Anatomy 4.4
November 15, 2011 Dr. Melissa Calilao
Accessory Glands of the GIT OUTLINE I. Salivary Glands a) Functions b) Types of Cells c) Interlobular Ducts d) Types of Salivary Glands e) Major Salivary Glands II. Liver a) Functions b) Surface of the Liver c) Peritoneal Attachments d) Divisions of the Liver e) Blood Vessels f) Portocaval Anastomoses g) Lymphatic Drainage h) Nerve Supply i) Biliary Tract j) Liver Histology III. Gallbladder a) Parts b) Cystic Duct c) Blood Supply and Lymphatic Drainage d) Nerve Supply e) Histology IV. Pancreas a) Relations b) Parts c) Pancreatic Duct d) Arterial Supply e) Venous Drainage f) Lymphatic Drainage g) Nerve Supply h) Exocrine Functions i) Endocrine Functions
Figure 1. Secretory Units
B.
Objectives: Enumerate the major salivary glands and classify each based on the nature of its secretion. State the important anatomic relationships, surfaces and peritoneal attachments of the liver. Differentiate between classical and functional divisions of the liver. Describe the circulation of blood within the liver. Describe the intrahepatic biliary flow. Enumerate the sites of portocaval anastomoses and explain the clinical significance of such. Describe the innervation, blood supply, and lymphatic drainage of the liver. Describe the location of the gallbladder and its anatomic relations. Describe the innervation, blood supply and lymphatic drainage of the gallbladder. Identify parts of the extrahepatic biliary system.
TYPES OF CELLS (SECRETORY UNITS) Serous cells usually pyramidal in shape, with a broad base o narrow apical surface with short, irregular microvilli o o rounded nuclei with basophilic cytoplasm usually form a spherical mass of cells called acinus or o alveolus with a small lumen at the center Mucous cells cuboidal to columnar in shape o o nuclei are oval and pressed towards the base of the cells due to presence of mucous in the cytoplasm o often organized as tubules, consisting of cylindrical arrays of secretory cells surrounding a lumen
nd
State the relations between the CBD and pa ncreatic duct as they open into the 2 portion of the duodenum. Describe the pancreas and its location, as well as its parts and noting important anatomic relations.
State the exocrine and endocrine functions of the pancreas. Describe the innervation, blood supply and lymphatic drainage of the pancreas.
I. SALIVARY GLANDS A.
FUNCTIONS Wet and lubricate the oral cavity and its contents Initiate the digestion of carbohydrates Secrete substances such as: IgA – Major immunoglobulin found in secretions that o protects mucosal surfaces against pathogens Lysozymes – hydrolyze the walls of certain bacteria o Lactoferrin – binds iron, a nutrient necessary for bacterial o growth
Figure 2. Epithelial components of a submandibular gland lobule
C.
Group 17 | Esguerra, Eslao, Esling, Espelimbergo, Esternon, Estevanez, Estrada, Estrellado
INTERLOBULAR DUCTS (TUBULAR SYSTEM)
Intercalated ducts Where secretory end pieces empty into o Lined by simple cuboidal epithelial cells, with o presence of striations Empty into or join to form striated ducts o
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Striated ducts o Characterized by radial striations that extend to form the bases of the cells to the level of the central nuclei Radial striations – plasma membrane infoldings with elongated mitochondria that are aligned parallel to the infolded membranes Cells are columnar in shape o o Striated ducts of each lobule converge and drain into interlobular or excretory ducts – located in the CT septae separating the lobules; initially lined with pseudostratified or stratified cuboidal epithelium, distally lined with stratified columnar epithelium Myoepithelial cells – present in basal lamina of o glands or ducts which function to propel secretions upon contraction
Histology o Morphology: Compound tubulo-alveolar gland or branched tubulo-acinar gland o Nature of secretion: purely serous o White structures are fat cells o Basophilic cytoplasm o Rounded nucleus at base o High in Alpha amylase and proline-rich proteins, which are antimicrobial and have calcium-binding property o Parotid glands may become acutely inflamed as a result of retrograde bacterial infection from the mouth via the parotid duct o May also become infected via the bloodstream, as in mumps
D. TYPES OF SALIVARY GLANDS
E.
