Digestive system

• Digestion


  The process by which food is broken down into simple molecules that can be absorbed into the bloodstream
• Enzyme


  A protein that speeds up the rate of chemical reactions in cells and is not used up in the process
• Amylase


  An enzyme that chemically digests starch by breaking it down into the sugar maltose
• Maltose


  A sugar produced when amylase breaks down starch
• Oesophagus


  The food pipe that pushes swallowed food along by a wave-like movement of muscles known as peristalsis
• Stomach


  An expandable muscular bag that physically churns and temporarily stores food, and releases juices that continue the chemical digestion of food
• Small intestine


  Where food from the stomach enters, and the enzyme maltase breaks down maltose into glucose which can be absorbed into the bloodstream
• Maltase


  An enzyme that breaks down maltose into glucose
• Glucose


  A simple sugar that can be absorbed into the bloodstream
• Villi


  Finger-like projections in the small intestine that provide an increased surface area for nutrient absorption
• Pancreas


  Where digestive enzymes that pass into the small intestine are produced
• Liver


  The largest internal organ, which produces bile to help digest fats and breaks down harmful substances
• Bile


  A substance produced by the liver that helps digest fats in the small intestine
• Large intestine


  A long, tube-like organ that reabsorbs water from fully digested food and prepares undigested food for egestion as faeces
• Faeces


  Undigested food that is temporarily stored in the rectum before being passed out through the anus
• Why do we need food?
• Organ system


  A group of organs that work together to carry out one or more functions
• Stages of human nutrition

  1. Ingestion: food is taken into the mouth

  2. Digestion: food is broken down

  3. Absorption: digested food is passed into the blood and carried to cells

  4. Assimilation: digested food is used by the body for energy and to build new cells

  5. Egestion: undigested food is released as waste
• Physical digestion


  Food is broken down into smaller pieces by the teeth, tongue and churning action of the muscles in the stomach
• Chemical digestion


  Food is broken down further by digestive enzymes and other digestive juices in the stomach
• Why does food have to be digested in order to be useful to the body?
• Mouth


  • Food is ingested through the mouth, the teeth physically digest food, and the enzymes in saliva chemically digest it
• Types of teeth


  • Incisors - bite, cut or slice
  • Canines - grasp or tear
  • Premolars - crush or grind
  • Molars - crush or grind
• Why does the physical and chemical breakdown of food have to begin before it is swallowed?
• What is the term used to describe the wave-like movement of food through the oesophagus?
• Stomach


  • Has a strong muscular wall to churn and physically digest food and is covered in a layer of mucus to protect the wall of the stomach from the corrosive action of hydrochloric acid
• Small intestine


  • Is covered in a network of finger-like projections called villi to increase surface area for absorption, is long to increase the surface area for absorption and is covered in a dense network of capillaries to absorb material into the bloodstream
• What is an enzyme?
• What is the function of the pancreas and liver in human digestion?
• Large intestine


  The major function is to reabsorb water from fully digested food into the blood, and to prepare undigested food for egestion as faeces
• Key terms


  • digestion
  • enzymes
  • amylase
  • maltose
  • oesophagus
  • stomach
  • small intestine
  • maltase
  • glucose
  • villi
  • pancreas
  • liver
  • bile
  • large intestine
  • faeces