BIOH122 Human Biological Science 2

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1 BIOH122 Human Biological Science 2 Session 14 Digestive System 2 Pancreas, Liver, Small Intestine Bioscience Department Endeavour College of Natural Health endeavour.edu.au

Session Plan o Pancreas Anatomy & Histology Pancreatic juice Functions o Liver and gall bladder Anatomy & Histology Bile Functions o Small intestine

2 Session Plan o Pancreas Anatomy & Histology Pancreatic juice Functions o Liver and gall bladder Anatomy & Histology Bile Functions o Small intestine Anatomy and Histology Intestinal Juice and Brush Border Enzymes Chemical and Mechanical digestion Endeavour College of Natural Health endeavour.edu.au 2

3 Pancreas Endeavour College of Natural Health endeavour.edu.au 3

4 Anatomy of the Pancreas The pancreas: retroperitoneal gland o Size:12 15 cm long and 2.5 cm thick, o Location: Posterior to the greater curvature of the stomach. o Three parts: a head, body, and tail o Head close to curve in C-shaped duodenum Two major ducts: Convey the secretions into the small intestine Pancreatic duct (duct of Wirsung) Accessory duct (duct of Santorini) Endeavour College of Natural Health endeavour.edu.au 4

5 Anatomy of the Pancreas Endeavour College of Natural Health endeavour.edu.au 5

Histology of the Pancreas o Acini - dark clusters 99% of gland Exocrine portion Secrete pancreatic juice o Islets of Langerhans- pale staining cells 1% of

6 Histology of the Pancreas o Acini - dark clusters 99% of gland Exocrine portion Secrete pancreatic juice o Islets of Langerhans- pale staining cells 1% of gland Endocrine portion Secrete hormones glucagon, insulin, somatostatin, and pancreatic polypeptide Endeavour College of Natural Health endeavour.edu.au 6

7 Histology of the Pancreas Endeavour College of Natural Health endeavour.edu.au 7

8 Composition and Functions of Pancreatic Juice o a clear, colourless liquid o Produced liters/day o ph of 7.1 to 8.2 o Contains water, some salts, sodium bicarbonate, and several enzymes o Sodium bicarbonate: converts the acid stomach contents to a slightly alkaline ph ( ), halting stomach pepsin activity and promoting activity of pancreatic enzymes Endeavour College of Natural Health endeavour.edu.au 8

9 Composition and Functions of o Digestive enzymes: Pancreatic Juice Pancreatic amylase: digest Starch Pancreatic lipase: digest triglycerides Proteases: digest proteins Trypsinogen - activated by enterokinase (a brush border enzyme) Chymotrypsinogen - activated by trypsin Procarboxypeptidase - activated by trypsin Proelastase - activated by trypsin Trypsin inhibitor - combines with any trypsin produced inside pancreas Ribonuclease and deoxyribonuclease: digest RNA and DNA Endeavour College of Natural Health endeavour.edu.au 9

10 Regulation of Pancreatic Secretions Hormones secreted by Small intestine: o Secretin Stimulates secretion of pancreatic juice that are rich in bicarbonate ions, promotes normal growth and maintenance of pancreas, enhances effects of CCK. o Glucose-dependent insulinotropic peptide (GIP) Stimulates pancreatic beta cells to release insulin. o Cholecystokinin (CCK) Stimulates secretion of pancreatic juice rich in digestive enzymes, promotes normal growth and maintenance of pancreas, enhances effects of secretin. Endeavour College of Natural Health endeavour.edu.au 10

11 Regulation of Pancreatic Secretions Endeavour College of Natural Health endeavour.edu.au 11

12 Liver and Gallbladder Endeavour College of Natural Health endeavour.edu.au 12

13 Liver and Gallbladder o The liver: Weight: the heaviest gland in the body about 1.4 kg in an average adult Size: the second largest organ in the body after the skin. Location: inferior to the diaphragm and occupies most of the right hypochondriac and part of the epigastric regions of the abdominopelvic cavity o The gallbladder: Size: Pear-shaped sac 7 10 cm long Location: in a depression of the posterior surface of the liver Endeavour College of Natural Health endeavour.edu.au 13

