Digestive System II Lecture Notes PDF

Biology 460 Lecture Number: 20 Digestive system II Ahmed Mahgoub MD [email protected] Department of Anatomical Sciences School of Medicine, St. George’...

Biology 460 Lecture Number: 20 Digestive system II Ahmed Mahgoub MD [email protected] Department of Anatomical Sciences School of Medicine, St. George’s University Session ID: lect20  Copyright All course materials, whether in print or online, are protected by copyright. The work, or parts of it, may not be copied, distributed, or published in any form, printed, electronic, or otherwise. As an exception, students enrolled in this course at St. George’s University School of Medicine and their BIOL460 | Lecture 15 | Cardiovascular System IV: Anatomy of Vessels faculty are permitted to make electronic or print copies of all downloadable files for personal and classroom use only, provided that no alterations to the documents are made and that the copyright statement is maintained in all copies. ‘View only’ files, such as lecture recordings, are explicitly excluded from download, and creating copies of these recordings by students and other users is strictly illegal. The author of this document has made the best effort to observe current copyright law and the copyright policy of St. George's University. Users of this document identifying potential violations of these regulations are asked to bring their concerns to the attention of the author. Session ID: biol460  Your Objectives will show here! Objectives Name and describe the abdominopelvic regions. Identify the organs of the digestive system. Describe the basic processes performed by the digestive system. Describe the structure and function of the layers that form the wall of BIOL460 | Lecture 15 | Cardiovascular System IV: Anatomy of Vessels the gastrointestinal (GI) tract. Describe the innervation of the GI tract and the plexuses that form the enteric nervous system. Describe the peritoneum and peritoneal folds. Describe the arrangement of visceral and parietal peritoneum. Describe and identify retroperitoneal vs. intraperitoneal organs. Describe the location, structure, function, and secretion of the salivary glands. Describe the structure and functions of the tongue. Describe the structure and function of the lingual papillae. Describe the structure and function of the taste buds. Describe the structure and function of the pharynx. Describe the anatomy, histology, and functions of the esophagus. Session ID: biol460  GENERAL CHARACTERISTICS Major Organs: Oral Cavity: Site of food intake and the start of digestion (mechanical and enzymatic). Esophagus: Muscular tube that transports food to the stomach. Stomach: Holds and digests food with enzymes and acid. Small Intestine: Main site for nutrient absorption (duodenum, jejunum, ileum). Large Intestine: Absorbs water and forms waste (colon, rectum, anus). Supporting Organs: Liver: Produces bile for digestion of fats. Pancreas: Secretes digestive enzymes and hormones (e.g., insulin). Gallbladder: Stores and concentrates bile.  Functions of the Digestive System Ingestion: The process of taking in food through the mouth. Secretion: The release of enzymes, acid, and mucus to aid digestion (e.g., saliva, gastric acid). Propulsion: Peristalsis: Rhythmic muscle contractions move food along the GI tract. Digestion: Mechanical Digestion: Physical breakdown of food (e.g., chewing, stomach churning). Chemical Digestion: Enzymatic breakdown of macromolecules (carbohydrates, proteins, fats) into absorbable units. Absorption: Transfer of nutrients, water, and electrolytes from the GI tract into blood or lymphatic vessels (mainly in the small intestine). Excretion (Defecation): Elimination of indigestible substances and waste products from the body via the rectum and anus.  