Fundamentals of Anatomy & Physiology: Chapter 24 - The Digestive System

Chapter 24 The Digestive System Lecture Presentation by Lee Ann Frederick University of Texas at Arlington © 2015 P...

Chapter 24 The Digestive System Lecture Presentation by Lee Ann Frederick University of Texas at Arlington © 2015 Pearson Education, Inc.  34 34:. Major Organs of the Digestive Tract Oral Cavity (Mouth) Ingestion, mechanical processing with accessory organs (teeth and tongue), moistening, mixing with salivary secretions Pharynx Muscular propulsion of materials into the esophagus Esophagus Transport of materials to the stomach Stomach Chemical breakdown of materials by acid and enzymes; mechanical processing through muscular contractions Small Intestine Enzymatic digestion and absorption of water, organic substrates, vitamins, and ions Large Intestine Dehydration and compaction of indigestible materials in preparation for elimination Anus © 2015 Pearson Education, Inc.  Accessory Organs of the Digestive System Teeth Mechanical processing by chewing (mastication) Tongue Assists mechanical processing with teeth, sensory analysis Salivary Glands Secretion of lubricating fluid containing enzymes that break down carbohydrates Liver Secretion of bile (important for lipid digestion), storage of nutrients, many other vital functions Gallbladder Storage and concentration of bile Endocrine > directly Pancreas - secrete into Exocrine cells secrete buffers blood stream and digestive enzymes; Endocrine cells secrete hormones Exocrine > - through a. duct © 2015 Pearson Education, Inc.  The Digestive Tract Six Functions of the Digestive System 1. Ingestion 2. Mechanical processing physical 3. Digestion 4. Secretion 5. Absorption 6. Excretion © 2015 Pearson Education, Inc. 4  The Digestive Tract Ingestion Occurs when materials enter digestive tract via the mouth Mechanical Processing = Physical Digestion Crushing and shearing Makes materials easier to propel along digestive tract Digestion The chemical breakdown of food into small organic fragments for absorption by digestive epithelium © 2015 Pearson Education, Inc. 5  The Digestive Tract Secretion Release of water, acids, enzymes, buffers, and salts By epithelium of digestive tract and glandular organs Absorption Movement of organic substrates, electrolytes, vitamins, and water across digestive epithelium Into interstitial fluid of digestive tract Excretion Removal of waste products from body fluids Process called defecation removes feces https://www.youtube.com/watch?v=zr4onA2k_LY © 2015 Pearson Education, Inc. 6  Digestive Tract Layers Histological Organization of the Digestive Tract Four major layers of the digestive tract 1. Mucosa innermost layer 2. Submucosa muscle layer 3. Muscularis externa 4. Serosa mucosa layer submucosa protective muscularis externa serosar © 2015 Pearson Education, Inc. 7  Mesenteric intestine Small - artery and vein Circular > - stimulate/promote Mesentery folds absorption Producing mucus and other secretions Mucosa Submucosa Glands and blood vessels can be found Muscularis externa Thicker smooth muscle layer Serosa (visceral peritoneum) © 2015 Pearson Education, Inc. Outermost layer for protection Figure 24-3 The Structure of the Digestive Tract (Part 2 of 2). Circular fold Mucosal epithelium Mucosa Lamina propria Villi Mucosal glands Submucosal gland Muscularis mucosae Lymphatic vessel Mucosa Artery and vein Submucosa Submucosal plexus Muscularis Circular muscle externa layer Serosa Myenteric plexus (visceral peritoneum) Longitudinal muscle layer © 2015 Pearson Education, Inc.  