Anatomy and Physiology Marieb’s Human Anatomy and Physiology Ninth Edition Marieb w Hoehn Chapter 23 ** Digestive System ** Stomach Small/Large Intestine Salivary Glands Liver Slides 1-15; 80 min (with review of syllabus and Web sites) [Lecture 1] Slides 16 – 38; 50 min [Lecture 2] 118 min (38 slides plus review of course Web sites and syllabus)

Overview….Where have you been? Figures from: Marieb, Human Anatomy &Physiology, Pearson, 2013

Stomach Rugae flatten as stomach fills Stomach can hold about 1-1.5 liters of material Gastric glands M G cells D cells Greater curvature Stomach Functions: - Mixing - Reservoir - Secretion of gastric juice - Digestion, anti-bacterial action, facilitates absorption of vitamin B12 - Secretion of gastrin, somatostatin Range of stomach volume is about 50 ml (empty) to about 4L, or 1 gallon (very distended). Rugae flatten as stomach fills

Blood Supply and Drainage of Stomach Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001

Lining and Gastric Glands of Stomach Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001

Gastric Secretions mucus (cardia) from goblet cells and mucous glands protective to stomach wall hydrochloric acid from parietal cells needed to convert pepsinogen to pepsin ‘p’ in parietal and ‘p’ in pH pepsinogen from chief cells inactive form of pepsin intrinsic factor from parietal cells required for vitamin B12 absorption pepsin from pepsinogen in presence of HCl protein splitting enzyme mucus, gastrin, somatostatin from pyloric glands protective to stomach wall gastrin and somatostatin are hormones H.Pylori is difficult to eradicate, so three medications are used simultaneously. This is called "Triple Therapy". The best treatment at present is called OAC, taken for 7 days: O = Omeprazole (which decreases the acid level in the stomach) A = Amoxicillin (a penicillin antibiotic). C = Clarithromycin (an antibiotic related to erythromycin) OMC is used in those who are penicillin allergic, where M = Metranidazole. INFANTS ONLY rennin (chymosin) gastric lipase

Secretion of H+ by Parietal Cells Important functions of the stomach pH (1.5 – 2.0) - kills microorganisms - denatures proteins - breaks down plant material and CT in meats - activates pepsin Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001

Liver, Bile ducts, Pancreas and Small Intestine Figures from: Marieb, Human Anatomy &Physiology, Pearson, 2013

Three Parts of Small Intestine Figure from: Hole’s Human A&P, 12th edition, 2010 “Mixing bowl”; acid neutralization Bulk of chemical digestion and nutrient absorption occurs here The ‘bowel’ consists of the small and large intestines. Vitamin B12 absorption Main functions of small intestine: 1) chemical digestion 2) absorption of nutrients (90%) from chyme

Blood Supply and Drainage of Small Intestine Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001

Wall of Small Intestine Figure from: Hole’s Human A&P, 12th edition, 2010 Plicae circulares – permanent circular folds of mucosa that further increase surface area for absorption – do not flatten out with distention like rugae of stomach. Especially prominent in lower duodenum and upper jejunum Submucosa of duodenum contains mucus-secreting glands (Brunner’s glands) that protect the small intestine

Intestinal Villi & Glands Enterocyte = Intestinal Cell Figure from: Saladin, Anatomy & Physiology, McGraw Hill, 2007 Intestinal glands secrete an abundant watery fluid that helps absorb products of digestion. They also contain enteroendocrine cells (enterokinase, gastrin, secretin, CCK)

Intestinal Epithelium Figure from: Hole’s Human A&P, 12th edition, 2010 Microvilli further increase the surface area available for absorption in the small intestine Form a ‘brush border’ on the intestine Digestive enzymes are embedded in the membrane of microvilli Main function of plicae, villi, and microvilli is to increase the surface area for absorption (from about 3.6 ft2 to about 2200 ft2!)

