digestive 1

• Food plays a vital role in the survival of the species
• Food gives energy to the organisms that enables them to carry out many activities for each day
• Activities enabled by food energy

  • A predator chasing a prey
  • A prey escaping a predator
• Organisms are able to obtain their energy from the foods they eat through digestion
• Digestion of food is carried out by organs and substances of the digestive system
• Mechanical digestion


  1. Ingestion

  2. Digestion

  3. Absorption

  4. Elimination
• Peristalsis


  Successive waves of involuntary contraction passing along the walls of a hollow muscular structure such as the esophagus or intestine
• Organs of the digestive system

  • Mouth
  • Esophagus
  • Stomach
  • Small intestine
  • Pancreas
  • Liver
  • Gallbladder
  • Large intestine
  • Rectum
  • Anus
• Ingestion


  Food enters the mouth
• Digestion


  Food is broken down into smaller pieces or parts
• Absorption


  Digested molecules of food, water and minerals are absorbed by the small intestine
• Elimination


  Undigested part of food is eliminated as waste
• Most animals have a tube-like digestive system with a mouth at one end and an anus at the other
• Digestive enzymes help break down large molecules into smaller ones
• Digestive glands in the stomach lining produce acids and enzymes that digest protein foods
• The walls of the small intestine contain folds lined with finger-like projections called villi, which are covered in even smaller projections called microvilli
• The pancreas produces digestive juices with enzymes that break down carbohydrates, fats and proteins
• The liver produces bile, a digestive juice
• The gallbladder stores bile produced by the liver
• The large intestine absorbs water from the undigested food and changes the waste from liquid to solid
• The rectum is the lower end part of the large intestine where waste is stored before being eliminated through the anus
• Diseases of the digestive system can be treated, detected, and prevented
• Learning competency


  • Explain how diseases of the digestive system are prevented, detected, and treated
• Gastrointestinal diseases


  • Diarrhea
  • Colorectal cancer
• Functional diseases


  Gi tract looks normal but doesn't move properly
• Structural diseases


  Bowel looks abnormal and doesn't work properly, may need surgical removal
• Constipation


  Hard to have a bowel movement, infrequent stools, may cause anal problems
• Irritable bowel syndrome (IBS)


  Functional condition where colon muscle contracts more or less often, triggered by certain foods, medicines, and stress
• Hemorrhoids


  Swollen blood vessels in the anal canal, can be internal or external
• Anal fissure


  Split or crack in the lining of the anal opening, caused by hard or watery stools
• Anal fistula


  Abnormal tube-like passageway from the anal canal to a hole in the skin near the anus
• Colorectal cancer


  Cancer that starts in the colon or rectum, often has no symptoms until advanced
• Colitis


  Chronic inflammation of the inner lining of the colon, can have various causes
• Colonoscopy


  Endoscopic examination of the large intestine and rectum using a flexible tube with a camera
• Many gastrointestinal diseases can be prevented or minimized by maintaining a healthy lifestyle, practicing good bowel habits, and getting screened for cancer
• Other gastrointestinal diseases


  • Peptic ulcer disease
  • Gastritis
  • Gastroenteritis
  • Celiac disease
  • Gallstones
  • Appendicitis
  • Dyspepsia
  • Pancreatitis
  • Short bowel syndrome
  • Whipple's disease
  • Zollinger-Ellison syndrome
  • Hepatitis