Lecture Overview. Digestive System (cont d) A&P II Lecture Notes Pages

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1 ** Digestive System ** (cont d) A&P II Lecture Notes Pages Lecture Overview Gall Bladder/Ducts Pancreas GI Tract Movements Chemistry of Digestion Secretion and Absorption Metabolism 2 Liver, Bile ducts, Pancreas and Small Intestine Figures from: Marieb, Human Anatomy &Physiology, Pearson,

2 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 4 Schematic of Bile/Pancreatic Ducts See p. 104 in Lecture notes Figures from: Tortora, Principles of Anatomy & Physiology, 11 th edition, Wiley, Pancreas Exocrine (digestive) and endocrine (metabolic) functions Completes digestion of proteins that was started in the stomach 6 2

Innervation of the Alimentary Canal The alimentary canal has extensive sympathetic and parasympathetic innervation - mainly in the muscularis externa - regulates its tone and the strength, rate, and

ANS increases activities of digestive system and relaxes sphincters sympathetic division of ANS generally inhibits digestive actions and contracts sphincters 7 Movements In/Through the Alimentary

tubular structures by which contents are forced onward toward the opening. (Triggered by pacesetter cells.

3 Innervation of the Alimentary Canal The alimentary canal has extensive sympathetic and parasympathetic innervation - mainly in the muscularis externa - regulates its tone and the strength, rate, and velocity of muscular contractions submucosal plexus controls secretions/blood flow (Meissner s) myenteric plexus controls gastrointestinal motility/sphincters (Auerbach s) parasympathetic division of ANS increases activities of digestive system and relaxes sphincters sympathetic division of ANS generally inhibits digestive actions and contracts sphincters 7 Movements In/Through the Alimentary Canal Mastication = chewing Deglutition = swallowing Mixing movements segmentation (small intestine) pendular motion Peristalsis - The wavelike muscular contractions of the alimentary canal or other tubular structures by which contents are forced onward toward the opening. (Triggered by pacesetter cells.) 8 Enzymes and Metabolic Reactions Enzymes are Biological catalysts control rates of metabolic reactions; unchanged in reaction involved in hydrolytic reactions globular proteins with specific shapes *substrate specific end in ase shape of active site (3D) determines which substrate(s) the enzyme can act on Figure From: Marieb & Hoehn, Human Anatomy & Physiology, 9 th ed., Pearson Enzymes work optimally under specific conditions of temperature and ph 9 3

4 Secretions/Absorptions in Digestive Tract Mouth/Saliva about 1.5 L/day saliva produced moistens food binds food particles dissolves food for tasting cleans teeth and mouth Salivary amylase produced by salivary glands Works optimally at mouth ph of Hydrolyzes starch into maltose (disaccharide)/glucose Anti-microbial (IgA and lysozyme) Pharynx/Esophagus no enzymes/hormones 10 Secretions/Absorption in Digestive Tract - Stomach Enzymes: - Pepsin (protease) -Lipase * Other exocrine factors: -HCl -Mucous - Intrinsic Factor Hormones: - Gastrin ( Go hormone) Figure from: Anatomy & Physiology 2 Lecture Notes, W. Hunter, 2012 Absorbed substances: -Water -Glucose -Salts - Alcohol 11 mucus (cardia) from goblet cells and mucous glands protective to stomach wall pepsinogen from chief cells inactive form of pepsin pepsin from pepsinogen in presence of HCl protein splitting enzyme Gastric Secretions INFANTS ONLY rennin (chymosin) gastric lipase hydrochloric acid from parietal cells needed to convert pepsinogen to pepsin p in parietal and p in ph intrinsic factor from parietal cells required for vitamin B 12 absorption mucus, gastrin, somatostatin from pyloric glands protective to stomach wall gastrin and somatostatin are hormones 12 4

fats into fatty acids and glycerol Brush border enterokinase converts trypsinogen to trypsin gastrin/somatostatin hormonesthat stimulate/inhibit acid secretion by stomach cholecystokinin (CCK)

5 Secretions/Absorption in Digestive Tract Small Intestine * Figure from: Anatomy & Physiology 2 Lecture Notes, W. Hunter, 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 Brush border enterokinase converts trypsinogen to trypsin gastrin/somatostatin hormonesthat 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 See Table in Marieb for a great summary of digestive enzymes 14 Absorption in the Small Intestine monosaccharides and amino acids through facilitated diffusion and active transport electrolytes and water through diffusion, osmosis, and active transport 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 15 5

