Week 2

• Oral cavity


  Separated into two regions by the upper and lower dental arches consisting of the teeth and alveolar bone that supports them
• Oral vestibule


  • Horseshoe-shaped, is between the dental arches and the deep surfaces of the cheeks and lips-the oral fissure opens into it and can be opened and closed by muscles of facial expression, and by movements of the lower jaw

  
• Oral cavity proper


  • Enclosed by the dental arches
• Oral vestibule


  • Surrounded externally by lips and cheeks
  • Surrounded internally teeth and gums
  • Covered mucous membrane
  • Free-edged fold – labial frenula extending from gingiva to upper and lower lips
  • Parotid duct opens – 2nd maxillary molar

  
• Lymph drainage of oral vestibule

  • Superficial structures regional lymph nodes for superficial structures (submandibular & submental) terminal lymph nodes (deep cervical nodes: superior = jugulodigastric and inferior = Jugulo-omohyoid)
  • Deep structuresregional lymph nodes of deep structures (retropharyngeal) deep cervical nodes
• Arterial supply of lips

  • Upper lip: Superior labial branches of facial + infraorbital arteries
  • Lower lip: Inferior labial branches of the facial + mental arteries

  
• Innervation of lips


  • Upper lip: Superior labial branches of infraorbital n. (CN V2)
  • Lower lip: Inferior labial branches of mental n. (CN V3)

  
• Oral cavity proper


  • Bordered anteriorly + lateral: teeth + gums
  • Roof: hard palate + soft palate
  • Floor: tongue and mucous membranes
  • Entrance between oral cavity proper and pharynx bordered by 2 pairs of folds, between folds = palatine tonsils

  
• Palatoglossal arch


  • Anterior fold
• Palatopharyngeal arch


  • Posterior fold
• Lymph drainage of oral cavity proper

  • Follows same rules as oral vestibule
  • Superficial cervical nodes
  • Deep cervical nodes
• Floor of oral cavity proper

  • Muscular diaphragm composed of the paired mylohyoid muscles
  • Two cord-like geniohyoid muscles above the diaphragm, which run from the mandible in front to the hyoid bone behind
  • The tongue, which is superior to the geniohyoid muscles

  
• Tongue


  • Has a dorsal/superior surface and an inferior surface
  • Superior surface has a V-shaped groove = terminal sulcus of the tongue which points to the foramen cecum
  • Terminal sulcus divides the tongue transversely into an anterior part (2/3) in the oral cavity proper and a posterior part (1/3) in the oropharynx
  • Numerous lingual papillae on the surface (vallate, foliate, fungiform, filiform)
  • Vallate, foliate and fungiform papillae have taste buds
  • Frenulum of the tongue found on the inferior surface connecting the floor of mouth to the tongue

  
• Extrinsic muscles of tongue

  • Palatoglossus
  • Styloglossus
  • Hyoglossus
  • Genioglossus (Attaches to geniotubercles)

  
• Intrinsic muscles of tongue

  • Superior longitudinal
  • Inferior longitudinal
  • Vertical
  • Transverse

  
• Blood supply of tongue

  • Arterial: lingual a
  • Venous: lingual vein into internal jugular v
• Innervation of tongue


  • Tip of tongue submental nodes
  • Sides submandibular inferior deep cervical
  • Centreinferior deep cervical (jugulo-omohyoid)
  • Posterior superior deep cervical (jugulodigastric)

  
• Adult teeth


  • 32 teeth: 16 in upper and 16 in lower jaw
  • On each side in both maxillary and mandibular arches: 2 incisors, 1 canine, 2 premolars, 3 molars
  • Dental formula: 2123/2123
• Blood supply of teeth

  • Inferior alveolar artery supplies all lower teeth, divides opposite first premolar into incisor (anterior teeth) and mental branches (leaves the mental foramen to supply chin)
  • Anterior and posterior superior alveolar arteries supply all upper teeth, posterior supplies molar and premolar teeth, anterior supplies incisor and canine teeth

  
• Venous drainage of teeth

  • Inferior alveolar veins from lower teeth and superior alveolar veins from upper teeth drain into pterygoid plexus of veins in the infratemporal fossa into maxillary vein retromandibular vein internal jugular vein
  • Small veins from this plexus pass through small emissary foramina in base of skull to connect with cavernous sinus in cranial cavity (infection can spread)

  
• Lymph drainage of teeth

  • Upper teeth deep cervical (jugulo-digastric)
  • Lower front submental
  • Lower back submandibular
• Salivary glands


  Glands that open or secrete into the oral cavity, most are small glands in the submucosa or mucosa of the oral epithelium lining the tongue, palate, cheeks, and lips, and open into the oral cavity directly or via small ducts, in addition to these small glands are much larger glands which include the paired parotid, submandibular and sublingual glands

  
• Rule of thumb: the larger the salivary gland the more likely it is to be benign; the smaller the gland the more likely it is to be malignant

  
• Parotid gland


  • Largest of the 3 paired salivary glands
  • Irregular shape due to parotid bed
  • Entirely outside the boundaries of the oral cavity in a shallow triangular-shaped trench formed by the sternocleidomastoid muscles behind, ramus of mandible in front, and the base of the trench is formed by the external acoustic meatus and the posterior aspect of the zygomatic arch
  • Anterior to and below lower half of ear
  • Superficial, posterior and deep to ramus of mandible
  • Extends from lower border of mandible up to zygomatic arch
  • Posteriorly covered by sternocleidomastoid muscle
  • Anterior: ramus of mandible
  • Posterosuperior: external acoustic meatus
  • Encloses the facial nerve, retromandibular vein, and external carotid artery from superficial to deep
  • Enclosed within the split investing layer of deep cervical fascia (making the parotid sheath)

