Accessory Glands of the Gastrointestinal Tract (PDF)

ANATOMY | TRANS 4 Accessory Glands of the Gastrointestinal Tract DR. MARGARITA CONCEPCION T. CABALLES, MD, DPPS | 01/22/2024 | Version 1 OUTLINE I. GROSS ANATOMY...

ANATOMY | TRANS 4 Accessory Glands of the Gastrointestinal Tract DR. MARGARITA CONCEPCION T. CABALLES, MD, DPPS | 01/22/2024 | Version 1 OUTLINE I. GROSS ANATOMY OF ACCESSORY GLANDS OF I. Gross Anatomy of II. Histology of Accessory THE GASTROINTESTINAL TRACT Accessory Glands of the Glands of the A. INTRODUCTION OF ACCESSORY GLANDS Gastrointestinal Tract Gastrointestinal Tract A. Introduction of Accessory A. Histology of Secretory Cells Glands B. Histology of the Salivary B. Gross Anatomy of the Glands Salivary Glands C. Histology of the Liver C. Gross Anatomy of the D. Histology of the Biliary Tree Liver and Gallbladder D. Gross Anatomy of the E. Histology of the Pancreas Biliary Ducts and III. Cases Gallbladder IV. Review Questions V. References VI. Appendix ❗️ Must know 💬 Lecturer 📖 Book 📋 Previous Trans SUMMARY OF ABBREVIATIONS GIT Gastrointestinal Tract IVC Inferior Vena Cava RUQ Right Upper Quadrant RLQ Right Lower Quadrant LUQ Left Upper Quadrant LLQ Left Lower Quadrant R Right L Left Figure 1. Organs associated with the GIT [Junquiera] HPN Portal Hypertension Organs associated with GIT LEARNING OBJECTIVES → Major salivary glands ✔ Identify the accessory glands of the Digestive System ▪ Parotid gland ✔ Describe the gross anatomy of the accessory glands ▪ Sublingual gland ✔ Describe the histology of the accessory glands ▪ Submandibular gland ✔ Enumerate and describe the major salivary glands and classify → Liver each based on the nature of its secretion → Gallbladder ✔ Describe the important anatomic relationships, surfaces, and → Pancreas peritoneal attachments of the liver including its innervation, Products of these glands facilitate transport and digestion of food blood supply, and lymphatic drainage within the GIT ✔ Describe the structural organization of the liver ✔ Enumerate and describe the structure-function relationships in B. SALIVARY GLANDS the liver ✔ Differentiate between classical and functional divisions of the liver ✔ Describe the circulation of blood within the liver and the intrahepatic blood flow ✔ 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 ✔ Describe the histology of the pancreas, biliary tree, and gallbladder ✔ 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 Paired exocrine glands Functions → Lubrication ▪ Wets the oral cavity and its contents and lubricate food during mastication → Digestion ▪ Initiates carbohydrate digestion → Protection LE 4 TG 19 | M. Cruz, V. Cuasay, L. Cueva, M. Cunan, J. Cunanan, J. TE | K. Cruz AVPAA | C. Cabuyao, C. Cambas, M. PAGE 1 TRANS 4 Curso, F. Custodio Carating of 24 ANATOMY | LE4 Accessory Glands of the Gastrointestinal Tract | Dr. Margarita Concepcion T. Caballes, MD, DPPS ▪ Serves as an intrinsic “mouthwash” → Nerves would reach the gland via the tympanic branch of ▪ Secretes protective substances: tympanic nerve → lesser petrosal n. → otic ganglion → parotid − IgA: principal immunoglobulin and exocrine secretions branches of auriculotemporal n. (CN V3) − Lysozymes: enzyme that digests walls of certain bacteria − Lactoferrin: protein that binds to iron SUBMANDIBULAR GLAND o Iron: essential element in bacterial cell 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 Figure 3. Parotid gland (encircled in red) Largest of salivary glands Parotid duct (Stensen’s duct) → opens in the parotid papilla located opposite to upper 2nd molar tooth → passes in front of the masseter muscles and pierces the buccinator muscles and mucous membrane to empty into the oral cavity Located in each cheek near the ear enclosed by a parotid sheath 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 Type of secretion: purely serous Embedded in the parotid gland: → Parotid plexus of the facial n. (CN VII) and its branches ▪ CN VII is only embedded within the gland, but it does not innervate the parotid gland → Retromandibular vein → External carotid artery → Parotid lymph nodes Figure 6. Sublingual caruncle (encircled in red); Submandibular duct (green structure encircled in green) Lies beneath the lower border of the mandible body Divided into superficial and deep parts by mylohyoid muscle Type of secretion: Mixed gland, predominantly serous Has a duct called the submandibular duct (Wharton’s Duct) → ~5cm long → Arises from portion of the gland that lies between the mylohyoid and hyoglossus muscles → Opens to sublingual caruncle (see Figure 6.) ▪ Orifices of the submandibular duct are visible ▪ Saliva often seen trickling from it Arterial Supply: → Submental artery Drainage: → Accompany vein Figure 4. Parotid Gland innervation → Lymphatic vessels of the glands Innervation: → Deep cervical lymph nodes (jugulo-omohyoid lymph node) → Parasympathetic motor supply: glossopharyngeal n. (CN IX) Innervation: ▪ Stimulation of parasympathetic fibers produces thin, watery → Parasympathetic secretomotor supply: facial nerve (CN VII) saliva Produces ⅔ of the total saliva → Sympathetic fibers derived from the cervical ganglia through the external carotid artery ANATOMY Accessory Glands of the Gastrointestinal Tract PAGE 2 of 24 ANATOMY | LE4 Accessory Glands of the Gastrointestinal Tract | Dr. Margarita Concepcion T. Caballes, MD, DPPS SUBLINGUAL GLAND Morphology Branched Branched Branched acinar tubuloacinar tubuloacinar Physiologic - α-amylase - α-amylase - α-amylase Importance - proline-rich - proline-rich - proline-rich proteins proteins proteins - lysozyme - lysozyme (by serous (by serous demilunes) demilunes) Ganglion Otic Submandibul Submandibul