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Download Ch. 23 Digestion
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Digestive System Chapter 23 QUIZ PICTURE Absorption of Nutrients The passage of digested molecules of food, water, minerals, and vitamins from the lumen of the GI tract into the mucosal cells by active or passive transport into blood or lymph Upper esophageal Tonic contractions are shown by sphincters; most are smooth muscle, some are skeletal. Lower esophageal Oddi Pyloric Ileocecal Internal anal External anal Fig. 22-9, pg: 691 Slide 11 Quiz Picture Homeostatic Imbalance Peritonitis Inflammation of peritoneum Puncture wound of abdomen Salivary Glands Parotid Glands- located anterior to ear Sublingual Glands- located in floor of mouth Submandibular Glands- located under jaw Function: produce saliva- mostly water, salivary amylase, antimicrobials Saliva moistens food, starts starch breakdown, dissolves food chemicals for taste Homeostatic Imbalance Mumps Inflammation of parotid gland Passed by saliva In males can lead to testes infection Homeostatic Imbalance Halitosis Inhibited saliva production No saliva=no washing of mouth Cavities, anaerobic bacteria make hydrgen sulfide, methyl mercaptan and cadaverine which smell like rotten eggs, feces and corpes Mouth, Pharynx, Esophagus Mouth- place where mechanical breakdown of food begins with chewing Pharynx- has 2 skeletal muscle layers whose contractions propel food into esophagus Esophagus- long tube to stomach posterior to trachea; conduit for food; peristalsis (alternate waves of contraction/relaxation of muscle that propels food to stomach) Swallowing uses contraction of tongue, upper pharynx constrictors, and laryngeal muscles. Is voluntarily initiated, but medullary swallowing center coordinates muscles. Fig. 22-10, pg: 692 Slide 29 Stomach Chemical breakdown of proteins begins here food becomes chyme upper end to esophagus is cardiac portion; fundus is top middle is body and end is pylorus Quiz Picture Stomach Histology Epithelium- simple columnar 1. Gastric pits- primarily goblet cells 2. Gastric glands- below gastric pits Neck Cells- produce acidic mucous Parietal Cells- secrete HCl and Intrinsic Factor Chief Cells- produce pepsinogen to digest protein Enteroendocrine Cells- release hormones; gastrin, histamine, endorphins, serotonin, cholecystekinin, somatostatin Stomach Mucosal Barrier Bicarbonate rich mucous on stomach wall Epithelial cells connected by tight junctions Gastric Gland cells impermeable to HCl Damaged epithelial cells replaced quickly; lining shed every 3-6 days Functions of Stomach Protein digestion- only enzymatic type that occurs here Secretion of IF- essential for intestinal absorption of B12; B12 deficiency causes Pernicious Anemia Control of Gastric Secretion Neural Control- CN X (Vagus)- stimulation causes increase of all gland secretion Gut Brain local reflexes Hormonal Control- Gastrin- stimulates secretion of enzymes and HCl and hormones of small intestine Homeostatic Imbalances Gastroesophageal reflux disease (GERD) Heartburn Stomach acid travels back up esophagus Hiatal hernia Damage to esophagus if prolonged Homeostatic Imbalances Gastric Ulcers Erosion of stomach wall Breach mucosal barrier Stress, medicines, bacteria (helicobacter pylori Small Intestine Three Sections 1. Duodenum 2. Jejunem 3. Ilium Peritoneum Serous membrane- double membrane Mesentery is a sheet of 2 serous membranes fused back to back; holds part of the GI tract together; extends from body wall to digestive organs; provides route for blood/lymphatic vessels and nerves Quiz Picture Quiz Picture Sm Int 2) villi fingerlike projections on mucosa Surface cells for absorption Contains capillary bed and lacteal (lymph capillary) Made of cells 3) microvilli tiny plasma membrane projections of absorptive cells of mucosa Fuzzy appearance called brush border Brush border enzymes located here On a single cell Histology of Small Intestine Epithelium- simple columnar with goblet cells; enteroendocrine cells that secrete