Abdominal Quadrants and Their Clinical Significance Right Upper Quadrant (RUQ): Contains liver, gallbladder, part of the pancreas. Clinical Relevance: Gallstones, hepatitis, cholecystitis. Left Upper Quadrant (LUQ): Contains stomach, spleen, part of the pancreas. Clinical Relevance: Gastric ulcers, splenic rupture. Right Lower Quadrant (RLQ): Contains appendix, cecum. Clinical Relevance: Appendicitis, ovarian cysts. Left Lower Quadrant (LLQ): Contains descending colon, sigmoid colon. Clinical Relevance: Diverticulitis, bowel obstruction.  PERITONEUM Overview: The peritoneum is a serous membrane that lines the abdominal cavity and covers abdominal organs. Layers: Parietal Peritoneum: Lines the abdominal wall. Visceral Peritoneum: Covers the surface of internal organs. Peritoneal Cavity: A potential space between the parietal and visceral layers containing a small amount of fluid to reduce friction. Peritoneal Folds: Mesentery: Supports intestines and contains blood vessels, nerves, and lymphatics. Omenta: Greater and lesser omentum provide fat storage and protect organs. Ligaments: Attach organs to each other or to the abdominal wall (e.g., falciform ligament for the liver). Clinical Relevance: Peritonitis: Inflammation of the peritoneum, often due to infection or perforation. Ascites: Accumulation of fluid in the peritoneal cavity, commonly seen in liver disease.  Peritoneal Folds Mesentery: Anchors the small intestine to the posterior abdominal wall. Contains blood vessels, lymphatics, and nerves. Greater Omentum: Large fatty fold that hangs from the stomach and drapes over intestines. Provides protection, insulation, and fat storage. Lesser Omentum: Connects the stomach and duodenum to the liver. Falciform Ligament: Attaches the liver to the anterior abdominal wall and diaphragm. Mesocolon: Anchors the colon to the posterior abdominal wall.  Ligaments and Omenta of the Peritoneum Ligaments: Falciform Ligament: Connects the liver to the anterior abdominal wall and diaphragm. Divides the liver into left and right lobes. Hepatoduodenal Ligament: Part of the lesser omentum; connects the liver to the duodenum. Contains the portal triad: portal vein, hepatic artery, and bile duct. Gastrocolic Ligament: Part of the greater omentum; connects the stomach to the transverse colon. Omenta: Greater Omentum: § A large apron-like fold of fat and peritoneum. § Drapes from the stomach over the intestines, providing protection, fat storage, and limiting infection spread. Lesser Omentum: § Connects the stomach and duodenum to the liver. § Contains the hepatoduodenal and hepatogastric ligaments.  Intraperitoneal vs Retroperitoneal Organs Intraperitoneal organs are organs that lie within the peritoneum in the abdominal cavity. Retroperitoneal organs are organs that are external to the peritoneal lining in the abdominal cavity.  Primary Retroperitoneal Secondary Retroperitoneal Intraperitoneal Organs Organs Organs Completely surrounded by peritoneum Always retroperitoneal Originally intraperitoneal, became retroperitoneal Stomach Kidneys Pancreas (except tail) Liver Adrenal glands Duodenum (except first part) Spleen Ureters Ascending Colon Jejunum and Ileum Aorta and Inferior Vena Cava Descending Colon Transverse and Sigmoid Colon Esophagus (abdominal portion) Upper two-thirds of the Rectum Gallbladder Rectum (lower third) Histological Layers of GI Tract: Mucosa: Innermost lining, responsible for secretion and absorption. Submucosa: Contains blood vessels, nerves, and glands. Muscularis Externa: Two layers of muscle for peristalsis. Serosa/Adventitia: Outer connective tissue covering. 1. Mucosa – Epithelium Wall of the GI Tract Lining the lumen Variable – Lamina propria Loose CT below the epithelium Richly vascularized ( blood and lymphatic) Mucosa associated lymphoid tissue (MALT) – Muscularis interna/ mucosae Muscle type is fixed One to Two layers 2. Submucosa Dense irregular connective tissue –Submucosal / Meissner’s plexus (Enteric nervous system) Autonomic plexus –Glands –Blood & lymphatic vessels 3. Muscularis Externa – Muscle type - smooth/skeletal – Various layers of muscle in various orientation – Myenteric / Auerbach’s plexus Also an autonomic plexus Function = peristalsis 