Accessory Glands of the Gastrointestinal Tract PDF
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University of the East Ramon Magsaysay Memorial Medical Center
Margarita Concepcion T. Caballes, MD
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This document provides lecture notes on Accessory Glands of the Gastrointestinal Tract. It covers topics like the gross anatomy and histology of various glands, as well as learning objectives and summary of abbreviations.
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ANATOMY-LEC: LE 4 | TRANS 4 Accessory Glands of the Gastrointestinal Tract MARGARITA CONCEPCION T. CABALLES, MD | Lecture Date (01/13/2025) OUTLINE I. GROSS ANATOMY OF ACCESSORY GL...
ANATOMY-LEC: LE 4 | TRANS 4 Accessory Glands of the Gastrointestinal Tract MARGARITA CONCEPCION T. CABALLES, MD | Lecture Date (01/13/2025) OUTLINE I. GROSS ANATOMY OF ACCESSORY GLANDS OF I. Gross Anatomy of III. Review Questions THE GASTROINTESTINAL TRACT Accessory Glands of IV. Formative Quiz Gastrointestinal Tract V. References A. INTRODUCTION OF ACCESSORY GLANDS A. Introduction VI. Appendix B. Salivary Glands C. Liver D. Biliary Ducts and Gallbladder E. Pancreas II. Histology of Accessory Glands of Gastrointestinal Tract A. Salivary Glands B. Liver C. Biliary Tree and Gallbladder D. Pancreas SUMMARY OF ABBREVIATIONS GIT Gastrointestinal Tract IVC Inferior Vena Cava LUQ Left Upper Quadrant RLQ Right Lower Quadrant CBD Common Bile Duct ❗️ Must know 📣 Lecturer 📖 Book 📋 Previous Trans Figure 1. Organs associated with the GIT [Junquiera] LEARNING OBJECTIVES ✔ Identify the accessory glands of the Digestive System Organs associated with GIT ✔ Describe the gross anatomy of the accessory glands →Major salivary glands ✔ Enumerate and describe the major salivary glands ▪ Parotid gland ✔ Describe the important anatomic relationships, ▪ Sublingual gland surfaces, and peritoneal attachments of the liver as ▪ Submandibular gland well as its innervation, blood supply, and lymphatic →Liver drainage. →Gallbladder ✔ Differentiate between classical and functional →Pancreas divisions of the liver Products of these glands facilitate transport and digestion ✔ Describe the circulation of blood within the liver and of food within the GIT the intrahepatic blood flow B. MAJOR SALIVARY GLANDS ✔ Enumerate the sites of portocaval anastomoses and explain it clinical significance ✔ Describe the location and anatomic relations of the gallbladder as well as its innervation, blood supply, and lymphatic drainage ✔ Describe the parts of the pancreas, its location and important anatomic relations, as well as innervation, blood supply, and lymphatic drainage ✔ State the exocrine and endocrine functions of the pancreas ✔ State the relations between CBD and pancreatic duct as they open into the 2nd portion of the duodenum Figure 2. Major Salivary glands [Junquiera] Paired exocrine glands Functions: LE 4 TRANS 4 VER 1 TG-A24: Alo, Ang, Aquino, Asuncion, Baron, Bornasal,, TE: S. Bresnan AVPAA: M. Acuña, K. Page 1 of 23 Bueno, Cabal, Cabrera Cambay, K. Casumbal →Lubrication Figure 4. Innervation of Parotid gland [Clinically Oriented Anatomy 8th Ed.] ▪ Wets the oral cavity and its contents and lubricate Innervation: food during mastication →Parasympathetic motor supply: glossopharyngeal n. →Digestion (CN IX) ▪ Initiates carbohydrate digestion ▪ Stimulation of parasympathetic fibers produces thin, →Protection watery saliva ▪ Serves as an intrinsic “mouthwash” →Sympathetic fibers derived from the cervical ganglia ▪ Secretes protective substances: through the external carotid nerve plexus on the − IgA: principal immunoglobulin and exocrine external carotid artery secretions →Nerves would reach the gland via the tympanic branch − Lysozymes: enzyme that digests walls of certain of tympanic nerve → lesser petrosal n. → otic ganglion bacteria → parotid branches of auriculotemporal n. (CN V3) − Lactoferrin: protein that binds to iron o Iron: an essential element in bacterial cell SUBMANDIBULAR GLAND (SUBMAXILLARY GLAND) nutrition; Unavailability of iron would lead to bacterial cell death →Prevention of tooth decay →Taste perception PAROTID GLAND Figure 5. Arterial supply of the Submandibular gland [Clinical Anatomy and Operative Surgery] Figure 3. Parotid gland [Netter’s Atlas of Human Anatomy] Largest of salivary glands Located in each cheek near the ear enclosed by a parotid sheat derived from the investing layer of a deep cervical fascia Has an irregular shape Wedged between the ramus of the mandible and the mastoid process Parotid duct (Stensen’s duct) Figure 6. Sublingual caruncle [Netter’s Atlas of Human Anatomy] →Opens in the parotid papilla located opposite to upper 2nd molar tooth Lies beneath the lower border of the mandible body →Passes in front of the masseter muscles and pierces the Divided into superficial and deep parts by mylohyoid buccinator muscles and mucous membrane to empty muscle into the oral cavity Arterial Supply: Submental artery Type of secretion: Purely serous Drainage: Embedded in the parotid gland: →Accompany vein →Parotid plexus of the facial n. (CN VII) and its branches →Lymphatic vessels of the glands ❗️ ▪ CN VII is only embedded within the gland, but it →Deep cervical lymph nodes (jugulo-omohyoid lymph DOES NOT innervate the parotid gland node) →Retromandibular vein Type of secretion: Seromucous gland, predominantly →External carotid artery serous →Parotid lymph nodes Submandibular duct (Wharton’s duct) →~5 cm long →Arises from portion of the gland that lies between the mylohyoid and hyoglossus muscles →Opens to sublingual caruncle ▪ Orifices of the submandibular duct are visible ▪ Saliva often seen trickling from it Innervation: →Parasympathetic secretomotor supply: Facial nerve (CN VII) ANATOMY Accessory Glands of the Gastrointestinal Tract | Margarita Concepcion T. Caballes Page 2 of 23 salivary gland of all saliva SUBLINGUAL GLAND C. MINOR SALIVARY GLANDS