Anatomy & physiology of pancreas

Seminar on anatomy and physiology of Pancreas with emphasis on Surgically important aspects

1. Anatomy & Physiology of the Pancreas Sanjay George

2. Anatomy Derived from ‘Pan’ – all ‘ Kreas ’ – flesh 15-20cm long, 2.5 – 3.8cm broad, 1.2 – 1.8cm thick Weighs 80g Situated in retroperitoneum

3. Contd.. Divided: Head – 30% Body and Tail – 70% Head corresponds with the curve of duodenum overlying the body of the 2 nd 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.

4. 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.

5. Histology 80-90% of pancreatic tissue – Exocrine acinar tissue organised as lobules Pancreatic duct Interlobular & Intralobular ducts ductules acini Main duct – Columnar cells Ductules – Cuboidal cells Acinar cells clumped around central lumen which communicates with duct system.

6. Histology Clusters of endocrine cells distributed throughout called Islets of Langerhans Islet: 75% - B Cells – Insulin 20% - A Cells – Glucagon 5% - D Cells – Somatostatin Small number of pancreatic polypeptide cells B cells form inner core surrounded by other cells. Capillaries draining islet cells drain into portal vein.

7. Blood Supply Arterial: Pancreatic Branches of splenic artery Superior pancreaticoduodenal artery Inferior pancreaticoduodenal artery Venous: Drain into splenic, superior mesenteric and portal veins

8. Lymphatics Head & Neck – Pancreaticoduodenal Body & Tail - Pancreaticosplenic

9. Nerve Supply Parasympathetic – Vagus Sympathetic – plexuses around its arteries

10. Embryology Time 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 6 th 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

11. Embryology Malrotation of ventral bud in 5 th week – annular pancreas. Mode of ductule fusion in 7 th week produces various possible ductular patterns. Anatomy of main duodenal papilla – ampulla of vater is also variable.

12. Physiology In response to food – secretes digestive enzymes in an alkaline bicarbonate rich fluid. Secretion enhanced by: Secretin Cholecystokinin Vagal Stimulation Within cells enzymes are in inactive form.

13. 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

14. Contd.. Hormones: Insulin Glucagon Somatostatin

15. Total Removal of Pancreas Diabetes 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 digestion Pancreatic insufficiency – loss of 30% of calorific value of ingested food.

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