Digestive Tract Layers whole respiratory tract composed by these 4 layers. The Mucosa Only for small intestine we can found that the innermost layer is folded Is the inner lining of digestive tract Folded to increase surface area for absorption Is a mucous membrane consisting of: F Epithelium, digestive moistened by glandular secretions Mucus secreting membrane Enteroendocrine cells secrete hormones that coordinate activities of the digestive tract and accessory glands Lamina propria of areolar tissue © 2015 Pearson Education, Inc. 10  Digestive Tract Layers The Submucosa Is a layer of dense irregular connective tissue Surrounds muscularis mucosae Has large blood vessels and lymphatic vessels May contain exocrine glands Secrete buffers and enzymes into digestive tract © 2015 Pearson Education, Inc. 11  Digestive Tract Layers The Muscularis Externa Is dominated by smooth muscle cells Involved in: churning> peristalsis - Mechanical processing Movement of materials along digestive tract squeezing them section by section The Serosa Serous membrane covering muscularis externa Outer binding and protective layer © 2015 Pearson Education, Inc. 12  Movement of Digestive Materials The Movement of Digestive Materials muscularis externa By muscular layers of digestive tracte Consist of visceral smooth muscle tissue along digestive tract trigger muscular contraction Cells undergo spontaneous depolarization Triggering wave of contraction through entire muscular sheet Peristalsis Consists of waves of muscular contractions Moves a bolus along the length of the digestive tract © 2015 Pearson Education, Inc. 13  Initial State Longitudinal muscle Circular muscle From To mouth anus 1 Contraction of circular muscles behind bolus Contraction 2 Contraction of longitudinal muscles ahead of bolus Contraction Contraction 3 Contraction in circular muscle layer forces bolus forward w u wave © 2015 Pearson Education, Inc.  Digestive Tract Regulation control digestive tract Three parts to Control of Digestive Functions Local Factors Prostaglandins, histamine, and other chemicals released into interstitial fluid May affect adjacent cells within small segment of digestive tract Coordinate response to changing conditions For example, variations in local pH, chemical, or physical stimuli Affect only a portion of tract © 2015 Pearson Education, Inc. 15  Digestive Tract Regulation Control of Digestive Functions Neural Mechanisms Control Movement of materials along digestive tract Secretory functions Motor neurons Control smooth muscle contraction and glandular secretion Located in myenteric plexus © 2015 Pearson Education, Inc. 16  Digestive Tract Regulation Neural Mechanisms only operate when local factor present Short reflexes Are responsible for local reflexes Control small segments of digestive tract Operate entirely outside of CNS control X going to CNS. Long reflexes Higher level control of digestive and glandular activities Control large-scale peristaltic waves Involve interneurons and motor neurons in CNS May involve parasympathetic motor fibers that synapse in the myenteric plexus © 2015 Pearson Education, Inc. 17  Digestive Tract Regulation Hormonal Mechanisms Most aspects of digestive function Are produced by enteroendocrine cells in digestive tract hormones Reach target organs after distribution in bloodstream © 2015 Pearson Education, Inc. 18  Because the bolus will move away and stop triggering the local factors so brain will help stimulting 2 Neural Control Mechanisms E The movement of materials along the digestive tract, as well as many secretory functions, is primarily controlled by local factors. CNS Short reflexes are triggered by chemoreceptors or stretch receptors in the walls of the Long digestive tract; the controlling neurons are located in the myenteric plexus (myenteric reflex reflexes). subrosa Myenteric Muscular Long reflexes involving interneurons and motor neurons in the CNS provide a higher level of control over digestive and plexus layer glandular activities, generally controlling large-scale peristalsis that ↑ externa Short reflex - Peristalsis and moves materials from one region of the digestive tract to another. Long reflexes may involve parasympathetic motor fibers - Stretch receptors, segmentation in the glossopharyngeal (N