Presence of serous demilunes Usually mucous, except for small serous glands at the bases of circumvallate papillae Contains plasma cells releasing IgA Produces remaining 10% of total saliva volume D. LIVER Figure 7. Sublingual gland [Netter’s Atlas of Human Anatomy] Figure 9. Liver [Lecturer’s PPT] Largest internal gland, 2nd largest organ after the skin In adults: →Weighs ~1,500 g (1.5 kg) →~2.5% of the adult body weight In mature fetus: →Hematopoietic organ →5% of the body weight LOCATION OF THE LIVER Figure 8. Sublingual fold [Netter’s Atlas of Human Anatomy] Found in the upper part of the abdominal cavity, Almond-shaped gland beneath the diaphragm Located beneath mucous membrane or sublingual fold of Greater part of the liver is situated under the cover of the the floor of the mouth close to the frenulum of the tongue right costal margin Smallest and most deeply situated of the salivary glands Normal liver lies deep to the 7th - 11th ribs (right side); Type of secretion: Mixed gland, predominantly mucous crosses the midline towards the left nipple Sublingual Duct (Duct of Rivinus): 8-20 sublingual ducts open into the mouth on the summit of the sublingual fold Arterial supply: →Sublingual a. (branch of lingual a.) →Submental a. (branch of facial a.) Innervation: →Parasympathetic motor supply: facial nerve (CN VII) via chorda tympani and submandibular ganglion →Postganglionic fibers pass directly to the gland (same as submandibular gland) Table 1. Summary of the Major Salivary glands Submandibular Sublingual Parotid gland gland gland Mixed, Mixed, predominantly Purely serous predominantly Figure 10. Location of the Liver [Lecturer’s PPT] Secretion mucous serous Morphology Branched Branched Branched Table 2. Associated structures with the position of the Liver acinar tubuloacinar tubuloacinar α-amylase α-amylase α-amylase Anteriorly Posteriorly proline-rich proline-rich Diaphragm Diaphragm proteins proteins Right and Left costal Right Kidney proline-rich Physiological lysozyme lysozyme importance proteins (by serous (by serous margins Hepatic flexure of colon demilunes) demilunes) Right and Left pleura Duodenum Ganglion Otic Submandibular Submandibular Lower margins of both Gallbladder Innervation CN IX CN VII CN VII lungs Inferior vena cava Wharton’s Xiphoid process Esophagus Stensen’s Sublingual duct/ Ducts duct/Parotid Submandibular duct/Ducts of Anterior abdominal wall Fundus of the stomach duct Rivinus in the subcostal angle duct Smallest of all Others Largest major Produces ⅔ major salivary glands ANATOMY Accessory Glands of the Gastrointestinal Tract | Margarita Concepcion T. Caballes Page 3 of 23 ▪ Duodenum Liver moves with the excursions of the diaphragm: ▪ Right colic or hepatic flexure →Located more inferiorly when one is erect due to gravity ▪ Right kidney →Palpation of the liver during physical examination ▪ Right suprarenal gland ▪ Begin palpation over the RLQ near the anterior iliac ▪ Gallbladder spine (ASIS) Diaphragmatic Surface ▪ Then, palpate the liver with 1 or 2 hands, palm down, →Smooth, dome-shaped and convex where it is related to position and move 2-3 cm upwards towards the the concavity of the inferior surface of the diaphragm lower costal margin ▪ Separates it from the pleura, lungs, pericardium, and ▪ Ask your patient to take a deep breath heart − During this time, liver can be felt moving →Falciform ligament: Divides the liver into its anatomical downward due to the movement of the diaphragm ▪ Liver may be felt hitting the caudal aspect of the 📣 right and left lobes Divided by the Falciform and Coronary ligaments palpating hand ▪ Palpate the bottom margin to feel the texture of the liver edge (e.g. soft, hard, firm, or nodular) ❗️ →Round ligament of liver: Remnant of left umbilical vein ▪ Figure 13. Anterior view of the Liver showing the falciform ligament (pointed by red arrow) and round ligament (encircled in red) [Lecturer’s PPT] Figure 11. Surface anatomy of the Liver [Clinically Oriented Anatomy 8th Ed.] FUNCTIONS OF THE LIVER Synthesis of major plasma proteins Gluconeogenesis, glycogenesis, and lipogenesis Detoxification and conjugation of ingested toxins Amino acid deamination (producing urea) Storage of Vitamin A (in hepatic stellate or Ito cells) and other fat-soluble vitamins Removal of effete erythrocytes (by Kupffer cells) Figure 14. Lateral view of the Liver showing Storage of iron complexes with the protein ferritin the Diaphragmatic surface (Purple) and Visceral surface (Orange) [Lecturer’s PPT] SURFACES OF THE LIVER Inferior Margin of the Liver →Area in between the anterior aspect of the diaphragmatic surface and the visceral surface Clinical importance: Only portion of the liver that can be palpated during physical examination Normal inferior margin texture: Sharp, soft, smooth In children: Inferior liver margin extends 1-2 fingerbreadths below the right costal margin In thin adults: Inferior liver margin extends 1 fingerbreadth below the right costal margin In obese or athletic adults (with well-developed rectus abdominis muscles): Margin would be difficult to palpate Figure 12. Lateral view of the Liver showing the Diaphragmatic surface (Purple) and Visceral surface (Orange) [Lecturer’s PPT] Anterior Aspect Posterior Aspect Visceral or Posteroinferior Surface →Relatively flat or slightly concave visceral surface →Separated anteriorly by its sharp inferior border which 📣 follows right costal margin and inferior to the diaphragm Bears an H-shaped pattern →Irregularly shaped due to impressions or contact of Figure 15. Inferior margin of the Liver [Netter’s Atlas of Human Anatomy] structures adjacent to it: ▪ Abdominal esophagus ▪ Stomach ANATOMY Accessory Glands of the Gastrointestinal Tract | Margarita Concepcion T. Caballes Page 4 of 23 LIVER FISSURES The lesser omentum has 2 parts: Visceral or Posteroinferior Surface →Hepatoduodenal ligament →Bears multiple fissures and impressions from contact ▪ Thick portion at the free edge of the lesser omentum with other organs ▪ Extends from the porta hepatis and first part of the →Bears an H-shaped pattern of fissures duodenum Right Limb / Right Sagittal Fissure / Cantlie Line ▪ Contains the portal triad →Continuous groove formed anteriorly by: →Hepatogastric ligament ▪ Fossa of the gallbladder (anteriorly) ▪ Thinner, sheet-like remainder of the lesser omentum ▪ Groove or sulcus of the IVC (posteriorly) ▪ Extends from the groove of ligamentum venosum and Left Limb / Left Sagittal Fissure / Umbilical Fissure the lesser curvature of the stomach →Formed by the fissure of: CYSTOHEPATIC TRIANGLE (CALOT’S TRIANGLE) ▪ ligamentum venosum (remnant of ductus venosus) ▪ ligamentum teres hepatis (round ligament from left umbilical vein) Horizontal Limb / Porta Hepatis →Horizontal fissure that contains the hepatic duct (HD), proper hepatic artery, and portal vein →Contains the lymphatics, sympathetic & parasympathetic nerve fibers Figure 18. Cystohepatic Triangle [Lecturer’s PPT] Surgical landmark in the visceral surface of the liver Small, anatomical space in the abdomen located at the porta hepatis of the liver Boundaries include: →Medially: common hepatic duct →Laterally: cystic duct Figure 16. Posteroinferior view of the liver showing the →Superiorly: inferior edge of the liver H-shaped pattern of fissures [Lecturer’s PPT] Contents →Right hepatic artery: Formed from the bifurcation of the LESSER OMENTUM proper hepatic artery into the right and left branches →Cystic artery: Arises from the hepatic artery; Supplies the gallbladder →Lymph node of Lund: 1st lymph node of the gallbladder →Other lymphatics ❗️Clinical Importance: During laparoscopic cholecystectomy, a minimally invasive surgical removal of the gallbladder →In this procedure, the triangle is carefully dissected by the surgeon, and its contents and borders are identified →It allows the surgeon to take into account any anatomical variation and permits safe ligation and ❗️division of the cystic duct and cystic artery Right Hepatic Artery: Must be identified by the surgeon, prior to ligation of the cystic artery PERITONEAL ATTACHMENTS Figure 17. Lesser omentum [Netter’s Atlas of Human Anatomy] Seen at the visceral surface of the liver Passes from the liver to the lesser curvature of the stomach and the first 2 cm of the superior part of the ❗️ duodenum Portal triad (revealed when the lesser omentum is dissected): Figure 19. Peritoneal attachments of the Liver [Lecturer’s PPT] Falciform ligament →Common bile duct →Double-layered fold of peritoneum derived from the →Hepatic artery proper ventral mesentery →Hepatic portal vein ANATOMY Accessory Glands of the Gastrointestinal Tract | Margarita Concepcion T. Caballes Page 5 of 23 →Attaches anterior surface of the liver to anterior Hepatorenal Recess abdominal wall above the umbilicus, and to the →Postero-superior extension of the subhepatic space diaphragm →In between the Right kidney and Right visceral surface →Has a sickle-shaped free margin of the liver ▪ Contains the ligamentum teres hepatis (round →Communicates anteriorly with Right subphrenic recess ligament) of liver →Contains the ligamentum teres hepatis (round 📣 Clinical Correlation: Peritonitis Inflammation of the peritoneum results in formation of ligament) of liver localized abscess or pus →Passes on to the anterior and then the superior surface →Right side: More common area of peritonitis due to of the liver greater frequency of a ruptured appendix or →Splits into two to form the second peritoneal attachment perforated duodenal ulcers (coronary ligament) →Subphrenic recess: Common site of accumulation of Coronary ligament abscesses →Formed from the splitting of the falciform ligament In bedridden patients: →Attaches liver to the diaphragm →Pus from the right subphrenic recess will drain into →Has anterior and posterior layers that come together the hepatorenal recess laterally and form: ▪ Hepatorenal recess: most gravity-dependent part ▪ Right triangular ligament of the peritoneal cavity when patient is supine − Formed from the right free lateral margin ▪ Left triangular ligament LOBES OF THE LIVER − Formed from the left free lateral margin CLASSICAL (ANATOMICAL) DIVISION OF THE LIVER − Merges with the left tip of the liver forming the appendix fibrosa hepatis or fibrous appendix of the liver →Peritoneal layers forming the coronary ligament are widely separated and form an area devoid of peritoneum called “Bare area of liver” ▪ Areas without peritoneum: − Bare area of liver − Groove for the IVC − Gallbladder bed − Porta hepatis POTENTIAL SPACES Figure 21. Falciform Ligament (red line) Separates liver into a larger R lobe and a much smaller L lobe via falciform ligament and the left sagittal fissure found at the midline plane Figure 20. Lateral view of the Liver showing the different potential spaces [Clinically Oriented Anatomy 8th Ed.] Formation of potential spaces in the abdominal cavity occurs due to the reflection of the peritoneum over the liver →Normal conditions: peritoneal surfaces are in contact →Abnormal conditions (i.e., accumulation of gas or fluid): Figure 22. Posteroinferior view of the liver showing the separation of peritoneal surfaces, forming spaces Quadrate and Caudate lobes Subphrenic Recess →Superior extension of the peritoneal cavity in between On the visceral surface devoid of the gallbladder and IVC, anterior and posterior aspects of the liver and the right and left sagittal fissures course on each side diaphragm The transverse porta hepatis separates the two accessory →Separated into right and left subphrenic recess by lobes of the anatomical right lobe falciform ligament → Anteriorly: Quadrate Lobe Subhepatic Space → Posteriorly: Caudate Lobe →Portion of peritoneal cavity immediately inferior to the ▪ Caudate lobe is not named because of its caudal liver position but because it appears to have a tail in the form of an