digestive system

• Digestion: the of breaking down large insoluble molecules of food into smaller soluble molecules which can be readily absorbed by the body. Digestion involves the physical (e.g., teeth) and chemical (enzymes) breakdown of food.  
• Mouth: Food starts its journey from the mouth or the oral cavity. Chemical digestion in the mouth consists of salivary amylase (contained in saliva), which digests starch into maltose. Physical digestion consists of the chewing, grinding and mixing of food into smaller pieces by the teeth and tongue. Digestive processes in the mouth form bolus.  
• Esophagus: This is a muscular tube, that pushes bolus to the stomach by peristalsis (involuntary constriction and relaxation of muscles, creating movements that push contents of the canal forward).  
• Stomach: It serves as a muscular bag. Takes in food from the esophagus. It produces enzymes and digestive juices. This mix of enzymes and digestive juices breaks down food. Chemical digestion of proteins to polypeptides by pepsin (the chief digestive enzyme in the stomach, breaks down proteins to polypeptides) at a pH of 2 maintained by the release of hydrochloric acid (HCL). HCL destroys harmful microorganisms present in food particles. Food is then passed into the small intestine in small portions.  
• Pancrease: contains hormones which regulate blood glucose levels, creates natural juices called pancreatic enzymes to break down food. Proteases, amylase and lipase is secreted.  
• Gal Bladder: Small pouch like organ. Stores bile, a fluid produced by the liver that helps break down of fatty foods (lipids).
• Small intestine: A thin, long tube present behind the stomach. It helps to further digest food coming from the stomach, after which, nutrients are absorbed for the body.  

  1.  Breakdown of proteins and polypeptides by protease into amino acids.   

  2. Breakdown of starch into glucose by amylase.  

  3. Breakdown of maltose into glucose by maltase.

  4. Breakdown of lipids by bile (physical digestion) through emulsification, lipids broken down by lipase into fatty acids, glycerol and other alcohols.  
• Large intestine: A long, tube-like organ that is connected to the small intestine and one end and the anus at another. The purpose of the large intestine is to absorb water and salts from the material that has not been digested as food and get rid of any waste products left over. Waste products are stored until ejection by the anus.  
• Rectum: The last several inches of the large intestine closest to the anus.  
• Anus: The opening far at the end of the digestive system tract through which waste products are removed from the body.  
• Saliva moistens food making it easier to swallow and contains enzyme amylase which begins breaking down carbohydrates.
• Teeth are used to tear and grind up food so it can be swallowed more easily.
• Labelled diagram

  A) teeth

  B) liver

  C) stomach

  D) mouth

  E) salivary glands

  F) pharynx

  G) esophogus

  H) small intestine

  I) large intestine

  J) pancrease

  K) Anus

  L) Rectum

  M)