Minor salivary glands Scattered within palatine cavity only o Named according to location o Secrete only 10% of the total volume of saliva, but o account for approximately 70% of the mucous secreted Under local neural control o Major salivary glands o Secrete in response to parasympathetic activity induced by physical, chemical, and psychological stimuli o Large, include the Parotid, Submandibular/Submaxillary, and Sublingual Glands
MAJOR SALIVARY GLANDS (3 PAIRS)
Figure 4. Parotid Gland (L-lobules, L-lobules, each containing many secretory units; S-supporting S-supporting tissue septa, conveying blood vessels, nerves and large E- excretory ducts)
Arterial supply - External carotid artery (ECA) and its superficial terminal branches (Superficial temporal and maxillary aa.)
Venous drainage - Retromandibular v.
Lymphatic drainage - Parotid and Deep cervical nodes
Nerve supply Parasympathetic: Secretomotor supply from the o Parasympathetic: Secretomotor glossopharyngeal nerve (via the tympanic branch, the Lesser Petrosal nerve, the Otic ganglion, and the Auriculotemporal nerve) o Sympathetic: Plexus around ECA
Figure 3. Salivary Glands
I.
Parotid Glands Gross o Largest of the salivary glands o Wedge-shaped o Situated below the external auditory meatus o Lies in a deep hollow behind the r amus of the mandible, and in front of the sternocleidomastoid muscle o Secretes 25% of total saliva o Stensen’s/Parotid duct emerges from the anterior border of the gland, runs toward the lateral surface of the masseter muscle, pierces the buccinator muscle, opens opposite the nd upper 2 molar tooth, into the parotid papilla of the oral cavity
Group 17|Esguerra, Eslao, Esling, Espelimbergo, Esternon, Estevanez, Estrada, Estrellado
II.
Submandibular/Submaxillary glands Gross o Partly below the mandible o Seen in the submandibular triangle Histology Wharton’s Duct o branched tubuloacinar gland, both mucous and serous, predominantly serous with basophilic cytoplasm o secretes lyzozyme o goes along with the tongue and empties into the sublingual caruncle o
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o o
o
produces 70% of total saliva Striated ducts are larger than in sublingual glands (predominantly mucous glands) Determines the role of the striated duct in modifying isotonic basic saliva to produce hypotonic saliva
Figure 6. Sublingual gland
Arterial Supply and Venous Drainage - Facial and Lingual artery and veins
Lymphatic drainage - Submandibular and Deep cervical nodes
Figure 5. Submandibular glands
Nerve supply Parasympathetic: Secretomotor supply is from the facial o Parasympathetic: nerve via the chorda tympani & the submandibular ganglion (Superior Salivary nucleus of CN VII) (increases secretions) o Sympathetic: Plexus around facial and lingual a. (Decreases secretion)
Arterial Supply and Venous drainage - Facial & Lingual (artery & vein)
Lymphatic drainage - Retromandibular and Deep cervical nodes
Nerve supply Parasympathetic: secretomotor supply is from the o facial nerve via the chorda tympani & the submandibular ganglion (Superior Salivary nucleus of CN VII) o Sympathetic: Sympathetic: Plexus around facial and lingual a.
III.
Sublingual glands Gross o Smallest o Seen on the floor of mouth, beneath mucus membrane, close to the midline o 8-20 sublingual ducts which empty into sublingual folds but a few may open into the sublingual caruncle o Secretes 5% of the total saliva
*In the human submandibular and sublingual glands, serous and mucous cells are arranged in a characteristic pattern. The mucous cells form tubules, but their ends are capped by serous cells, which constitute the serous demilunes CLINICAL CORRELATION
or dry mouth is associated with difficulties in chewing, or Xerostomia swallowing, tasting, and speaking, dental caries, and atrophy of the oral mucosa. It is a chronic autoimmune disorder characterized by lymphocytic infiltration of the exocrine glands, particularly the salivary and lacrimal gland
II. LIVER -
Largest mass of glandular tissue in the body Largest internal organ: 1.5 kg Found in the abdominal cavity beneath the diaphragm lies mainly in the RUQ occupies most of the Right hypochondrium and upper epigastric extends into the left hypochondrium Biliary ducts: Right and left join to form thecommon thecommon hepatic duct Common/bile duct: hepatic duct + cystic duct Blood supply: Portal vein – 70-80% Hepatic artery – 20%
Figure 7. Location of sublingual duct openings
Histology o branched tubulo-acinar gland formed of serous and mucous cells o mucous cells more predominant o serous cells are present almost exclusively on demilunes of mucous tubules o Histologically lung-like appearance
Group 17|Esguerra, Eslao, Esling, Espelimbergo, Esternon, Estevanez, Estrada, Estrellado
A.