elongated papillary (caudate) process ANATOMY Accessory Glands of the Gastrointestinal Tract | Margarita Concepcion T. Caballes Page 6 of 23 ▪ Caudate process - extends to the right in between Left side: Segments 2, 3, 4 the IVC and the porta hepatis, connecting caudate → Blood supply: hepatic artery, portal duct vein (drained by and right lobes of liver its own bile) Table 3. Eight hepatic segments FUNCTIONAL DIVISION OF THE LIVER Segment I Posterior/caudate segment II L posterior lateral III L anterior lateral IV L medial V R anterior medial VI R anterior lateral VII R posterior lateral VIII R posterior medial Refer to appendix for the terminology for subdivisions of 📣 liver Clinical importance: Hepatic Lobectomy R and L hepatic arteries and duct, and R and L hepatic portal veins do not communicate. Thus, possible to perform Hepatic Lobectomy Can be dissected separately due to different blood supply Figure 23. Functional Division of Liver lobes IVC and gallbladder separates liver into right and left BLOOD SUPPLY OF THE LIVER lobes that are much more equal in size → Almost equal but right lobe is somewhat larger The right and left branches of the hepatic artery, hepatic portal vein, and the right and left hepatic ducts are distributed to the right and left lobes respectively HEPATIC SEGMENTATION OF THE LIVER Figure 25. Main Blood Supply of Liver The liver has a dual blood supply → a dominant venous source → a lesser arterial one Blood flow → Hepatic Portal vein: 70% → Hepatic artery: 20-25% Figure 24. Hepatic Segmentations The liver can be further subdivided into four divisions and then into eight surgically resectable hepatic segments → Each receive a secondary or tertiary branch of the portal triad → Each segment has its own blood supply, served independently by branches of hepatic artery and portal vein and drained by its own bile duct Posterior / Caudate Segment (Segment 1) → Unique because it receives blood supply and bile duct drainage from both right and left portions of the portal triad Right side: Segments 5, 6, 7, 8 Figure 26. Overview of the blood vessels in the Liver → Blood supply and bile duct drainage: right portion of the portal triad ANATOMY Accessory Glands of the Gastrointestinal Tract | Margarita Concepcion T. Caballes Page 7 of 23 PORTAL VEIN BLOOD FLOW TO THE LIVER Brings 75-80% of the blood to the liver Drains venous blood from entire GIT →Carries all of the nutrients absorbed by the alimentary 📣 tract to the sinusoids of the liver (except for lipids) Lipids are absorbed and bypassed via the lymphatic 📋system Oxygen-poor, nutrient-rich Formed by superior mesenteric vein and splenic vein behind neck of the pancreas at the level of L1 ❗️ Runs behind first portion of duodenum, to the right border of lesser omentum then to porta hepatis where it splits into the right and left branches It branches repeatedly upon entering hilum of the liver until it reaches the area of the classic hepatic lobule Figure 28. Direction of blood flow in the Liver Hepatic artery (30%) and Hepatic portal vein (70%) brings blood to liver → Hepatic artery - brings oxygenated blood to the liver → Hepatic portal vein - brings venous blood, rich in nutrients As the blood vessels would branch, the arterial and venous blood are conducted by liver sinusoids into central vein of ❗️ each hepatic lobule, then into right, left hepatic veins, and then open directly into the IVC 📣 CLINICAL CORRELATION: Portal Hypertension❗️ An increase in the pressure within the portal vein Primary cause: → Blockage of blood vessels in the intrahepatic portal vein tree, usually caused by Cirrhosis ▪ Cirrhosis – chronic disease of the liver marked by the degeneration of the cells, inflammation and fibrous Figure 27. Distributing veins in the periphery of the hepatic thickening of tissue lobule – typically a result of alcoholism, hepatitis or other PORTAL VENULE infections As the portal vein branches out, it reaches the area of Other causes: portal triad as the portal venule → Block in intrahepatic portal vein tree This further branch into distributing veins around → Impaired outflow of blood from the liver periphery of classic hepatic lobule which sends branch to → Excessive flow of splanchnic or hepatic arterial blood inlet venules, which eventually empty to sinusoids to the liver CENTRAL VEIN Leaves the lobules at its base by merging with larger sublobular veins Sublobular veins would converge to form two or more large hepatic veins that would drain into the IVC HEPATIC ARTERY Branch of celiac plexus or celiac trunk Supply 20-25% of blood flow → Distributed initially to non-parenchymal structures particularly the intrahepatic bile ducts Oxygen rich 📣 Ramifies parallel with portal vein branches The common hepatic artery gives off the gastroduodenal artery and hepatic artery proper which would give off the R and L hepatic arteries Defects in blood flow in portal hypertension → Blood in portal circulation needs to find a way to (space intentionally left blank) return to the systemic or caval system due to blockage of some blood vessels ANATOMY Accessory Glands of the Gastrointestinal Tract | Margarita Concepcion T. Caballes Page 8 of 23 ▪ Varices: often due to the obstructed blood flow Looks for alternative pathways/routes: anastomoses through the portal vein which would carry blood from → To provide alternative routes of circulation when there the intestine, pancreas, and the spleen to the liver is blockage in the liver or portal vein Esophageal hemorrhage → Ensures that venous blood from the gastrointestinal →If there is persistence of portal hypertension (HPN), this tract still reaches the heart through the inferior vena is the most dangerous complication of portal HPN cava without going through the liver part of the →Rupture of different esophageal varices peritoneal cavity when patient is supine PARAUMBILICAL ANASTOMOSIS PORTO-SYSTEMIC ANASTOMOSES Portal: Paraumbilical veins