IX), vagus muscularis chemoreceptors PO2 , PCOr pH ,. movements (N X), or pelvic nerves that synapse in the myenteric plexus. submucosa mucosa L Buffers, acids, Secretory cells 3 enzymes released Hormonal Control Mechanisms [ 1 Local Factors Local factors are the primary stimulus The digestive tract produces for digestion. V hormones that affect almost e g. Carried by. Coordinate the responses to changes every aspect of digestion. These Enteroendocrine bloodstream in the pH of the contents of the lumen, fluid hormones are peptides protein.. cells more produced by enteroendocrine getting ( physical distortion& of the wall of the digestive tract, or the presence of cells, endocrine cells in the thingsTestine chemicals - either specific nutrients or epithelium of the digestive Hormones chemical messengers released by tract. released cells of the mucosa. ↳ then trigger nervous © 2015 Pearson Education, Inc. hormonal system by soing reflux [short , long]  tract ① TAIX) digestive. > - chemical + affect pot value/osmotic pressure. > - change Th local factors. ↓ stomach stimulate stretch receptors on wall chemoreceptors [change in pH] ↓ signals to both CNS [long reflux] they ad # [Short myenteric plexus peristalsis & E reflnx] segmentation movements. # 7 secretory cells 3 Local factors secrate enzymes/acids / buffers. ~ enter endocrine cells ↓ hormones into bloodstream - Mixing of food instead of food forward squeezing - peristalsis bolns - keeping pushing  The Oral Cavity The Saliva Moistening and lubricating materials in the mouth Dissolving chemicals that stimulate taste buds and provide sensory information Initiating digestion of complex carbohydrates by the enzyme salivary amylase (ptyalin or alpha- amylase) The Teeth Chew (masticate) food © 2015 Pearson Education, Inc. 20  The Oral Cavity and Esophagus The Pharynx (Throat) Passageway for solid food, liquids, and air Food passes through the pharynx to the esophagus The Esophagus A hollow muscular tube Conveys solid food and liquids to the stomach Swallowing deglntition Also called deglutition Can be initiated voluntarily Proceeds automatically © 2015 Pearson Education, Inc. 21  The Stomach Major Functions of the Stomach 1. Storage of ingested food 2. Mechanical breakdown of ingested food 3. Disruption of chemical bonds in food material by acid and enzymes 4. Production of intrinsic factor, a glycoprotein required for absorption of vitamin B12 in small intestine > - only digest protein - > churning important for making RBC annemia if > - get 22 © 2015 Pearson Education, Inc. deficient  Rugge -↑ surface area for absorption 2. Fundus (villi) Esophagus Fundus 3. Body 4. Pylorus Cardia Longitudinal muscle layer Left gastroepiploic Circular vessels muscle layer Body Pyloric Lesser curvature sphincter (medial surface) Oblique muscle layer overlying mucosa Duodenum * XI surface area Rugae Vfor mechanical X folding processing Greater curvature (lateral surface) Pyloric canal ↳49 Pylorus Pyloric antrum The structure of the stomach wall © 2015 Pearson Education, Inc.  The Stomach Gastric Glands In fundus and body of stomach Extend deep into underlying lamina propria Each gastric pit communicates with several gastric glands Parietal cells Chief cells © 2015 Pearson Education, Inc. 24  stomach wall mucosa > - gastric pit Copen to gastric gland) > mucous epithelium e preventstoma damaged - > · secrete machs - by. sice Layers of the Stomach Wall Mucosa gap Gastric pit (opening to gastric gland) Mucous epithelium Protect stomach HCl from. Lamina propria Muscularis mucosae Submucosa Artery and Muscularis externa vein Oblique muscle Circular muscle Lymphatic vessel Longitudinal muscle Myenteric Serosa plexus © 2015 Pearson Education, Inc.  