Lecture 3

• The teeth = secondary dentition

  1. Incisors front of mouth, designed to cut off piece of food
  2. Cuspids (canines = pointed), spike into foods allow for tearing and only have 1 root
  3. premolars (bicuspids) and molars, good at crushing and grinding food as jaw moves laterally, have 3-4 roots

  
• Mastication = chewing
• muscles of mastication role:

  1. close jaws
  2. slide/rock lower jaw side to side
  3. chewing involves mandibular - elevation and depression, protraction and retraction, medial and lateral movement
  4. tongue & cheeks move food across teeth
• Muscles of mastication include:

  1. temporalis
  2. masseter
  3. lateral pterygoid
  4. medial pterygoid

  
• Major salivary glands:

  A) parotid gland

  B) tongue

  C) sublingual gland

  D) submandibular gland

  
• roles of saliva:

  1. lube and cleaning by serous fluid and mucus
  2. facilitation of taste
  3. protection against acid and bacteria such as - antibacterial enzymes (lysozyme, IgA), bicarbonate and calcium ions
  4. digestion by salivary amylase (ptyalin), lingual lipase
• regulation of saliva production:

  1. almost entirely due to neural control
  2. parasympathetic (watery) and sympathetic (mucoid) activity increase secretion
  3. PS controlled by salivatory centre in brain stem driven by - local stimuli (taste & touch), central stimuli (smell & sight of food, etc), (learned) reflex
• the salivon is a 2 stage process:

  1. initial isotonic fluid mainly containing NaCl and or mucus
  2. passes along duct, salt reabsorption and hydrogen carbonates and potassium secretion leads to hypotonic, alkaline fluid

  flow rate important!

  
• parotid gland:

  1. largest salivary gland
  2. predominantly serous secretion
  3. 50% salivary volume
  4. main source salivary amylase and proline-rich proteins
  5. parasypathetic supply via CN IX (glassopharnygeal)
  6. sympathetic supply from superior cervical ganglion
• parotid gland

  
• submandibular gland:

  1. mixed serous & mucous secretion
  2. 45% salivary volume
  3. main source lysozyme and lactoperoxidase
  4. parasympathetic supply via CN VII (facial -> chorda tympani -> lingual nerve)
  5. sympathetic supply from superior cervical ganglion (travels w/ facial artery)
• sublingual gland:

  1. predominantely mucous secretion
  2. 5% salivary volume
  3. main source lingual lipase
  4. parasympathetic supply via CN VII (facial nerve)
  5. sympathetic supply form superior cervical ganglion
• ptyalin alpha-amylase: initial digestion of polysaccharides

  starch and other large polysaccharides made up of alpha 1,4 and alpha 1,6 linkages, latter causes branches

  alpha amylases only cut at alpha 1,4 sites and not adjacent to alpha 1,6 sites

  pH optimum about 7, denatured pH 4
• lingual lipase: initial digestion of triglycerides

  1. cleave outer fatty acids off triglycerids, leaving diacyl glycerol
  2. pH optimum about 4, stable in stomach but denatured by pancreatic proteases, works together w/ gastric lipase
• cephalic phase of GI activity:

  1. combination of stimuli, some conscious and some not
  2. mediated by parasympathetic as salivary secretion via facial and glossopharyngeal nerves (CN VII & CN IX) and control of GI motility and secretion via vagus (CN X)
  3. vagus also carries afferent fibres contribute to feedback system
• oesophagus:

  1. 25cm long and 2cm wide
  2. stratified squamous epithelium, thrown into folds
  3. submucosal oesophageal glands secrete mucus to facilitate passge of food bolus
  4. innervated by fibres from oesophageal plexus
• the oesophagus

  A) muscularis mucosae

  B) mucosa

  C) submucosa

  D) muscularis externa

  E) adventitia

  F) stratified squamous epithelium

  G) lamina propia

  H) muscularis mucosae

  
• swallowing phases:

  A) voluntary

  B) pharyngeal

  C) oesophageal

  
• taste sensors are specialised epithelial cells:

  1. ion channel-based sensor = salty and sour
  2. GPCR-based sensor = sweet, umami & bitter

  
• taste buds:

  A) IX

  B) VII

  C) serous gland