Digestive System

The Digestive System

Phases:
  • Ingestion
  • Movement
  • Mechanical and chemical digestion
  • Absorption
  • Elimination
Types:
  • Mechanical (physical)
    • Chewing
    • Tearing
    • Grinding
    • Mashing
    • Mixing
  • Chemical
    • Enzymatic reactions to improve digestion of
    • Carbohydrates
    • Proteins
    • Lipids

Digestive system organization:

Gastrointestinal
  • Tube within a tube
  • Direct link/path between organs
  • Structures:
    • Mouth
    • Pharynx
    • Esophagus
    • Stomach
    • Small intestine
    • Large intestine
    • Rectum
Mouth:
  • Teeth mechanically break down food into small pieces. Tongue mixes food with saliva (contains amylase, which helps break down starch)
  • Epiglottis is a flap-like structure at the back of the throat that closes over the trachea preventing food from entering it
  • It is located at the pharynx
Esophagus:
  • Approximately 20 cm long
  • Functions:
    • Secrete mucus
    • Moves food from the throat to the stomach using muscle movement called peristalsis
    • If acid from the stomach gets in here that’s Heartburn

Stomach:

  • J-shaped muscular bag that stores the food you eat, breaks it down into tiny pieces
  • Mixes food with digestive juices that contain enzymes that break down proteins and lipids
  • Acid (HCI) in the stomach kill bacteria
  • Food found in stomach is called chyme

Small intestine:

  • Small intestines are 7 meters long
  • Lining on the walls have finger like projections called Villi, to increase surface area
  • The Villi are covered in microVilli which further increases surface area for absorption.
  • Nutrients from food pass into the bloodstream through the small intestine walls
  • When the absorb nutrients it absors 80% water
  • It also absorbs minerals, vitamins, proteins, and carbohydrates,lipids
  • Secrets digestive enzymes but it’s main job is absorption

Large intestine:

  • About 1.5 meters long (5ft)
  • Accepts what the small intestines don’t
  • Rectum (Short terms storage which holds feces before it is expelled)
  • Functions:
  1. Bacterial digestion (Breaking down of carbohydrates)
  2. Absorbs more water
  3. Concentrate wastes

Accessory Organs in the Glands:

Liver:

  • Directly affects digestion by producing bile.
  • Bile helps digest fats
  • Filters out toxins from drugs and alcohol

Gallbladder:

  • Stores bile from the liver, releases into the small intestine
  • Fatty diets can cause gallstones

Pancreas:

  • Produces digestive enzymes to digest fats, carbs, and proteins
  • Regulates blood sugar by producing insulin