ar ar Innervation CN IX CN VII CN VII Others Largest major Produces ⅔ Smallest of all salivary gland of all saliva major salivary glands Figure 7. Sublingual gland (encircled in red) Ducts Stensen’s Wharton’s Sublingual duct/Parotid duct/Subman duct/Ducts of duct dibular duct Rivinus Opening of Parotid Sublingual Sublingual duct papilla caruncle fold opposite the upper 2nd molar MINOR SALIVARY GLANDS 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 C. LIVER Figure 8. Sublingual fold (encircled in red) Smallest and most deeply situated of the salivary glands Almond-shaped gland Located beneath mucous membrane or sublingual fold of the floor of the mouth close to the frenulum of the tongue Type of secretion: Mixed gland, predominantly mucous → Serous glands are only found at serous demilunes → Serous demilunes secrete lysozymes that destroy the bacterial wall Has a duct called the Sublingual Duct (Duct of Rivinus) → 8-20 sublingual ducts open into the mouth on the summit of the sublingual fold Arterial Supply: Figure 9. Liver → Sublingual a. (branch of lingual a.) → Submental a. (branch of facial a.) Largest internal gland, 2nd largest organ after the skin Innervation: In adults: → Parasympathetic motor supply: facial nerve (CN VII) via chorda → Weighs ~1,500g (1.5kg) tympani and submandibular ganglion → ~2.5% of the adult body weight → Postganglionic fibers pass directly to the gland (same as In mature fetus: submandibular gland) → Hematopoietic → 5% of the body weight Table 1. Summary of the major salivary glands Parotid Submandibu Sublingual lar Secretion Purely serous Mixed, Mixed, predominantly predominantly serous mucous ANATOMY Accessory Glands of the Gastrointestinal Tract PAGE 3 of 24 ANATOMY | LE4 Accessory Glands of the Gastrointestinal Tract | Dr. Margarita Concepcion T. Caballes, MD, DPPS LOCATION OF THE LIVER 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) Storage of iron complexes with the protein ferritin SURFACES OF THE LIVER Figure 10. Location of the Liver Figure 13. Lateral view of the Liver showing the Diaphragmatic surface (Purple) and Visceral surface (Orange) Figure 11. Surface anatomy of the Liver Found in the upper part of the abdominal cavity, beneath the diaphragm; mostly in the Right Upper Quadrant (RUQ) Greater part of the liver is situated under the cover of the right costal margin Normal liver lies deep to the 7th - 11th ribs (right side); crosses the midline towards the left nipple Liver moves with the excursions of the diaphragm: → Located more inferiorly when one is erect due to gravity → Palpation of the liver during physical examination Figure 14. Anterior view of the Liver showing the falciform ▪ Begin palpation over the RLQ near the anterior iliac spine ligament (pointed by red arrow) and round ligament (encircled in ▪ Then, palpate the liver with 1 or 2 hands, palm down, red) position and move 2-3cms upwards towards the lower costal margin ▪ Ask your patient to take a deep breath; during this time, liver can be felt moving downward due to the movement of the diaphragm ▪ Liver may be felt hitting the caudal aspect of the palpating hand ▪ Palpate the bottom margin to feel the texture of the liver edge (e.g. soft, hard, firm, or nodular) Figure 15. Posteroinferior view of the Liver showing the round ligament (encircled in red) Diaphragmatic Surface → Continuous with the anterior, superior, and posterior aspects → Smooth, dome-shaped and convex where it is related to the concavity of the inferior surface of the diaphragm ▪ Separates it from the pleura, lungs, pericardium, and heart Figure 12. Palpation of the Liver during physical examination → Covered with visceral peritoneum except posteriorly by the FUNCTIONS OF THE LIVER Production and secretion of bile ❗️ bare area → Falciform ligament ▪ Divides the liver into its anatomical R and L lobes Synthesis of major plasma proteins → Round ligament of liver (see Figure 15.) Gluconeogenesis, glycogenesis, and lipogenesis ▪ Remnant of umbilical vein ANATOMY Accessory Glands of the Gastrointestinal Tract PAGE 4 of 24 ANATOMY | LE4 Accessory Glands of the Gastrointestinal Tract | Dr. Margarita Concepcion T. Caballes, MD, DPPS → Round ligament & small paraumbilical veins Figure 17. Posteroinferior view of the liver showing the H-shaped ▪ Course the free edge of the falciform ligament pattern of fissures Anterior Aspect Posterior Aspect Visceral or Posteroinferior Surface Visceral or Posteroinferior Surface → Bears multiple fissures and impressions from contact with other → Relatively flat or slightly concave visceral surface organs → Separated anteriorly by its sharp inferior border which follows → Bears an H-shaped pattern of fissures right costal margin and inferior to the diaphragm Right Limb / Right Sagittal Fissure/Cantlie Line → Covered by visceral peritoneum except in the fossa of the → Continuous groove formed by: gallbladder and the porta hepatis ▪ Fossa of the gallbladder (anteriorly) → Irregularly shaped due to impressions of structures adjacent to ▪ Groove or sulcus of the IVC (posteriorly) it: Left Limb / Left Sagittal Fissure/Umbilical Fissure ▪ Abdominal esophagus → Formed by the fissure of the ligamentum venosum (remnant ▪ Stomach of ductus venosus) and ligamentum teres hepatis (round ▪ Duodenum ligament from left umbilical vein) ▪ Right colic or hepatic flexure Horizontal Limb / Porta Hepatis ▪ Right kidney → Horizontal fissure that contains the hepatic duct (HD), proper ▪ Right suprarenal gland hepatic artery, and portal vein ▪ Gallbladder → Contains the lymphatics, sympathetic & parasympathetic nerve fibers LESSER OMENTUM Figure 16. Inferior margin of the Liver Inferior Margin of the Liver Figure 18. Lesser