Systemic: Superficial veins of anterior abdominal wall Caput Medusae / Medusa’s Head →Occurs when the collaterals are used and there is always high pressure or too much blood volume →Appearance of distended and engorged superficial epigastric veins which are seen radiating from the umbilicus across the abdomen →Like medusa’s head, there is a snake-like appearance of veins on the abdomen Figure 29. Esophageal Anastomosis Porto-venous system would communicate with the systemic venous system📣 Figure 30. Portal-Systemic Anastomoses Esophageal →formed in the submucosa of the esophagus Paraumbilical →formed in the submucosa of the paraumbilical veins Rectal →formed in the submucosa of the anal canal Retroperitoneal →formed in the posterior aspects of the retroperitoneal viscera In cases of portal circulation obstruction, blood from GIT can still reach the right side of the heart through IVC by these collateral routes📣 →These alternate routes are available because the hepatic portal vein and its tributaries have no valves; blood can still flow in a reverse direction to the IVC📣 →If volume of blood and pressure become excessive, varicose veins will be present📣 ESOPHAGEAL ANASTOMOSIS Figure 31. Caput Medusae/Medusa’s Head Portal: Esophageal branches of left gastric vein RECTAL ANASTOMOSIS Systemic: Esophageal Veins draining middle 3rd of Portal: Superior rectal veins esophagus Systemic: Middle and Inferior rectal veins Esophageal varicosities Hemorrhoids: →Due to the increase in pressure of these anastomosis →Caused by persistence of HPN in rectal anastomosis (overuse), there are veins that could enlarge in the esophagus and become varices → ANATOMY Accessory Glands of the Gastrointestinal Tract | Margarita Concepcion T. Caballes Page 9 of 23 RETROPERITONEAL ANASTOMOSIS Lymphatic vessels of the liver occur as the following: Portal: Veins of ascending colon, descending colon, → Superficial lymphatics duodenum, pancreas, & liver ▪ In the subperitoneal fibrous capsule of the liver Systemic: Renal, lumbar, & phrenic veins (Glisson’s capsule) which forms its outer surface Retroperitoneal varicose portocaval anastomosis: → Deep lymphatics →Caused by persistence of HPN in rectal anastomosis ▪ In the connective tissue which accompany the ramifications of portal triad and hepatic veins Most lymph is formed in the perisinusoidal spaces of Disse and drains to the deep lymphatics in the surrounding intra-lobular portal triads Lymph from the liver flows in two directions → Superiorly ▪ From the upper liver flows to the lymph nodes located in the thorax → Inferiorly ▪ From the lower liver flows to the lymph nodes located in the abdomen Figure 32. Retroperitoneal Anastomosis LYMPHATIC DRAINAGE OF THE LIVER Figure 35. Overview of the lymphatic drainage system in the Liver NERVE SUPPLY OF THE LIVER Figure 33. Subperitoneal fibrous capsule of the Liver (Glisson’s capsule) Figure 36. Nerve Supply of Liver Nerves of the liver are derived from the hepatic plexus → Largest derivative of the celiac plexus → Accompanies the branches of the hepatic artery and hepatic portal vein into the liver → Consists of sympathetic fibers from celiac plexus and parasympathetic fibers from the anterior and posterior vagal trunks → Nerve fibers accompany the vessels and biliary ducts of the portal triad → Function: vasoconstriction Figure 34. Perisinusoidal spaces of Disse draining into the nearby hepatic triad ANATOMY Accessory Glands of the Gastrointestinal Tract | Margarita Concepcion T. Caballes Page 10 of 23 LIVER REGENERATION 📖 Conveys bile from the liver to the duodenum Bile Extraordinary capacity for regeneration Controlled by chalones →Produced continuously by the liver and stored and → Self-regulating concentrated in the gallbladder, which releases it → Circulating substances which inhibit the mitotic division intermittently when fat enters the duodenum of certain cell types →Emulsifies the fat so that it can be absorbed in the distal → Compensatory Hyperplasia intestines ▪ When tissue is injured or partially removed, there will Bile duct be a decrease in the number of circulating chalones →Forms in the free edge of the lesser omentum by the and a burst in the mitotic activity of the liver cells union of the cystic duct and the common hepatic duct ▪ Repeated damage to the liver would lead to the about 5-15 cm depending on where the cystic duct joins accumulation of your fibrous tissue and fats making the common hepatic duct (varies per person) the liver firm and impeding blood flow through the →Descends posterior to the superior part of the liver duodenum and lies in the groove of the posterior ❗️ CLINICAL CORRELATION: Liver Cirrhosis Chronic disease of the liver marked by degeneration of surface of the head of the pancreas →At the left side of the descending part of the duodenum, the bile duct comes in contact with main pancreatic duct the cells, inflammation and fibrous thickening of tissue →Hepatopancreatic ampulla Typically a result of alcoholism or ▪ A dilation formed by the union of the bile duct and the Continuous or repeated damage pancreatic duct as they run obliquely through the wall → Disorganized liver structure of duodenum → Lead to accumulation of fibrous tissue and fats ▪ Would open into the duodenum as the major making the liver firm and impeding the blood flow duodenal papilla through the liver At the distal end of the bile duct, there is a thickened → To provide alternative routes of circulation when there circular muscle called sphincter of the bile duct is blockage in the liver or portal vein →Once this contracts, bile cannot enter the ampulla in the Ensures that venous blood from the gastrointestinal tract duodenum. Hence, the bile will back up and pass along still reaches the heart through the inferior vena cava the cystic duct for concentration and storage without going through the liver part of the peritoneal cavity when patient is supine E. BILIARY DUCTS AND