4. Serosa/Adventitia –Connective tissue with or without a lining epithelium. Above the diaphragm –adventitia Below the diaphragm –serosa ORAL CAVITY  ORAL CAVITY TONGUE Accessory organ Highly muscular-intrinsic and extrinsic groups of muscles Functions: Formation and movement of bolus in the oral cavity X Saliva Oropharynx Speech ? Taste Tongue TONGUE http://www.pathologyoutlines.com CIRCUMVALLATE PAPILLAE Taste Buds Each taste bud is made up of the following cells: 1. Gustatory Receptor Cells 2. Supporting Cell 3. Basal cells  SALIVARY GLANDS Gland- invagination of epithelial tissue into connective tissue, product secreted via ducts or via blood stream. 2 Types: Minor - Located in the mucous membrane. labial(lips), buccal(cheeks), palatal(palate), lingual(tongue). Major – 3 pairs: parotid, sublingual, submandibular Sublingual gland Parotid gland Submandibular gland  The four major parts of the salivon the acinus, intercalated duct, striated duct, and excretory duct are color-coded. The three columns on the right of the salivon compare the length of the different ducts in the three salivary glands. The red-colored cells of the acinus represent serous-secreting cells, and the yellow-colored cells represent mucus-secreting cells. The ratio of serous-secreting cells to mucus-secreting cells is depicted in the acini of the various glands. Major Salivary Glands: 1. Parotid – Serous 2. Submandibular – Mixed 3. Sublingual – Mixed  PAROTID GLAND Parotid- para-otid (alongside the ear) Serous gland Covered by capsule, divided into lobules Duct empties into oral cavity- 2nd upper molar H & E: Acinar cells- granular appearance, abundant RER SUBLINGUAL GLAND Located beneath the tongue Mixed gland, abundant mucous units H&E: Mucous units are pale staining, nucleus pushed to the side Serous units granular  SUBMANDIBULAR GLAND Located on the floor of the oral cavity Mixed gland- contains more serous than mucous secreting units Ducts empty lateral to the lingual frenulum H&E Mucous units are pale staining, nucleus pushed to the side Serous units granular Serous units Mucous units  Gland Type of Secretion Acini Type Other Features Largest salivary gland, high amylase Parotid Gland Serous Purely serous acini content in secretion Predominantly serous Intermediate size, serous acini Submandibular Mixed (Serous > acini, few mucous acini predominate over mucous acini, Gland Mucous) with serous demilunes serous demilunes are present Smallest salivary gland, mostly Predominantly mucous Mixed (Mucous > mucous acini, serous demilunes Sublingual Gland acini with serous Serous) present but fewer compared to demilunes submandibular gland  Pharynx The pharynx is a muscular tube that connects the nasal and oral cavities to the esophagus and larynx. Nasopharynx It plays a crucial role in both the respiratory and digestive systems. Regions of the Pharynx: Oropharynx Nasopharynx: Behind the nasal cavity; primarily involved in respiration. laryngopharynnx Oropharynx: Located behind the oral cavity; directs food from the mouth to the esophagus. Trachea Esophagus Laryngopharynx: Leads to the esophagus and larynx; a common pathway for both air and food.  Esophagus Straight collapsible muscular tube approximately 25 cm long. Passageway for substances between pharynx and stomach 4 constrictions Passes through the diaphragm @T10 Physiological sphincter  Histology of the Esophagus 1. Mucosa: -Nonkeratinized stratified Squamous epithelium -Esophageal cardiac glands 2. Submucosa: - Esophageal glands proper 3. Muscularis -> Muscle types – Upper 1/3rd Skeletal – Middle 1/3rdSkeletalàSmooth – Lower 1/3rd Smooth 4. Adventitia Pathologies of the Esophagus Barrett’s Esophagus GERD  Lamina Epithelium propria Muscularis mucosae submucosa Adventicia Mu scu lar is GASTROESOPHAGEAL JUNCTION A B Barium swallow Radiograph of esophageal after wallowing barium meal. This left posterior oblique (LPO) view demon51J'ates two of' the three normal constrictions (impressions) caused by the arch of' the aorta and left main bronchus. The phrenic ampulla, which is seen only radiographically, is the distensible part of the esophagus superior to the diaphragm.  