Chapter 26 - B - Digestive System - Stomach Intestines Accessory Organs Lecture Notes PDF

HHP:1100 HUMAN ANATOMY The Digestive System II Stomach, Intestines, Accessory Digestive  Lecture Overview Human Anatomy 1. Stomach 2. Small Intestine 3. Large Intestine 4. Accessory Digestive Organs 2  To R...

HHP:1100 HUMAN ANATOMY The Digestive System II Stomach, Intestines, Accessory Digestive  Lecture Overview Human Anatomy 1. Stomach 2. Small Intestine 3. Large Intestine 4. Accessory Digestive Organs 2  To Review … Human Anatomy 1. GI tract is a continuous tube including: – Oral cavity – Pharynx – Esophagus – Stomach – Small intestine – Large intestine, – Anal canal 3  1. Stomach Mechanical Human Anatomy Digestion Function: mechanical, chemical digestion of the bolus Mechanical digestion: 3 layers of muscularis tunic – Outer – longitudinal layer – Middle – circular layer – Inner – oblique layer – Function: mix contents, break apart into smaller pieces for chemical 4 digestion  1. Stomach Human Anatomy Chemical Digestion Chemical digestion via gastric acid – Hydrochloric acid (HCl), pepsinogen, etc. Chyme – once bolus has mixed with gastric acid, it becomes a pasty, semisolid mixture (after 2-6 hours) 5  1. Stomach Human Anatomy Gross Anatomy Four regions of stomach: 1. Cardia 2. Fundus 3. Body 4. Pyloris - pyloric sphincter 6  1. Stomach Human Anatomy Gross Anatomy Greater curvature: Lesser curvature: Internal surface of the stomach has gastric folds called rugae 7  1. Stomach Human Anatomy Omenta Greater omentum extends inferiorly like an apron from the greater curvature of stomach and covers most abdominal organs Lesser omentum connects the lesser curvature of the stomach and the proximal end of the small intestine to the liver 8  1. Stomach Human Anatomy Heartburn Due to reflux: acid from stomach moves into the esophagus, irritating the mucosa 3 common causes: – Weakened lower esophageal sphincter due to fats, alcohol, or chocolate reacting with stomach acids – Hiatal hernia – weak spot in diaphragm allows stomach to move upward – Increased pressure due to obesity, overfull stomach, or lying down 9  2. Small Intestine Human Anatomy Small intestine finishes chemical digestion and is site for most nutrient absorption – ~10 feet long – At least 12 hour transit time 3 specific segments: 1. Duodenum 2. Jejunum 3. Ileum 10  2. Small Intestine Human Anatomy Gross Anatomy 1. Duodenum – C-shaped, ~10-12 inches long – Originates at pyloric sphincter – Receives bile to emulsify fat – Receives pancreatic secretions for digestion 11  2. Small Intestine Human Anatomy Gross Anatomy 2. Jejunum – Middle portion of small intestine – Primary region for chemical digestion and nutrient absorption 12  2. Small Intestine Human Anatomy Gross Anatomy 3. Ileum – Final segment of small intestine – Distal end terminates at ileocecal valve, a sphincter that controls the entry of materials into the large intestine 13  2. Small Intestine Human Anatomy Histology Mucosal, submucosal tunics form circular folds (plicae circularis) Villi — microscopic fingerlike projections on surface of the circular folds Microvilli — fingerlike projections on the surface of the villi 14  3. Large Intestine Human Anatomy Large intestine forms three-sided perimeter around small intestine – Larger diameter than the small intestine – Approximately 5 ft long Functions: – Fluid, ion absorption – Compacts undigestible wastes, solidifies them into feces – Stores feces until defecation 15  3. Large Intestine Human Anatomy Longitudinal muscle forms bundles called teniae coli – Contraction of teniae coli bunch up large intestine into many sacs, collectively called haustra 16  3. Large Intestine Human Anatomy Gross Anatomy and Regions Structures: – Cecum – Ascending colon – Transverse colon – Descending colon – Sigmoid colon – Rectum – Anal canal 17  3. Large Intestine Human Anatomy Cecum Cecum is the first part of large intestine – Sac located in lower right quadrant of abdomen – Vermiform appendix – Ileocecal valve 18  3. Large Intestine Human Anatomy Ascending Colon Ascending colon: right lateral border of abdomen Near inferior border of the liver, it makes a 90˚ turn to left: right colic flexure (hepatic 19 flexure)  3. Large Intestine Human Anatomy Transverse Colon Transverse colon originates at the right colic flexure, approaches the spleen in the upper left abdominal quadrant Makes 90 ˚ turn 20 inferiorly at the  3. Large Intestine Descending, Sigmoid Human Anatomy Colon Descending colon originates at the left colic flexure – Left side of the abdomen – Terminates at sigmoid colon Sigmoid colon has a shape resembles the letter S – Terminates as the 21 rectum  3. Large Intestine Human Anatomy Rectum and Anal Canal Rectum is a muscular tube