Anatomy & Physiologyof the PancreasSanjay George
AnatomyDerived from ‘Pan’ – all ‘Kreas’ –flesh15-20cm long, 2.5 – 3.8cmbroad, 1.2 – 1.8cm thickWeighs 80gSituated in retroperitoneum
Contd..Divided:Head – 30%Body and Tail – 70%Head corresponds with the curve of duodenumoverlying the body of the 2nd lumbar vertebra andthe venacava.Aorta and superior mesenteric vessels lie behindthe neck.Near upper border of neck superior mesentericvein joins splenic vein to form portal vein.
Contd..Coming of side of pancreatic headand passing to the left and behindsuperior mesenteric vein is uncinateprocess.Tip of pancreatic tail extends upto thesplenic hilum.
Histology80-90% of pancreatic tissue – Exocrine acinar tissueorganised as lobulesPancreatic duct Interlobular & Intralobular ductsductules aciniMain duct – Columnar cellsDuctules – Cuboidal cellsAcinar cells clumped around central lumen whichcommunicates with duct system.
HistologyClusters of endocrine cells distributed throughout calledIslets of LangerhansIslet:75% - B Cells – Insulin20% - A Cells – Glucagon5% - D Cells – SomatostatinSmall number of pancreatic polypeptide cellsB cells form inner core surrounded by other cells.Capillaries draining islet cells drain into portal vein.
Blood SupplyArterial:Pancreatic Branches of splenicarterySuperior pancreaticoduodenal arteryInferior pancreaticoduodenal arteryVenous:Drain into splenic, superiormesenteric and portal veins
EmbryologyTime Event1 Day 26 Dorsal Pancreatic duct arises from dorsal side ofduodenum2 Day 32 Ventral Bud arises from base of hepatic diverticulum3 Day 37 Contact occurs between the 2 buds. Fusion by end of 6thweek4 Week 6 Ventral bud produces the head and uncinate process5 Week 6 Ducts Fuse6 Week 6 Ventral duct and distal portion of dorsal duct form themain duct7 Week 6 Proximal duct forms the duct of Santorini8 Month 3 Acini appear9 Months 3-4 Islets of Langerhans Appear & become active
EmbryologyMalrotation of ventral bud in 5th week –annular pancreas.Mode of ductule fusion in 7th weekproduces various possible ductularpatterns.Anatomy of main duodenal papilla –ampulla of vater is also variable.
PhysiologyIn response to food – secretes digestiveenzymes in an alkaline bicarbonate richfluid.Secretion enhanced by:SecretinCholecystokininVagal StimulationWithin cells enzymes are in inactive form.
Pancreatic Secretions Electrolytes: Cations: Na+, K+, Ca2+, Mg2+, Zn2+ Anions: HCO3-, Cl- and traces of SO42-, HPO42- Enymes: Pancreatic alpha-amylase Pancreatic lipase Pancreatic esterase Pancreatic pro-phospholipase A2 Pancreatic proteolytic enymes: Trypsinogen Chymotrypsin Pro – carboxypeptidase A and B Ribonuclease Deoxy-ribonuclease Pro-elatase Trypsin inhibitor
Total Removal of PancreasDiabetes mellitus due to pancreaticendocrine deficiency of insulinnDevelopment of digestive disturbances:Increase of faecal fats – bulky, foulsmelling, pale and greasy stoolsIncreased faecal nitrogen due toincomplete proteolysisNo abnormality of carbohydrate digestionPancreatic insufficiency – loss of 30% ofcalorific value of ingested food.