Biology 460 Lecture Number: 20 Digestive system II Ahmed Mahgoub MD [email protected] Department of Anatomical Sciences School of Medicine, St. George’s University Session ID: lect20  Your Objectives will show here! Objectives Describe the anatomy, histology, and functions of the stomach. Describe the anatomy, histology, and functions of the small intestine. Describe the anatomy, histology, and functions of the large intestine. Describe the anatomy and histology of the rectum and anal canal. Compare the internal and external anal sphincters. BIOL460 | Lecture 15 | Cardiovascular System IV: Anatomy of Vessels Describe the anatomy, histology, and functions of the liver. Describe the path of blood flow through the liver. Describe the anatomy, histology, and functions of the gallbladder. Describe the anatomy of the biliary tree. Discuss gallstones, the potential sites where gallstones can be lodged and explain the effects on the bile flow. Describe the anatomy, histology, and functions of the pancreas. Describe the location of the spleen and its relationship to surrounding structures. Describe the blood supply of the foregut and spleen. Describe the blood supply of the midgut. Describe the blood supply of the hindgut. Describe the hepatic portal system and major veins of the digestive system. Discuss Gallstones, hemorrhoids, intestinal obstruction, peptic ulcer, appendicitis, pancreatitis, hepatitis, and colorectal cancer. Session ID: biol460 Overview of the GI System: Foregut, Midgut, and Hindgut Region Organs Function Blood Supply Esophagus, Stomach, Liver, Ingestion, mechanical and Celiac Trunk Gallbladder, Spleen, chemical digestion, bile Foregut Pancreas, Proximal and enzyme secretion Duodenum Distal Duodenum, Digestion and absorption Superior Mesenteric Jejunum, Ileum, Cecum, of nutrients Artery (SMA) Midgut Appendix, Ascending Colon, First 2/3 of Transverse Colon Distal 1/3 of Transverse Absorption of water and Inferior Mesenteric Artery Hindgut Colon, Descending Colon, electrolytes, storage, and (IMA) Sigmoid Colon, Rectum excretion of waste  Blood Supply of the GI System: Foregut, Midgut, and Hindgut Region Main Artery Organs Supplied Key Branches Celiac Trunk Esophagus, Stomach, Left Gastric Artery, Splenic Liver, Spleen, Pancreas, Artery, Common Hepatic Foregut Duodenum (proximal to Artery major papilla), Gallbladder Superior Mesenteric Duodenum (distal to Ileocolic Artery, Right Colic Artery (SMA) major papilla), Artery, Middle Colic Artery Midgut Jejunum, Ileum, Cecum, Appendix, Ascending Colon, First 2/3 of Transverse Colon Inferior Mesenteric Distal 1/3 of Transverse Left Colic Artery, Sigmoid Artery (IMA) Colon, Descending Arteries, Superior Rectal Hindgut Colon, Sigmoid Colon, Artery Rectum STOMACH Holding reservoir and mixing chamber Major secretions: mucus, gastrin, intrinsic factor, acid, pepsinogen, gastric lipase The stomach is made up of four main parts: 1. Cardia 2. Fundus 3. Body 4. Pyloric  Histology of the Stomach 1. Mucosa: -Simple Columnar epithelium -Lamina propria -Muscularis Mucosa 2.Submucosa -No glands 3. Muscularis - 3 layers: -Inner oblique -middle circular -outer longitudinal 4.Serosa The simple columnar epithelium with mucous cells invaginates into the lamina propria to form gastric pits and gastric glands. Several gastric glands open into a gastric pit or foveolae. The epithelium of the stomach is comprised of the following specialized cells: -Mucous cells -Parietal cells -Chief cells -Enteroendocrine cells -Regenerative cells Peptic ulcers Physiological vs Anatomical Sphincter Gastroduodenal junction Celiac trunk  SMALL INTESTINES Longest portion of the GI tract (approximately 6 meters in length). Located between the stomach and large intestine, responsible for most digestion and nutrient absorption. Divisions of the Small Intestine: § Duodenum: C-shaped, about 25 cm long, receives chyme from the stomach, bile from the liver, and pancreatic enzymes. § Jejunum: Middle section, approximately 2.5 meters, primarily responsible for nutrient absorption. § Ileum: Final part, about 3.5 meters, absorbs bile salts and any remaining nutrients; connects to the cecum of the large intestine via the ileocecal valve.  