Secretions of Small Intestine peptidase – breaks down peptides into amino acids sucrase, maltase, lactase – break down disaccharides into monosaccharides intestinal lipase – breaks down fats into fatty acids and glycerol enterokinase – converts trypsinogen to trypsin gastrin/somatostatin – hormones that stimulate/inhibit acid secretion by stomach cholecystokinin (CCK) – hormone that inhibits gastric glands, stimulates pancreas to release enzymes in pancreatic juice, stimulates gallbladder to release bile, and relaxes hepatopancreatic sphincter (of Oddi) secretin – stimulates pancreas to release bicarbonate ions in pancreatic juice; stimulates gall bladder to release bicarbonate-rich bile Brush border See Table 23.32 in Marieb for a great summary of digestive enzymes

Movements of the Small Intestine Movements in local segments can occur without stimulation by parasympathetic NS. However, nervous stimulation accelerates segmentation and peristalsis. peristalsis – pushing movements segmentation – ringlike contractions that aid in mixing and slowing peristalsis overdistended or irritated wall triggers “peristaltic rush” resulting in diarrhea “Long distance” movements are triggered by stomach filling: - gastroenteric reflex (↑ motility and secretion along length of small intestine) - gastroileal reflex (relaxation of ileocecal sphincter)

Absorption in the Small Intestine monosaccharides and amino acids through facilitated diffusion and active transport absorbed into blood electrolytes and water through diffusion, osmosis, and active transport absorbed into blood vitamins fat-soluble dissolve in dietary fats (vit A,D,E,K) Water-soluble through diffusion, except B12 (active transport) Vitamin K (large intestine) – with other lipids absorbed into blood

Absorption of Fats in the Small Intestine Figure from: Hole’s Human A&P, 12th edition, 2010 fatty acids and glycerol several steps absorbed into lymph into blood Chylomicrons contain TG, cholesterol, and phospholipids

Large Intestine The bowel includes the small and large intestines. The main forms of Inflammatory Bowel Disease are Crohn's disease and ulcerative colitis (UC). Accounting for far fewer cases are other forms of IBD, which are not always classified as typical IBD: Collagenous colitis Lymphocytic colitis Ischaemic colitis Diversion colitis Behçet's disease Indeterminate colitis The main difference between Crohn's disease and UC is the location and nature of the inflammatory changes. Crohn's can affect any part of the gastrointestinal tract, from mouth to anus (skip lesions), although a majority of the cases start in the terminal ileum. Ulcerative colitis, in contrast, is restricted to the colon and the rectum.[4] Pathophysiology in Crohn's disease vs. ulcerative colitis: Crohn's disease Ulcerative colitis Autoimmune disease Widely regarded as an autoimmune disease No consensus Cytokine response Associated with Th17[5] Vaguely associated with Th2 Microscopically, ulcerative colitis is restricted to the mucosa (epithelial lining of the gut), while Crohn's disease affects the whole bowel wall ("transmural lesions"). Finally, Crohn's disease and ulcerative colitis present with extra-intestinal manifestations (such as liver problems, arthritis, skin manifestations and eye problems) in different proportions. Rarely, a definitive diagnosis of neither Crohn's disease nor ulcerative colitis can be made because of idiosyncrasies in the presentation. In this case, a diagnosis of indeterminate colitis may be made. Although a recognised definition, not all centres refer to this. Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001 *

Histology of the Large Intestine Figures from: Hole’s Human A&P, 12th edition, 2010 Walls of large intestine are much thinner than the small intestine, however, the lumen is larger Note lack of villi and presence of numerous goblet cells (mucus) No enzymes produced; any digestion is from previously introduced enzymes or bacteria

Functions of Large Intestine little or no digestive function absorbs water, bile salts, and electrolytes secretes mucus (lubrication, binding, protection, pH) conversion of bilirubin (uro- and stercobilinogen) houses intestinal flora (~800 species of bacteria) and absorbs vitamins liberated by bacterial action (K, B5, and Biotin); produces intestinal gas (flatus) forms and stores feces carries out defecation Receives about 500 ml of indigestible material per day and reduces the volume to about 150 ml of feces.

