Anatomy, Histology, & Embryology of the Pancreas

Transcription

1 Anatmy, Histlgy, & Embrylgy f the Pancreas *Pancreas is secndary retrperitneal, with the exceptin f the tail, the fregut. Anatmy f Pancreas Lcatin: Within the curve f the dudenum, lcated in the epigastric and left hypchndriac regins Surface Prjectin: Surface prjectin f is different depending n the part f it, and will be entailed later. Tpgraphy: tuches the dudenum, the spleen, the left kidney, the lwer brder f the stmach. Functin: releases secretins in an excrine fashin, namely pancreatic juice, which it then secretes int the dudenum thrugh the majr dudenal papilla, r papilla f Vater. This majr pancreatic duct is als called the duct f Wirsung. Endcrine secretins include glucagn and insulin int the bld.

2 Parts: Head lcated between L1-2 in curve f the dudenum, t the descending and hrizntal parts f it. develps mainly frm the ventral pancreatic bud, except the upper part, which is frm the drsal pancreatic bud. Is lcated right t the sup mesenteric a/v.sp = head f pancreas is anterir lc t IVC, right renal a/v, left renal v Uncinate prcess- at lwer head behind sup mesenteric a/v Neck - shrt, 1-2cm, sup mesenteric a/v g behind the ntch belw neck, called pancreatic ntch. Ant surface f neck cvered with peritneum, and mves alng with mvements f pylrus f stmach. Sup mesenteric v and splenic v cmbine behind the neck f pancreas, t frm prtal v. Bdy L1-2, in frnt f vert clumn, psterir t lesser sac Has 3 surfaces: Ant cvered by peritneum, and indirectly cntacts pst stmach, lies in flr f lesser sac, helps frm gastric bed > Pst - cntact with arta, sup mesenteric a/v, L kidney & renal vessels, and L suprarenal gland, Splenic a runs in trtus path superir t it, and has grve fr splenic v. Inf - tuches 3rd and 4th part f dud Omental tubersity in sup surface f bdy belw celiac trunk, cntact with visceral surface f liver. (T12-L1 midline) Tail lc. at left cstal arch, 2-3 fingers lat t T12, runs t hilum f spleen. Can be retrperitneal r intraperitneal. If shrter, than usually retrperitneal, like the rest f pancreas. Then a small peritneal ligament = pancreaticlineal lig extends frm tip f tail > hilum f spleem. Splenic a/v enter spleen thrugh this ligament. If lnger, intraperitneal, and splenic a/v can g directly t spleen. Ducts: Main pancreatic duct = Duct f Wirsung, duct f ventral pancreatic bud, begins in tail and runs alng entire pancreas, till head, where it turns inf and runs with cmmn bile duct. Opens at majr dudenal duct Ampulla f Vater, which is gaurded by sphincter f Oddi, after jining bile duct. Accessry pancreatic duct = Santrini s duct can pen int main r minr dudenal papilla, smetimes bth. minr dudenal papilla lcated 2cm abve majr ne, Begins in lwer prtin f the head, and drains small prtin f head and bdy. Clinical NOTE - Bile ducts is embedded int a grve n the pst/sup side f the head. If tumrs are lcated within the head, this can blck bile flw int the dudenum, resulting in jaundice. Bld Supply: B/c develps frm FOREGUT supplied by branches f celiac trunk. Splenic a supplies derivatives f drsal pancreatic bud > neck, bdy, tail f pancreas lcated n shallw grve n sup/pst side f pancreas. 10 branches, that can frm arterial arcades (netwrks) with branches frm gastrdudenal a and sup mesenteric a Sup pancreaticdudenal a (gastrdudenal a) & Inf pancreaticdudenal a (sup mesenteric a ) splits int ant/pst branches t supply the head f the pancreas Mst veins empty int splenic v, which is embedded int the back f the pancreas itself