Lamina propria Gastric Mucous pit cells Neck Hol factor intristc tamin Cells of ↑ Gastric 1 secrete or auction of to Glands for Birt Biz that Parietal RBC vitamin O a cells lack sythesisnaemic cannot RBC - Gastric much gland G cell 8 - gastrin productiona stimulate of parietal Chief cells ③ chief cells. > - secrete pepsinogen. Smooth ↳ muscle inactive. cell > - can be converted by. Gastric gland HCl into pepsin © 2015 Pearson Education, Inc. (active). 3 Major types of cells in stomach wall. Parietal deficiency of VBI O cells - RBC > - X Sythesis secrete intrisic factor to absorb MinBla > - anemia > - polypeptide. > - Secrete by parietal cells of stomach. · Secrete HCl. G well ② G cells [master cell &] stimulate ↓ ↓ > secrete gastrin chief parietal - > - stimulate prod of chief & cell selli parietal cells ⑤ Chief cells Linactive enzymes > - secrete pepsinger into Hel > - convert pepsin by Lactive) ~ digest protein into. by pepsin. peptides 4 D cells > - Secrete Somatostatin > - inhibit the secretion of gastrin by G-cells which inhibit prod of chief & parietal cells.  The Stomach absorbing Bir Parietal Cells For tamin Secrete (intrinsic factorS and hydrochloric acid (HCl) will protein digestive if activated > Stomach Chief Cells - TT enzyme be digested. Secrete pepsinogen (inactive proenzyme) Pepsinogen is converted by HCl in the gastric lumen to pepsin (active proteolytic enzyme) HCl work best In low pH > pepsin, gepsinogen. - Pyloric Glands Located in the pylorus - produce mucous secretion Scattered with enteroendocrine cells Facilitating production of chief and G cells produce gastrin parietal cells D cells release somatostatin, a hormone that inhibits release of gastrin © 2015 Pearson Education, Inc. 27  The Stomach Digestion and Absorption in the Stomach Stomach performs preliminary digestion of proteins by pepsin primarily digest it Some digestion of carbohydrates (by salivary amylase) Lipids (by lingual lipase) Stomach. peptides pepsin. by protein > - > - © 2015 Pearson Education, Inc. 28  The Stomach absorb accidentally > - alcohol > - a spirin Digestion and Absorption in the Stomach Stomach contents Become more fluid pH approaches 2.0 Pepsin activity increases Protein disassembly begins Although digestion occurs in the stomach, nutrients are not absorbed there © 2015 Pearson Education, Inc. 29  of Hal b Production KEY 1 Diffusion Hydrogen ions (H+) are generated *D inside a parietal cell as the enzyme Parietal cell Carrier-mediated carbonic anhydrase converts CO2 transport and H2O to carbonic acid (H2CO3), CO2 + H2O ATP which then dissociates. require Active transport Carbonic Countertransport anhydrase 2 exchange 4 ? from a > more - A countertransport mechanism The hydrogen ions are lower cone to ejects the bicarbonate ions into H2CO3 actively transported into the a higher conc the interstitial fluid and imports lumen of the gastric gland. chloride ions into the cell. X called shift. chlorida 3 HCO3− HCO3− + H+ H+ Hal Interstitial fluid Cl− Cl− Cl− negative 3 a a left. Alkaline is tide The chloride ions then diffuse charge across the cell and exit through Lumen of open chloride channels into the gastric Enters lumen of the gastric gland. gland bloodstream Summary video © 2015 Pearson Education, Inc. Hee production in parietal cells. carbonic ① Co2 + tro > HL LOS anhydrase - * H2 Woz > H + HCOs I get He ② Counter transport mechanism. > - Hros is pumped out. > - el- is injected ⑤ 25 then diffuse out of the cell through the chloride channel. ① H + Tons are transported actively out of the cells actively. + H + Ce => Hel.  Regulation of Gastric Activity Regulation of Gastric Activity Production of acid and enzymes by the gastric mucosa can be: Controlled by the CNS Regulated by short reflexes of ENS Regulated by hormones of digestive tract Three phases of gastric control 1. Cephalic phase ① 2. Gastric phase ② 3. Intestinal phase ③ © 2015 Pearson Education, Inc. 31  1 CEPHALIC PHASE > - send signals to the stomach mucous > - stimulate Sight, smell, taste, or thoughts of food cells , chief cells , parietal cells to Central nervous system secrete Vagus nerve (N X) macns , pepsinogen & Hal respectively , Submucosal plexus sensation CNS sight > - > - Mucous Mucus cells submucosal > - plexus. 7 Chief Pepsinogen means an cells Parietal HCl Gastrin. 7 cells G cells G cell. KEY Stimulation Stimulation © 2015 Pearson Education, Inc. ① Cephalic phrase stimulated thought by our smell. > - stimulate CNS , > - signals r sent through vagus nerve > - stimulate stomach & > - stimulate Omucous cells O parietal cells cells. Chief ↓ ↓ ↓ Secrete Hal+ Secrete pepsinogen , Secrete muchs intoisic factor ① G wells ↓ which stimulate to secrete gastrin production of chief & parietal cells ,  After a big 2 ① Stomach wall is stretched GASTRIC PHASE meal I ② Local factors stimulate stretch receptor 3. The stomach wall distort FI Neural Response 4.pH is changes 5. Detected by chemoreceptors 1. Receive signals -> send signal as short reflux to the stomach wall (submucosal and myenteric plexuses 2. -> further ask the cell there to secrete more enzymes and secretion AES F 3. Digestion of protein begins Submucosal and Distension Stretch 4. The digested peptide is also a stimulus receptors myenteric plexuses for G cells Elevated pH Chemoreceptors carried by Mucous Mucus bloodstream cells Chief Pepsinogen cells Mixing Parietal waves Gastrin HCl cells G cells Partly digested KEY peptides Stimulation Stimulation © 2015 Pearson Education, Inc. ② phrase > - really after a big meal in stimulate 3 (Stretch distension > - the long > - the stomach wall got stretched. receptor > - PH is altered/chemicals. 3 stimulate (chemoreceptor. both scimulate the submucosal & pleans. myenteric > - stimulate churning action of stomach cradges M > - Chief all r > - parietal cell > - G well > - gastrin - > mucous cell part a  We pass the food the small intestine 3 INTESTINAL PHASE Stretch of small intestine Neural Responses is stimulated by local factors and they will send inhibitory signals to stomach wall Enterogastric Myenteric reflex plexus * carried by bloodstream Chief cells > - X pepsinogen Parietal > X Hal. Duodenal cells - stretch and Peristalsis chemoreceptors food bolus ↳ CCK Presence of lipids and chyme GIP carbohydrates KEY Inhibition Secretin Decreased pH © 2015 Pearson Education, Inc. Last - the third phrase. When food is passing from stomach to small intestine. > - They need to inhibit the digestion action in the stomach. How they know & how to inhibit ?? of 3 & Presere carbohydrates & lipids Stimulus. ② I beaut of Hee] Decreased pH c ①I② Secretin inhibit chief cells + parietal cells + Peristalsis. Stimulus 3 : duodenal stretch receptor + chemoreceptor. # inhibit myenteric plexus.  The Small Intestine The Small Intestine Plays key role in digestion and absorption of nutrients 90 percent of nutrient absorption occurs in the small intestine © 2015 Pearson Education, Inc. 35  Segments of the Small Intestine Duodenum Jejunum Ileum Large intestine Rectum The positions of the duodenum, jejunum, and ileum in the abdominopelvic cavity © 2015 Pearson Education, Inc.  The Small Intestine The Duodenum The segment of small intestine closest to stomach “Mixing bowl” that receives chyme from stomach and digestive secretions from pancreas and liver Functions of the duodenum: To receive chyme from stomach To neutralize acids before they can damage the absorptive surfaces of the small intestine X absorption yet. © 2015 Pearson Education, Inc. 37  The Small Intestine The Jejunum Is the middle segment of small intestine Is the location of most: Chemical digestion Nutrient absorption The Ileum The final segment of small intestine Ends at the ileocecal valve A sphincter that controls flow of material from the ileum into the cecum of the large intestine © 2015 Pearson Education, Inc. 38  The Small Intestine brush border ↓ enzymes. Intestinal A Glands my * Brush border enzymes Integral membrane proteins ↳ On surfaces of intestinal microvilli Break down materials in contact with brush border > - for starch digestion © 2015 Pearson Education, Inc. 