Receptive relaxation reflex PDF

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Receptive relaxation reflex: when the first bite of meal gets swallow, it causes the stomach to distent, once this happens peristalsis of stomach begins, churn the food into liquid from which will go to SI, which absorption begins peristalsis are governed by pacemakers because they fire action potentials, begins gentle and gets stronger with time muscular contraction of the stomach helps churn chime which mixes with gastric secretion and pushes food through pyloric sphincter Digestion begins in the mouth under salivary & gastric enzymes, partially digest starch, proteins, and fats Most digestion occurs in small intestine, stomach doesn’t do much nutrient absorption. Stomach has folds called rugae, the opening of the folds are called gastric pits Different types of gastric cells: Goblet Cells- Produce Mucous Parietal Cells- Produce HCI Chief Cells- Produce pepsinogen G Cells- Produce Gastrin D Cells- Produce Somadostatin (for digestion) Stem Cells- replaces epithelium Intrinsic factor is secreted by gastric mucosa (parietal cells), which is required for B12 absorption. B12 produces RBC, NOT enough B12 means you have pernicious anemia and the treatment is B12 injections or orally B12. ** IF INTRINSIC FACTOR NOT WORKING PROPERLY YOU HAVE PERNICIOUS ANEMIMA** Gastric juice is made up of water and exocrine secretions, they are HIGHLY ACIDIC, and produces 2-4 L/DAY PRONTON PUMP: take hydrogen and take it into lumen of stomach. ** THE MORE PROTON PUMP IS STIMULATE THE MORE HYDROGEN WILL BE PUMP INTO LUMEN AND MORE ACIDIC STOMACH WILL BE. Acid secretion is regulated by gastrin, histamine, neurotransmitter. Gastrin is a weak stimulator of proton pump; however, gastrin stimulates histamine, histamine stimulates HCI stronger. Histamine binds to H2 receptors Function of stomach acid is the breakdown of proteins, activates pepsinogen to pepsin, produces optimal PH for pepsin action which is important to begin protein digestion, and kills microbes The stomach is protected by a mucous coat also protects against pepsin, the coat contains bicarbonate (alkalie) which keeps ph level neutral, and it secreted from epithelial cells. The tight junctions between cells keep acid and pepsin within cell Stomach ulcers causes coat to breakdown Drugs to produce stomach ulcers: Ibuprofen, any anti-inflammatory drugs Digestion and absorption in stomach are minimal, alcohol and aspirin absorbed across stomach due to lipid solubility. Gastritis: inflammation of the stomach Peptic Ulcer: Erosion of the stomach or duodenal mucous. Due to Depletion of mucous coat (gastric ulcer) or Hyperacidity (DUODENAL ULCER)

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Helicobacter Pylori (H. Pylori) resides in the GI tract, it’s the cause of most gastric and duodenal ulcers. Treatment antibiotic and proton pump Gastritis is the inflammation of the stomach mucos, its caused by the breakdown of protective barriers, it will result in histamine release, and the histamine will cause acid production. Duodenal ulcers are protected by bicarbs, the major cause its excessive gastric acid or inadequate bicarbon. Small intestine function absorption, most of the absorption is done in the duodenum and jejunum (most). B12, bile salts, electrolytes absorbed in ileum, the absorption is rapid due to increased surface area. Villus are fingerlike fold, they are projected into the lumen, covered with columnar epithelium, they have goblet cells. Villus contain lymphocytes, blood capillaries, and lymphatic vessels. The blood capillaries are responsible for absorption of carbs and amino acids, the lymphatic vessels are responsible for fats. Intestinal Mobility: 1st. Peristalsis- relatively slow, moves things forward 2nd Segmentation- muscular constriction of lumen 3rd Migratory Motor Complexes- occurs during fasting, helps clear small intestine, prevents bacteria growth in intestine. Large Intestine extents from the ileocecal valve to anus, receives chime from ileum. Major function of large intestine is water absorption, vitamin B & K , electrolytes **HOWEVER SMALL INTESTINE ABSORPBS MOST WATER** Cecum is a blind pouch, open only @ 1 end (beg. of large intestine There is no villi in the large intestine Haustra- pouches; if the wall becomes weaken you can get diverticulum/diverticulitis Mucosa has Goblet cells Intestinal Micribiota (microflora) found in colon., important for proper digestive funtciton and to guard against inflammatory disorder. The function is to produce folic acid and vitamin K (important for blood clottings), ferment indigestive chime molecules, tissue protector, and outcompete pathogens. Antibiotic therapy kills normal flora, high use of antibiotic therapy correlated with IBS, Crohns, ulcerative colitis. The effect of the antibiotic is diarrhea which cause content to move quickly meaning there is no time for water absorption. Small intestine does most water absorption, water absorption occurs fast due to osmotic graded created by active reabsorption of ions. Diarrhea is excessive fluid on feces, cause by CHOLERA which can kill or lactose intolerance in which the lactose in the lumen will extets osmotic pressure. Defecation is waste material excreted, occurs when the anal sphincter relax and contration of other muscles raises rectal pressure Liver is the largest internal organ, it produces bile. Hepatocytes form hepatic plates and the plates are separated by sinusoids. Sinusoids are large capillary spaces, they allow intimate contact between blood & hepatocytes. Sinusoids are also good for blood delivery. The liver has the amazing ability to regenerate itself due to mitotic division of hepatocytes , once original mass is stored cell division ceases.

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Liver fibrosis is the accumulation of collagen, which can lead to cirrhosis Alcohol and viral hepatitis leads to liver fibrosis Hepatic portal system: Intestinal absorption go to the liver before anything for protection Bile is produced by the hepatocytes and secreted into bile canaliculi, the bile canaliculi are drained at the periphery of each lobule by bile ducts, which drains into hepatic ducts Cirrhosis: occurs when liver lobules are destroyed and replaced by fibrotic scar tissue. Cause- chronic alcohol use, viral hepatitis, biliary obstruction Treatment- remove inflammation cause, antiviral drugs Enterohepatic circulation: (bile enters SI to aid fat absorption)...