14 o Liver: Anatomy of the Liver and Right and Left lobes Falciform ligament Quadrate lobe Caudate lobe Ligamentum teres (round ligament) Right and left coronary ligaments Gallbladder Endeavour College of Natural Health endeavour.edu.au 14

15 Anatomy of the Gallbladder o Gallbladder: Fundus Body Neck Endeavour College of Natural Health endeavour.edu.au 15

16 Histology of the Liver Endeavour College of Natural Health endeavour.edu.au 16

17 Histology of the Liver o Hepatocytes: Major functional cells of the liver Metabolic, secretory, and endocrine functions Secrete bile: a yellow, brownish, or olive-green liquid serves as both an excretory product and a digestive secretion. o Bile canaliculi: Small ducts between hepatocytes that collect bile produced by the hepatocytes. Bile flow: Bile canaliculi Bile ductules Bile ducts Right and left hepatic ducts Common hepatic duct joins the Cystic duct Common bile duct Small intestine o Hepatic sinusoids o Central Vein o Stellate reticuloendothelial (Kupffer) cells Endeavour College of Natural Health endeavour.edu.au 17

18 Bile flow Endeavour College of Natural Health endeavour.edu.au 18

19 Histology of the Gallbladder Histology: o Mucosa: Simple columnar epithelium arranged in rugae o Submucosa: not present o Muscular coat: smooth muscle fibers Contraction of the smooth muscle fibers ejects the contents of the gallbladder into the cystic duct. o Serosa or visceral peritoneum Functions of the gallbladder: To concentrate the bile produced by the liver (up to tenfold) by absorbing water and ions. To store bile until it is needed in the small intestine. Endeavour College of Natural Health endeavour.edu.au 19

Blood Supply to the Liver o Double blood supply: from Hepatic artery: oxygenated blood from branch of the aorta Hepatic portal vein: Nutrient rich blood

20 Blood Supply to the Liver o Double blood supply: from Hepatic artery: oxygenated blood from branch of the aorta Hepatic portal vein: Nutrient rich blood from stomach, spleen and intestines o Hepatic vein: All blood eventually leave the liver via hepatic vein Endeavour College of Natural Health endeavour.edu.au 20

21 Composition and Function of Bile o Secreted by hepatocytes ml of bile/day a yellow, brownish, or olive-green liquid ph 7.6 to 8.6 o Transported by a duct system to the gallbladder for concentration and temporary storage. o Excretory product: containing components of worn-out red blood cells o Digestive secretion Endeavour College of Natural Health endeavour.edu.au 21

22 Composition and Function of Bile o Components: Water, cholesterol and several ions A phospholipid called lecithin Bile salts = Na and K salts of bile acids: digestive product Play a role in emulsification, the breakdown of large lipid globules into a suspension of small lipid globules. Aid in the absorption of lipids following their digestion. Bile pigments = bilirubin from haemoglobin: excretory product Endeavour College of Natural Health endeavour.edu.au 22

23 Regulation of Bile Secretion o Parasympathetic impulses and vagus nerves o Cholecystokinin(CCK) o Secretin Endeavour College of Natural Health endeavour.edu.au 23

24 Functions of Liver o Carbohydrate metabolism: maintains normal blood glucose level by Glycogenolysis: Break down glycogen to glucose and release the glucose into the bloodstream Gluconeogenesis: Convert certain amino acids, triglycerides and lactic acid to glucose. Glycogenesis: Converts glucose to glycogen and triglycerides for storage. Endeavour College of Natural Health endeavour.edu.au 24

25 Functions of Liver o Lipid metabolism: Storage: Hepatocytes store some triglycerides; Lipolysis: Break down fatty acids to generate ATP; Lipogenesis: Synthesize lipoproteins, which transport fatty acids, triglycerides, and cholesterol to and from body cells; Cholesterol synthesize Synthesize bile salts from cholesterol Endeavour College of Natural Health endeavour.edu.au 25

26 Functions of Liver o Protein Metabolism: Deamination: Removes NH2 (amine group) from amino acids so can use what is left as energy source Urea cycle: Converts resulting toxic ammonia (NH3) into urea for excretion by the kidney Protein synthesis: Synthesizes plasma proteins alpha and beta globulins, albumin, prothrombin, and fibrinogen. Converts one amino acid into another amino acids Endeavour College of Natural Health endeavour.edu.au 26

