DS

• Digestion


  The mechanical and chemical breakdown of foods into forms that cell membranes can absorb
• Organs of the digestive system

  • Carry out processes of ingestion, propulsion, absorption and defecation
• Digestion process


  1. Saliva + enzyme + food = BOLUS

  2. Bolus + stomach + acid = CHYME
• Exocrine glands


  • Stomach
  • Liver
• Endocrine glands


  • Thyroid
  • Pancreas
• Enzymes


  Catalysts of chemical reactions
• Amylase


  Secreted by the pancreas and salivary glands (found in saliva)
• Peptase


  Splitting of proteins into smaller peptide fractions (found in stomach and acidic)
• Lipase


  Breaks down fats into fatty acids and glycerol
• Accessory organs


  • Salivary glands
  • Liver
  • Gallbladder
  • Pancreas
• Salivary glands


  • Secrete saliva, which contains enzymes that initiate breakdown of carbohydrates
• Liver


  • Produces bile, which emulsifies fat
• Gallbladder


  • Stores bile and introduces it into small intestine
• Pancreas


  • Produces and secretes pancreatic juice, containing digestive enzymes and bicarbonate ions, into small intestine
• Alimentary canal


  • Mouth
  • Pharynx
  • Esophagus
  • Stomach
  • Small intestine
  • Large intestine
  • Rectum
• Alimentary canal


  • Muscular tube about 8 meters long
• Mouth


  • Ingests food
  • Mechanically breaks up solid particles using saliva
  • Prepares food for chemical digestion
• Mastication


  The action of mechanically breaking up solid particles in the mouth
• Tongue


  • Thick, muscular organ that occupies the floor of the mouth and nearly fills the oral cavity when the mouth is closed
• Palate


  • Forms the roof of the oral cavity and consists of a hard anterior part and a soft posterior part
• Teeth


  • The hardest structures in the body
  • Primary (deciduous) teeth numbering 20
  • Secondary (permanent) teeth numbering 32
• Salivary glands


  • Secrete saliva
  • Serous cells produce a watery fluid with a digestive enzyme called salivary amylase
  • Mucous cells secrete mucous
• Esophagus


  • Hollow, muscular tube that carries food and liquid from your throat to your stomach
  • Muscles in your esophagus propel food down to your stomach
  • Common symptom is heartburn, a burning sensation in the middle of your chest
  • Problems include acid reflux and GERD (gastro-esophagial reflux disease)
• Peristalsis


  Wave-like muscle contractions
• Stomach


  • J-shaped, pouch-like organ, about 25-30 centimeters long
  • Mucus from the goblet cells and the mucous glands is protective to stomach wall and a lubricant
  • Cephalic phase - sight, taste, smell, or thought of food triggers parasympathetic reflexes, gastric juice is secreted
  • Gastric phase - food in stomach chemically and mechanically stimulates release of gastrin, which stimulates secretion of gastric juice
  • Intestinal phase - as food enters small intestine, it stimulates intestinal cells to release intestinal gastrin, which promotes secretion of gastric juice from stomach wall
• Gastric absorption


  • Gastric enzymes begin breaking down proteins, but the stomach is not well-adapted to absorb digestive products
  • The stomach does absorb some water, certain salts, and certain lipid-soluble drugs, as well as alcohol
• Pancreas


  • Has a dual function as both an endocrine gland and exocrine gland
  • The exocrine function is to secrete digestive juice, called pancreatic juice
• Pancreatic juice


  Contains enzymes that digest carbohydrates, fats, proteins, and nucleic acids
• Liver


  • The largest internal organ
  • Located in the upper-right abdominal quadrant just beneath the diaphragm
• Liver functions


  • Produces glycogen
• Gallbladder


  • Small, pear-shaped organ on the right side of the abdomen, just beneath the liver
  • Holds a digestive fluid called bile that's released into the small intestine
• Bile


  A yellowish-green liquid that hepatic cells continuously secrete
• Bile salts


  • Aid digestive enzymes
• Small intestine


  • Tubular organ that extends from the pyloric sphincter to the beginning of the large intestine
  • Completes digestion of the nutrients in chyme, absorbs products of digestion, and transports the remaining residue to the large intestine
• Secretin


  Stimulates the pancreas to release bicarbonate ions in pancreatic juice
• Large intestine


  • Has little or no digestive function
  • Absorbs water and electrolytes
  • Secretes mucus
• Feces


  Composed of materials not digested or absorbed, including water, electrolytes, mucus, and bacteria