Pharynx

INTRODUCTION:
  • Pharynx is a conical fibromuscular tube forming the upper part of air and food passages
  • 12-14cm long ends at c6
  • Width :3.5cm at base; 1.5cm at pharyngo-oesophageal junction
  • Division of Pharynx:
  1. NASOPHARYNX:Base of skull(basioociput and basi sphenoid) to soft palate
  2. OROPHARYNX:Plane of hard palate to hyoid bone
  3. LARYNGOPHARYNX:Hyoid bone to lower border of cricoid cartilage
STRUCTURE OF PHARYNGEAL WALL:
  • From outwards:
  1. Mucus membrane :Pseudostratified ciliated columnar (in nasopharynx) & Stratified squamous epithelium
  2. Pharyngeal aponeurosis
  3. Pharyngobasilar fascia
  4. Fibrous layer lining muscular coat
  5. Muscular coat
  6. Longitudinal muscles(internal layer)
  7. Constrictors
  8. Buccopharyngeal fascia
  9. Covers pharynx externally
  10. Pharyngeal plexus of nerves
  • Pharyngeal diverticulum is a protustion of mucosa between the two parts of inferior constrictor muslce of the pharynx
MUSCLES OF PHARYNX:
  • LONGITUDINAL MUSCLES
  • Pharyngeal aponeurosis
  1. Origin:medial aspect of styloid process
  2. Gap between middle and superior constrictor
  3. NS: glossopharyngeal

  •  Palatopharyngeus
  1. Origin: upper surface of palatine aponeurosis as 2 fasiculi
  2. Moves along inner aspect of the constrictor
  3. NS:

  •  pharyngael plexus
  1. Salpingopharyngeus
  2. Origin: cartilage of the auditory tube near the pharyngeal opening of it.
  3. All the 3 are inserted as a conjoint sheet at the post border of thyroid cartilage and lat aspect of epiglottis
CONSTRICTORS OF PHARYNX:
  • Superior Constrictor
  1. Lies in wall of nasopharynx and oropharynx
  2. Wide origin
  3. Post border of med pterygoid plate &pterygoid hamulus
  4. Pterygomandibular raphae
  5. Post end of mylohyoid line
  6. Mucus membrane on side of tongue 
  7. Lower part covered by middle constrictor.
  • Middle Constrictor(Hypopharynx)
  1. Origin: lower part of stylohyoid ligament & lesser and greater cornu of hyoid
  2. Inferiorly overlapped by inferior constrictor.
  • Inferior Constrictor: Thickest of the 3
  1. Thyropharyngeus: obliquely displaced
  2. Origin:oblique line of thyroid cartilage & inferior cornu of thyroid
  • b. Cricopharyngeus: transversly displaced
  1. Origin: ant part of cricoid cartilage between attachment of cricothyroid and articulation of inferior cornu
  2. Muscles of 2 sides act as a sphincter
  3. Function– prevent the entry of air in to the oesophagus in the interval between swallowing
  4. So sphincter relaxes during swallowing
  5. Contracts between the acts of swallowing.
  6. Insertion:All of the fibres get inserted into the median fibrous raphae Extending from Pharyngeal tubercle→ oesophagus
  • Killian’s Dehiscence:
  • Potential gap b/w weak area of pharyngeal wall seen in cricopharynx.
  • Gateway of Tear →perforation can occur at this site during oesophagostomy. 
NERVE SUPPLY :
  • Sensory nerve supply of pharyngeal mucous membrane: Nasopharynx by maxillary nerve , Glossopharyngeal nerve by oral pharynx, Laryngeal pharynx by the internal laryngeal branch of vagus nerve
  • Pharngeal Plexus of Nerves: Almost all of the nerve supply to the pharynx, whether motor or sensory, is derived from the pharyngeal plexus
  • Formed by the pharyngeal branches of the glossopharyngeal and vagus nerves with contributions from the superior cervical sympathetic ganglion.
  • The pharyngeal branch of the vagus supplies all the muscles of the pharynx Excluding stylopharyngeus, which is supplied by the glossopharyngeal nerve

Exam Question
  • Killian’s Dehiscence seen in cricopharynx
  • Nasopharynx mucous membrane is supplied by the maxillary nerve 
  • Glossopharyngeal nerve innervates Mucous membrane of the oral pharynx
  • Mucous membrane of Laryngeal pharynx is supplied by the internal laryngeal branch of vagus nerve
  • When a large bolus of food is swallowed, the hyoid bone moves anteriorly to open the pharynx mediated by geniohyoid
  • Geniohyoid is supplied by ansa cervicalis branch of C1
  • Pain sensation from oropharynx is carried by IX nerve
  • All muscles of the pharynx are supplied by pharyngeal plexus, except stylopharyngeus
  • Pharyngeal diverticulum is a protustion of mucosa between the two parts of inferior constrictor muslce of the pharynx
  • Lower border of pharynx is at the level of c6

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