Simple Pharmanotes

  Small Intestine: It is present between the stomach and large intestine . It starts at duodenum and ends at ileocaecal junction . It lies in the abdominal cavity surrounded by large intestine. Length is  5 Meters and diameter is 1 . 5 inches . Provides Chemical as well as mechanical digestion . Main site for chemical digestion and absorption of food . Contains “ Three ” parts, Duodenum Jejunum . Ileum . Duodenum. First part . Starts near the pyloric sphincter of the stomach. “ C ” shaped . Smallest part is only 25 cm . Contains openings of bile duct and pancreatic duct . It has little acidic pH . Jejunum. Middle part . Present between duodenum and ileum . 3 Feet in length. Ileum. Last part . Starts after jejunum and ends at the large intestine at “Ileocaecal Junction ”. Contains ileocaecal sphincter . 6 feets in length. Cells of Small Intestine: Absorptive Cells : Modified columnar epithelium . Contains “ Microvilli '' provides greater surface area. P

  Acid Secretion in Stomach: Overview: Gastric acid (HCl) is secreted by parietal cells located within oxyntic glands of the stomach.  The main purpose of stomach acid is to make the pH of the gastric contents sufficiently acidic to allow activation of pepsinogen to pepsin .  The activated pepsin is a strong proteolytic enzyme . Stomach walls have protection against pepsin and HCl action while other parts of GIT are not protected. Stomach is the only part of GIT which has a lower pH . Mechanism of Gastric Acid formation and Secretion: Gastric Acid is formed by combining carbon dioxide and water to form carbonic acid .  The hydrogen ion of carbonic acid is transported into the stomach lumen while the resultant bicarbonate ion is transported into the bloodstream.  This bicarbonate ion is later transported into the lumen of the duodenum where it is used to neutralize the previously generated gastric acid. Molecular Mechanism: CO 2 within parietal cells is converted, by carbonic