GALLBLADDER BILE DUCT Figure 39. Sphincter of the bile duct GALLBLADDER Figure 37. Formation of the Bile duct from the union of the cystic duct and the common hepatic duct Figure 40. Gallbladder (encircled in red) Where bile would be stored and concentrated Pear-shaped sac Capacity of 30-50 ml of bile Figure 38. Connection between the bile duct and the main Attached to inferior surface of live pancreatic duct into the duodenum (Hepatopancreatic Stores and concentrates bile ampulla) ANATOMY Accessory Glands of the Gastrointestinal Tract | Margarita Concepcion T. Caballes Page 11 of 23 Borders: NERVE SUPPLY OF THE GALLBLADDER →Anteriorly: anterior abdominal wall and inferior surface Sympathetic and parasympathetic vagal fibers form the of the liver celiac plexus →Posteriorly: transverse colon; first and second part of →Gallbladder contracts in response to cholecystokinin duodenum (CCK) PARTS OF THE GALLBLADDER ▪ Enteroendocrine cells of duodenum →Stimulus: fatty food Vagus nerve: parasympathetic Right phrenic nerve: somatic afferent fibers F. PANCREAS Figure 41. Parts of the gallbladder Fundus (Red bracket) →Rounded part and projects below the inferior margin of the liver, at the tip of the 9th costal cartilage in the MCL Body/Corpus (Green bracket) →Lies in contact with the 2nd portion of the duodenum →Projects upward, downward, and into the left Neck (Purple bracket) →Constricted portion which becomes continuous with the Figure 43. The pancreas and its major parts cystic duct Elongated structure that lies in the epigastric and LUQ of →Makes an S-shaped bend the abdomen Infundibulum (Hartmann’s pouch) Soft and lobulated; yellowish in color →Located in the free edge of the lesser omentum and Situated at the posterior abdominal wall behind the bulges into the cystic duct peritoneum Cystic duct Can be seen when liver is lifted →Duct of gallbladder measuring around 2-4 cm long Two Functions: →Pars spiralis →Exocrine secretion: secretes pancreatic juice from the ▪ Initial or proximal part: tortuous portion acinar cells that would enter the duodenum through the ▪ The spiral valve (of Heister) contains mucosal main and accessory pancreatic ducts duplications that would regulate the filling and →Endocrine secretion: secretes glucagon and insulin from emptying of the gallbladder the pancreatic islets of Langerhans that would enter the →Pars glabra blood ▪ Distal end: smooth portion PARTS OF THE PANCREAS Head → Disc-shaped structure → Lies in the concavity of the duodenum to the right of the superior mesenteric vessels → Uncinate process: part of the head which extends to the left behind the superior mesenteric vessels → Rests posteriorly on the IVC renal artery and vein, and left renal vein Neck → Constricted portion that connects the head of the pancreas to the body → Lies at the beginning of the portal vein and the origin of the superior mesenteric artery from the aorta Figure 42. Tortuous part and the Smooth part Body BLOOD SUPPLY OF THE GALLBLADDER → Run upward to the left across the midline, somewhat triangular when you do a cross-section Arterial Supply Tail → Comes from cystic artery from the right hepatic artery → Part that comes in contact with the hilum of the spleen Venous Drainage → Lies anterior to the left kidney, where it is closely related → Neck & cystic duct: drain into the portal vein via cystic to the splenic hilum and left colic flexure vein → Relatively mobile and passes between the layers of the → Fundus & body: directly to visceral surface of liver splenorenal ligament with the splenic vessels LYMPH DRAINAGE OF THE GALLBLADDER Cystic lymph nodes → Hepatic nodes → Celiac nodes ANATOMY Accessory Glands of the Gastrointestinal Tract | Margarita Concepcion T. Caballes Page 12 of 23 PANCREATIC DUCTS BLOOD SUPPLY OF THE PANCREAS Figure 46. Arterial supply of the Pancreas Figure 44. Pancreatic duct of Wirsung Arterial Supply Main pancreatic duct begins at the tail and runs at the →Derived mainly from the branches of the tortuous parenchyma of the gland to the pancreatic head splenic artery → Usually unites with bile duct to form a short dilated ▪ Head, Neck, Tail: supplied by splenic artery hepatopancreatic ampulla (of Vater) which opens into ▪ Head of the pancreas is supplied by: the descending part of the duodenum at the summit of the ○ Anterior and posterior superior major duodenal papilla pancreaticoduodenal artery; branch of Accessory pancreatic duct (of Santorini) drains the gastroduodenal artery upper part of the head of the pancreas; opens into the ○ Anterior and posterior inferior duodenum at the summit of the minor duodenal papilla pancreaticoduodenal artery; branch of superior → Due to anatomical variation, not all may have this duct mesenteric artery There are smooth muscle sphincters that prevent reflux ○ Both arteries would anastomose with each other of digestive secretions and duodenal content back to the Venous Drainage common bile duct and pancreatic duct →Comes from pancreatic veins → Sphincter of pancreatic duct ▪ Splenic vein → Sphincter of bile duct ▪ Superior mesenteric vein → Sphincter of hepatopancreatic ampulla LYMPH DRAINAGE OF THE PANCREAS Table 4. Sphincters of the gallbladder and pancreas and their function Smooth Muscle Sphincter Function Sphincter of bile duct Controls the flow of bile Sphincter of pancreatic duct Prevents reflux of bile into the duct Sphincter of Oddi Prevents the duodenal content from entering the ampulla Figure 47. Celiac node of the pancreas Lymph vessels of pancreas ultimately drain into the celiac node Lymph nodes are situated along the arteries that would supply the gland Figure 45. Sphincters of the bile duct, pancreatic duct, and Have an extensive lymphatic drainage that intermingles the hepatopancreatic ampulla with the lymphatic vessels of other organs (space left intentionally blank) (space left intentionally blank) ANATOMY Accessory Glands of the Gastrointestinal Tract | Margarita