FUNCTIONS Aids in the emulsification of fat Produces bile Filtration of blood Heparin synthesis
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B. o
SURFACE OF THE LIVER
C.
Diaphragmatic surface Convex, smooth Subphrenic recesses : superior extensions of the peritoneal cavity Separated into right and left by the falciform the falciform ligament Subhepatic space: supracolic compartment inferior to the liver Hepatorenal recess (Hepatorenal pouch/Morison pouch): posterosuperioir extension of the subhepatic space o Fluid draining from the omental bursa flows here anterior layer is continuous on the left with the right layer of the falciform ligament posterior layer is continuous with right layer of the lesser omentum
o
* all recesses of the peritoneal cavity are potential spaces with
enough peritoneal fluid for lubrication o o o
Anterior aspect Posterior aspect Visceral (posteroinferior) Flat; concave Covered with peritoneum except at the bed of the gallbladder and the portahepatis Portahepatis: transverse fissure in the middle visceral surface of the liver o Gives passage to the portal vein, hepatic artery, hepatic nerve plexus, hepatic ducts, and lymphatic vessels o Related to: Right kidney Right suprarenal gland Hepatic flexure Duodenum Gallbladder Fundus of the stomach Abdominal esophagus o Impressions Renal Esophageal Duodenal Colic Fecal Gastric Suprarenal Visceral surface shows an H-shaped pattern (2 vertical limbs and 1 horizontal limb) o Left limb of the “H” Divides surface into right and left lobes Fissure for ligamentumtereshepatis (remains of the left umbilical vein) Fissure for ligamentumvenosum ( remains of the ductusvenosus) o Right limb of the “H” Gallbladder fossa - Between the right lobe and quadrate lobe Sulcus for inferior vena cava – between the right lobe and caudate lobe o Horizontal limb of the “H” the portahepatis or hilum of the liver between caudate and quadrate lobe
Group 17|Esguerra, Eslao, Esling, Espelimbergo, Esternon, Estevanez, Estrada, Estrellado
PERITONEAL ATTACHMENTS OF THE LIVER Falciform Ligament o attaches the liver to the anterior wall of the abdominal cavity up to the level of the diaphragm o its free edge forms the ligamentum teres passes on to the anterior and then t he superior surfaces o of the liver then splits into 2 layers right layer: layer: forms the upper layer of the coronary ligament; free ligament; free margin forms the right triangular ligament left layer: layer: forms the upper layer of the left triangular ligament Coronary ligament: ligament : has an upper and lower layer which encloses an area of the liver devoid of peritoneum known as the bare area; attaches the right lobe of the liver to the diaphragm Right triangular ligament: ligament : V-shaped fold of peritoneum formed by the right extremity of the coronary ligament; connects the posterior surface of the right lobe of the liver to the diaphragm Left triangular ligament: ligament : attaches the left lobe of the liver to the diaphragm; communicate with appendix fibrosa at the left tip of liver Areas devoid of Peritoneum o Bare area o Area proximal to the inferior vena cava o Gallbladder in contact with liver bed o Portahepatis
D. TYPES OF DIVISIONS OF THE LIVER& LOBES OF LIVER Table 1. Liver lobe divisions
Lobes
Classical Right Lobe: subdivided into quadrate and caudate Left lobe
Functional Left Lobe: including quadrate and caudate lobes Right lobe
Lobes of liver o Right lobe larger than the left lobe blood supply of functional right lobe: right hepatic artery venous and lymphatic drainage: right hepatic vein and hepatic duct o Left lobe extends to left hypochondrium th reaches the upper border of the 6 rib blood supply: left hepatic artery venous and lymphatic drainage: left hepatic vein and hepatic duct o Quadrate lobe lower portion of the classical right lobe o Caudate lobe upper portion of the classical right lobe
*refer to appendix for summarized table
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Retroperitoneal anastomosis veins of ascending colon, descending colon, duodenum, pancreas and liver (portal) with renal, lumbar and phrenic veins (systemic) o retroperitoneal varicose portocaval anastomosis
o
G.
