digestive

• Digestive system


  Complex set of organs, glands, and ducts that work together to transform food into nutrients for cells
• Functions of the digestive system

  • Ingestion
  • Digestion
  • Absorption
  • Elimination
• Ingestion


  Consumption of solid or liquid food, usually through the mouth
• Digestion


  Breakdown of large organic molecules into smaller molecules that can be absorbed
• Absorption


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


  Removal of undigested material and other waste products from the body as feces
• The digestive system consists of the digestive tract and associated organs
• Portions of the digestive tract

  • Oral cavity (mouth)
  • Pharynx (throat)
  • Esophagus
  • Stomach
  • Small and large intestines
  • Anus
• Associated organs of the digestive system

  • Salivary glands
  • Liver
  • Pancreas
• The digestive tract is open at the mouth and anus, so the inside is continuous with the outside environment
• Food entering the digestive tract may contain useful nutrients, indigestible components, and harmful materials
• The inner lining of the digestive tract serves as a protective barrier while allowing for the absorption of nutrients
• Tunics (layers) of the digestive tract

  • Mucosa
  • Submucosa
  • Muscularis
  • Serosa or adventitia
• Mucosa


  Innermost tunic consisting of epithelium, lamina propria, and muscularis mucosae
• Submucosa


  Layer of loose connective tissue containing nerves, blood vessels, and small glands
• Muscularis


  Layer of smooth muscle, including an inner circular layer and an outer longitudinal layer
• Serosa/adventitia


  Outermost layer, either a serous membrane (peritoneum) or a connective tissue layer
• Peritoneum


  Serous membrane lining the abdominal cavity and covering the abdominal organs
• Visceral peritoneum


  Serous membrane covering the organs
• Parietal peritoneum


  Serous membrane lining the abdominal cavity wall
• Mesenteries


  Connective tissue sheets that hold abdominal organs in place and provide a route for blood vessels and nerves
• Lesser omentum


  Mesentery connecting the lesser curvature of the stomach to the liver and diaphragm
• Greater omentum


  Mesentery connecting the greater curvature of the stomach to the transverse colon and posterior body wall
• Omental bursa


  Cavity or pocket created by the folding of the greater omentum
• Retroperitoneal organs


  Abdominal organs that lie along the abdominal wall and have no mesenteries
• If a pin is placed completely through both folds of the greater omentum, it would pass through two layers of simple squamous epithelium (visceral peritoneum)
• Structures of the oral cavity

  • Lips
  • Cheeks
  • Tongue
• Mastication


  Chewing, the mechanical breakdown of food in the oral cavity
• Frenulum


  Thin fold of tissue attaching the anterior tongue to the floor of the mouth
• Types of teeth


  • Incisors
  • Canines
  • Premolars
  • Molars
• Permanent/secondary teeth


  Adult teeth that replace the primary/deciduous teeth
• Tooth structure


  • Crown
  • Neck
  • Root
  • Pulp cavity
  • Dentin
  • Enamel
• Late teens or early twenties


  When the person is old enough to have acquired some degree of wisdom
• Permanent teeth


  Also called secondary teeth, they are replacements for the 20 primary teeth, or deciduous (milk or baby) teeth, which are lost during childhood
• Tooth


  • Crown with one or more cusps (points)
  • Neck
  • Root
• Crown


  The visible portion of a tooth
• Neck


  The small region between the crown and the root
• Root


  The largest region of the tooth and anchors it in the jawbone
• Pulp cavity


  Filled with blood vessels, nerves, and connective tissue, called pulp
• Dentin


  A living, cellular, calcified tissue surrounding the pulp cavity