General Histology of the Small Intestine 4 basic layers: 1. Mucosa Epithelium – simple columnar with goblet cells Intestinal glands (crypts of Lieberkuhn): Enterocytes, Goblet cells, Paneth cells, Enteroendocrine cells and M cells Lamina propria – loose connective tissue and abundant mucosa-associated lymphoid tissue Muscularis mucosa – smooth muscle General Histology of the Small Intestine 2. Submucosa Dense Connective Tissue The lymphatic tissue of the lamina propria may extend into the submucosa 3. Muscularis Externa 2 layers of smooth muscles: Outer-> longitudinal muscle Inner -> circular 4. Serosa The small intestine is covered in serosa except for 2nd, 3rd, 4th part of the duodenum Bowel Obstruction  Adaptations of the Small Intestine Circular folds (Plicae Circulares) Folds of mucosa and submucosa Villi Fingerlike projection of the mucosa -> epithelium with a core of lamina propria Microvilli -> Brush border Projection of the apical membrane of the absorptive cells microanatomy.net  DUODENUM Porta Hepatis C shaped tube 25 cm long Distinguishing characteristics: Bile duct -Appearance of circular folds Pancreatic -Opening of the hepatopancreatic duct duct -Brunners glands in submucosa -> alkaline secretion DUODENUM 4 Basic Layers: 1. Mucosa Epithelium – simple columnar -Enterocytes -Goblet cells -Paneth cells -Stem cells -Enteroendocrine 2. Submucosa Brunners glands 3. Muscular externa- 2 layers 4. Serosa 1st part intraperitoneal rest is retroperitoneal JEJUNUM Distinguishing characteristics: Long, branched circular fold Diseases of the Jejunum -Celiac Disease JEJUNUM ILEUM Distinguishing Characteristics: Blunted circular folds Submucosa: Aggregated lymphoid tissue- Peyer’s patches  Blood Supply of the Small Intestine Arterial Supply: Superior Mesenteric Artery (SMA): Primary source of blood for the small intestine. Duodenum: Supplied by both the Celiac Trunk (via the gastroduodenal artery) and the SMA. Jejunum and Ileum: Supplied by branches of the SMA called jejunal and ileal arteries. Venous Drainage: Superior Mesenteric Vein (SMV): Drains blood from the small intestine. The SMV joins with the splenic vein to form the hepatic portal vein, which carries nutrient-rich blood to the liver for processing. Lymphatic Drainage: Lacteals: Specialized lymphatic vessels in the villi that absorb fats and drain into the mesenteric lymph nodes. Lymph eventually drains into the thoracic duct, which empties into the venous system. The Superior Mesenteric Artery  Overview of the Large Intestine The large intestine is approximately 1.5 meters long, extending from the ileocecal valve to the anus. Its primary functions include absorption of water and electrolytes, formation of feces, and excretion. Divisions of the Large Intestine: Cecum: First part, located in the right lower quadrant; receives content from the ileum. Colon: Divided into ascending, transverse, descending, and sigmoid sections. Rectum: Terminal portion, leading to the anal canal. Anal Canal: Ends at the anus, controlling defecation through the internal and external sphincters. Unique Features: Teniae Coli: Three bands of longitudinal muscle that create haustra (sacculations). Haustra: Pouch-like segments that facilitate the absorption of water. Epiploic Appendages: Fat-filled pouches attached to the colon. Functions: Absorption of remaining water and electrolytes from indigestible food. Formation and storage of feces. Fermentation of some undigested materials by gut bacteria (producing vitamins B and K). LARGE INTESTINE  LARGE INTESTINE Transverse Colon Ileocecal valve opens the small intestine into the large intestine Function: Descending Colon -completion of digestion Ascending X -absorption