3 Lymph Drainage lymph vessels fllw the arteries and drain int pancreatisplenic ndes that lie alng splenic arteries. The nes by the head g t pylric lymph ndes, as well. These tw sets f ndes drain int celiac, hepatic, and sup mesenteric lymph ndes Innervatin PNS (Para Sympethatic Nervus System) (+) digestin, secretin, vasdilatin. Peritneal ligaments: Frm CN X, carries pre ggl fibers t submucsal and myenteric plexus within walls f rgans, with shrt pst ggl PNS fibers. G t parenchyme (acinar cells and islets f Langerhans) Inc Insulin secretin, Inc glucagn secretin SNS (Sympathetic Nervus System) (-) digestin, secretin, vascnstrictin SNS > (T5-T9) frm thracic splanchnic n > artic hiatus > celiac ggl plexus arund the celiac trunk > pst ggl fibers run with branches f celiac trunk. G t pancreatic glands and parenchyme (pancreatic acinar cells and islets f Langerhans) dec insulin secretin, inc glucagn secretin Peritneal ligaments: nne,except fr the tail smetimes, which can be lcated within the pancreaticlienal ligament. Histlgy Pancreas slide Structures t Identify: Intercalated duct Intralbular duct a/v/capillaries Islets f Langerhans Secretry acinus A,B,D, cells CT septa lbules General Infrmatin Digestive gland with head, neck, bdy, tail regins Mixed gland with endcrine and excrine functins

4 Excrine: Tubulacinar glands manily cmpsed f serus secretry units Secretins prtelytic enzymes Prtelytic End-peptidases: trypsingen, chemtrypsingen Expeptidases: prcarbxypeptidases, praminpeptidases, alpha amylases, lipases nuclelytic enzymes Has hrmnal/ neural cntrl regulatin: Secretin inc. fluid secretin, CCK pr enzyme secretin Chyme f stmach and dudenum stimulate enterendcrine cells t secrete CCk and Secretin causes pancreas t secrete Frms mst f pancreas, has tightly packed serus acini circular gland, small circular lumen, darkly stained. zymgen cells arranged in lbule fashin Lbules seperated by thin intralbular, and interlbular CT septa have bld vessels, interlbular ducts, pacinian crpsucles Pacinian crpsucle - cncentric circles, lighter than surrunding acini, is a sensry receptr Endcrine: Islets f Langerhans (Pancreatic Islets) highly vascularized epithelid tissue alpha, beta, delta, cells in periphery, beta cells als in center. light staining, glbular, with thin CT capsule surrunding it. Pyramid shaped cells facing central lumen, Secretins g t large vacular netwrk f capillaries just utside the islets, Excretes int intercalated duct, lined by lw cubidal epithelium

5 Alpha cells glucagn inc amunt f glucse in bld Beta cells insulin dec amunt f glucse in bld Delta cells -Smatstatin inhibits the ther tw Duct flw: Within the islets, flw int pale staining centr acinar cells within lumen intercalated (same as intralbular) ducts interlbular ducts (simple cubidal epith) in interlbular CT septa larger ducts (als interlbular, but with stratified clumnar epith) Embrylgy Develpment f Pancreas Enddermal lining f frgut frms tw utgrwths, ventral pancreatic bud and drsal pancreatic bud Within bth buds, enddermal tubules surr. by mesderm > branch t frm acinar cells and ducts (excrine part). Clumps f cells within excrine part frm, and becme the future islets (endcrine part) Remember hw the dudenum rtates 90 degrees clckwise? Because f this, the ventral bud (ant) rtates als drsally (pst) and fuses with the drsal bud already there t frm adult pancreas Ventral bud = uncinate prcess and lwer part f head f pancreas Drsal bud = rest f pancreas Main pancreatic duct (f Wirsung) = frmed by distal drsal bud and all f ventral bud Acc pancreatic duct (f Santrini) = prx part f drsal bud Endderm rigin = acinar cells, islet cells, simple clumnar and cubidal lined parts f duct system Visceral mesderm = CT surrunding them, and a/v/capillaries Surce: