Parts and Functions of the Human Digestive System

• Food


  A nourishing substance that we take into our body through eating or drinking
• Metabolism


  The process of how the cells use the energy that they obtained from food digestion
• Ingestion


  Food is taken into the mouth and broke down by chewing and grinding of the teeth, being lubricated by the saliva and changing the chemical composition of the food
• The Mouth (Oral Cavity)

  • Mastification or chewing breaks, cuts and grinds food into smaller pieces
  • The tongue helps mix the saliva with the food
  • Saliva lubricates the food and begins its chemical digestion
• Pharynx or throat


  Connects the mouth to the esophagus and serves as a passageway for both food and air
• Epiglottis


  A flap connected to pharynx which closes the windpiper upon swallowing the food
• Bolus


  The rounded soft mass of chewed food
• Esophagus


  A muscular tube that food passes through to the stomach
• Peristalsis


  The series of involuntary, wavelike muscular contractions that usually occur in the digestive tract
• The stomach


  • A muscular expandable organ located on the left side of the upper abdomen
  • It contains glands that secrete acid (HCI or Hydrochloric acid) and enzymes (pepsin) that continue the digestion of the food
• Chyme


  The transformation of bolus into semi-liquid food mass
• Small intestine


  • 6-7 meters long and about 2-4 cm wide
  • Where 90% of chemical digestion and absorption of food nutrients occur
  • Its function is to absorb nutrients and minerals from the food
• 3 segments of the small intestine

  • Duodenum
  • Jejunum
  • Ileum
• Jejunum


  Absorbs sugar, amino acids and fatty acids
• Ileum


  Absorbs vitamin B12, bile salts and other nutrients which jejunum does not absorb
• Villi


  Finger-like projections that provide a huge space for the absorption of nutrients molecules
• Pancreas


  • A long, narrow gland that stretches from the spleen to about halfway through duodenum
  • It secretes pancreatic juice, a mixture of water, digestive enzymes, bicarbonate and electrolytes
  • It breaks down protein, fats and carbohydrates
• Liver


  • The largest organ of the body in terms of mass and also the largest gland
  • It produces bile
• Bile


  A yellowish-brown fluid that aids chemical digestion by helping the small intestine with emulsification and digestion of lipids/fats
• Gallbladder


  A green pear shaped sac that stores and concentrates excess bile
• Large Intestine or Colon


  • The leftovers waste material move into large intestine which solidify the food waste product and store it until it is ready to he defecated
  • Responsible for the reabsorption of water and minerals salts and temporarily stores the undigested food
• Rectum


  An expandable storage organ of undigested food
• Anus


  The opening where the feces or stool is released
• Stages of Digestion


  1. Ingestion

  2. Digestion (Mechanical and Chemical)

  3. Absorption/Assimilation

  4. Elimination/Excretion
• Ingestion


  The process in which food is taken into the mouth and broke down by chewing and grinding of the teeth, being lubricated by the saliva and changing the chemical composition of the food
• Digestion


  Mechanical Digestion - physically breaking down of food into smaller pieces

  Chemical Digestion - the process of breaking down of food with the help of digestive enzymes from the saliva as well as secretion of acids that the body can absorb
• Absorption/Assimilation


  The process of taking up the fluid and other substances by the body tissues
• Elimination/Excretion


  The process of removing the metabolic wastes products from the body in a form of stool or feces