F1i: Structure & function of the pharynx

  • 12.5cm tube like structure: base of skull → C6
  • Connects posterior nasal & oval cavities to larynx & oesophagus
  • NASOPHARYNX: CONCHAE → SOFT PALATE
    • Wall of nasopharynx contains Eustachian Tube
    • Which connects nasopharynx to middle ear
    • Nasopharynx has pseudo-stratified columnar epithelium
    • Mucous secretion from Goblet Cells, humidifier + filters air
  • OROPHARYNX: SOFT PALATE → HYOID BONE
    • Mouth leads to oropharynx
    • Allows passage of air + food
    • Non-keratinising stratified squamous epithelium
    • Palatine tonsils lie in lateral walls
  • LARYNGOPHARYNX: HYOID BONE → OESOPHAGUS
    • Lingual tonsils
    • Non-keratinising stratified squamous epithelium

Swallowing

  • Swallowing = a reflex necessary to move a bolus of food from mouth → stomach
    • Afferents: glossopharyngeal (IX) + vagus (X)
    • Control: swallowing centre of medulla
    • Efferents: Vagus (X) to pharynx + oesophagus
  • 3 phases:
    1. Oral (voluntary)
    2. Pharyngeal
    3. Oesophageal (involuntary)

1) Oral phase

  • Tongue forms a food bolus
  • Tongue pushes food bolus into oropharynx by pushing up & against hard palate

2) Pharyngeal phase

  • Respiration inhibited for 1 – 2 seconds
  • Food passes to upper oesophagus
  • Nasopharynx closed by contraction of tensor + levator palati
  • Aryepiglottic folds are approximated → completely occluding larynx
  • Larynx is elevated 3cm by contraction of infrahyoid muscles, stylopharyngeus, palatopharyngeus → larynx raised & epiglottis swings
  • Down to close larynx
  • Bolus of food pushed into oesophagus by contraction of pharynx + opening of OPPER OESOPHAGEAL SPHINCTER

3) Oesophageal Phase

  • Food in upper oesophagus propelled forward by peristaltic contractions KA 1° PERISTALTIC CONTRACTIONS
  • Upper oesophageal sphincter contracts → LES relaxes
  • Gravity promotes fluid + food descent
  • 2° PERISTALTIC WAVES due to ENTERIC NS of oesophagus stimulated by stretch receptors of oesophagus