Anatomy of Oral Cavity, Pharynx & Oesophagus Dr. Vishal Sharma

Oral Cavity

Parts of Oral Cavity

Floor of mouth

Lymphatic drainage

Intrinsic tongue muscles

Extrinsic tongue muscles

Coronal section of tongue

Actions of tongue muscles Inferior Longitudinal: moves tip up & down Superior Longitudinal: moves tip up & down Transverse: narrows & lengthens tongue Vertical: flattens & depresses tongue Genioglossus: Prevents tongue from falling back Styloglossus: Pulls tongue up & back Palatoglossus: Pulls tongue back Hyoglossus: Depresses tongue

Nerve Supply of Tongue Anterior 2/3 Posterior 1/3 Sensory Lingual Glossopharyngeal Motor Hypoglossal *** Taste Chorda tympani *** except palatoglossus which is supplied by pharyngeal plexus

Nerve Supply of Tongue

Papillae in tongue

Papillae in tongue Lingual taste buds sit on lateral borders of raised papillae. They are classified as: Fungiform: at tip & sides of tongue Circumvallate: just in front of terminal sulcus Foliate: at posterior lateral margins of tongue Filiform: centre of tongue, have no taste buds

Papillae in tongue

Tongue Map ? Sweet = Sucrose Salty = NaCl Sour = HCl Bitter = Quinine Umami = Glutamate

Taste Bud

Taste Pathway

Pharynx

Divisions

Divisions

Lower Limit of Nasopharynx Lower border of soft palate or Junction b/w hard & soft palate Oropharynx Tip of epiglottis or Body of hyoid bone or Base of vallecula Hypopharynx Lower border of cricoid or Lower border of C6 vertebra

Anterior Relations

Nasopharynx

Nasopharyngeal isthmus

Nasopharyngeal Isthmus Separates nasopharynx from oropharynx Bounded anteriorly by soft palate & posteriorly by mucosal ridge on nasopharyngeal wall called Passavant’s ridge (due to palatopharyngeus) Closure of this isthmus prevents nasal regurgitation & nasal intonation

Parts of Oropharynx

Parts of Oropharynx

Oropharyngeal Isthmus

Oropharyngeal Isthmus Separates oral cavity from oropharynx Boundaries are: Superior: Junction between hard & soft palate Inferior: Circumvallate papillae Lateral: Anterior tonsillar pillars (palatoglossus)

Waldeyer’s Tonsillar Ring

Waldeyer's tonsillar ring Vertically oriented, sub-epithelial lymphoid tissue ring located in pharynx, thought to function as a barrier to infection in first few years of life. Named after nineteenth century German anatomist Heinrich Wilhelm Gottfried von Waldeyer-Hartz.

Parts of Hypopharynx

Coronal section of Pharynx

Layers of Pharyngeal Wall Mucosa: ciliated columnar in nasopharynx & stratified squamous elsewhere Pharyngo-basilar fascia Longitudinal muscles: stylo-pharyngeus + salpingo-pharyngeus + palato-pharyngeus Constrictor muscles: superior + middle + inferior Bucco-pharyngeal fascia

Muscles

Structures Passing Between Skull Base & Superior Constrictor (Sinus of Morgagni) Eustachian tube + Levator palatini + Tensor palatini + Ascending palatine artery Between Superior & Middle Constrictors Glossopharyngeal nerve & Stylopharyngeus muscle Between Middle & Inferior Constrictors Internal Laryngeal nerve & Superior Laryngeal artery Below Inferior Constrictor Recurrent Laryngeal nerve & Inferior Laryngeal artery

Nerve Supply Nasopharynx: pterygo-palatine ganglion (V2) Oropharynx: glossopharyngeal & vagus nv Hypopharynx: Superior & recurrent laryngeal nv All muscles by pharyngeal nerve plexus (vagus nv carrying cranial part of accessory nv) except stylopharyngeus (glossopharyngeal nv) & cricopharyngeus (also by recurrent laryngeal)

