Grade 8 Human digestive system

• Digestion


  1. Ingestion

  2. Transport of food

  3. Secretion of materials

  4. Digestion of food

  5. Absorption process

  6. Excretion
• Ingestion


  The process of eating, putting food into the mouth
• Transport of food


  The wavelike contraction or peristalsis of the muscular walls of the different organs of the digestive tract transports the chewed food to the different organs of digestion
• Secretion of materials


  The secretions of the different digestive glands (saliva, gastric juice, etc.) lubricate, soften, and liquefy foods, and contain enzymes that simplify complex food materials. Other glands secrete substances (bile and bicarbonate ions) that adjust the pH of the food
• Digestion of food


  Physical/mechanical digestion breaks down food into small pieces. Chemical digestion changes the chemical composition of food through enzyme action
• Absorption process


  Brings the final products of digestion (nutrients) from the small intestine for distribution to all parts of the body via blood and lymph vessels
• Excretion


  The process of removing waste products (undigested residue or feces) from the body through the anus
• Organs of the digestive system

  • Mouth
  • Pharynx
  • Esophagus
  • Stomach
  • Small intestine
  • Large intestine
  • Rectum
  • Anus
• Mouth/Buccal cavity


  • Ingests food, breaks down food mechanically and chemically, contains teeth, tongue, salivary glands
• Pharynx


  • Common passageway for digestion and respiration, swallowing raises epiglottis to cover trachea
• Esophagus


  • Muscular tube that conveys food from pharynx to stomach, peristalsis facilitates movement
• Stomach


  • Pear-shaped organ connected to esophagus, contains gastric glands that secrete hydrochloric acid, pepsinogen, and mucus to aid digestion, churns food into chyme
• Small intestine


  • Long, coiled tube (duodenum, jejunum, ileum), organ of complete digestion and absorption, intestinal glands secrete final digestive enzymes
• Large intestine/Colon


  • Temporarily stores undigested residue/feces, divided into ascending, transverse, and descending colon, has caecum and appendix
• Rectum


  • Warehouse for undigested residue/feces, anal canal/anus is the exit point
• Accessory organs of digestion

  • Salivary glands
  • Gastric glands
  • Intestinal glands
  • Liver
  • Pancreas
• Liver


  Largest organ, secretes bile which neutralizes acidity and emulsifies fats to facilitate enzyme action
• Pancreas


  Gland that functions as both exocrine (secretes digestive enzymes into duodenum) and endocrine (secretes hormones)
• Gastroenterologists are doctors who specialize in diagnosing and treating problems of the gastrointestinal tract and the liver