Omentum → Area in between the anterior aspect of the diaphragmatic surface and the visceral surface Seen at the visceral surface of the liver → To palpate, examiner should: Passes from the liver to the lesser curvature of the stomach and ▪ Place the left hand posteriorly at the lower ribcage and the the first 2cm of the superior part of the duodenum right hand on the patient’s right upper quadrant lateral to the Portal triad (revealed when the lesser omentum is dissected): rectus abdominis and inferior to the costal margin → Common bile duct ▪ Ask the patient to take a deep breath as the examiner → Hepatic artery proper presses posteriorly → Hepatic portal vein → Clinical importance: The lesser omentum has 2 parts: ▪ Only portion of the liver that can be palpated during physical → Hepatoduodenal ligament examination ▪ Thick portion at the free edge of the lesser omentum ▪ Normal inferior margin texture: ▪ Extends from the porta hepatis and first part of the − sharp, soft, and smooth duodenum ▪ In children: ▪ Contains the portal triad − Inferior liver margin extends 1-2 fingerbreadths below the → Hepatogastric ligament right costal margin ▪ Thinner, sheet-like remainder of the lesser omentum ▪ In thin adults: ▪ Extends from the groove of ligamentum venosum and the − Inferior liver margin extends 1 fingerbreadth below the lesser curvature of the stomach right costal margin ▪ In obese or athletic adults (with well-developed rectus CYSTOHEPATIC TRIANGLE abdominis muscles) − Margin would be difficult to palpate LIVER FISSURES Figure 19. Cystohepatic Triangle ANATOMY Accessory Glands of the Gastrointestinal Tract PAGE 5 of 24 ANATOMY | LE4 Accessory Glands of the Gastrointestinal Tract | Dr. Margarita Concepcion T. Caballes, MD, DPPS a.k.a. Calot’s Triangle Surgical landmark in the visceral surface of the liver POTENTIAL SPACES Small, anatomical space in the abdomen located at the porta hepatis of the liver Boundaries include: → Medially: common hepatic duct → Laterally: cystic duct → Superiorly: inferior edge of the liver ▪ Abdominal esophagus Contents: → Right hepatic artery ▪ Formed from the bifurcation of the proper hepatic artery into the right and left branches → Cystic artery (arises from hepatic artery) ▪ Supplies gallbladder → Lymph node of Lund ▪ 1st lymph node of the gallbladder → Other lymphatics Important during laparoscopic cholecystectomy to identify the borders correctly especially in taking out the gallbladder. Must be taken into account any anatomical variations to know which one to ligate. Figure 21. Lateral view of the Liver showing the different potential PERITONEAL ATTACHMENTS spaces 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): separation of peritoneal surfaces, forming spaces Subphrenic Recess → Superior extension of the peritoneal cavity in between anterior and posterior aspects of the liver and diaphragm → Separated into right and left subphrenic recess by falciform ligament Subhepatic Space → Portion of peritoneal cavity immediately inferior to the liver Figure 20. Peritoneal attachments of the Liver Hepatorenal Recess → Postero-superior extension of the subhepatic space Falciform Ligament → In between the R kidney and R visceral surface of the liver → Double-layered fold of peritoneum derived from the ventral → Communicates anteriorly with R subphrenic recess mesentery → Attaches anterior surface of the liver to anterior abdominal wall above the umbilicus, and to the diaphragm CLINICAL CORRELATION: Peritonitis → Has a sickle-shaped free margin Inflammation of the peritoneum results in formation of localized ▪ Contains the ligamentum teres hepatis (round ligament) of abscess or pus liver → Right side → Contains the ligamentum teres hepatis (round ligament) of liver ▪ More common area of peritonitis due to greater → Passes on to the anterior and then the superior surface of the frequency of a ruptured appendix or perforated duodenal liver ulcers → Splits into two to form the second peritoneal attachment → Subphrenic recess (coronary ligament) ▪ Common site of accumulation of abscesses Coronary Ligament In bedridden patients: → Formed from the splitting of the falciform ligament → Pus from the right subphrenic recess will drain into the → Attaches liver to the diaphragm hepatorenal recess → Has anterior and posterior layers that come together laterally ▪ Hepatorenal recess and form: − most gravity-dependent part of the peritoneal cavity ▪ Right triangular ligament when patient is supine − Formed from the right free lateral margin ▪ Left triangular ligament − Formed from the left free lateral margin − 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 MUST KNOW ❗️ If asked to identify during practicals, alway put the complete name: round ligament of the liver ANATOMY Accessory Glands of the Gastrointestinal Tract PAGE 6 of 24 ANATOMY | LE4 Accessory Glands of the Gastrointestinal Tract | Dr. Margarita Concepcion T. Caballes, MD, DPPS ▪ Caudate process - extends to the right in between the IVC and the porta hepatis, connecting caudate and right lobes of liver FUNCTIONAL DIVISION OF THE LIVER Figure 22. Pus from the subphrenic recess draining into the hepatorenal recess in bedridden patients LOBES OF THE LIVER CLASSICAL (ANATOMICAL) DIVISION OF THE LIVER Figure 25. Functional Division of Liver lobes IVC and gallbladder separates liver into right and left 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 23. 