39  brush boarder enzyme. The Small Intestine I Meth a type - enteropeptidase. > enteropeptidase -. used to ↓ activate pancreatic Proenzyme Intestinal Glands 11 trypsinogen > - trypsin. inactivate enzyme Enteropeptidase A brush border enzyme M trypSrated Activates pancreatic proenzyme trypsinogen Enteroendocrine cells Produce intestinal hormones such as gastrin, cholecystokinin, and secretin small In - ↓ Summary video cu intestive ↓ to inhibit used the stomachs © 2015 Pearson Education, Inc. 40  Columnar epithelial cell Mucous cell Lacteal Nerve Capillary network Lamina propria Lymphatic vessel Smooth muscle cell Arteriole Venule Internal structures in a single villus, showing the capillary and lymphatic supplies © 2015 Pearson Education, Inc.  The Pancreas accessory organ Histological Organization Pancreatic acini Are lined with simple cuboidal epithelium Acinar cells and epithelial cells of duct system secrete pancreatic juice – exocrine function Pancreatic islets Endocrine tissues of pancreas Secrete insulin and glucagon into bloodstream © 2015 Pearson Education, Inc. 42  Pancreas function can perform both exocrine & endocrine pancreatic acint > exocrine (enzymes (pancreatic juice) E - tissue islets. Pancreatic > - endocrine (hormones ductless) e.. insulin g & glucagon.  Pancreatic duct Connective tissue septum ↑ 444 produce Exocrine cells in pancreatic acini sortant for im/ enzyme estion Endocrine cells in d+ 9 pancreatic islet into Diagram of the cellular go organization of the pancreas. enzymesintestine Common Pancreatic Lobules small bile duct duct Tail of I pancreas Accessory Body of pancreatic pancreas ↓ ↓ duct & 44 Head of Duodenal ↑ pancreas papilla Duodenum The gross anatomy of the pancreas. The head of the pancreas is tucked in to a C-shaped curve of the duodenum that begins at the pylorus of the stomach. © 2015 Pearson Education, Inc.  X # To D The Pancreas panareus enzyme. nucleases > - alpha amylase > - proteases & Pancreatic Alpha-Amylase > - Lipase > - pepticlases. Carbohydrase that breaks down starches Pancreatic Lipase Breaks down complex lipids and releases products (e.g. fatty acids) that are easily absorbed Nucleases Break down nucleic acids Proteolytic Enzymes [produce in inactive form) Proteases break large protein complexes Peptidases break small peptides into amino acids Secreted as inactive proenzymes Activated after reaching small intestine © 2015 Pearson Education, Inc. 44  The Liver Performs essential metabolic and synthetic functions Histological Organization of the Liver lobules Liver lobules , The basic functional units of the liver The Physiology of the Liver 1. Metabolic regulation 2. Hematological regulation 3. Bile production © 2015 Pearson Education, Inc. 45  hepatocytes 1 mm Interlobular Bile Branch of Bile septum duct hepatic portal vein Portal area ductules A diagrammatic view of liver structure, showing relationships among lobules © 2015 Pearson Education, Inc.  The Liver Metabolic Regulation The liver regulates: 1. Composition of circulating blood 2. Nutrient metabolism 3. Waste product removal 4. Nutrient storage 5. Drug inactivation © 2015 Pearson Education, Inc. 47  The Liver The Functions of Bile Dietary lipids are not water soluble Mechanical processing in stomach creates large why bile salt need to drops containing lipids es exit ! Pancreatic lipase is not lipid soluble Interacts only at surface of lipid droplet Bile salts break droplets apart (emulsification) Increases surface area exposed to enzymatic attack Creates tiny emulsion droplets coated with bile salts © 2015 Pearson Education, Inc. 48  The Gallbladder The Gallbladder can contract relax Is a hollow, pear-shaped, muscular sac Stores and concentrates bile prior to excretion into small intestine Regions of the Gallbladder 1. Fundus 2. Body 3. Neck © 2015 Pearson Education, Inc. 49  Round ligament Left hepatic duct Right hepatic duct Left hepatic artery Cystic duct Common hepatic Gallbladder duct Fundus Body Neck Common bile duct Hepatic portal vein Common hepatic artery Hepatopancreatic sphincer. Right gastric artery A view of the inferior surface of the liver, showing the position of the gallbladder and ducts that transport bile from the liver to · the gallbladder and duodenum. © 2015 Pearson Education, Inc.  