6 Absorption of Fats in the Small Intestine Figure from: Hole s Human A&P, 12 th edition, 2010 fatty acids and glycerol gy several steps absorbed into lymph into blood Chylomicrons contain TG, cholesterol, and phospholipids 16 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 = 7-8) and neutralize acid coming from stomach Pancreatic proteolytic enzymes 17 Pancreatic Proteolytic Enzymes Enteropeptidase (Enterokinase) (brush border of sm. intestine) Trypsinogen Trypsin Pancreas Chymotrypsinogen yp Procarboxypeptidase Proelastase (Proenzymes, Zymogens) Chymotrypsin yp Carboxypeptidase Elastase (Active enzymes) Dipeptides, tripeptides, amino acids Proteins Purpose of proteolytic enzymes is to continue breakdown of proteins that began in the stomach 18 6

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

for enzyme action) Lacteals Gallbladder Contraction Bile Triglycerides Cholesterol Fat Soluble Vitamins Acidic Chyme Enters Duodenum Cholecystokinin (CCK) Relaxation of hepatopancreatic sphincter

7 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 19 Secretin Bile and Pancreatic ducts Regulation of Pancreas/Intestinal Digestion HCO 3-, PO 4 3- ph to 8 (req. for enzyme action) Lacteals Gallbladder Contraction Bile Triglycerides Cholesterol Fat Soluble Vitamins Acidic Chyme Enters Duodenum Cholecystokinin (CCK) Relaxation of hepatopancreatic sphincter Lipases (emulsification) Fatty acids, monoglycerides (brush border) Enterokinase Trypsinogen Trypsin Pancreas Chymotrypsinogen Trypsinogen Procarboxypeptidase Proelastase Carboxypeptidase Elastase Nucleases (DNA, RNA) Nucleotides Portal Vein (proenzymes, zymogens) Amylase (glycogen, starches) Proteins Mono-, di-, trisaccharides Action of brush border enzymes Key Di- and tripeptides Stimulation Subclavian vein Conversion to chylomicrons Monosaccharides Amino acids 20 Absorption in the Small Intestine monosaccharides and amino acids through facilitated diffusion and active transport electrolytes and water through diffusion, osmosis, and active transport 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 21 7

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

Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001 23 Basal Metabolic Rate (BMR) Basal metabolic rate (BMR) a measure of the rate at which body expends energy at rest (kcal/hr) primarily

8 Absorption of Fats in the Small Intestine Figure from: Hole s Human A&P, 12 th edition, 2010 fatty acids and glycerol gy several steps absorbed into lymph then into blood Chylomicrons contain TG, cholesterol, and phospholipids 22 Overview of Cellular Metabolism Metabolism The sum of all the chemical reactions that occur in an organism ETS KEEP THIS OVERALL SCHEME IN MIND AS WE GO INTO DETAILS Figure from: Martini, Anatomy & Physiology, Prentice Hall, Basal Metabolic Rate (BMR) Basal metabolic rate (BMR) a measure of the rate at which body expends energy at rest (kcal/hr) primarily reflects energy needed to support activities of organs varies with gender, body size, body temperature, and endocrine function calculated as Calories/M 2 /hr On average, from all the types of foodstuffs consumed, 1 L of O 2 yields about Cal Can calculate BMR based on O2 consumption: O 2 consumed (L/hr) x Cal/L body area (M 2 ) Average values: Males 38-40; Females BMR is profoundly affected by circulating thyroid hormone levels BMR is proportional to body weight Body s basal metabolic rate (BMR) falls 10% during sleep and about 40% during prolonged starvation 24 8

also be used to synthesize glucose via gluconeogenesis.

9 Pyruvate is a Key Junction in Metabolism Lipogenesis Glycogenolysis Glycogenesis Pyruvate is used to synthesize amino acids and Acetyl CoA * Lipolysis Pyruvate can also be used to synthesize glucose via gluconeogenesis. Figure from: Martini, Anatomy & Physiology, Prentice Hall, Carbohydrate Metabolism 26 Protein Metabolism 27 9

10 Lipid Metabolism 28 10

Digestive Lecture Test Questions Set 4

Digestive Lecture Test Questions Set 4 1. Which of the following is not associated directly with the small intestine: a. villi b. circular folds c. microvilli d. haustrae e. secretin 2. The largest (longest)