LEC 22: MOUTH & STOMACH

• Mouth and associated organs

  • Stratified squamous epithelial mucosa-lined cavity
  • Lips & cheeks have a core of skeletal muscle covered by skin
• Structures of the mouth

  • Hard palate
  • Soft palate
  • Tongue
• Hard palate


  Food manipulation
• Soft palate


  Closing nasopharynx
• Tongue


  • Skeletal muscle
  • Mixing with saliva
  • Swallowing
  • Speech production
  • Papillae: houses taste buds
• Major and minor salivary glands

  • Produce saliva containing: water, electrolytes, enzymes (salivary amylase, lingual lipase), mucins, lysozymes, antibodies
• Teeth

  • Enamel covered crowns
  • Neck surrounded by gingiva
  • Root embedded in the mandible
• Functions of the mouth


  • Ingestion
  • Lip and cheeks help in food manipulation
  • Palate: food manipulation & closes the nasopharynx during swallowing
  • Tongue: food repositioning, mixing with saliva, swallowing, speech production
  • Teeth: tear and grind food to initiate mechanical breakdown
  • Salivary glands: produce saliva containing enzymes for chemical digestion
  • Mouth: mechanical and chemical digestion
• Functions of saliva


  • Moisten and lubricate food for swallowing
  • Contains enzymes (salivary amylase & lingual lipase) that initiate the breakdown of carbohydrates and lipids
  • Cleanse oral cavity and teeth: Removes food particles and bacteria
  • Maintain oral pH balance: Prevents tooth decay
  • Contains antibacterial components (lysozymes and antibodies): Provides protection against oral pathogens
• Regulation of salivation

  • Neural regulation: Parasympathetic stimulation increases salivary gland activity, Sympathetic stimulation decreases salivation
  • Hormonal regulation: Acetylcholine & adrenaline modulate salivary gland function
  • Sensory regulation: Detect the presence of food triggers neural signals that stimulates salivary gland secretion
  • Psychological factors: Sight, smell, thought of food can stimulate salivation through neural pathways
• Differences between deciduous and permanent teeth

  • Deciduous: Initial set of teeth ("baby teeth"), Total: 20 teeth, Grows at the age of 6 months, Replaced by permanent teeth at 6-7 years old, 2 incisors, 1 canine, 2 molars
  • Permanent: Replaces deciduous teeth, Total: 32 teeth, Incisors, canines, premolar, molar, 2 incisors, 1 canine, 2 premolars, 3 molars, Lasts a lifetime
• Pharynx

  • Common passage way for food, fluids, air
  • Divided into: nasopharynx, oropharynx, laryngopharynx
  • Muscular contractions propel food into esophagus
• Esophagus

  • Extends from pharynx to stomach
  • Gastroesophageal (cardiac) Sphincter: Keeps it closed when food is not being swallowed, Prevents the backflow of stomach contents into esophagus
  • Esophageal lining: Stratified squamous epithelium, Protection against abrasion and damage
  • Muscular contracts in esophageal wall (peristalsis) propels food bolus to stomach
• Mechanisms of swallowing

  1. Oral phase: Voluntary, Tongue pushes bolus to the back of mouth, Sensory receptors triggers swallowing reflex

  2. Pharyngeal phase: Involuntary, Elevation of soft palate prevents food from entering the nasal cavity, Closure of the nasopharynx and elevation of the larynx prevent food from entering the trachea

  3. Esophageal phase: Involuntary, Bolus propelled downward through esophagus by peristalsis, Food reaches stomach

  4. Coordination: Coordinated by the swallowing center in the brainstem, Receives input from sensory receptors in the mouth and throat
• Regions of the stomach

  • Cardia
  • Fundus
  • Body
  • Pylorus
• Stomach lining

  • Simple columnar epithelium with goblet cells
  • Gastric glands in mucosa produce gastric juice
• Changes in alimentary canal structure for digestive function

  • Stomach mucosa forms rugae for expansion
  • Gastric glands secrete gastric juice containing: hydrochloric acid, Pepsinogen, Mucous
  • Rugae and gastric pits increase surface area for secretion and absorption
  • Muscularis mucosae & smooth muscle layers allow peristalsis and mixing of food with gastric juice
  • Sphincters: Regulates food movement into and out of stomach
• Cell types in gastric juice secretion

  • Parietal cells: Secrete hydrochloric acid (HCl)
  • Chief cells: Secrete pepsinogen (an inactive enzyme)
  • Surface mucous cells & mucous neck cells: Secrete mucous
  • Enteroendocrine cells: Secrete chemical messengers and hormones
• Tooth structure

  • Cementum: Anchors root to the periodontal ligaments holding the tooth
  • Dentin: Underlies enamel and surrounds the pulp cavity that contains blood and nerve supply
• Swallowing

  1. Buccal phase (voluntary): Occurs in mouth where the bolus of food is forced into the oropharynx by the tongue

  2. Pharyngeal-esophageal phase (involuntary): Food is squeezed through the pharynx and into the esophagus, Controlled by the swallowing centre of the medulla and pons
• Mucous helps protect the epithelium from the hydrochloric acid of the stomach
• what are the four types of teeth called?

  incisors, canines, premolar, molar
• swallowing is coordinated by what and where?

  swallowing centre in brainstem
• what happens during oral phase?

  tongue pushes bolus to the back of the mouth
• what happens during esophageal phase?

  bolus is propelled downward through esophagus by peristalsis