Functions of The Gallbladder CK : ① contraction of gallbladder ② release of pancreativ enzymes. Physiology of the Gallbladder Stores bile Releases bile into duodenum, but only under stimulation of intestinal hormone cholecystokinin (CCK) CCK Hepatopancreatic sphincter remains closed Bile exiting liver in common hepatic duct cannot flow through common bile duct into duodenum Bile enters cystic duct and is stored in gallbladder © 2015 Pearson Education, Inc. 51 danmer duodenum common be duct closed normally beat of the hepatopancreatic sphincter is closed. > under - influence of CC gall bladder contract > - bile is squeezed into duodenum.  1 The liver secretes bile continuously— 2 about 1 Bile becomes more liter per day. concentrated the longer it remains in the gallbladder. Liver both release of trigger from Duodenum eT & secretion 3 bile pancreas CCK The release of CCK by the 4 duodenum triggers① dilation In the lumen of of the hepatopancreatic the digestive tract, Lipid sphincter(( and contraction ② bile salts break of the gallbladder.( This ejects droplet the lipid droplets bile into the duodenum apart by emulsification. through the duodenal ampulla. Physiology of the gallbladder. © 2015 Pearson Education, Inc.  Coordination of Secretion and Absorption Neural and Hormonal Mechanisms Coordinate activities of digestive glands Regulatory mechanisms center around duodenum Where acids are neutralized and enzymes added © 2015 Pearson Education, Inc. 53  Coordination of Secretion and Absorption Neural Mechanisms of the CNS Prepare digestive tract for activity (parasympathetic innervation) Inhibit gastrointestinal activity (sympathetic innervation) Coordinate movement of materials along digestive tract (the enterogastric, gastroenteric, and gastroileal reflexes) Motor neuron synapses in digestive tract release neurotransmitters © 2015 Pearson Education, Inc. 54  Coordination of Secretion and Absorption Intestinal Hormones Intestinal tract secretes peptide hormones with multiple effects In several regions of digestive tract In accessory glandular organs © 2015 Pearson Education, Inc. 55  Coordination of Secretion and Absorption Hormones of Duodenal Enteroendocrine Cells Coordinate digestive functions production stimulate of chief & parietal cell. Gastrin > - Secretin > inhibit - & peristalsis 11 Gastric inhibitory peptide (GIP) & contraction of gall bladder Cholecystokinin (CCK) secretion of digestive enzyme pancreatio Join Vasoactive intestinal peptide (VIP) in into duodenu. Enterocrinin © 2015 Pearson Education, Inc. 56  Coordination of Secretion and Absorption Gastrin Is secreted by (G cells· in duodenum When exposed to incompletely digested proteins Promotes increased stomach motility Stimulates acids and enzyme production Hel pepsinogen. Secretin Is released when chyme arrives in duodenum Increases secretion of bile and buffers by liver and pancreas neutralize acid from stomach - © 2015 Pearson Education, Inc. 57  Coordination of Secretion and Absorption Gastric Inhibitory Peptide (GIP) Is secreted when fats and carbohydrates enter small intestine Cholecystokinin (CCK) Is secreted in duodenum When chyme contains lipids and partially digested proteins Accelerates pancreatic production and secretion of digestive enzymes Relaxes hepatopancreatic sphincter and contract gallbladder Ejecting bile and pancreatic juice into duodenum © 2015 Pearson Education, Inc. 58  Coordination of Secretion and Absorption Vasoactive Intestinal Peptide (VIP) Stimulates secretion of intestinal glands Dilates regional capillaries Inhibits acid production in stomach