digestive system

• Digestive system


  A continuous tube that begins at the mouth and ends at the anus
• Digestive system


  • Length of about 30 feet in average adult
  • 3 functions: digestion of food nutrients, absorption of nutrients, elimination of solid wastes
• Mouth


  The beginning of the digestive system
• Salivary glands


  • Parotid
  • Sublingual
  • Submandibular
• Saliva production


  1. Sensory organs send message to brain

  2. Brain sends message to salivary glands

  3. Salivary glands secrete chemicals to begin digestive process
• Tongue


  • Muscle covered with mucous membrane
  • Has rear portion called root, tip, and central body
  • Covered with taste buds and papillae
  • Tastes sweet, sour, salt, bitter, and umami
• Teeth


  • Used for chewing food (mastication)
  • Break apart food and mix with saliva to form bolus
• Swallowing


  1. Muscular constrictions move bolus through pharynx and into esophagus

  2. Blocks opening to larynx to prevent food entering airway
• Esophagus


  • Food moved down by peristalsis
  • Lower esophageal sphincter permits passage of food but not backup of stomach contents
• Stomach


  • Muscular, expandable organ
  • Upper portion is fundus, lower portion is antrum
  • Hydrochloric acid and gastric juices convert food to chyme
  • Chyme passes through pyloric sphincter valve into small intestine
• Small intestine


  • About 21 feet long and 1 inch diameter
  • Duodenum, jejunum, and ileum sections
• Liver


  • Produces bile which drains into duodenum, some stored in gallbladder
  • Helps digest fats, stores iron and fat-soluble vitamins
• Gallbladder


  • Stores and concentrates bile
  • Discharges bile into duodenum when chyme fat leaves stomach
• Pancreas


  • Secretes pancreatic juice containing digestive enzymes and bicarbonate ions into duodenum
  • Vital for digestion, person would starve without it
• Jejunum and ileum


  • Lined with villi that slow passage of food and allow nutrient absorption
  • Villus capillaries absorb amino acids and glucose, villus lacteals absorb fatty acids
• Large intestine


  • About 4-5 feet long and 2.5 inches diameter
  • Absorbs remaining water and nutrients, stores and eliminates waste
• Rectum and anus


  • Rectum stores feces until expelled through anus
  • Nervous system stimulates desire to defecate, external anal sphincter is consciously relaxed to expel waste
• Digestive system

  A continuous tube that begins at the mouth and ends at the anus
• Digestive system

  • Length of about 30 feet in average adult
  • 3 functions: digestion of food nutrients, absorption of nutrients, elimination of solid wastes
• Mouth

  The beginning of the digestive system
• Salivary glands

  • Parotid
  • Sublingual
  • Submandibular
• Saliva production

  1. Sensory organs send message to brain

  2. Brain sends message to salivary glands

  3. Salivary glands secrete chemicals to begin digestive process
• Tongue

  • Muscle covered with mucous membrane
  • Has rear portion called root, tip, and central body
  • Covered with taste buds and papillae
  • Tastes sweet, sour, salt, bitter, and umami
• Teeth

  • Used for chewing food (mastication)
  • Break apart food and mix with saliva to form bolus
• Swallowing

  1. Muscular constrictions move bolus through pharynx and into esophagus

  2. Blocks opening to larynx to prevent food entering airway
• Esophagus

  • Food moved down by peristalsis
  • Lower esophageal sphincter permits passage of food but not backup of stomach contents
• Stomach

  • Muscular, expandable organ
  • Upper portion is fundus, lower portion is antrum
  • Hydrochloric acid and gastric juices convert food to chyme
  • Chyme passes through pyloric sphincter valve into small intestine
• Small intestine

  • About 21 feet long and 1" diameter
  • Duodenum, jejunum, and ileum sections
• Liver

  • Produces bile which drains into duodenum, some stored in gallbladder
  • Helps digest fats, stores iron and fat-soluble vitamins
• Gallbladder

  • Stores and concentrates bile
  • Discharges bile into duodenum when chyme fat leaves stomach
• Pancreas

  • Secretes pancreatic juice containing digestive enzymes and bicarbonate ions into duodenum
  • Vital to digestion, person would starve without it
• Jejunum and ileum

  • Lined with villi that slow food passage and allow nutrient absorption
  • Villus capillaries collect amino acids and glucose, villus lacteals collect fatty acids
• Large intestine

  • About 4-5 feet long and 2 1/2 inches diameter
  • Absorbs remaining water and nutrients, stores and eliminates waste
• Rectum and anus

  • Rectum stores feces until expelled through anus
  • Nervous system stimulates desire to defecate, external anal sphincter relaxed to expel waste