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 26. Hepatic Segmentations The liver can be further subdivided into four divisions and then into eight surgically resectable hepatic segments Figure 24. Posteroinferior view of the liver showing the Quadrate and → Each receive a secondary or tertiary branch of the portal Caudate lobes triad → Each segment has its own blood supply, served independently On the visceral surface, the right and left sagittal fissures would by branches of hepatic artery and portal vein and drained by course on each side its own bile duct The transverse porta hepatis separates the two accessory lobes of Posterior / Caudate Segment (Segment 1) the anatomical right lobe → Unique because it receives blood supply and bile duct drainage → Anteriorly: Quadrate Lobe from both right and left portions of the portal triad → Posteriorly: Caudate Lobe Right side: Segments 5, 6, 7, 8 ▪ Caudate lobe is not named because of its caudal position → Blood supply and bile duct drainage: right portion of the portal but because it appears to have a tail in the form of an triad elongated papillary (caudate) process Left side: Segments 2, 3, 4 ANATOMY Accessory Glands of the Gastrointestinal Tract PAGE 7 of 24 ANATOMY | LE4 Accessory Glands of the Gastrointestinal Tract | Dr. Margarita Concepcion T. Caballes, MD, DPPS → Blood supply: hepatic artery, portal duct vein (drained by its PORTAL VEIN own bile) Brings 75-80% of the blood to the liver Drains venous blood from entire GIT Table 2. Eight hepatic segments → carries all of the nutrients absorbed by the alimentary tract to I Segment Posterior/caudate segment → 📋 the sinusoids of the liver (except for lipids) Oxygen-poor, nutrient-rich Formed by superior mesenteric vein and splenic artery behind II L posterior lateral neck of the pancreas at the level of L1 III L anterior lateral Runs behind first portion of duodenum, to the right border of lesser IV L medial omentum then to porta hepatis where it splits into the right and left V R anterior medial branches It branches repeatedly upon entering hilum of the liver until it VI R anterior lateral reaches the area of the classic hepatic lobule VII R posterior lateral VIII R posterior medial Refer to appendix for the terminology for subdivisions of liver Clinical application: Hepatic Lobectomy → Done when there is malignancy or mass in an area of the liver that should be removed → If a section of the liver is removed, there will be no excessive bleeding because you are just removing a certain part which has its own blood supply → The surgery will not be bloody and other segments won’t be compromised as these have its independent blood supply BLOOD SUPPLY OF THE LIVER Figure 29. Distributing veins in the periphery of the hepatic lobule PORTAL VENULE As the portal vein branches out, it reaches the area of portal triad as the portal venule This further branch into distributing veins around periphery of classic hepatic lobule which sends branch to inlet venules, which eventually empty to sinusoids Figure 27. Main Blood Supply of Liver CENTRAL VEIN Leaves the lobules at its base by merging with larger sublobular The liver has a dual blood supply veins → a dominant venous source Sublobular veins would converge to form two or more large → a lesser arterial one hepatic veins that would drain into the IVC Blood flow → Hepatic Portal vein - 70% HEPATIC ARTERY → Hepatic artery - 20-25% 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 Figure 28. Overview of the blood vessels in the Liver ANATOMY Accessory Glands of the Gastrointestinal Tract PAGE 8 of 24 ANATOMY | LE4 Accessory Glands of the Gastrointestinal Tract | Dr. Margarita Concepcion T. Caballes, MD, DPPS BLOOD FLOW TO THE LIVER PORTOCAVAL ANASTOMOSES Figure 30. 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 Figure 31. Esophageal Anastomosis Primary cause: → Blockage of blood vessels in the intrahepatic portal vein → Portal: Esophageal branches of left gastric vein tree, usually caused by Cirrhosis → Systemic: Esophageal Veins draining middle 3rd of esophagus ▪ Cirrhosis → Esophageal varicosities − chronic disease of the liver marked by the ▪ Due to the increase in pressure of these anastomosis degeneration of the cells, inflammation and fibrous (overuse), there are veins that could enlarge in the thickening of tissue esophagus and become varices − typically a result of alcoholism, hepatitis or other − Varices: often due to the obstructed blood flow through infections the portal vein which would carry blood from the Other causes: intestine, pancreas, and the spleen to the liver → Block in intrahepatic portal vein tree → Esophageal hemorrhage → Impaired outflow of blood from the liver ▪ If there is persistence of portal hypertension (HPN), this is → Excessive flow of splanchnic or hepatic arterial blood to the the most dangerous complication of portal HPN liver ▪ Rupture of different esophageal varices Defects in blood flow in portal hypertension Paraumbilical Anastomosis → Blood in portal circulation needs to find a way to return to → Portal: Paraumbilical veins the systemic or caval system due to blockage of some blood → Systemic: Superficial veins of anterior abdominal wall vessels → Caput Medusae / Medusa’s Head Looks for alternative pathways/routes: anastomoses ▪ Occurs when the collaterals are used and there is always → To provide alternative routes of circulation when there is high pressure or too much blood volume blockage in the liver or portal vein ▪ Appearance of distended and engorged superficial Ensures that venous blood from the gastrointestinal tract still epigastric veins which are seen radiating from the umbilicus reaches the heart through the inferior vena cava without going across the abdomen through the liver part of the peritoneal cavity when patient is ▪ Like medusa’s head, there is a snake-like appearance of supine veins on the abdomen ANATOMY Accessory Glands of the Gastrointestinal Tract PAGE 9 of 24 