LYMPHATIC DRAINAGE The lymphatic vessel of the liver occurs as: o Superficial lymphatics (in fibrous capsule of the liver) which forms its outer surface drains to hepatic lymph nodes Deep lymphatics (in connective tissue) which accompany o the ramification of the portal triad and hepatic veins. Space of Mall o lymph from sinusoids is brought to an area between the stromal of periportal area and hepatocytes o Between the outermost hepatocytes and stroma of the portal triad o it travels with the portal triad but in different direction Celiac nodes o majority of the lymph vessels from the liver enter the lymph nodes in the portahepatis and eventually pass to the celiac nodes Posterior mediastinal lymph lymph nodes o vessels from the bare area of the liver pass through the diaphragm to the posterior mediastinal lymph nodes Lymph Flow : Portal area (space of mall)→ hepatic lymph nodes →celiac lymph nodes →cisterna chy li li of the thoracic duct
Figure 8. Liver divisions
E.
F.
BLOOD VESSELS OF THE LIVER Hepatic Portal vein o Bring 75-80% of blood to the liver o portal blood, containing about 40% more oxygen than blood returning to the heart from the systemic circuit to sustain the liver parenchyma. o it is formed by superior mesenteric and splenic veins posterior to the pancreas. o it ascends anterior to the IVC as part of the portal triad in the hepatoduodenal ligament. Hepatic artery o it accounts for 20-25% of blood receives by the liver to nonparenchymal structures particularly the intrahepatic bile ducts. o it is a branch of the celiac trunk maybe divided into: Common hepatic artery- from celiac trunk to the origin of the gastroduodenal artery. Hepatic artery proper-from the gastrdoudenal artery to the bifurcation of the hepatic artery
PORTOCAVAL ANASTOMOSES
- Portal hypertension may be caused by block in intrahepatic portal vein tree, cirrhosis, impaired outflow of blood from the liver, excessive flow of splanchnic or hepatic arterial blood to the liver Esophageal o Esophageal branches of left gastric (portal) with rd esophageal veins draining middle 3 of esophagus (systemic) o Esophageal varicosities: esophageal hemorrhage : most dangerous complication of the portal HPN Rectal Superior rectal veins (portal) with middle and inferior o rectal veins (systemic) Superior rectal veins (portal) with middle and inferior o rectal veins (systemic) o Hemorrhoidal piles: swollen/inflamed vascular structures in the anal canal Para-umbilical Paraumbilical veins(portal) with superficial veins of o anterior abdominal wall (systemic) Caput Medusae: distended and engorged paraumbilical o veins radiating from the umbilicus
H. NERVE SUPPLY The nerves of the liver are derived from the hepatic plexus
which accompanies the branch of the hepatic artery and hepatic portal vein. o
I.
Sympathetic fibers from celiac plexus
Parasympathetic fibers from the anterior vagal trunk
Bile o produced by hepatocytes golden yellow or greenish yellow o o alkaline water containing sodium bicarbonate, bile salts, bile pigments, cholesterol, lecithin and mucin aids in the breaking down of fats o o stored and concentrated (thru absorption of water and salts) in the gallbladder when digestion is not take place o first collected by the bile cannaliculi or bile capillaries between hepatocytes nd Common bile duct drains into 2 part of the duodenum at the ampulla of vater.
Group 17|Esguerra, Eslao, Esling, Espelimbergo, Esternon, Estevanez, Estrada, Estrellado
