KP - 07 Fisiologi Gastrointestinal

• Professor of Physiology
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• Digestive (GI) Tract Actions include Ingestion, which occurs when material enters via the mouth, Mechanical Processing, which involves Crushing/Shearing to make material easier to move through the tract, Digestion, which is the Chemical breakdown of food into small organic compounds for absorption, Secretion, which involves the Release of water acids, buffers, enzymes & salts by the epithelium of the GI tract and glandular organs, Absorption, which is the Movement of organic substrates, electrolytes, vitamins & water across the digestive epithelium, and Excretion, which involves the Removal o
• Peristaltic waves are largely responsible for moving chyme along the ascending colon.
• In a short reflex defecation, feces enter the rectum, causing distension, and an impulse reaches the plexus mienterikus.
• This large contraction propels the colon contents a considerable distance toward the anus.
• Sphincter ani relaksasi terjadi selama defekasi.
• Mucus lubricates and helps fecal matter to stick together.
• In a long reflex defecation, the rectum is distended, a signal is sent to the spinal cord, and the colon, descending and sigmoid, send a signal to the parasympathetic nervous system.
• Peristaltic waves in the colon desenden and sigmoid mendorok feses ke anus.
• Reflex defecation involves the rectum emptying itself due to a signal from the spinal cord.
• Mass Movements are several strong contractions in the transverse and descending colon.
• Stomach Gastric gland cells include Mucous neck cells which produce mucus to lubricate and protect, Intrinsic factor produced by Parietal cells in gastric glands of the pyloric region which binds with and makes more readily absorbed in the ilium, and Hydrochloric acid produced by Parietal cells with a low pH that acts as a bactericidal, denatures proteins, and provides the proper pH for pepsin.
• The duodenum and jejunum are major sites of nutrient absorption.
• The anal canal is simple columnar to stratified squamous from superior to inferior.
• The cecum is the proximal end of the large intestine, extending approximately 6cm inferiorly past the ileocecal junction to form a blind sac.
• The vermis appendix is a small blind tube extending approximately 9cm from the blind sac, containing many lymph nodes.
• The smooth muscle layer of the anal canal is even thicker than that of the rectum.
• The large intestine extends from the ileocecal junction to the anus and consists of the cecum, colon, rectum, and anal canal.
• Chyme is a mixture of food and stomach secretions.
• Lymph nodes called Peyer’s Patches are numerous in the mucosa and submucosa of the ileum.
• The colon consists of four parts: the ascending colon, transverse colon, descending colon, and sigmoid colon.
• The external anal sphincter is a skeletal muscle, located at the inferior end of the canal.
• The internal anal sphincter is the superior end of the anal canal.
• The anal canal is the last 2 to 3 cm of the digestive tract, beginning at the inferior end of the rectum and ending at the anus.
• Secretion sources include Mucus from Surface and neck mucus cells which lubricates and protects, Intrinsic factor from Parietal cells in gastric glands of the pyloric region which binds with and makes more readily absorbed in the ilium, and Hydrochloric acid from Parietal cells with a low pH that acts as a bactericidal, denatures proteins, and provides the proper pH for pepsin.
• The small intestines consist of three parts: Duodenum, Jejunum, and Ileum, with a length of approximately 4.6 to 9 meters (14 to 29 feet).
• The Duodenum has circular folds, where the mucosa and submucosa form a series of folds.
• The Duodenum has villi, which are tiny fingerlike projections of the mucosa, simple columnar epithelium, contains blood capillary network and lacteals.
• The Duodenum is the site of greatest amount of digestion and absorption, with 8 to 8.5 liters of water entering the small intestine per day.
• The Duodenum contains two small mounds, the Major Duodenal Papilla and the Lesser Duodenal Papilla, located 2/3 of the way down the descending part.
• Chemical breakdown of food involves breaking covalent bonds by digestive enzymes.
• The Duodenum begins with a short superior end, which is where it exits the pylorus of the stomach, and ends in a sharp bend, where it joins the jejunum.
• Digestion involves the breakdown of food molecules for absorption into circulation.
• At the Major Duodenal Papilla, the common bile duct and pancreatic duct join to form the Hepatopancreatic Ampular Sphincter which empties into the duodenum.
• Mechanical breakdown of food involves breaking large food particles into smaller pieces.
• Regulation of stomach emptying involves the coordination of secretion and absorption.
• Absorption involves the removal of molecules out of the digestive tract into circulation for distribution to the body.
• The Hepatopancreatic Sphincter regulates the opening of the ampular and its internal surface has modifications which increase surface area about 600 fold.
• Regulation of Gastric Emptying involves the Neural enterogastric reflex, Hormonal (enterogastrone) mechanisms, and Carbohydrate-rich chyme which quickly moves through the duodenum.