ANATOMY | LE4 Accessory Glands of the Gastrointestinal Tract | Dr. Margarita Concepcion T. Caballes, MD, DPPS Figure 32. Portal-Systemic Anastomoses Figure 34. Retroperitoneal Anastomosis → Portal: Veins of ascending colon, descending colon, duodenum, pancreas, & liver → Systemic: Renal, lumbar, & phrenic veins → Retroperitoneal varicose portocaval anastomosis ▪ Caused by persistence of HPN in the retroperitoneal anastomosis Figure 33. Caput Medusae/Medusa’s Head LYMPHATIC DRAINAGE OF THE LIVER Rectal Anastomosis → Portal: Superior rectal veins → Systemic: Middle and Inferior rectal veins → Hemorrhoids ▪ Caused by persistence of HPN in rectal anastomosis Retroperitoneal Anastomosis Figure 35. Subperitoneal fibrous capsule of the Liver (Glisson’s capsule) ANATOMY Accessory Glands of the Gastrointestinal Tract PAGE 10 of 24 ANATOMY | LE4 Accessory Glands of the Gastrointestinal Tract | Dr. Margarita Concepcion T. Caballes, MD, DPPS Figure 38. 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 LIVER REGENERATION Extraordinary capacity for regeneration Controlled by chalones → Self-regulating Figure 36. Perisinusoidal spaces of Disse draining into the nearby → Circulating substances which inhibit the mitotic division of hepatic triad certain cell types → Compensatory Hyperplasia Lymphatic vessels of the liver occur as the following: ▪ When tissue is injured or partially removed, there will be a → Superficial lymphatics decrease in the number of circulating chalones and a burst ▪ In the subperitoneal fibrous capsule of the liver (Glisson’s in the mitotic activity of the liver cells capsule) which forms its outer surface ▪ Repeated damage to the liver would lead to the → Deep lymphatics accumulation of your fibrous tissue and fats making the liver ▪ In the connective tissue which accompany the ramifications firm and impeding blood flow through the liver 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 CLINICAL CORRELATION: Liver Cirrhosis portal triads Chronic disease of the liver marked by degeneration of the Lymph from the liver flows in two directions cells, inflammation and fibrous thickening of tissue → Superiorly Typically a result of alcoholism or ▪ From the upper liver flows to the lymph nodes located in the Continuous or repeated damage thorax → Disorganized liver structure → Inferiorly → Lead to accumulation of fibrous tissue and fats making the ▪ From the lower liver flows to the lymph nodes located in the liver firm and impeding the blood flow through the liver abdomen → To provide alternative routes of circulation when there is blockage in the liver or portal vein Ensures that venous blood from the gastrointestinal tract still reaches the heart through the inferior vena cava without going through the liver part of the peritoneal cavity when patient is supine D. BILIARY DUCTS AND GALLBLADDER BILE DUCT Figure 37. Overview of the lymphatic drainage system in the Liver NERVE SUPPLY OF THE LIVER Figure 39. Formation of the Bile duct from the union of the cystic duct and the common hepatic duct ANATOMY Accessory Glands of the Gastrointestinal Tract PAGE 11 of 24 ANATOMY | LE4 Accessory Glands of the Gastrointestinal Tract | Dr. Margarita Concepcion T. Caballes, MD, DPPS GALLBLADDER Figure 42. the gallbladder (encircled in red) Where bile would be stored and concentrated Pear-shaped sac Capacity of 30-50 ml of bile Figure 40. Connection between the bile duct and the main Attached to inferior surface of liver pancreatic duct into the duodenum (Hepatopancreatic ampulla) Stores and concentrates bile 💬 Borders: Conveys bile from the liver to the duodenum → Anteriorly: anterior abdominal wall and inferior surface of the Bile liver → Produced continuously by the liver and stored and → Posteriorly: transverse colon; first and second part of concentrated in the gallbladder, which releases it intermittently duodenum when fat enters the duodenum PARTS OF THE GALLBLADDER → Emulsifies the fat so that it can be absorbed in the distal intestines Bile duct → Forms in the free edge of the lesser omentum by the union of the cystic duct and the common hepatic duct about 5-15 cm depending on where the cystic duct joins the common hepatic duct (varies per person) → Descends posterior to the superior part of the duodenum and lies in the groove of the posterior 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 → Hepatopancreatic ampulla ▪ A dilation formed by the union of the bile duct and the pancreatic duct as they run obliquely through the wall of duodenum ▪ Would open into the duodenum as the major duodenal papilla At the distal end of the bile duct, there is a thickened circular Figure 43. Parts of the gallbladder muscle called sphincter of the bile duct → Once this contracts, bile cannot enter the ampulla in the Fundus (Red bracket) duodenum. Hence, the bile will back up and pass along the → Rounded part and projects below the inferior margin of the cystic duct for concentration and storage 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 cystic duct → Makes an S-shaped bend Infundibulum (Hartmann’s pouch) → Located in the free edge of the lesser omentum and bulges into the cystic duct Cystic duct → Duct of gallbladder → Pars spiralis - Initial part: tortuous portion ▪ The spiral valve (of Heister) contains mucosal duplications that would regulate the filling and emptying of the gallbladder → Pars glabra - Distal end: smooth portion Figure 41. Sphincter of the bile duct ANATOMY Accessory Glands of the Gastrointestinal Tract PAGE 12 of 24 ANATOMY | LE4 Accessory Glands of the Gastrointestinal Tract | Dr. Margarita Concepcion T. Caballes, MD, DPPS → 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 Body → Run