  
• Innervation of parotid gland

  • Parotid plexus of CNVII (facial nerve) is embedded in the parotid gland but does not innervate it
  • Parotid sheath and overlying skin is innervated by the auriculotemporal nerve (a branch of CN V3) and the great auricular nerve (a branch of the cervical plexus from C2 and C3)
  • Parasympathetic component: glossopharyngeal nerve (CN IX) supplies presynaptic secretory fibres to the otic ganglion, postsynaptic parasympathetic fibres are conveyed to the gland by the auriculotemporal nerve (from V3), stimulation produces thin, watery saliva
  • Sympathetic component: derived from the cervical ganglia through the external carotid nerve plexus on the external carotid artery, will reduce saliva secretion
  • Sensory nerve fibres reach the gland through the auriculotemporal nerve from the mandibular division of trigeminal nerve

  
• Structures exiting at the periphery of the parotid gland

  • External carotid artery and nerve plexus
  • Retromandibular vein
  • Parotid duct
  • Posterior auricular artery and vein
  • Superficial temporal artery and vein accompanied by auriculotemporal nerve and temporal branch of facial nerve

  
• Parotid bed


  • Between mastoid process and mandibular ramus
  • Base is against zygomatic arch
  • Apex at angle of mandible
  • Posterior belly of digastric
  • Auriculotemporal nerve (which will supply it)
  • Stylohyoid muscle
  • Medial pterygoid (muscle of mastication)
  • Mandibular ramus
  • Masseter

  
• Parotid duct


  • Leaves horizontally from the anterior edge of parotid gland
  • At the anterior border of the masseter the duct crosses masseter medially, pierces the buccinators and EXITS the oral cavity through a small orifice opposite the 2nd maxillary molar tooth
  • 1 fingers breadth inferior to zygomatic arch
  • Superficial to masseter
  • Perforates the buccinators

  
• You can also get an accessory parotid duct
• Submandibular gland


  • Smaller than the parotid glands, but larger than the sublingual glands
  • Each is hook shaped and the larger arm of the hook is directed forward in the horizontal plane below the mylohyoid muscle and is therefore outside the boundaries of the oral cavity
  • Larger superficial part of the gland
  • Smaller arm of the hook (or deep part) of the gland loops around the posterior margin of the mylohyoid muscle to enter and lie within the floor of the oral cavity where it is lateral to the root of the tongue

  
• Submandibular duct


  • Emerges from medial side of deep part of gland in oral cavity and passes forward to open on summit of a small sublingual caruncle (papilla) beside base of frenulum of tongue
  • The lingual nerve loops under submandibular duct, crossing first lateral side and then medial side of the duct, as nerve descends anteromedially through floor of oral cavity and then ascends into tongue

  
• Sublingual gland


  • Smallest of the three major paired salivary glands
  • Almond shaped and is immediately lateral to the submandibular duct and associated lingual nerve in the floor of the oral cavity
  • Drains into the oral cavity via numerous small ducts (minor sublingual ducts) which open onto the crest of the sublingual fold
  • More anterior part of the gland is drained by a duct (major sublingual duct) that opens together with the submandibular duct on the sublingual caruncle

  
• Innervation of salivary glands


  • Parasympathetic innervation to all salivary glands in the oral cavity is by branches of the facial nerve [VII], which join branches of the maxillary [V2] and mandibular [V3] nerves to reach their target destinations

  
• Oesophagus


  • Muscular tube (25 – 30cm)
  • Extends from pharynx, opposite cricoid cartilage (C6) to the stomach opposite T11
  • Has 3 parts: cervical, thoracic, abdominal
  • Internal circular and external longitudinal layer of muscles
  • Upper third – voluntary striated muscle
  • Middle third – mixture of both muscle types
  • Lower third – involuntary smooth muscle
• Cervical oesophagus


  • C6
  • Pharyngo-oesophageal junction constricted by the cricopharyngeal part of the inferior constrictor
  • Narrow

  
• Rest of the sublingual fold

  More anterior part of the gland is drained by a duct (major sublingual duct) that opens together with the submandibular duct on the sublingual caruncle

  
• Parasympathetic innervation


  To all salivary glands in the oral cavity is by branches of the facial nerve [VII], which join branches of the maxillary [V2] and mandibular [V3] nerves to reach their target destinations

  
• Oesophagus


  • Muscular tube (25 – 30cm)
  • Extends from pharynx, opposite cricoid cartilage (C6) to the stomach opposite T11
  • Has 3 parts: Cervical, Thoracic, Abdominal

  
• Cervical oesophagus


  • Pharyngo-oesophageal junction constricted by the cricopharyngeal part of the inferior constrictor
  • Narrowest part
  • Inclines slightly left - enters superior mediastinum

  
• Thoracic oesophagus


  • Enters superior mediastinum
  • Between trachea and vertebral column
  • Lies anterior to T1-T4
  • Inclines left – pushed to median plane by aortic arch (T4-T T5)
  • Compressed anteriorly by root of lung
  • Descends to posterior mediastinum
  • Passing posterior and to the right of aortic arch
  • Inferior to arch – deviates left as it passes through oesophageal hiatus (T10)
  • Right crus of the diaphragm