Anatomy & physiology of pancreas

Anatomy & Physiologyof the PancreasSanjay George

AnatomyDerived from ‘Pan’ – all ‘Kreas’ – flesh

15-20cm long, 2.5 – 3.8cm broad, 1.2 – 1.8cm thick

Weighs 80gSituated in retroperitoneum

Contd..Divided:

Head – 30%Body and Tail – 70%

Head corresponds with the curve of duodenum overlying the body of the 2nd lumbar vertebra and the venacava.

Aorta and superior mesenteric vessels lie behind the neck.

Near upper border of neck superior mesenteric vein joins splenic vein to form portal vein.

Contd..

Coming of side of pancreatic head and passing to the left and behind superior mesenteric vein is uncinate process.

Tip of pancreatic tail extends upto the splenic hilum.

Histology80-90% of pancreatic tissue – Exocrine acinar tissue

organised as lobulesPancreatic duct Interlobular & Intralobular ducts

ductules aciniMain duct – Columnar cellsDuctules – Cuboidal cellsAcinar cells clumped around central lumen which

communicates with duct system.

HistologyClusters of endocrine cells distributed throughout called

Islets of Langerhans Islet:

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 Supply

Arterial:Pancreatic Branches of splenic artery

Superior pancreaticoduodenal arteryInferior pancreaticoduodenal artery

Venous:Drain into splenic, superior mesenteric and portal veins

LymphaticsHead & Neck – PancreaticoduodenalBody & Tail - Pancreaticosplenic

Nerve Supply

Parasympathetic – Vagus Sympathetic – plexuses around its arteries

EmbryologyTime Event

1 Day 26 Dorsal Pancreatic duct arises from dorsal side of duodenum

2 Day 32 Ventral Bud arises from base of hepatic diverticulum

3 Day 37 Contact occurs between the 2 buds. Fusion by end of 6th week

4 Week 6 Ventral bud produces the head and uncinate process

5 Week 6 Ducts Fuse

6 Week 6 Ventral duct and distal portion of dorsal duct form the main duct

7 Week 6 Proximal duct forms the duct of Santorini

8 Month 3 Acini appear

9 Months 3-4 Islets of Langerhans Appear & become active

Embryology

Malrotation of ventral bud in 5th week – annular pancreas.

Mode of ductule fusion in 7th week produces various possible ductular patterns.

Anatomy of main duodenal papilla – ampulla of vater is also variable.

PhysiologyIn response to food – secretes digestive enzymes in an alkaline bicarbonate rich fluid.

Secretion enhanced by:SecretinCholecystokininVagal Stimulation

Within 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

Contd..

Hormones:InsulinGlucagonSomatostatin

Total Removal of PancreasDiabetes mellitus due to pancreatic endocrine deficiency of insulinn

Development of digestive disturbances:Increase of faecal fats – bulky, foul smelling, pale and greasy stools

Increased faecal nitrogen due to incomplete proteolysis

No abnormality of carbohydrate digestionPancreatic insufficiency – loss of 30% of calorific value of ingested food.

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