of water, ions, vitamins Colon -production of vitamins B & K -formation and expulsion of waste material Consists of 4 parts Rectum Sigmoid Colon  LARGE INTESTINE Distinguishing features -haustra, haustra tenia coli -tenia coli, -epiploic appendages -abundance of goblet cells, no villi Appendix- wormlike structure attached to the cecum, containing large amounts of lymphoid tissue. Diseases of the large intestine X Appendicitis Diverticular disease  Mucosa Epithelium- simple columnar with goblet cells Intestinal glands/crypts of lieberkuhn Lymphatic nodules Submucosa- dense connective tissue A Muscularis Tenia coli, haustra Serosa – epiploic appendages B C RECTOANAL JUNCTION/ANAL CANAL Blood Supply  Blood Supply of the Large Intestine Arterial Supply: Superior Mesenteric Artery (SMA): Supplies the cecum, ascending colon, and proximal two-thirds of the transverse colon. Key branches: Ileocolic Artery: Supplies the cecum and appendix. Right Colic Artery: Supplies the ascending colon. Middle Colic Artery: Supplies the proximal transverse colon. Inferior Mesenteric Artery (IMA): Supplies the distal third of the transverse colon, descending colon, sigmoid colon, and rectum. Key branches: Left Colic Artery: Supplies the descending colon. Sigmoid Arteries: Supply the sigmoid colon. Superior Rectal Artery: Supplies the upper rectum.  Blood Supply Venous Drainage: Superior Mesenteric Vein (SMV): Drains blood from the regions supplied by the SMA, eventually draining into the hepatic portal vein. Inferior Mesenteric Vein (IMV): Drains blood from regions supplied by the IMA, typically joining the splenic vein before reaching the portal system. Rectal shelves The Large Intestine - Rectum (of Houston) Taenia Coli at rectosigmoid junction become one continuous layer of muscle instead of three discrete bands. It also thickens which helps expel feces. Rectosigmoid junction RECTUM- between these two landmarks Pectinate (dentate) line – where endoderm meets ectoderm Anal canal 75  RECTUM/ANAL CANAL Features: Rectum – transverse rectal folds Anal canal - anal columns Epithelium – Simple columnar to stratified squamous Highly vascularized Internal anal sphincter – smooth muscle Internal External anal sphincter – skeletal muscle External Pectinate line Colorectal cancer Hemorrhoids  INNERVATION OF THE DIGESTIVE SYSTEM The Enteric nervous system (ENS)is responsible for intrinsic innervation of the GI Tract. It is made up of the Meissner’s and Auerbach’s plexus , found in the submucosa and muscular layers respectively. Motor neurons, interneurons, and sensory neurons all interact in response to the various stimuli of the digestive tract. The craniosacral parasympathetic system and the sympathetic system form synapses with the ENS. In this way they are responsible for extrinsic regulation of motility and secretions of the digestive tract. The sensory receptors in the gut respond to chemical and mechanical changes and synapse with ENS, ANS, and CNS. INNERVATION OF THE DIGESTIVE SYSTEM  ACCESSORY GLANDS Liver Pancreas Gall Bladder LIVER Diaphragm Location – right upper quadrant Second largest organ Intraperitoneal Falciform ligament 4 lobes Right lobe Functions- endocrine/exocrine organ, detoxification, storage, lipolysis IVC Caudate lobe. Portal ? triad Quadrate lobe Liver Anatomy and Functions Liver Anatomy and Functions - The liver is the largest internal organ, located in the right upper quadrant of the abdomen. - It is divided into four lobes: right, left, caudate, and quadrate. - Functions: - Carbohydrate metabolism: stores glucose as glycogen. - Lipid metabolism: synthesis of cholesterol and lipoproteins. - Protein metabolism: synthesizes plasma proteins such as albumin. - Hepatic Lobule: - The functional unit of the liver, organized around the central vein. - Hepatocytes perform metabolic, detoxification, and synthetic functions. - Blood from the hepatic portal vein and hepatic artery flows through sinusoids to the central vein.  