upward to the left across the midline, somewhat triangular when you do a cross-section Tail Figure 44. Tortuous part and the Smooth part → Part that comes in contact with the hilum of the spleen → Lies anterior to the left kidney - where it is closely related to the BLOOD SUPPLY OF THE GALLBLADDER splenic hilum and left colic flexure Arterial Supply → Relatively mobile and passes between the layers of the → Comes from cystic artery from the right hepatic artery splenorenal ligament with the splenic vessels Venous Drainage → Neck & cystic duct: drain into the portal vein via cystic vein PANCREATIC DUCTS → Fundus & body: directly to visceral surface of liver LYMPH DRAINAGE OF THE GALLBLADDER Cystic lymph nodes → Hepatic nodes → Celiac nodes NERVE SUPPLY OF THE GALLBLADDER Sympathetic and parasympathetic vagal fibers form the celiac plexus → Gallbladder contracts in response to cholecystokinin (enteroendocrine cells of duodenum) → Stimulus: fatty food Vagus nerve: parasympathetic Right phrenic nerve: somatic afferent fibers PANCREAS Figure 46. Pancreatic duct of Wirsung Main pancreatic duct begins at the tail and runs at the parenchyma of the gland to the pancreatic head → Usually unites with bile duct to form a short dilated hepatopancreatic ampulla (of Vater) which opens into the descending part of the duodenum at the summit of the major duodenal papilla Accessory pancreatic duct (of Santorini) drains the upper part of the head of the pancreas; opens into the duodenum at the summit of the minor duodenal papilla → Due to anatomical variation, not all may have this duct There are smooth muscle sphincters that prevent reflux of digestive secretions and duodenal content back to the common bile duct and pancreatic duct → Sphincter of pancreatic duct → Sphincter of bile duct Figure 45. The pancreas and its major parts → Sphincter of hepatopancreatic ampulla Elongated structure that lies in the epigastric and left upper Table 3. Sphincters of the gallbladder and pancreas and their function quadrant of the abdomen Sphincter Function Soft and lobulated; yellowish in color Situated at the posterior abdominal wall behind the peritoneum Can be seen when liver is lifted Sphincter of the bile duct Controls the flow of bile Two Functions: → Exocrine secretion: secretes pancreatic juice from the acinar Sphincter of the pancreatic duct Prevents reflux of bile into the cells that would enter the duodenum through the main and duct accessory pancreatic ducts → Endocrine secretion: secretes glucagon and insulin from the Sphincter of Oddi Prevents the duodenal content pancreatic islets of Langerhans that would enter the blood from entering the ampulla PARTS OF THE PANCREAS Head → Disc-shaped structure → Lies in the concavity of the duodenum to the right of the superior mesenteric vessels ANATOMY Accessory Glands of the Gastrointestinal Tract PAGE 13 of 24 ANATOMY | LE4 Accessory Glands of the Gastrointestinal Tract | Dr. Margarita Concepcion T. Caballes, MD, DPPS Lymph vessels of pancreas ultimately drain into the celiac node Lymph nodes are situated along the arteries that would supply the gland Have an extensive lymphatic drainage that intermingles with the lymphatic vessels of other organs 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 Sensory → Sympathetic and vagal pathways through celiac ganglia but are limited to greater splanchnic nerves II. HISTOLOGY OF THE ACCESSORY GLANDS OF THE Figure 47. Sphincters of the bile duct, pancreatic duct, and the GASTROINTESTINAL TRACT hepatopancreatic ampulla A. HISTOLOGY OF SECRETORY CELLS BLOOD SUPPLY OF THE PANCREAS CELLS OF SECRETORY UNITS Arterial Supply Figure 48. Arterial supply of the Pancreas → Derived mainly from the branches of the tortuous splenic artery Figure 50. Components of secretory units in the three major salivary − Head, Neck, Tail: supplied by splenic artery glands; Red - serous-secreting cells; Yellow - mucus-secreting cells − Head: supplied by the anterior and posterior superior pancreaticoduodenal artery and from the anterior and Capsule posterior inferior pancreaticoduodenal superior → moderately dense connective tissue surrounding major salivary mesenteric artery glands o Both arteries would anastomose with each other Septa Venous Drainage → divides the secretory portions of the gland into lobes and → Comes from pancreatic veins lobules ▪ Splenic vein Secretion of the gland ▪ Superior mesenteric vein → either serous, seromucous, or mucous depending on its content of the glycoprotein mucin LYMPH DRAINAGE OF THE PANCREAS Salivon → 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 o Serous cells o Mucous cells o Myoepithelial cells Figure 49. Celiac node of the pancreas ANATOMY Accessory Glands of the Gastrointestinal Tract PAGE 14 of 24 ANATOMY | LE4 Accessory Glands of the Gastrointestinal Tract | Dr. Margarita Concepcion T. Caballes, MD, DPPS Tubuloacinar secretory units → Combining short mucous tubules with distal clusters of serous cells called serous demilunes or semilunar caps → Terminal secretory units merge to form small intercalated ducts which are also lined by secretory cells and drain into larger ducts called striated ducts MYOEPITHELIAL CELLS Figure 51. Serous acinus composed of pyramidal serous cells (left); Parotid gland composed of serous acini (right); (SD: striated duct, A: serous acini, ID: intercalated duct) Pyramidal with a broad base Rounded nuclei with basophilic cytoplasm → 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) Figure 54. Schematic diagram showing myoepithelial cells Secrete enzymes and proteins Inside the basal lamina surrounding acini, tubules, and the MUCOUS CELLS proximal ends of the duct system Contractile cells