science long quiz'

• Digestive system


  Responsible for the processing and uptake of nutrition
• Every cell in an organism needs energy and an array of nutrients to remain alive
• Types of food nutrients


  • Carbohydrates (sugars)
  • Lipids (fats)
  • Proteins
• The body generally cannot utilize food in its most complex form as a source of energy
• There is a need for food to be broken down
• Digestive system


  • Has three main functions: digestion of food, absorption of nutrients and elimination of solid food waste
• Digestion


  1. Mechanical digestion

  2. Chemical digestion
• Mechanical digestion


  Takes place within the mouth and the stomach, food is acted upon mechanically or physically by the teeth and the tongue to break it down into smaller pieces
• Chemical digestion


  The chemical breakdown of large, complex food molecules into smaller, simpler nutrient molecules that can be absorbed by the blood, digestive enzymes are needed to hydrolyze and break down starch into glucose, proteins into amino acids, and fats into fatty acids and glycerol
• Absorption


  The process in which substances pass into the bloodstream, where they can circulate throughout the body, occurs mainly in the small intestine
• Elimination


  Any remaining matter from food that cannot be digested and absorbed passes into the large intestine as waste, the waste later passes out of the body through the anus
• Digestive system


  Includes the digestive tract and its accessory organs, which process food into molecules that can be absorbed and utilized by the cells of the body
• Digestive tract


  Also called the alimentary canal or gastrointestinal tract, consists of long continuous tube that extends from the mouth to the anus
• Accessory organs of the digestive system


  • Salivary gland
  • Liver
  • Gall bladder
  • Pancreas
• Ingestion


  Digestion starts when food is taken into the mouth
• Mechanical breakdown


  Chewing breaks the food into small pieces
• Chemical digestion in the mouth


  Saliva softens and wets the food and also initially starts chemical digestion through the enzymes present in it
• Peristalsis


  Muscle contractions in the esophagus help move the food down to the stomach
• Digestion in the stomach


  Stomach juices made by the body help digest food, the stomach muscles churn and help mix the food and break it into even smaller pieces
• Digestion in the stomach


  Digestive glands in the stomach lining produce acids and enzymes that digest proteins, a thick mucus layer helps keep this acidic chemical environment from destroying the tissues of the stomach
• Absorption in the small intestine


  Digested molecules of food are absorbed through the small intestine, the walls of the small intestine contain many folds that are lined up with tiny fingerlike protrusions called villi, these villi are in turn covered with even smaller protrusions called microvilli, these structures increase the surface area through which nutrients are absorbed
• Elimination


  The undigested parts of food or those that were not absorbed by the body are eliminated as feces