Human Digestion System

• Digestion: The process that converts macromolecules (in food) into simpler monomers that can be adsorbed and used by the cells of the body
• • 4 Main Groups of Food and Monomers
  • Carbohydrates: monosaccharides
  • Lipids: fatty acids
  • Proteins: amino acids
  • Nucleic Acid: nucleotides
• • Digestion occuts through 2 processes:
  • Mechanical digestion: large particles of food are broken into smaller pieces of food through physical processes
  • Ex: chewing & churning food in the stomach
  • Chemical digestion: (enzymes & acids) break bonds in macromolecules into the building blocks for adsorption by cell
• Parts of the Digestive System

  • Alimentary canal (tube that food travels through)
  • mouth -> pharynx -> esophagus -> stomach -> small intestine (+ duodenum) -> large intestine (colon) -> rectum -> anus
  • Accessory organs
  • Structures that assist in digestion, but food doesn't actually pass through them
  • Make & secrete enzymes/chemicals to aid in digestion
  • Salivary glands (mouth)
  • Liver (+ gallbladder)
  • Pancreas
• Digestion System - Mouth

  • Mechanical
  • food physically broken by teeth into pieces & tongue tumbles food
  • bolus is formed & swallowed
• Digestion System - Salivary Gland

  • Releases salivary amylase (enzyme) which chemically breaks down starch into sugar
  • saliva = water & salivary amylase
• Digestive System - Pharynx

  • space behind the tongue -> swallowing
• Digestive System - Epiglottis

  • Blocks the trachea -> keeps food out (prevents choking)
  • chew, swallow
• Digestive System - Esophagus

  • Mechanical
  • food is moved along via. peristalsis
  • wave-like muscular contractions -> squeezes bolus
• Digestive System - Cardiac sphincter

  • Ring-shaped muscle that prevents food from moving back to esophagus
• Digestive System - Liver

  • Two important functions
  • Produce bile
  • Breaks fat into smaller droplets
  • stored in gallbladder
  • release from GB into duodenum to break up fats
  • Filter & removes toxins from blood
• Digestive System - Gallbladder

  • Stores & releases bile
• Digestive System - Stomach

  • Storage: many folds - can hold 2-4 liters of food/fluid
  • Chemical
  • gastric juices are secretes into the stomach
  • pepsin: enzyme breaks protein into amino acids
  • HCL: needed for pepsin activation
  • mucus: protects stomach lining for HCL
  • Mechanical
  • Stomach muscles churn and mix food & gastric juices into thick material called chyme.
  • Chyme leaves via the pyloric sphincter into the small intestine in a “controlled release”
• Digestive System - Duodenum (1st Part of SI)

  • First 10 in. of SI
  • Important site of chemical digestion w/ enzymes/chemicals secretes by the liver/gallbladder & pancreas
• Digestive System - Pancreas

  • Accessory organ
  • secrete enzymes into DDM to aid in chemical digestion in chyme
  • lipase - fats
  • trypsin - protein
  • secretes buffers to neutralize acidic chyme from stomach
• Digestive System - Small Intestine (remain)

  • Chyme travels 6 m. (18 ft.)through the remaining of SI
  • Small nutrients are also reabsorbed into body circulation from SI
  • Lined with villi = finger-like projections which increase SA in intestine for more nutrient adsorption
• Digestive System - Large Intestine (Colon)

  • Water from leftover digested food is adsorbed back into body tissues
  • Feces are solidified & formed
• Digestive System - Rectum

  • Stores feces until full
  • Nerve impulse from brain contracts the anus
• Digestive System - Anus

  • Feces exit here