Digestive System

• Major functions of the digestive system

  • Ingestion and Mastication
  • Propulsion and Mixing
  • Secretion
  • Digestion
  • Absorption
  • Elimination
• Ingestion

  The intake of solid or liquid food into the stomach
• Mastication

  The process by which the teeth chew food in the mouth to begin the process of digestion
• Mastication

  • Involves digestive enzymes and other enzymes that cause the digestion of the food
• Propulsion

  The movement of food from one end of the digestive tract to the other
• Propulsive movements

  • Swallowing, or deglutition
  • Peristalsis
  • Mass movements
• Mixing

  The movement of food back and forth in the digestive tract, without forward movement
• The time it takes for food to travel the length of the digestive tract is usually about 24–36 hours
• Secretion

  Substances added to lubricate, liquefy, buffer, and digest the food as it moves through the digestive tract
• Secretions

  • Mucus or sometimes serous is being erected while the food travels around the mouth towards the digestive tract
  • Mucus secreted along the entire digestive tract, lubricates the food and the lining of the tract
• Digestion

  Breakdown of large organic molecules into their component parts
• Digestion

  • Mechanical Digestion - mastication and mixing of food
  • Chemical Digestion - accomplished by digestive enzymes
• Amylase

  Enzyme involved in the digestive system, e.g. salivary amylase and pancreatic amylase
• Absorption

  Movement of molecules out of the digestive tract and into the blood or into the lymphatic system
• Absorption

  • Intestines have a lot of absorption
• Elimination

  Process by which the waste products of digestion are removed from the body
• Organs of the digestive system

  • Digestive tract - continuous coiled hollow tube
  • Accessory digestive organs - salivary glands, teeth, pancreas, liver, gallbladder
• Organs of the alimentary canal

  • Mouth
  • Pharynx
  • Esophagus
  • Stomach
  • Small intestine
  • Large intestine
• Lips (Labia)


  Protect the anterior opening of the mouth
• Lips


  • Muscular structures formed mostly by the orbicularis oris muscle and connective tissue
  • The outer surfaces of the lips are covered by skin
  • The keratinized stratified epithelium of the skin is thin at the margin of the lips and is not as highly keratinized as the epithelium of the surrounding skin
• Keratinized stratified epithelium


  Not a single layer and has keratin, which is the epithelium for skin
• Cheeks


  Forms the lateral walls of the oral cavity
• Cheeks


  • They consist of an interior lining of moist stratified squamous epithelium and an exterior covering of skin
  • The substance of the cheek includes the buccinator muscle which flattens the cheek against the teeth
  • The substance of the cheek includes the buccal fat pad which rounds out the profile on the side of the face
• Palate


  The roof of the oral cavity
• Palate


  • Separates the oral and nasal cavities and prevents food from passing into the nasal cavity during chewing and swallowing
  • The palate consists of two parts: the hard palate which forms the anterior roof and is bony, and the soft palate which forms the posterior roof and is non-bony, consisting of skeletal muscle and connective tissue
• Uvula


  A posterior projection from the soft palate
• Fauces


  The posterior boundary of the oral cavity which is the opening into the pharynx, or throat
• Palatine Tonsils


  Are in the lateral wall of the fauces
• Vestibule


  The space between the lips externally and the teeth and gums internally
• Oral Cavity


  The area contained by the teeth
• Tongue


  Attached at the hyoid and styloid processes of the skull, and by the lingual frenulum
• Tongue


  • Its function is to move the food in the mouth
  • It also participates in speech and swallowing
  • It is composed of intrinsic muscles that change its shape, and extrinsic muscles that involve the protrusion or retraction of the tongue and its movement from side to side
• Frenulum


  A structure related to the tongue
• Terminal sulcus


  A groove that divides the tongue into the anterior 2/3 and posterior 1/3
• Anterior part of tongue


  • Has papillae, some of which have taste buds
• Posterior part of tongue

  • Has no papillae and a few scattered taste buds
  • Contains lymphoid tissue embedded in the posterior surface: the lingual tonsil
• Palatine tonsils


  Are located near the opening of the oral cavity into the pharynx
• Lingual tonsils


  Are located on the posterior surface of the tongue, which also places them near the opening of the oral cavity into the pharynx
• Tonsils are lymphatic tissues that play an important role in the body's immune mechanism
• Large, multicellular salivary glands

  • Parotid glands
  • Submandibular glands
  • Sublingual glands