Enterocrinin Is released when chyme enters small intestine Stimulates mucin production by submucosal breamtype glands of duodenum b of much's for for muchs © 2015 Pearson Education, Inc. 59  When leaves stomach & chyme the enter the duodenum > - GIP , ock , Secretin. > - enterocriain > - secte mucin which break down muchs ,  Ingested food Hormone Action Food in partly-digested stomach protein Acid production by parietal cells KEY stimulates inhibits Gastrin Stimulation of gastric motility; mixing waves increase in intensity Release of insulin GIP from pancreas Release of pancreatic enzymes and buffers Chyme in duodenum Secretin and CCK Bile secretion and ejection of bile from gallbladder facilitates Dilation of intestinal VIP capillaries facilitates NUTRIENT Material Nutrient absorption UTILIZATION arrives in BY ALL TISSUES jejunum © 2015 Pearson Education, Inc.  The Large Intestine Four Regions of the Colon 1. Ascending colon ↑ 2. Transverse colon 3. Descending colon 4. Sigmoid colon Functions of the Large Intestine Reabsorption of water Compaction of intestinal contents into feces Absorption of important vitamins produced by bacteria Vitamin K. E coli Storage of fecal material prior to defecation © 2015 Pearson Education, Inc. 61  Aorta Splenic vein Hepatic portal vein Superior mesenteric artery Right colic Superior Inferior mesenteric vein (hepatic) mesenteric vein flexure Inferior vena cava Left colic (splenic) flexure Greater omentum (cut) Transverse colon Descending colon Left colic vein Middle colic artery and vein Inferior Right colic mesenteric artery and vein artery Left colic artery Ascending colon Haustra Omental appendices Intestinal arteries and veins Rectal Ileocecal valve artery Sigmoid arteries Cecum and veins Appendix Teniae coli Sigmoid flexure a Sigmoid colon The gross anatomy and regions of the large intestine © 2015 Pearson Education, Inc.  The Large Intestine The Rectum Forms last part of digestive tract Is an expandable organ for temporary storage of feces Movement of fecal material into rectum triggers urge to defecate The Anal Canal Is the last portion of the rectum © 2015 Pearson Education, Inc. 63  The Large Intestine Absorption in the Large Intestine Reabsorption of water Reabsorption of bile salts In the cecum Transported in blood to liver Absorption of vitamins K, biotin and Vitamin B5 (pantothenic acid) produced by bacteria Absorption of organic wastes © 2015 Pearson Education, Inc. 64  Digestion The Processing and Absorption of Nutrients Breaks down physical structure of food Disassembles component molecules Molecules released into bloodstream are: Absorbed by cells Broken down to provide energy for ATP synthesis Or used to synthesize carbohydrates, proteins, and lipids © 2015 Pearson Education, Inc. 65  Digestion Digestive Enzymes Break molecular bonds in large organic molecules Carbohydrates, proteins, lipids, and nucleic acids Are divided into classes by targets Carbohydrases break bonds between simple sugars Proteases break bonds between amino acids Lipases separate fatty acids from glycerides © 2015 Pearson Education, Inc. 66  Digestion break down starch care door nucleotides break Digestive Enzymes ↑ > - can Brush border enzymes break nucleotides into: Sugars Phosphates Nitrogenous bases © 2015 Pearson Education, Inc. 67  Digestion Water Absorption Cells cannot actively absorb or secrete water All movement of water across lining of digestive tract: Involves passive water flow down osmotic gradients Ion Absorption Occurs by active transport, diffusion or carrier- mediated transport © 2015 Pearson Education, Inc. 68  Digestive Dietary Input Secretions Food and drink Saliva 2000 mL 1500 mL Gastric secretions 1500 mL 5000 mL Liver (bile) 1000 mL Pancreas (pancreatic juice) 1000 mL Water Reabsorption Intestinal 9000 mL secretions Small intestine 2000 mL reabsorbs 7800 mL 1200 mL Colonic mucous Colon reabsorbs secretions 1400 200 mL 1250 mL mL 150 mL lost