Digestive - Kate

• Motility


  Possible due to plexus (submucosal and myenteric) and smooth muscle
• Types of motility


  • Peristalsis
  • Segmentation
• Peristalsis


  Moves food down the GI tract and coordinated muscle movement, wave like motion
• Segmentation


  Random smooth muscle contraction to mix food with digestive secretions
• Peristalsis location


  Esophagus and stomach
• Segmentation location


  Small intestine
• Stomach function


  Digestion and storage
• Chyme


  Semi digested food using gastric juice
• Cells in the stomach

  • Mucous neck cells
  • Parietal cells
  • Chief cells
• Chief cells secrete


  Pepsinogen (inactive enzyme) and active pepsin breaks down proteins
• Mucous neck cells secrete

  Mucus as a protection against the acid
• Parietal cells secrete


  HCl to change pepsinogen to pepsin and Intrinsic factor cause Vit B12 absorption
• Pepsinogen activation


  HCL will cause the activation of Pepsin
• HCl production


  1. ATP production

  2. HCl production
• ATP production


  Acetylcholine, gastrin, and histamine all bind to their receptors causes intracellular Ca levels to increase Ca activates protein kinase. Protein kinase converts ADP to ATP (adds a phosphate ADP) Once ATP is produced for 3 pumps are now functional and HCl can be produced
• HCl production


  CO2 and H2O combine to form HCO3, (CO2 is the byproduct of cellular metabolism) HCO3 is broken down to Hydrogen and bicarbonate by enzyme anhydrase The bicarbonate leaves the parietal cell and enters the capillary in exchange for chloride (Cl) via the alkaline tide (transport protein) The hydrogen leaves the parietal cell and enters the gastric lumen in exchange for (K) via the potassium-proton- pump (transport protein) Chloride that entered the parietal cell and potassium that entered the parietal cell both leave the parietal cell together and enter the gastric lumen via potassium chloride pump
• Substances produced by the pancreas

  • Lipase: fat digestion
  • Amylase: carbohydrate digestion
  • Trypsin: protein digestion
  • Bicarbonate: neutralize HCl this causes lipas, amylase, and tripson can function properly
• Functions of the liver

  • Plasma proteins - clotting proteins
  • Chemicals - detoxification
  • RBC - synthesis during fetal life
  • Vitamins - activates Vit D
  • Glucose - glycogen
  • Ammonia into Urea
  • Aids Bilirubin Metabolism
  • Production of Bile - bile salts and amino acids
• Bile function


  Emulsification of lipids
• Bile production


  Bile is made in the liver
• Bile storage


  Stored in the gallbladder for concentration
• Bile secretion


  Secreted in the gallbladder
• Bile release hormone


  CCK cholecystokinin
• Gastrin function


  Chyme production and food is further broken down due to partials and gastric juice (Vagal stimulation)
• Gastrin secretion


  The G cell
• Gastrin release causes


  HCl, intrinsic factor, pepsin
• CCK function


  Detects fats and protein
• CCK secretion


  In the small intestines by I cells
• CCK release causes


  Bile, pancreatic enzymes, trypsinogen, lipase, and amylase
• Secretin function


  Stimulates chemoreceptors, Causes stretching & acid when there is chyme in the duodenum
• Secretin secretion


  S cells in the duodenum
• Secretin release causes


  secretes bicarbonate, water, and bile production
• Phases of digestion


  • Mechanical Digestion
  • Chemical Digestion
  • Cephalic Phase
  • Gastric phase
  • Intestinal phase
• Mechanical Digestion


  Grinding occurs in the teeth
• Chemical Digestion


  Chemicals in the stomach by gastric juice and into the duodenum
• Fat soluble vitamins


  • Vitamin DEKA
• Fat soluble vitamin absorption


  Aids and absorption through Micelles and Diffusion
• Water soluble vitamins


  • Vitamin C and Vitamin B and others
• Water soluble vitamin absorption

  Through Active and passive transport
• Carbohydrate digestion


  Amylase causes breakdown