Skeletal system

• Digestive System


  Food undergoes six major processes: 1. Ingestion, 2. Propulsion, 3. Mechanical digestion, 4. Chemical digestion, 5. Absorption, 6. Defecation
• Ingestion


  Process of eating
• Propulsion


  1. Passing of food down the GI tract

  2. Swallowing: voluntary

  3. Peristalsis: reflex, involuntary, involves alternating contractions of muscles in body walls of GI organs
• Mechanical digestion


  1. Prepares food for chemical digestion

  2. Includes chewing, mixing with saliva by tongue action, churning in stomach
• Chemical digestion


  1. Catabolic steps in which food is broken down to basic building blocks

  2. Accomplished by enzymes in digestive juices
• Absorption


  Passage of food particles into the blood-lymph
• Defecation


  Elimination of indigestible food substances
• Main Parts of Human Digestive System

  • Mouth
  • Esophagus
  • Stomach
  • Small Intestine
  • Large Intestine
• Accessory Parts of Human Digestive System

  • Liver
  • Pancreas
  • Gallbladder
  • Salivary Gland
• Mouth


  There are two major processes which take place: 1. Mastication (Chewing) - Breaks down large food molecules, increases surface area of food particles. 2. Secretion of Saliva - Contains salivary amylase (ptyalin) that digests starch to maltose, lubricates and moistens food.
• Salivary Glands


  • Parotid
  • Submaxillary
  • Sublingual
• Teeth or Dentes


  • Bonelike structure in the mouth that usually use for mastification or chewing
  • Parts: Crown, Neck, Root
  • Types: Incissors, Canines, Premolars, Molars
• Tongue


  Special organ for the sense of tastes, assists in mastification, deglutition and speech
• Pharynx


  Short tube shaped like a cone, connects the mouth to the esophagus
• Esophagus


  • Mucus muscular membrane lined tube
  • Peristalsis: Involuntary process of muscular contraction forcing the bolus (food) down to the stomach
• Stomach


  • Hollow, muscular holding pouch for food
  • Contains rugae: muscular folding surface responsible for expansion and contraction
  • Parts: Fundus, Body, Pylorus
  • Relaxed volume of about 45 ml, generally expands to hold about 1 litre of food, can hold as much as 4 liters
• Small Intestine


  • Coiled tube, about 7 meters long, where most digestion and absorption of nutrients take place
  • Parts: Duodenum, Jejenum, Ileum
  • Absorption parts are the villi
• Large Intestine or Colon


  • Wider, 1.5 meters long, responsible for the absorption of water molecules or fluid substances
  • Parts: Ascending, Transverse, Descending
  • Rectum stores the undigested food, Anus releases the stool or feces through defecation
• Liver


  • Largest organ in the mammalian body
  • Secretes bile which is stored in the gallbladder
  • Bile breaks down fats into tiny droplets through emulsification
  • Roles: Regulates sugar/glucose, Breaks down excess RBC, Storage of blood, Detoxification, Generation of heat
  • Endocrine gland that secretes Insulin, Exocrine gland that secretes pancreatic juice
• Pancreas


  Endocrine gland that secretes Insulin, Exocrine gland that secretes pancreatic juice containing lipase, trypsin and pancreatic amylase for digestion of lipids, proteins and starch
• Salivary Glands


  • Located near the mouth, produce and secrete saliva to help with chewing and swallowing
  • Types: Sublingual, Parotid, Submandibular
• Gallbladder


  • Pear-shaped sac attached to the liver, stores and concentrates bile produced by the liver
  • Bile salts act as emulsifying agents in the digestion and absorption of fats, cholesterol and bile pigments are excreted from the body in the bile