at the basal ends of secretory cells Its processes are “embracing” the associated secretory unit or duct Contractions of these cells help propel secretory products from acini into the duct system Their activity is important for moving secretory products into and through the ducts Table 4. Comparison of secretory units Serous Myoepithelial Mucous cells Figure 52. Mucous cells comprising mucus tubule (left); cells cells Submandibular gland - mixed gland with the presence of serous Shape Pyramidal Columnar Small, flattened and mucous acini [cuboidal to columnar mucous cells with nuclei Nuclei Round Compressed Compressed pressed at bases] (right) Apical Present Present - Secretory Cuboidal to columnar granules Oval nuclei pressed toward the bases of cells Organization Acinus Tubules Around → Due to accumulation of mucus (secretory product) secretory unit Often organized as cylindrical tubules or duct Contain apical granules with hydrophilic mucins that provide: Others Well-stain - Important for → Lubricating properties in saliva ed RER moving → Cause poor cell staining in routine preparations which is (basal 3rd) secretory responsible for its pale-staining appearance in micrographs products into and through the ducts Figure 53. Schematic diagram of seromucous gland with tubuloacinar secretory units (left); Seromucous gland with serous demilunes (right); (T: mucous tubules, A: serous acini, D: serous demilune) ANATOMY Accessory Glands of the Gastrointestinal Tract PAGE 15 of 24 ANATOMY | LE4 Accessory Glands of the Gastrointestinal Tract | Dr. Margarita Concepcion T. Caballes, MD, DPPS B. HISTOLOGY OF THE SALIVARY GLANDS SUBLINGUAL GLAND PAROTID GLAND Figure 57. Sublingual gland (M: mucous cells, ID: intralobular ducts, Figure 55. Lower magnification of parotid gland (left), Higher SM: striated muscle) magnification of serous acinus and intercalated duct (right); (S: septum, E: excretory duct, L: lobule, SC: serous cells, ID: intercalated duct) Morphology: branched tubuloacinar Secretion: mixed, predominantly mucous ❗️ ❗️ ❗️ ❗️ Few serous cells - only at serous demilunes Morphology: branched acinar Secretion: purely serous Recall Table 1. for the comparison of the major salivary glands Divided into numerous lobules, each containing many secretory units → Connective tissue septa - radiate between the lobules from an MINOR SALIVARY GLANDS outer capsule, and convey blood vessels, nerves, and large Usually mucous excretory ducts → Except for the small serous glands at the bases of Serous cells circumvallate papillae → Contain basophilic cytoplasm and round nuclei Plasma cells that release IgA are common within these glands → Secrete abundant α-amylase ▪ α-amylase - initiates the hydrolysis of carbohydrates and proline-rich proteins with antimicrobial and other protective C. HISTOLOGY OF THE LIVER properties STROMA SUBMANDIBULAR GLAND Figure 56. Submandibular gland (D: striated duct, M: mucous acinus, SD: serous demilune) Figure 58. Liver (M: mesothelial cells, C: liver capsule) Morphology: branched tubuloacinar Secretion: mixed, predominantly serous ❗️ ❗️ Liver’s supporting framework Continuous with Glisson’s capsule Presence of serous demilunes → Glisson’s Capsule (refer to Figure 58: “C”) → Short mucous tubules that combine with the distal clusters of ▪ Thin connective tissue capsule serous cells ▪ Made up of collagenous tissue → Secrete lysozyme ▪ Covered by mesothelial cells from peritoneum Thicker at hilum Vessels and ducts covered with CT all the way to their termination Blood vessels, nerves, lymphatic vessels, and bile ducts travel within the connective tissue stroma ANATOMY Accessory Glands of the Gastrointestinal Tract PAGE 16 of 24 ANATOMY | LE4 Accessory Glands of the Gastrointestinal Tract | Dr. Margarita Concepcion T. Caballes, MD, DPPS PARENCHYMA SINUSOIDAL CAPILLARIES Vascular channels/capillaries between anastomosing plates of hepatocytes in the hepatic lobules Emerge from peripheral branches of the portal vein and hepatic artery 💬 Converge into the lobule central vein Venous and arterial blood mix in these sinusoids Anastomosing sinusoids have thin, discontinuous linings of fenestrated endothelial cells surrounded by sparse basal lamina and reticular fibers → These discontinuities and fenestrations allow plasma to fill a narrow perisinusoidal space (space of Disse) ▪ Space between hepatocytes and plasma The direct contact between hepatocytes and plasma facilitates most key hepatocyte functions involving uptake and release of nutrients, proteins, and potential toxins Figure 59. Hepatic lobules 2 functionally important cells found in the sinusoids of the hepatic lobule: Functional tissue that makes up the bulk of liver → Stellate macrophages (Kupffer cells) Consists of thousands of polygonal hepatic lobules ▪ Found within the sinusoid lining → Made up of irregular plates of hepatocytes arranged radially ▪ Recognize and phagocytose aged erythrocytes which frees around a central vein 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 cell ▪ activities → Both Kupffer and Ito’s cells are difficult to find in routine preparations, requiring special staining Figure 60. Hepatic lobules under the microscope Portal triad → Consists of: ▪ Branch of the portal vein ▪ Branch of the hepatic artery ▪ Branch of the bile duct Figure 62. Hepatocyte and Sinusoids [Junquiera] Vascular channels between anastomosing plates of hepatocytes in the hepatic lobules Emerge from the peripheral branches of the portal vein and hepatic artery Converge in the lobule’s central vein → Venous and arterial blood mix in these sinusoids Figure 61. Portal triad under the microscope ANATOMY Accessory Glands of the Gastrointestinal Tract PAGE 