27 Functions of Liver o Processing of drugs and hormones: Detoxify substances such as alcohol and excrete drugs such as penicillin, erythromycin, and sulfonamides into bile. Chemically alter or excrete thyroid hormones and steroid hormones such as estrogens and aldosterone. o Synthesis of bile and bile salts o Excretion of waste products: Bilirubin from RBC recycling Endeavour College of Natural Health endeavour.edu.au 27

28 Functions of Liver o Storage: Fat soluble vitamins - A, B12, D, E, K and minerals iron and copper o Phagocytosis: aged RBCs, WBCS and some bacteria o Activation of vitamin D Endeavour College of Natural Health endeavour.edu.au 28

29 Small intestine Anatomy and Histology Endeavour College of Natural Health endeavour.edu.au 29

30 Small Intestine o The small intestine: Long tubular structure (2.5 cm in diameter and about 3 m in length), extends from the pyloric sphincter to the ileocecal sphincter. o Functions: Mix chyme with digestive juices and bring food into contact with mucosa for absorption Completes digestion of carbohydrates, proteins, and lipids; begins and completes digestion of nucleic acids. Absorbs about 90% of nutrients and water that pass through digestive system. Endeavour College of Natural Health endeavour.edu.au 30

31 Anatomy of the Small Intestine o Gross anatomical subdivisions: Duodenum Jejunum Ileum o Ileocecal sphincter Endeavour College of Natural Health endeavour.edu.au 31

32 Histology of the Small Intestine o Layers of small intestinal wall: Mucosa Submucosa Muscularis Serosa Endeavour College of Natural Health endeavour.edu.au 32

33 Histology of the Small Intestine o Mucosa: Composed of o The epithelial layer: Simple columnar epithelium contains Absorptive cells and Goblet cells o Intestinal glands: formed by glandular epithelial cells. Deep crevices o Lamina propria: areolar connective tissue with mucosaassociated lymphoid tissue (MALT) Solitary lymphatic nodules: most numerous in the distal part of the ileum Peyer s patches: in the ileum o Muscularis mucosae: smooth muscle Endeavour College of Natural Health endeavour.edu.au 33

34 Histology of the Small Intestine Cells of Intestinal glands: Absorptive cell Goblet cell Paneth cells Enteroendocrine cells: S cells CCK cells K cells o Intestinal Juice: The secretion of absorptive, goblet and paneth cells Endeavour College of Natural Health endeavour.edu.au 34

35 Histology of the Small Intestine o Submucosa: Duodenal (Brunner s) glands: In duodenum, secrete an alkaline mucus that helps neutralize gastric acid in the chyme. Lymphatic tissue of the lamina propria: may extends through the muscularis mucosae into the submucosa. o Muscularis: consists of 2 layers of smooth muscles. outer, thinner longitudinal and the inner, thicker circular fibers layer. o Serosa: Visceral peritoneum completely surrounds the small intestine except for a major portion of the duodenum. Endeavour College of Natural Health endeavour.edu.au 35

36 Special structural features o Special structural features of the small intestine: Circular folds (Plicae circularis) Villi Microvilli o Function: Massive increase in surface area of the small intestine to facilitate the process of digestion and absorption. Endeavour College of Natural Health endeavour.edu.au 36

37 Special structural features Circular folds (Plicae circularis) Villi Microvilli Endeavour College of Natural Health endeavour.edu.au 37

38 Special structural features o Circular folds/plicae circularis: Folds of the mucosa and submucosa Permanent ridges, about 10 mm long Begin near the proximal portion of the duodenum and end at about the midportion of the ileum. o Function: Enhance absorption by increasing surface area and causing the chyme to spiral, rather than move in a straight line, as it passes through the small intestine. Endeavour College of Natural Health endeavour.edu.au 38

39 Special structural features o Villi: Finger-like projections of the mucosa mm tall villi per square millimetre of small intestine Outer cover: Epithelial cells; Core: Lamina propria An arteriole, a venule, a blood capillary network, and a lacteal o Functions: Increase the surface area of the epithelium available for absorption and digestion Gives the intestinal mucosa a velvety appearance Nutrients absorbed by the epithelial cells covering the villus pass through the wall of a capillary or a lacteal to enter blood or lymph, respectively Endeavour College of Natural Health endeavour.edu.au 39

