyngeus (CN IX).

Blood Supply & Venous Drainage

  • Arterial supply (key sources):
    • Ascending pharyngeal artery (from external carotid)
    • Ascending palatine and tonsillar arteries (from facial)
    • Greater palatine and pharyngeal arteries (from maxillary)
    • Lingual artery
    • Superior and inferior laryngeal arteries
  • Venous drainage: pharyngeal venous plexus, largely behind the middle constrictor; drains to the internal jugular vein and communicates with the pterygoid plexus.

Nerve Supply

  • Motor innervation (all pharyngeal muscles except stylopharyngeus): pharyngeal plexus via CN X with contributions from CN XI (via cranial root of accessory)
  • Stylopharyngeus: CN IX (glossopharyngeal)
  • Sensory innervation: CN IX (mostly) and CN X (partly); maxillary nerve via pterygopalatine ganglion (nasopharynx); lesser palatine nerve and glossopharyngeal nerve (soft palate and tonsils).
  • Autonomic innervation (parasympathetic): greater petrosal nerve (CN VII) and lesser palatine branches of pterygopalatine ganglion; pharyngeal plexus composed of pharyngeal branches of CN X, CN IX, and sympathetic fibers; pharyngeal plexus also supplies most of the soft palate (except tensor veli palatini).

Lymphatics

  • Drainage to retropharyngeal lymph nodes or directly to upper and lower deep cervical nodes.

Applied Anatomy

  • Common clinical correlations:
    • Pharyngitis
    • Enlarged adenoids (pharyngeal tonsils)
    • Pharyngeal diverticulum (Killian’s dehiscence) – pharyngeal pouch
    • Pharyngeal cancer