BILIARY TRACT
hepatic plexus
J. LIVER HISTOLOGY i.
STRUCTURAL ORGANIZATION STROMA o Glisson’s Capsule: thin connective tissue o Thicker at hilum o Vessels and ducts covered with connective tissue all the way to termination/origin
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PARENCHYMA o Organized plated of hepatocytes: 80% liver cell population 1-2 spherical nuclei with nucleoli Acidophilic cytoplasm with basophilic bodies Numerous microvilli
Organelles: - Rough ER - sites for synthesis of plasma proteins (albumin, fibrinogen, prothrombin and lipoprotein) - Smooth ER – important in CHO metabolism, bile formation, catabolism of drugs and other toxic substances; also site of VLDL synthesis - Golgi complexes – important in concentrating and packaging secretory products - Mitochondria – energy production - Lysosomes – for turnover and degradation of organelles - Peroxisomes – oxidative metabolism of lipids, purines & alcohol; participate in cholesterol and bile acid synthesis Bile canaliculus - tubular space between two abutted hepatocytes, which forms a complex of anastomosing network - Empties from the canals of Hering to preductules of cholangioles into bile ductules which then end in the ducts in the portal spaces into bile ducts in - Bile ducts gradually enlarge and fuse to form the right ducts , which subsequently leave the and left hepatic ducts, liver as the common hepatic duct - Bile flow opposite of blood flow: center to periphery
F igure igure 9. Intrahepatic vascular strucuture
iii.
Blood always flows from periphery to the center of each hepatic lobule Intrahepatic vascular system: blood from portal vein and o hepatic artery is drained into the sinusoids → central venule →sublobular vein → hepatic vein → IVC HEPATIC LOBULE Functional units of the liver Composed of hepatocytes arranged into polyhedral structures Each lobule has three to six portal areas at its periphery and a vein) venule in the center (central (central vein) The portal zones at the corners consist of connective tissue in which the PORTAL TRIAD are embedded; portal triad consists of venule (from portal vein), arteriole (from the hepatic artery), and a branch of the bile duct (duct (duct of cuboidal epithelium)
SINUSOIDAL CAPILLARIES o Sinusoids Vascular channels between plates of hepatocytes that are o lined by fenestrated endothelium Contain Kupffer cells: cells: macrophages that belong to the o mononuclear phagocyte system that metabolize aged RBC’s, digest hemoglobin, secrete proteins related to immunological processes and destroy bacteria (later bacteria (later sent to space of Disse)
Hepatic Artery – 20-30% o Supply 20% of blood flow o Oxygen-rich Branch of celiac plexus o o Ramifies parallel with portal veins branches, some of which lead into the sinusoids o In the hepatic sinusoids, there is mixing of arterial and portal venous blood
PERISINUSOIDAL SPACE (SPACE OF DISSE) Where exchange of nutrients and waste products occur Subendothelial space that separates the endothelial cells o from the hepatocytes
o
ii.
BLOOD SUPPLY Portal Vein supply 80% of blood flow o nutrient-rich but oxygen-poor o from abdominal viscera o branches into portal venules to venules to the portal spaces o o Portal Venules venules that run around the o branch → distributing venules that periphery of each lobule and lead into the sinusoids as inlet venules o sinusoids: run radially, converging in the center to form central or centrolobular venule veins to form o central venules converge into sublobular veins to veins, which drains -> inferior vena cava large hepatic veins,
Group 17|Esguerra, Eslao, Esling, Espelimbergo, Esternon, Estevanez, Estrada, Estrellado
Figure 10.Lobule structures
Hepatic Lobule Structure and Function Classic Hepatic Lobule o Hexagon o Center: Central Venule o Angles: portal canals o Blood flow from 6 portal triad areas to a central venule o Emphasizes endocrine function of liver Portal Lobule o Triangular o Center: Portal Triad o Angles: Central Venule at each tip o Bile flow: from hepatocytes to bile duct of portal triad
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Emphasizes major exocrine function of liver: bile secretion Liver Acinus o Diamond or rhomboid in shape smallest functional unit of hepatic parenchyma o Area irrigated by terminal branch of the distributing vein o Short axis: terminal branches of portal triad o Long axis: line drawn between two central veins o Has 3 zones: Zone I o - periphery of classic lobule st - get most oxygen and nutrients (1 to receive) - can most readily carry out oxidative metabolism st - 1 to show morphologic changes after bile duct occlusion st - Last to die if circulation impaired, but 1 to regenerate Zone II o - Middle - Have intermediate range of metabolic functions Zone III o - closest to central venule - most central part of classic lobule - get least oxygen and nutrients - preferential sites of glycolysis, lipid synthesis and drug biotransformation st - 1 to undergo fatty accumulation and ischemic necrosis - Last to respond to toxic substances and bile stasis o
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Peritoneum completely covers the fundus of the gallbladder and binds its neck and body to the liver
A.