BILIARY TREE The biliary tree is the pathway for the flow of bile after its secretion from the hepatocytes Hepatocytes-> bile canaliculi -> bile ductules -> bile duct-> right and left hepatic ducts-> cystic duct-> common bile duct -> hepatopancreatic ampulla Biliary Tree Biliary Tree - The biliary tree is the pathway for bile flow from the liver to the duodenum. - Bile is produced by hepatocytes and flows into bile canaliculi, then into bile ducts. - Bile ducts converge into the right and left hepatic ducts, which form the common hepatic duct. - The cystic duct connects the gallbladder to the common bile duct. - Clinical Relevance: - Obstructive jaundice: caused by blockage of bile flow, commonly due to gallstones or tumors. - Gallstones: stones formed from bile components, can lead to biliary colic or cholecystitis.  GALL BLADDER Common Gall hepatic Bladder duct Pear shape organ, volume 30- Cystic duct 50mls Comm Simple columnar epithelium on bile duct Stores and concentrate bile Smooth muscle contracts under the influence of CCK Gallbladder Anatomy and Histology Gallbladder Anatomy and Histology - Pear-shaped organ that stores and concentrates bile. - Composed of a mucosal layer of simple columnar epithelium. - Smooth muscle layer contracts under the influence of cholecystokinin (CCK) to release bile. - Gallstones: - Formed from cholesterol or bilirubin, more common in people with high cholesterol or hemolytic disorders. - Risk factors: female, age over 40, obesity, and rapid weight loss. - Clinical implications include cholecystitis and biliary colic. Simple columnar epithelium Gall stones may be asymptomatic [common in fat, fertile, female of forty]; or, it may produce colic or acute cholecystitis Biliary colic – usually caused by spasm of the smooth muscle of the gall bladder in an attempt to expel the gall stones Acute cholecystits – pain in the right upper quadrant à may cause subdiaphragmatic parietal peritoneum irritation, which is supplied by the phrenic nerve [referred pain à right shoulder] Obstruction of biliary tree by gall stone or compression by pancreatic growth à obstructive jaundice. Impaction of stone in the ampulla can cause passage of infected bile into the pancreatic duct leading to pancreatitis PORTAL SYSTEM Splenic vein The liver has two sources of Right blood: gastric 1. Hepatic artery – oxygenated Superior 2. Hepatic portal vein – mesenteric deoxygenated, nutrient rich Portal system- capillary bed drains into another capillary bed The portal veins collects venous blood through veins with products of digestion from the abdominal part of the GIT, gallbladder, Alcoholic liver disease spleen & pancreas  PANCREAS Retroperitoneal gland Division: head ,body, tail, uncinate process Endocrine/Exocrine gland Superior Mesenteric artery and Secretes - Pancreatic digestive vein juices, Glycogen, Insulin, etc Greater duodenal papilla Pancreatic duct joins with CBD -> Hepatopancreatic ampulla (HPA), aka Ampulla of vater of duodenum Pancreatitis Pancreas Anatomy and Functions Pancreas Anatomy and Functions - Retroperitoneal gland with both endocrine and exocrine functions. - Exocrine function: secretion of pancreatic juice containing digestive enzymes like amylase, lipase, and proteases. - Endocrine function: islets of Langerhans produce insulin, glucagon, and somatostatin. - Clinical Conditions: - Pancreatitis: inflammation of the pancreas, often caused by gallstones or alcohol. - Pancreatic cancer: a serious condition with poor prognosis, often detected late. Exocrine Pancreas Pancreatic digestive juices cells in clusters called acini. Pancreatic amylase, trypsin, elastase Endocrine Pancreas Endocrine pancreas secretes: Insulin, glucagon, somatostatin, pancreatic polypeptide Islets of langerhans  Structure Mucosa Submucosa Muscularis Externa Serosa/Adventitia Esophagus Non-keratinized stratified Contains esophageal glands Inner circular and outer Adventitia (mostly) squamous epithelium. (mucus-secreting). longitudinal layer (skeletal Prominent muscularis mucosa. muscle in upper third, smooth