that readily expands to store accumulated fecal material prior to defecation Anal canal is the last few centimeters of the large intestine – Passes through an opening in the muscles of the pelvic floor – Internal and external anal sphincters relax 22 during defecation  3. Large Intestine Human Anatomy Clinical Applications Appendicitis: Diarrhea: Constipation: 23  3. Large Intestine Human Anatomy Clinical Applications Diverticulosis – development of diverticula (sac-like appendages) along the length of the colon Diverticulitis – inflammation of diverticula Thought to be caused by low fiber diet Treatment: Altered diet, pain medication, surgery 24  4. Accessory Digestive Organs Human Anatomy Accessory digestive organs include: 1. Liver 2. Gall bladder 3. Pancreas 4. Biliary apparatus 25  4. Accessory Digestive Organs Human Anatomy Liver Functions include: – Filters toxins from the blood – Breaks down old RBC’s – Produces bile 26  4. Accessory Digestive Organs Human Anatomy Liver Liver is located in right quadrant of abdomen Composed of 4 incompletely separated lobes: – Right and left lobes – major lobes  Separated by falciform ligament – Caudate lobe and quadrate lobe sometimes considered subdivisions of right lobe 27  4. Accessory Digestive Organs Human Anatomy Liver Vasculature Hepatic portal vein carries nutrient-rich blood from GI tract capillaries, spleen, and pancreas to liver Hepatic artery carries oxygen-rich blood to the liver Hepatic veins 28 empty into inferior  4. Accessory Digestive Organs Human Anatomy Gallbladder Gallbladder arises from inferior surface of the liver Functions to store and concentrate bile – Emulsifying agent for digestion of fats in small intestine 29  4. Accessory Digestive Organs Human Anatomy Biliary Apparatus Biliary apparatus: network of thin ducts that transport bile from liver and gall bladder to duodenum – Cystic duct – from gall bladder – Common hepatic duct – from liver – Common bile duct – junction of cystic and common hepatic 30  4. Accessory Digestive Organs Human Anatomy Pancreas Pancreas has both endocrine and exocrine functions – Endocrine functions: Production and secretion of insulin and glucagon – Exocrine functions: Production of pancreatic juice/enzymes 31  4. Accessory Digestive Organs Human Anatomy Clinical application Jaundice – Yellowing of skin, conjunctiva, and mucous membranes due to deposits of bilirubin (from breakdown of RBC’s) – Bilirubin is toxic to the nervous system, causing neural damage if too much accumulates 32  4. Accessory Digestive Organs Human Anatomy Clinical application 3 types of jaundice: – Obstructive jaundice – bile ducts are obstructed (by gall stones) so bile cannot drain out of the liver and overflows into the blood – Hemolytic jaundice – from RBC’s being broken down in large quantities – Physiologic jaundice – immature liver cannot excrete the bilirubin as quickly as it is being formed.  UV light converts bilirubin in the skin to 33 harmless molecules  Learning Outcomes Human Anatomy You Should Be Able To … 1. trace the pathway food travels as it enters the oral cavity and leaves the anus 2. describe the location of the stomach, small intestine, and large intestine relative to other body structures 3. list the general functions of the stomach 4. compare and contrast mechanical digestion and chemical digestion of food particles 5. explain the specialization of the muscularis tunic of the stomach compared with the rest of the GI tract 6. identify and describe the gross anatomy of the 34 stomach presented within this lecture  Learning Outcomes Human Anatomy You Should Be Able To … 7. identify the specific segments of the small intestine: duodenum, jejunum, ileum 8. describe the specializations of the small intestine’s tunics (circular folds (plicae circulares), villi, microvilli) compared with the rest of the GI tract 9. identify the specific segments and flexures of the large intestine 10.list the accessory digestive organs and describe their locations relative to other body structures 11.identify and describe the 4 lobes of the liver and the falciform ligament 35 12.describe the unique vasculature of the liver  Learning Outcomes Human Anatomy You Should Be Able To … 13.identify the general function of the gallbladder 14.identify the functions of the pancreas, differentiating endocrine and exocrine functions and the pancreatic cells associated with each 15.describe the structures and function of the biliary apparatus; trace the path of bile through the biliary apparatus 16.explain the importance of sphincter muscles along the GI tract and identify the regions separated by the following sphincter structures/valves: superior esophageal sphincter, cardiac sphincter, pyloric sphincter, iliocecal valve, 36