PARTS FUNDUS: FUNDUS: wide, blunt end that projects from the inferior lobe of th the liver at the right 9 costal cartilage BODY: BODY: main portion that contacts the liver, transverse colon, and superior part of the duodenum NECK: narrow, tapering end, opposite the fundus; directs to the portahepatis and joins the cystic duct INFUNDIBULUM/ INFUNDIBULUM/HARTMANN’S POUCH: funnel shaped cavity located close to the neck
Figure 12. Gallbladder
B. Figure 11. Liver acinus
Liver Regeneration Has extraordinary capacity for regeneration Controlled by chalones Self-regulating o o Compensatory hyperplasia – a process in which the remaining healthy hepatocytes begin to divide co ntinuing until the original mass of tissue is restored Liver cirrhosis Continuous or repeated damage to hepatocytes over a o long period of time by various ag ents such as ethanol, drugs or other chemicals, hepatitis virus (B,C, or D), parasites and autoimmune liver disease o Formation of disorganized hepatocytes Causes liver failure, and is usually fatal o
Connects the neck of the gallbladder to the common hepatic duct Passes between the layers of the lesser omentum, parallel to the common hepatic duct, joining it to form the (common)bile duct; (cystic duct + common hepatic duct = common bile duct) As the common bile duct, joins the pancreatic duct to form the nd Ampulla of Vater, which opens into the 2 part of the duodenum by the Major Duodenal Papilla; Papilla; (common bile duct + pancreatic duct = Ampulla of Vater) Contains mucosal duplications forming the spiral fold/spiral valve (of Heister) that regulates gallbladder filling and emptying; and offers additional resistance to sudden bile dumping
C.
III. GALLBLADDER -
Lies in the fossa for the gallbladder at the visceral surface of the liver, located at the junction of the left and right lobe Pear-shaped sac Can hold 30-50mL of bile Stores and concentrates bile
Group 17|Esguerra, Eslao, Esling, Espelimbergo, Esternon, Estevanez, Estrada, Estrellado
CYSTIC DUCT
BLOOD SUPPLY AND LYMPHATIC DRAINAGE CYSTIC ARTERY Supplies the gallbladder and the cystic duct o o Arises from the Right Hepatic Artery in the Cystohepatic Triangle of Calot (the Calot (the triangle between the common hepatic duct, cystic duct and visceral surface of the liver/free edge) CYSTIC VEINS Drains the neck of the gallbladder and cystic duct o
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Multiple, small veins that enter the liver after joining the veins that drain the hepatic ducts and proximal bile duct Veins from the fundus and the body of the gallbladder o pass directly into the hepatic sinusoids LYMPHATIC VESSELS Drainage is through the Cystic lymph node, node, which o drains into the Hepatic lymph node, node, which then drains into the Celiac lymph node o
D. NERVE SUPPLY
E.
The gallbladder and the cystic duct is supplied by the Celiac Plexus formed Plexus formed by sympathetic and parasympathetic vagal fibers Parasympathetic stimulation causes contractions of the gallbladder and relaxation of the sphincters at the hepatopancreatic ampulla. CCK , produced by the enteroendocrine cells of the duodenum, causes gallbladder contraction in response to c onsumption of fatty food (stimulus) Biliary tract pains are either circumscribed tenderness in the gallbladder region or colicky pain. Pain radiation: radiation: back, just below the tip of the right scapula, right shoulder, substernal area, anterior left chest
GALLBLADDER HISTOLOGY MUCOSA: Simple columnar epithelium with microvilli o o Tubuloacinar glands (mucous glands are present only in the neck) o Absence muscularis mucosa Lining epithelia with prominent mitochondria, microvilli and o intercellular spaces; indicative of absorptive cells (bile concentration achieved through water absorption) Absence of muscularis mucosa Muscular Layer Discontinuous o o Inner layer: longitudinally oriented; outer layer: diagonally oriented Presence of Serosal layer Rokitansky-Aschoff Sinuses: pseudodiverticula True Ducts of Luschka: aberrant vestigial bile ducts
F.