muscle in lower two-thirds). Stomach Simple columnar epithelium, Contains gastric glands, no Three layers: inner oblique, Serosa with gastric pits and glands lymphatic tissue. middle circular, and outer (chief, parietal, and mucous longitudinal. neck cells). Duodenum Simple columnar epithelium Brunner's glands (secrete Two layers: inner circular and Serosa (except for part with villi and microvilli, alkaline mucus to neutralize outer longitudinal. attached to the pancreas) Brunner's glands in the stomach acid). submucosa. Jejunum Simple columnar epithelium No Brunner's glands, but large Two layers: inner circular and Serosa with villi and microvilli, more plicae circulares (folds) and outer longitudinal. developed than duodenum. increased blood vessels. Ileum Simple columnar epithelium Contains Peyer's patches Two layers: inner circular and Serosa with villi and microvilli, Peyer’s (lymphoid follicles), and less outer longitudinal. patches (lymphoid tissue). prominent plicae circulares. Large Intestine Simple columnar epithelium No folds or villi, presence of Two layers: inner circular and Serosa (transverse colon), with goblet cells and no villi, lymphatic nodules and blood outer longitudinal (teniae coli: Adventitia (ascending and many crypts of Lieberkühn vessels, particularly in the longitudinal layer forms three descending colon, rectum). (mucous-secreting). appendix. distinct bands). Anal Canal Stratified squamous Submucosa contains Two layers: inner circular Adventitia (superior part) and epithelium (keratinized near hemorrhoidal vessels. (forms internal anal sphincter) a transition to skin externally. the external opening), and outer longitudinal mucous-secreting anal glands. (smooth muscle). Cell Type Location Function Special Features Types of Cells in the Mucosa of the Stomach Surface Mucous Lining the surface Secrete mucus to Produce alkaline Cells and gastric pits protect the stomach mucus rich in lining from acidic bicarbonate gastric juice Mucous Neck Cells In the neck region of Secrete mucus to Mucus secretion is gastric glands lubricate food and thinner than surface protect the stomach mucous cells Parietal Cells Gastric glands, Secrete hydrochloric HCl helps with especially in the acid (HCl) and digestion; intrinsic fundus and body intrinsic factor factor is essential for vitamin B12 absorption Chief Cells Deeper parts of Secrete pepsinogen Pepsinogen is gastric glands (inactive enzyme) converted to pepsin (fundus and body) in the presence of HCl for protein digestion Enteroendocrine Primarily in the Secrete gastrin, a Endocrine function; Cells (G Cells) antrum (pyloric hormone that stimulates HCl region) stimulates acid production in secretion parietal cells Stem Cells Near the neck of Responsible for Undifferentiated gastric glands regeneration of the cells that give rise to gastric epithelium other cell types in the stomach  Cell Type Location Function Special Features Enterocytes Lining the villi Absorb nutrients, Have microvilli (brush electrolytes, and water border) to increase surface area for Types of Cells in the Mucosa of the Duodenum absorption Goblet Cells Scattered along the villi Secrete mucus to Increase in number lubricate and protect distally along the small the intestinal lining intestine Paneth Cells Base of crypts of Secrete antimicrobial Part of the immune Lieberkühn peptides (defensins, defense system in the lysozyme) to protect small intestine against bacteria Enteroendocrine Cells Scattered throughout Secrete hormones like Involved in regulating the crypts secretin and digestion by releasing cholecystokinin (CCK) hormones that affect bile and pancreatic secretions Brunner’s Glands Cells In the submucosa but Secrete alkaline mucus Located specifically in opening into the to neutralize stomach the duodenum, protect mucosa acid entering the the intestinal lining duodenum from acidic chyme Stem Cells Base of crypts of Regenerate the Continuously replenish Lieberkühn epithelium the enterocytes, goblet cells, and Paneth cells