Concepcion T. Caballes Page 13 of 23 Secrete enzymes and proteins NERVE SUPPLY OF THE PANCREAS Sympathetic: inhibits secretion of digestive enzymes → Greater splanchnic (T5-T9) → Lesser splanchnic (T10-T11) Parasympathetic: stimulation of pancreas would lead to the increase of enzyme content of pancreatic sections → Vagus Nerve (CN X) Sensory → Sympathetic and vagal pathways through celiac ganglia but are limited to greater splanchnic nerves II. HISTOLOGY OF THE ACCESSORY GLAND OF THE Figure 22. Serous acinus packed with serous cells GASTROINTESTINAL TRACT Major salivary glands →Parotid Gland →Submandibular Gland →Sublingual Gland A. HISTOLOGY OF SALIVARY GLANDS CELLS OF SECRETORY UNITS Figure 23. Parotid Gland: Packed with serous acini MUCOUS CELLS Cuboidal to columnar Oval nuclei pressed toward the bases of cells →Due to the accumulation of the secretory product: Mucus Often organized as cylindrical tubules Figure 21. Components of secretory units in the three major salivary gland; Red: serous-secreting cells; Yellow: mucus-secreting cells Capsule →Moderately dense connective tissue surrounding major salivary glands Septa →Divides the secretory portions of the gland into lobes and lobules Secretion of the gland →Either serous, seromucous, or mucous depending on its content of the glycoprotein mucin Salivon Figure 24.. Mucous cell →Basic secretory unit of the salivary gland →4 major parts ▪ Excretory duct ▪ Striated duct ▪ Intercalated duct ▪ Acinus ○ Blind sac composed of secretory cells ○ 3 epithelial cell types that comprise the salivary secretory units oSerous cells oMucous cells oMyoepithelial cells SEROUS CELLS Pyramidal with a broad base Rounded nuclei with basophilic cytoplasm Figure 25. Mixed gland: Submandibular Gland →Due to accumulation of rough endoplasmic reticulum in the basal 3rd of the cell and the apex filled with zymogen (protein-rich secretory granules) Usually form spherical mass of cells with lumen in center (acinus or alveolus) ANATOMY Accessory Glands of the Gastrointestinal Tract | Margarita Concepcion T. Caballes Page 14 of 23 Serous cells →Contain basophilic cytoplasm and round nuclei →Secrete abundant α-amylase ▪ α-amylase initiates the hydrolysis of carbohydrates and proline-rich proteins with antimicrobial and other protective properties SUBMANDIBULAR GLAND Figure 26. Schematic diagram of a mixed gland (left). Seromucous gland with serous demilunes (right); (T: mucous tubules, A: serous acini, D: serous demilune) MYOEPITHELIAL CELLS Inside the basal lamina surrounding acini, tubules, and the proximal ends of the duct system Contractile cells at the basal ends of secretory cells Its processes are “embracing” the associated secretory Figure 28. Submandibular gland Morphology: branched tubuloacinar Secretion: mixed, predominantly serous ❗️ ❗️ unit or duct Presence of serous demilunes Contractions of these cells help propel secretory products →Short mucous tubules that combine with the distal from acini into the duct system clusters of serous cells Their activity is important for moving secretory products →Secrete lysozyme intro and through the ducts SUBLINGUAL GLAND Table 5. Comparison of different cells in secretory units SEROUS MUCOUS MYOEPITHELIAL CELLS CELLS CELLS Shape Pyramidal Columnar Small, flattened Nuclei Round Compressed Compressed Apical secretory Present Present - granules Around secretory Organization Acinus Tubules unit or duct Important for Well-stained moving secretory Others RER (basal products into 3rd) and through the ducts Figure 29. Sublingual gland Morphology: branched tubuloacinar Secretion: mixed, predominantly mucous ❗️ ❗️ PAROTID GLAND Few serous cells, only at serous demilunes Table 6. Characteristics of the major salivary glands PAROTID SUBMANDIBULAR SUBLINGUAL GLAND GLAND GLAND Mixed Purely Mixed (Serous Secretion (Mucous > serous > Mucous) Serous) Branched Branched Branched Morphology acinar tubuloacinar tubuloacinar α-amylase α-amylase proline rich proline-rich α-amylase ❗️ ❗️ Figure 27. Parotid Gland Physiologic proteins proteins proline-rich Morphology: branched acinar Importance lysozyme (by Lysozyme proteins Secretion: purely serous serous (by serous Divided into numerous lobules, each containing many demilunes) demilunes) secretory units Submandibu Ganglion Otic Submandibular →Connective tissue septa radiate between the lobules lar from an outer capsule, and convey blood vessels, Innervation CN IX CN VII CN VII nerves, and large excretory ducts ANATOMY Accessory Glands of the Gastrointestinal Tract | Margarita Concepcion T. Caballes Page 15 of 23 Produce ⅔ of Others all saliva Stensen’s duct Sublingual opens in Wharton’s ducts of parotid duct opens Rivinus papilla into sublingual open into opposite caruncle sublingual the upper fold 2nd molar MINOR SALIVARY GLANDS Usually mucous except for the small serous glands at the bases of circumvallate papillae B. HISTOLOGY OF THE LIVER Figure 30. Histology of the Liver STROMA Liver’s supporting framework Continuous with Glisson’s capsule Figure 32 and 33. Hepatic lobules →Glisson’s Capsule ▪ Thin connective tissue SINUSOIDAL CAPILLARIES ▪ Made up of collagenous tissue Vascular channels/capillaries between anastomosing ▪ Covered by mesothelial cells from peritoneum plates of hepatocytes in the hepatic lobules Thicker at hilum Emerge from peripheral branches of the portal vein and Vessels and ducts covered with CT all the way to their hepatic artery termination Converge into the lobule central vein Blood vessels, nerves, lymphatic vessels, and bile ducts →Venous and arterial blood mix in these sinusoids travel within the connective tissue stroma Anastomosing sinusoid have thin, discontinuous linings of fenestrated endothelial cells surrounded by sparse basal PARENCHYMA lamina and reticular fibers Functional tissue that makes up the bulk of liver →These discontinuities and fenestrations allow plasma to Consists of thousands of polygonal hepatic