EXTRAHEPATIC BILIARY SYSTEM The right and left hepatic bile duct converge converge to form the common hepatic duct The common hepatic duct and cystic duct come come together to form the common bile duct The common bile duct joins joins the main pancreatic duct to to form nd the Ampulla the Ampulla of Vater , that enters the 2 part of the duodenum through the major duodenal papilla
G. PARTS OF THE COMMON BILE DUCT Supraduodenal Retroduodenal Infraduodenal Intraduodenal
IV. PANCREAS -
Mixed exocrine-endocrine gland that produces digestive enzymes and hormones Exocrine – pancreatic juice from acinar cells Endocrine – glucagon and insulin from pancreatic islets of Langerhans An elongated structure that lies in the epigastrium and the left upper quadrant Soft and lobulated It crosses the pyloric plane (L1-L2 vertebral bodies) and situated on the posterior abdominal wall behind the peritoneum (retroperitoneal)
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A.
RELATIONS
Anteriorly (from (R) to (L)): - Transverse colon - Attachment of the transverse mesocolon - Lesser sac - Stomach - Spleen Posteriorly (from (R) to (L)): - Bile duct - Portal vein - Splenic vein - Inferior Vena Cava - Aorta - Origin of Superior Mesenteric Artery - Left Psoas muscle - Left suprarenal gland
B.
PARTS
Figure 13. Types of ducts in gallbladder
Figure 14. Pancreas
Group 17|Esguerra, Eslao, Esling, Espelimbergo, Esternon, Estevanez, Estrada, Estrellado
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HEAD
Disc shaped and lies within the concavity of the duodenum A part of the head extend to the left behind the superior mesenteric vessels and is called the uncinate process (or lingula of the pancreas) It rests posteriorly on the IVC, right renal artery and vein, o and left renal vein. o The bile duct lies in a groove on the postero-superior surface of the head or is embedded in its substance NECK
Accessory pancreatic duct (of Santorini) If present, drains the upper part of the head and then opens into the duodenum about 2 cm above t he main duct on the minor duodenal papilla o Frequently communicates with main pancreatic duct o
o o
D. ARTERIAL SUPPLY
Constricted portion of the pancreas and connects t he head of the body Lies in front of the beginning of the portal vein and the o origin of the superior mesenteric artery from the aorta BODY o
Runs upward to the left across the midline Lies to the left of the superior mesenteric vessels, passing over the aorta and L2 vertebra. Sometimes triangular in cross section o Lies in the epigastric area o Comes in contact with hilum of spleen o TAIL o Anterior to the left kidney and passes forward in the splenicorenal ligament o Comes in contact with the hilum of the spleen o o
C.
PANCREATIC DUCTS
Figure 16. Arterial supply of the pancreas
Derived mainly from the splenic artery Head & neck: (anterior and posterior) superior & (anterior and posterior) inferior pancreaticoduodenal arteries Superior pancreaticoduodenal a. is a branch of gastroduodenal a. Inferior pancreaticoduodenal a. is branch of superior superior mesenteric artery o Body & tail: Splenic body from celiac artery o
Figure 15. Pancreatic Ducts
E. VENOUS DRAINAGE
Main pancreatic duct (of Wirsung) Begins in the tail and runs the length of the gland, o receiving numerous tributaries Opens into the 2nd part of the duodenum about its middle o with the bile duct into a saclike dilatation called Ampulla of Vater(aka Vater(aka Hepatopancreatic papilla) papilla ) and into the Major duodenal papilla Sphincter of Oddi Circular muscles fibers which surround the Ampulla of o Vater and the terminal segments of the main pancreatic duct and common bile duct Functions to contract the Ampulla of Vater to prevent the o throw of bile during the basal state Prevents reflux o Presence of food relaxes the sphincter, allowing bile to o flow into the duodenum Without food, the sphincter is contracted o Figure 17. Venous drainage of pancreas
Group 17|Esguerra, Eslao, Esling, Espelimbergo, Esternon, Estevanez, Estrada, Estrellado
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F.