The Rectum, Anal Canal, and Anus Figure from: Hole’s Human A&P, 12th edition, 2010 Temporary storage of fecal material in rectum triggers the urge to defecate Internal anal sphincter is usually contracted but relaxes in response to distension. External sphincter must be tensed reflexively to retain feces Rectal valves Procto- = anus or rectum (Keratinzed strat. squamous epithelium)

Movements of Large Intestine slower and less frequent than those of small intestine mixing movements (haustral churning every 30 min) mass movements - usually follow meals (stimulated by distension of stomach and duodenum) gastrocolic reflex duodenocolic reflex peristaltic wave from transverse colon through rest of large intestine

All You Need to Know???

Parasympathetic Defecation Reflex Figure from: Saladin, Anatomy & Physiology, McGraw Hill, 2007 Note that this reflex opens the internal sphincter and closes the external sphincter Need voluntary relaxation of the external sphincter for defecation

Feces water (75%), solids (25%) electrolytes mucus bacteria (30% of solids) and sloughed epithelial cells bile pigments altered by bacteria provide color (mainly urobilins and stercobilins) odor produced by bacterial compounds (indoles and skatoles, phenols, H2S, ammonia) indigestible materials

Major Organs of Digestive System Figure from: Saladin, Anatomy & Physiology, McGraw Hill, 2007 Organs can be divided into the: Digestive tract (primary) (alimentary canal); tube extending from mouth to anus (about 30 ft.) Accessory organs; teeth, tongue, salivary glands, liver, gallbladder, and pancreas

Salivary Glands Figure from: Saladin, Anatomy & Physiology, McGraw Hill, 2007 Parasympathetic – CN VII and IX; sympathetic via cervical sympathetic chain.

Secretions of Salivary Glands Secretions are about neutral pH and continual due to basal parasympathetic stimulation, but increase after - presence, or anticipation of, food; - parasympathetic stimulation (watery, large volume) - sympathetic stimulation (viscous, small volume) Parotid glands clear primarily water, serous fluid rich in amylase mumps virus typically attacks here Food in mouth stimulates the nucleus of the tractus soliarius and this stimulates the salivatory nuclei in the pons/medulla send signals to salivary glands via the facial and glossopharyngeal nerves Submandibular glands primarily serous fluid some mucus, amylase Sublingual glands primarily mucus most viscous

Liver [ Hepat(o)- ] Round ligament is part of the falciform ligament that divides the lobes; remnant of fetal umbilical vein. Note that the vena cava does not enter the liver; it passes by Figure from: Martini, Anatomy & Physiology, Pearson Education, 2004

Arterial Supply and Venous Drainage of Liver Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001

Hepatic Lobule Hepatic lobules are the functional units of the liver (>100,000) Figure from: Saladin, Anatomy & Physiology, McGraw Hill, 2007

Paths of Blood and Bile in Hepatic Lobule Figure from: Hole’s Human A&P, 12th edition, 2010 Liver’s role as an accessory organ in digestion is production of bile Sinusoid Hepatic portal vein → sinusoids → central vein → hepatic veins → inferior vena cava Hepatic artery

Liver Functions (over 200!) Three general categories of function 1) Metabolic regulation Interconversion of carbohydrates, lipids, amino acids Removal of wastes Vitamin and mineral metabolism Drug inactivation Storage of fats, glycogen, iron, vit A/B12/D/E/K 2) Hematological regulation Phagocytosis and antigen presentation; ab removal Synthesis of plasma proteins Removal of circulating hormones Removal of worn-out RBCs (Kupffer cells) Removal or storage of toxins 3) Synthesis and secretion of bile (role in digestion) Know items in red