lobules fill a narrow perisinusoidal space (Space of Disse) →Made up of irregular plates of hepatocytes arranged ▪ Space between the hepatocytes and plasma radially around a central vein Direct contact between hepatocytes and plasma facilitates Portal triad most key hepatocyte functions involving uptake and →Consists of: Branch of portal vein, branch of the hepatic release of nutrients, proteins, and potential toxins artery, and branch of the bile duct 2 functionally important cells found in the sinusoids of the hepatic lobule: →Stellate macrophages (Kupffer cells) ▪ Found within the sinusoid lining ▪ Recognize and phagocytose aged erythrocytes which frees heme and iron for reuse or storage in ferritin complexes ▪ Antigen-presenting cells ▪ Remove bacteria or debris present in the portal blood →Hepatic stellate cells (Ito’s cells) ▪ Found in the perisinusoidal space ▪ With small lipid droplets that stores Vitamin A and other fat-soluble vitamins (ADEK) ▪ Produce extracellular matrix (ECM) components and cytokines that help regulate Kupffer cells activities →Both Kupffer and Ito’s cells are difficult to find in routine preparations, requiring special staining Figure 31. Portal Triad ANATOMY Accessory Glands of the Gastrointestinal Tract | Margarita Concepcion T. Caballes Page 16 of 23 →Numerous mitochondria ▪ Provides energy for the liver’s diverse activity and functions Figure 34. Hepatocytes and sinusoids Figure 35. K: Kupffer cells, E: endothelial cells, H: hepatocytes, HS: hepatic stellate cells, S: sinusoids, PS: perisinusoidal space Figure 36. Hepatocytes HEPATOCYTES STRUCTURE-FUNCTION RELATIONSHIPS IN LIVER Liver cells that make up hepatic lobules Large cuboidal or polyhedral epithelial cells Large, round, central nuclei →Contains peripherally dispersed chromatin and prominent nucleoli Eosinophilic cytoplasm →Due to the rich mitochondria →With a fine basophilic granularity due to the extensive free ribosome and rough endoplasmic reticulum Binucleated cells →50% are polypoid with 2-8 times the normal chromosome number Relatively long-lived for cells associated with the digestive system with an average life span of 5 months Capable of considerable regeneration when liver substance is lost to hepatotoxic processes, disease, or Figure 37. Structure-Function Relationship in liver surgery Classic hepatic lobule drain blood from portal vein and Highly versatile cells with diverse functions that are hepatic artery to the hepatic or the central vein reflected on their structures Portal lobule drains bile from hepatocytes to the bile duct; →Abundant rough ER involves the portal triad ▪ Synthesizes the plasma proteins such as fibrinogen, Hepatic acinus supplies oxygenated blood to the lipoprotein, albumin, and prothrombin hepatocytes in between 2 hepatic lobules is the central →Abundant smooth ER portal triads ▪ Contain the enzyme systems for biotransformation or detoxification of substances in the blood, which are then usually excreted with bile ○ Important in carbohydrate metabolism, bile formation, catabolism of drugs and other toxic (space intentionally left blank) compounds ○ Conjugates bilirubin to glucuronate →Peroxisomes ▪ Helps in the oxidative activity in the metabolism of lipids purines, alcohol and in gluconeogenesis ANATOMY Accessory Glands of the Gastrointestinal Tract | Margarita Concepcion T. Caballes Page 17 of 23 CLASSIC HEPATIC LOBULE Emphasizes the exocrine function of the liver →Drainage of bile from hepatocytes to bile duct Point of entry to the portal lobule = Interlobular bile duct of the portal triad of the classic lobule Triangular in shape →Center: Portal triad →Angles: Central vein Flow of bile →From: Regions of 3 classic lobules →Towards: Bile duct in the portal triad (center) Figure 38. Classic hepatic lobule. [DITKI Medical and Biological Sciences] Relatively long-lived for cells associated with the digestive system with an average life span of 5 months Capable of considerable regeneration when liver substance is lost to hepatotoxic processes, disease, or surgery Highly Figure 41. Portal lobule. [Lecturer’s video] Emphasizes the major endocrine function of the liver HEPATIC ACINUS Synthesis and secretion of major plasma proteins such as Smallest functional unit of the hepatic parenchyma fibrinogen, albumin, and transferrin Supplies oxygenated blood to hepatocytes Consists of stacks of anastomosing plates of hepatocytes, Area irrigated by a terminal branch of the distributing vein around 1 cell thick Diamond or rhomboid in shape →Separated by an anastomosing system of sinusoids that →Short axis: Terminal branches of the portal triads perfuse the cells with mixed portal and arterial blood between 2 classic lobules Hexagonal in shape →Long axis: Line drawn between the 2 central veins →Center: Terminal hepatic venule (central vein) closest to the short axis ▪ Relatively large venule into which sinusoids would drain →Angles: Portal canals Figure 42. Hepatic acinus. [Lecturer’s video] Hepatocytes are arranged in 3 concentric elliptical zones surrounding the short axis →Zone 1 Figure 39. Classic hepatic lobule. [Lecturer’s video] ▪ Receives the most oxygen and nutrients PORTAL LOBULE ○ Hepatocytes in this zone are the first to receive these resources ▪ Can most readily carry out functions requiring oxidative metabolism (e.g. protein synthesis) ▪ First to show morphologic changes after bile duct occlusion ▪ Last to die if circulation is impaired ○ However, hepatocytes in this zone will also be the first to regenerate →Zone 2 ▪ Intermediate range of metabolic functions between zones 1 and 3 →Zone 3 Figure 40. Portal lobule (Center: Portal triad; Angle: Central ▪ Closest to the central vein vein). [Lecturer’s video] ▪ Receives the least oxygen and nutrients ANATOMY Accessory Glands of the Gastrointestinal Tract | Margarita Concepcion T. Caballes Page 18 of 23 ▪ Preferential sites of glycolysis, lipid formation, and The hepatic, c