17 of 24 ANATOMY | LE4 Accessory Glands of the Gastrointestinal Tract | Dr. Margarita Concepcion T. Caballes, MD, DPPS Figure 63. Kupffer and Ito’s cells (K: Kupffer cells, E: endothelial cells, H: hepatocytes, HS: hepatic stellate cells, S: sinusoid, PS: perisinusoidal space [PPT] Anastomosing sinusoids have thin, discontinuous linings of fenestrated endothelial cells surrounded by sparse basal lamina and reticular fibers → These discontinuities and fenestrations allow plasma to fill a narrow perisinusoidal space (Space of Disse) ▪ the space between hepatocytes and plasma → This direct contact between hepatocytes and plasma facilitates most key hepatocyte functions involving uptake and release of nutrients, proteins, and potential toxins 2 functionally important cells found in the sinusoids of the hepatic lobule ▪ Found within the sinusoid lining 📋 → Specialized stellate macrophages (Kupffer cells) ▪ Recognize and phagocytose aged erythrocytes, freeing Figure 65. Schematic diagram of hepatocytes [Junquiera] Highly versatile cells with diverse functions that are reflected on heme and iron for reuse or storage in ferritin complexes their structures ▪ Antigen-presenting cells → Abundant rough ER ▪ Remove bacteria or debris present in the portal blood ▪ Synthesizes the plasma proteins such as fibrinogen, → Hepatic stellate cells (Ito’s cells) ▪ Found within the perisinusoidal space 📋 ▪ With small lipid droplets that store vitamin A and other fat lipoprotein, albumin, and prothrombin → Abundant smooth ER ▪ Contain the enzyme systems for biotransformation or soluble vitamins (Vit. ADEK) detoxification of substances in the blood, which are then ▪ Produce extracellular matrix components and cytokines that usually excreted with bile help regulate Kupffer cell activities − Important in carbohydrate metabolism, bile formation, catabolism of drugs and other toxic compounds HEPATOCYTES − Conjugates bilirubin to glucuronate Liver cells that make up hepatic lobules → Peroxisomes Large cuboidal or polyhedral epithelial cells ▪ Helps in the oxidative activity in the metabolism of lipids, Large, round, central nuclei purines, alcohol and in gluconeogenesis → Contains peripherally dispersed chromatin and prominent → Numerous mitochondria nucleoli ▪ Provides energy for the liver’s diverse activity and functions Eosinophilic cytoplasm STRUCTURE-FUNCTION RELATIONSHIPS IN LIVER → Due to the rich mitochondria → With a fine basophilic granularity due to the extensive free ribosomes and rough endoplasmic reticulum Binucleated Cells → 50% are polyploid with 2 to 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 surgery Figure 66. Concepts of Structure-Function Relationship in liver 💬 [Junqueira] Classic Hepatic lobule - drain blood from portal vein and 💬 Portal lobule - drains bile from hepatocytes to the bile duct; hepatic artery to the hepatic or the central vein involves the portal triad Figure 64. Hepatocytes ANATOMY Accessory Glands of the Gastrointestinal Tract PAGE 18 of 24 ANATOMY | LE4 Accessory Glands of the Gastrointestinal Tract | Dr. Margarita Concepcion T. Caballes, MD, DPPS 💬 Hepatic hepatocytes Acinus - supplies oxygenated blood to the PORTAL LOBULE → in between 2 hepatic lobules is the central portal triads CLASSIC HEPATIC LOBULE [Junquiera] Figure 69. Portal lobule Emphasize the exocrine function of the liver → 💬 → to drain bile from hepatocytes to the bile duct flow of bile from regions of 3 classic lobule toward the bile duct Morphologic access is the interlobular bile duct of the portal triad of the classic lobule Area drained by each bile duct is roughly triangular in shape: → Center: portal triad → Angles: Central vein at each tip Bile flows from the hepatocytes to the bile duct of portal triad HEPATIC ACINUS Figure 67. Classic hepatic lobule [Junquiera] or central vein 📋 Drains blood from the portal vein and hepatic artery to the hepatic Consists of stacks of anastomosing plates of hepatocytes around 1 cell thick Separated by anastomosing system of the sinusoids that perfuse the cells with the mixed portal and arterial blood Hexagonal in shape → Center: central vein or terminal hepatic venule → Corners: hepatic artery, portal vein → Angles: portal canals where the sinusoids drain Emphasizes the major endocrine function of the liver → Synthesize and secrete major plasma proteins ▪ fibrinogen, albumin, and transferrin Figure 70. Hepatic acinus [Junqueira] Represents the smallest functional unit of hepatic parenchyma Supply oxygenated blood to hepatocytes 💬 Diamond or rhomboid-shaped 💬 Area irrigated by a terminal branch of the distributing vein Smallest functional unit of the hepatic parenchyma → Short axis: defined by the terminal branches of portal triads that lie along the border between two classic lobules → Long axis: line drawn between two central veins closest to the short axis giving it a diamond or rhomboid shape Hepatocytes are arranged in 3 concentric elliptical zones surrounding the short axis: → Zone 1 (Purple) 💬 ▪ Receives the most oxygen, nutrients, and toxins 💬 At the centerFigure 68. Classic lobule [Junquiera] ▪ Hepatocytes nearest the portal triad will get the best is the central vein where sinusoids will drain oxygenation and nutrients ▪ Can most readily carry out functions that involve oxidative metabolism (ex. protein synthesis) ▪ First to regenerate ▪ First to show morphological changes after bile duct occlusion ▪ Last to die if circulation is impaired → Zone 2 (green) ▪ Intermediate range of metabolic functions between zones 1 and 3 → Zone 3 (white) ▪ Nearest the central vein; 💬 farthest from the short axis ▪ Receives the least oxygen and nutrients ANATOMY Accessory Glands of the Gastroint