Gallbladder [Cyst(o)-] Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001 Main function is to store and concentrate bile between meals, and release bile under the influence of CCK

Composition of Bile (Chole-) Yellowish-green liquid continually secreted by hepatocytes water bile salts (bile acids) derived from cholesterol emulsification of fats (increases surface area for digestive enzymes) helps absorption of fatty acids, cholesterol, and fat-soluble vitamins 80% are recycled (reabsorbed and reused) – enterohepatic circulation of bile 20% excreted in feces (disposes of excess cholesterol) bile pigments (bilirubin and biliverdin from breakdown of RBCs) electrolytes Gallstones most frequently occur in (5 F’s): fair, fat, female, fertile, forty.

Regulation of Bile Release from GB Figure from: Hole’s Human A&P, 12th edition, 2010 fatty chyme entering duodenum stimulates the GB to release bile (via CCK) Secretin causes the bile ducts (and pancreatic ducts) to secrete bile rich in HCO3-

Actions of Cholecystokinin (CCK) on Digestion Figure adapted from: Barrett, K., Gastrointestinal Physiology, Lange, 2006 CCK Contraction of Gallbladder Secretion of pancreatic enzymes Reduced emptying of stomach Relaxation of hepatopancreatic sphincter Protein, CHO, lipid absorption and digestion Matching of nutrient delivery to digestive and absorptive capability

Pancreas Exocrine (digestive) and endocrine (metabolic) functions Completes digestion of proteins that was started in the stomach

Blood Supply and Drainage of Pancreas Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001

Pancreatic Juice pancreatic amylase – splits glycogen into disaccharides pancreatic lipases – break down triglycerides pancreatic nucleases – digest nucleic acids bicarbonate ions – make pancreatic juice alkaline (pH = 8) and neutralize acid coming from stomach Pancreatic proteolytic enzymes…

Pancreatic Proteolytic Enzymes Enteropeptidase (Enterokinase) (brush border of sm. intestine) Know this chart Trypsinogen Trypsin Chymotrypsinogen Chymotrypsin Pancreas Procarboxypeptidase Carboxypeptidase Proelastase Elastase (Proenzymes, Zymogens) (Active enzymes) Dipeptides, tripeptides, amino acids Proteins Purpose of proteolytic enzymes is continued breakdown of proteins that began in the stomach

Regulation of Pancreatic Secretions acidic chyme stimulates release of secretin secretin stimulates release of watery pancreatic juice with bicarbonate and phosphate (= buffers; to  pH) CCK and parasympathetic NS stimulate production and secretion of pancreatic enzymes and zymogens The acini of the pancreas secrete enzymes/zymogens; the ducts secrete buffers (bicarbonate, phosphates)

Regulation of Pancreas/Intestinal Digestion Key + Stimulation Acidic Chyme Enters Duodenum + (brush border) + + Enterokinase Cholecystokinin (CCK) Secretin + Trypsinogen Trypsin + + + Gallbladder Contraction Relaxation of hepatopancreatic sphincter Chymotrypsinogen Procarboxypeptidase Proelastase Trypsinogen Carboxypeptidase Elastase Pancreas Bile and Pancreatic ducts (proenzymes, zymogens) Proteins Bile Lipases HCO3-, PO43- (emulsification) Nucleases (DNA, RNA) Amylase (glycogen, starches) Di- and tripeptides Triglycerides Cholesterol Fat Soluble Vitamins  pH to ≈ 8 (req. for enzyme action) Nucleotides Mono-, di-, trisaccharides Action of brush border enzymes Fatty acids, monoglycerides Lacteals Portal Vein Amino acids Conversion to chylomicrons Subclavian vein Monosaccharides

Life-Span Changes gums recede teeth become sensitive teeth may loosen or fall out heartburn more frequent constipation more frequent nutrient absorption decreases accessory organs age but the effects are less noticeable