Pancreatic veins – Tributaries of the splenic and superior mesenteric parts of the portal vein but most empty into the splenic veins
Pancreaticosplenic nodes o Major lymph drainage o Lie along the splenic artery o Most vessels drain into these and some to the Pyloric lymph nodes toward the celiac the celiac nodes or superiormesenteric nodes o Lymph nodes are situated along the arteries that supply the gland o Very extensive that’s why carcinoma spreads easily (intermingle with other lymph nodes)
G. NERVE SUPPLY Motor: Sympathetic: Greater splanchnic (T5-T9) Majority Lesser splanchnic (T10-T11) Decreases stimulation Parasympathetic: Parasympathetic: Vagus n. Stimulation Increases enzyme content Secretion is mediated by secretin and cholecystokinin Sensory: o Afferent fibers of sympathetic and vagal (parasympathetic) pathways through the celiac ganglia to greater splanchnic nerves Pain is felt over the epigastrum and back area o
LYMPHATIC DRAINAGE
CLINICAL CORRELATION Cancer of the head of pancreas often obstructs the bile duct and/or hepatopancreatic ampulla resulting in the retention of bile pigments, enlargement of the gallbladder, and obstructive jaundice. It may also cause obstruction of hepatic portal and inferior vena cava because it overlies these veins. Surgical resection of the pancreas is futile because of its extensive drainage in relation to its inaccessible lymph nodes and metastasis to the liver occurs early, via hepatic portal vein. Life expectancy for individuals afflicted with it usually is 2-3 months.
H. EXOCRINE FUNCTION
I.
Composed of : 1. Pancreatic 1. Pancreatic acini –composed of several serous cells 2.Intercalated 2.Intercalated ducts – merge to form larger interlobar ducts lined with columnar epithelium Secretes pancreatic juice rich in bicarbonate ions (HCO3-) and digestive enzymes (Proteases, Lipases, Nucleases and α amylases)
Most proteases are stored as zymogen (inactive form) granules of acinar cells Centroacinar cells- constitute the intraacinar portion of the intercalated duct and are only found in the pancreatic acini
ENDOCRINE FUNCTION Composed of : →Islets of Langerhans – compact spherical masses of endocrine tissue embedded within the acinar exocrine tissue. o numerous in the tail region of pa ncreas arranged in cords separated by a network of o fenestrated capillaries
Table 3. Types of Cells found in the Islets Hormone Hormone Cell Type Quantity Produced Function ~20% Glucagon Increases Alpha Cells blood glucose content ~70% Insulin Decrease Beta Cells blood glucose content ~5-10% Somatostatin Inhibits release of Delta Cells other islet cell hormones Pancreatic Rare Pancreatic Stimulates Polypeptide Polypeptide activity of Cells gastric chief cells (F Cells)
Table 2. Summary of pancreas nerve supply/visceral referred pain Referred site & Spinal Origin Nerve Supply clinical Cord example Inferior part of Vagus and Pancreatic the epigastric thoracic T8-T9 region (e.g. head splancnic nerves pancreatitis)
Gallbladder & Liver
Nerves derived from celiac plexus (sympathetic), vagus nerve (parasympatheti c), and right phrenic nerve (sensory)
T6-T9
Epigastric region and right hypochondriac region; may cause pain on posterior thoracic wall or right shoulder owing to diaphragmatic irritation
Group 17|Esguerra, Eslao, Esling, Espelimbergo, Esternon, Estevanez, Estrada, Estrellado
Page 10 of 11
APPENDIX:
Anatomical term
Right lobe
Left lobe
Functional/surgical term
Right (part of )the liver [Right portal lobe]
Left (part of )the liver [left portal lobe]
Posterior part of the liver
Right lateral division
Right medial division
Left medial devisor
Left lateral division
Posterior lateral segment SEGMENT VII [posterior superior area] Right anterior lateral segment SEGMENT VI [posterior inferior area]
Posterior lateral segment VIII [anterior superior area]
[Medial superior area] Left medial segment
Anterior medial segment V [anterior inferior area]
SEGMENT IV [medial inferior area= =quadrate lobe]
Lateral segment SEGMENT II [lateral superior area] Left lateral anterior segment SEGMENT III [lateral inferior area]
Right Left caudate caudate lobe lobe Posterior segment I
Group 17|Esguerra, Eslao, Esling, Espelimbergo, Esternon, Estevanez, Estrada, Estrellado
Caudate lobe
Page 11 of 11