intestinal Gastrin, Secretin, Cholecystikinin (CCK), GIP, VIP Intestinal Pits located above intestinal glands that are called Crypts of Leiberkuhn- secrete intestinal juice, lysozyme Brunner’s Glands- duodenum only; alkaline mucous Liver Digestive function- produce bile for transport to small intestine Other functions include storage of Vit. A, D, E, and K and production of proteins including albumin, clotting factors and production of cholesterol Gross anatomy of Liver About 3 pounds Divided into right and left lobes Bile produced in the liver leaves through the common hepatic duct which joins the Cystic Duct of the gall bladder to form the Common Bile Duct Under R costal margin from 5th to 10th rib Histology of Liver Functional Unit- Liver Lobule consisting of hepatocytes (liver cells) and vessels; hexagonal with each corner being a portal triad (artery, vein, bile duct); center is the central vein Sinusoids- leaky capillaries between liver cells; also Kupffer cells (macrophages Bile Canaliculi- canals between liver cells that take bile to bile ducts Homeostatic Imbalances Cirrhosis Chronic inflammation of the liver Obstructed blood flow through liver, portal hypertension Chronic alcoholism or hepatitis Bile Bile Salts- cholesterol derivatives; emulsify fats Phospholipids Fats Electrolytes Bile Pigments Gall Bladder Green muscular sac; about 4 inches long; stores bile until needed during digestion Major Stimulus for releaseCholecystekinin (CCK) Pancreas Retroperitoneal organ under stomach Endocrine and exocrine functions Digestive function is exocrine in nature; secretes pancreatic juice containing water, bicarbonate ions and enzymes Neural and hormonal control Secretin- release bicarb; CCK- release enzymes – pancreatic juice - on list Large Intestine About 4-5 feet long Function: absorb water from undigested food products and deliver waste to be eliminated Gross Anatomy Teniae Coli- Longitudinal muscle of muscularis is tightened up to form a line through the outside of the LI Haustra- pocket-like sacs formed due to tone of teniae Epiploic Appendages- fat filled pouches of visceral peritoneum on surface Quiz Picture Microscopic Anatomy Simple columnar Epithelium up to anal canal which is stratified squamous epithelium Deep crypts containing an enormous number of goblet cells; no digestive enzymes Homeostatic Imbalances Appendicitis Infection of appendix Blocked by feces, swells and cut of venous flow so appendix dies adolescence Homeostatic Imbalances Diarrhea/Constipation Watery stools/Hard stools Food rushed through large intestine Irritation of colon Bad diet Chemical Digestion/Absorption Chemical Digestion/Absorption Carbohydrates broken down into sugars Starts with salivary amylase in mouth and progresses to pancreatic amylase in small intestine and brush border enzymes in the microvilli Chemical Digestion/Absorption Proteins starts in stomach when pepsinogen is converted to pepsin by HCl environment of stomach Brush border enzymes and pancreatic enzymes (Trypsin/Chymotrypsin) digest proteins all the way to amino acids Chemical Digestion/Absorption Nucleic Acids broken down by pancreatic nucleases and by brush border enzymes in the small intestine Chemical Digestion/Absorption Lipids Small intestine is the only place that this occurs needs to be emulsified by bile into fat droplets some lipases secreted by pancreas as emulsifications get smaller they become micelles Chemical Digestion/Absorption Vitamins- A, D, E, and K are fat soluble and follow the absorption of fat; water soluble vitamins are absorbed by diffusion; B12 can only be absorbed if attached to IF; absorbed by endocytosis Electrolytes- absorbed by active and passive transport along entire small intestine Chemical Digestion/Absorption Water- directly coupled to solute intake; water chases particles and is absorbed by osmosis along the intestines Carbohydrates- facilitated diffusion and secondary active transport Proteins- coupled to the active transport of sodium ion Lipids- micelles by simple diffusion (into Lymph)