Arterial Supply Facial artery Lingual artery Ascending pharyngeal artery Ascending palatine artery Greater palatine artery Artery of pterygoid canal Superior laryngeal artery

Venous Drainage Upper pharynx: Pharyngeal venous plexus situated on middle constrictor  pterygoid venous plexus & internal jugular vein Lower pharynx: Inferior thyroid veins

Lymphatic Drainage Nasopharynx: upper deep cervical + retro- pharyngeal + parapharyngeal + posterior triangle Oropharynx: upper deep cervical + retro- pharyngeal + parapharyngeal Hypopharynx: deep cervical + parapharyngeal + paratracheal + supraclavicular

Killian’s Dehiscence

Killian’s Dehiscence Triangular weak area between thyropharyngeus & cricopharyngeus part of inferior constrictor Mucosa herniates through it to form hypo-pharyngeal pouch (Zenker’s diverticulum) Perforation occurs here during forceful oesophagoscopy (gateway of tears)

Oesophagus

Introduction Also called gullet 23 to 25 cm long Extends from crico-pharyngeal sphincter (C6 vertebra) to cardiac orifice of stomach (T11 vertebra)

Anterior Curvature Follows antero- posterior curve of vertebral column through neck, thorax (postr mediastinum) & upper abdomen

Lateral curvatures Starts in midline → deviates to left at C7 → returns to midline at T5 → deviates to left again at T7 to reach gastric cardia

Natural Constrictions

Natural Constrictions Site Vertebral Level Distance from central incisor Cricopharynx C 6 15 cm Aortic arch T 4 25 cm Lt main bronchus T 5 28 cm Oesophageal hiatus T 10 40 cm

Importance of constrictions Common sites for lodgement of oesophageal foreign bodies Common sites for caustic stricture of oesophagus

Descending thoracic aorta, Left gastric, Inferior phrenic Blood Supply Part Arterial Venous Cervical Inferior thyroid Thoracic Descending thoracic aorta, Bronchial Azygos, Hemi-azygos Abdominal Left gastric, Inferior phrenic Left gastric, Abdominal azygos

Oesophageal varices Left gastric vein is a site of portal-systemic anastomosis. Portal obstruction leads to varicose veins in lower oesophagus

Nerve Supply Cervical: recurrent laryngeal nerve & cervical sympathetic trunk Thoracic: vagal trunks, oesophageal plexus & thoracic sympathetic trunk Abdominal: vagal trunks & thoracic sympathetic trunk Esophageal pain mimics cardiac angina due to common nerve supply

Lymphatic Drainage deep cervical + posterior mediastinal + left gastric lymph nodes drain into coeliac lymph nodes thoracic duct

Histology

Histology Four coats from outside inwards: 1. Fibrous coat (adventitia) 2. Muscular coat (muscularis propria) 3. Submucous coat 4. Mucous coat

Detailed Histology

Mucous coat 1. Epithelium: non-keratinizing stratified sqamous 2. Lamina propria: loose areolar tissue with lymphoid aggregates 3. Muscularis mucosae: produces local movement of mucosa & helps in drainage of gland secretions

Mucous coat Pink, smooth, protective oesophageal mucosa leads to red, mamillated, secretory gastric mucosa across Z (zigzag) line at 38-40 cm from incisors. Higher Z line seen in Barret’s esophagus.

Z line in endoscopy

Barret’s esophagus

Submucous coat Loose supporting areolar tissue contains: Seromucous glands Blood vessels Lymphatic channels Parasympathetic ganglia forming Meissner's nerve plexus

Muscularis propria External longitudinal muscle Internal circular muscle Parasympathetic ganglia forming Auerbach's nerve plexus lies b/w them Upper 1/3: striated muscle Middle 1/3: striated & smooth Lower 1/3: smooth muscle

Fibrous coat (adventitia) Layer of loose, supportive fibrous tissue Conducts major vessels & nerves longitudinally A serosa formed by visceral peritoneum replaces adventitia of intra-abdominal segment of oesophagus

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