40 Special structural features o Microvilli: Projections of the apical (free) membrane of the absorptive cells. 1 µm-long cylindrical, membrane-covered projection contains a bundle of actin filaments (allow movement) 200 million microvilli per square millimetre of small intestine. o Functions: Form brush border, extending into the lumen of the small intestine Increase the surface area of the plasma membrane and allows larger amounts of digested nutrients can diffuse into absorptive cells in a given period. Contains several brush-border enzymes that have digestive functions Endeavour College of Natural Health endeavour.edu.au 40

41 Intestinal Juice and Brush Border Enzymes o Intestinal juice: a clear yellow fluid, secreted by intestinal glands About 1 2 litres/day. ph: 7.6 slightly alkaline Contains water and mucus, brush-border enzymes and lysozyme o Brush-border enzymes: Carbohydrate digesting enzymes: ɑ-dextrinase, maltase, sucrase, and lactase Protein-digesting enzymes: peptidases (aminopeptidase and dipeptidase) Nucleotide-digesting enzymes: nucleosidases and phosphatases Endeavour College of Natural Health endeavour.edu.au 41

42 Intestinal Juice and Brush Border o Functions: Enzymes o Intestinal juice: Absorption of substances from the chyme as they come in contact with the villi. o Brush border enzymes: Digestion at brush border Digestion in the lumen of the small intestine. Endeavour College of Natural Health endeavour.edu.au 42

43 Small intestine chemical and mechanical digestion Endeavour College of Natural Health endeavour.edu.au 43

Mechanical Digestion in the Small o Segmentation: Localized, mixing contractions that occur in portions of intestine distended by a large volume of chyme.

44 Mechanical Digestion in the Small o Segmentation: Localized, mixing contractions that occur in portions of intestine distended by a large volume of chyme. o Migrating motility complex (MMC): The type of peristalsis that occurs in the small intestine when distension of the small intestinal wall lessens. Intestine Marieb, and Hoehn, 2011 Endeavour College of Natural Health endeavour.edu.au 44

45 Regulation of Secretion and Motility o Enteric reflexes that respond to the presence of chyme increase intestinal motility VIP (vasoactive intestinal polypeptide) stimulates the production of intestinal juice segmentation depends on distention which sends impulses to the enteric plexus and CNS distention produces more vigorous peristalsis 10 cm per second o Sympathetic impulses decrease motility Endeavour College of Natural Health endeavour.edu.au 45

46 Chemical Digestion in the Small Intestine o Digestion by pancreatic juice, bile, and intestinal juice. o Breakdown of nutrients into absorbable forms carbohydrates proteins lipids Endeavour College of Natural Health endeavour.edu.au 46

47 Readings and Resources o Tortora, GJ & Derrickson, B Principles of Anatomy and Physiology, 14th edn, Wiley. o Harris, P, Nagy, S & Vardaxis, N 2010, Mosby s Dictionary of Medicine, Nursing and Health Professions, 2nd edn, Mosby Elsevier. o Guyton, AC & Hall, JE 2011, Textbook of Medical Physiology, 12th edn, Saunders Elsevier. o Marieb, EN & Hoehn, K 2011, Human Anatomy and Physiology, 9th edn, Benjamin Cummings Pearson. o Moore, KL, Dalley, AF & Agur, AMR 2010, Clinically Orientated Anatomy, 6th edn, Lippincott, Williams & Wilkins. Endeavour College of Natural Health endeavour.edu.au 47

48 Copyright COMMONWEALTH OF AUSTRALIA Copyright Regulations 1969 WARNING This material has been reproduced and communicated to you by or on behalf of the Endeavour College of Natural Health pursuant to Part VB of the Copyright Act 1968 (the Act). The material in this communication may be subject to copyright under the Act. Any further reproduction or communication of this material by you may be the subject of copyright protection under the Act. Do not remove this notice. Endeavour College of Natural Health endeavour.edu.au 48

BIOH122 Human Biological Science 2

BIOH122 Human Biological Science 2 Session 15 Digestive System 2 Stomach and Accessory Structures Bioscience Department Endeavour College of Natural Health endeavour.edu.au Session Plan o Stomach anatomy