Anatomy And Physoilogy of the Pancreas.pptx

Surgical note

1. Anatomy And Physiology of the Pancreas Presented by: Bezawit Bewketu (SR1) Moderator: Dr. Getachew (Consultant General and HPBS Surgeon)

2. Outline Introduction Embryology of Pancreas Anatomy of Pancreas Developmental Anomalies of Pancreas Physiology of Pancreas Reference

3. Introduction The name ‘ pancreas ’ is derived from the Greek ‘ pan ’ (all) and ‘ kreas ’ (flesh). It is the most unforgiving organ Some have even described it as two organs in one It is a retroperitoneal organ In adult it weighs between 75 – 100 grams and is about 15 – 20 cm long

4. Embryology of Pancreas The pancreas begins development during the fourth week of gestation. Initially, dorsal and ventral buds arise from the foregut The dorsal bud typically appears first and ultimately develops into the superior head, neck, body, and tail of the mature pancreas.

5. The ventral bud develops as part of the hepatic diverticulum and maintains communication with the biliary tree throughout development. The ventral bud will become the inferior part of the head and uncinate process of the gland. Between the fourth and eighth weeks, the ventral bud rotates posteriorly in a clockwise fashion to fuse with the dorsal bud.

6. As pancreatic buds fuse their ducts anastomose, or open in to one another. Main pancreatic duct- duct of ventral bud Accessory pancreatic duct - from duct of dorsal bud

7. Anatomy of Pancreas It is a retroperitoneal organ that lies in an oblique position, sloping upward from the C-loop of the duodenum to the splenic hilum Has four parts: head ,neck, body and tail.

8. Anterior Relationship Posterior Relationship

9. Head of Pancreas

10. Uncinate process projection from the inferior part of the pancreatic head Extends medially to the left, posterior to the SMA

11. Neck of the pancreas

12. Body of Pancreas

13. 5/15/2024 14 . Posterior surface: Devoid of peritoneum Aorta , origin of SMA, Lt . suprarenal gland, Lt . kidney, Lt renal vessels Splenic vessels

14. Tail of Pancreas Is a small portion of the pancreas anterior to the left kidney Nestled in the hilum of the spleen near the splenic flexure of the left colon. Awareness of these anatomic relationships is important to avoid injury to the pancreatic tail during left colectomy or splenectomy

15. Pancreatic Ducts Main P ancreatic D uct usually only 2 to 3 mm in diameter runs midway between the superior and inferior borders of the pancreas, usually closer to the posterior than to the anterior surface Joins CBD to form common channel and drain in to the major duodenal papilla A ccessory P ancreatic D uct drains into the duodenum, a minor papilla can be identified approximately 2 cm proximal to the ampulla of Vater

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17. Arteria l Supply of Pancreas Blood supply comes from celiac and SMA Anterior SPDA Posterior SPDA Anterior IPDA Posterior IPDA Inferior pancreatic artery Splenic artery Dorsal pancreatic aa Great pancreatic aa( arteria pancreatica magna) Artery to the tail of pancreas( caudal artery) 5/15/2024 18

18. Anterior view

19. Posterior view

20. Variations in the arterial anatomy 5/15/2024 21 One out of five patients. The right hepatic artery, common hepatic artery, or gastroduodenal arteries can arise from the SMA. In 15% to 20% of patients, the right hepatic artery arises from the SMA (referred to as a replaced right hepatic artery ).

21. V enous drainage of Pancreas 5/15/2024 22 Superficial and similar to the arteries within the parenchyma of the pancreas. Anterior and posterior venous arcade within the head of the pancreas . The superior veins drain directly into the portal vein just above the neck of the pancreas. The posterior inferior arcade drains directly into the inferior mesenteric vein at the inferior border of the neck of the pancreas. These venous tributaries must be divided during a Whipple procedure.

22. Cont.. Gastrocolic trunk: Formed by the confluence of: middle colic vein , right gastro epiploic vein and anterior inferior pancreaticoduodenal vein. It drains to the SMV at the inferior border of the pancreas. Used as anatomic land mark for GI surgery. Traction on the transverse colon during colectomy can tear these fragile veins, which then retract into the parenchyma of the pancreas, making control difficult.

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24. Variation in portal vein anatomy

25. Lymphatic Drainage of Pancreas The lymphatic drainage from the pancreas is diffuse and widespread The profuse network of lymphatic vessels and lymph nodes draining the pancreas provides egress to tumor cells arising from the pancreas This contributes to the fact that pancreatic cancer often presents with positive lymph nodes and a high incidence of local recurrence after resection 27

26. The pancreatic lymphatics also communicate with lymph nodes in the transverse mesocolon and mesentery of the proximal jejunum. Tumors in the body and tail of the pancreas often metastasize to these nodes and lymph nodes along the splenic vein and in the hilum of the spleen.

27. Head of the pancreas and duodenum: Upper head drains to the subpyloric nodes Inferiorly drains to retropancreatic and antepancreatic nodes. Then to the celiac and superior mesenteric group of nodes and into the cisterna chyli . Body of pancreas: drain into the pancreaticosplenic nodes then to the celiac nodes. Tail of the pancreas: Drains to the splenic hilar nodes. 5/15/2024 29

28. Cont. 30

29. Innervation of pancreas Parasympathetic system- vagus nerve ( hepatic , bilateral gastric, bilateral celiac branches) Stimulate secretion Sympathetic system- abdomino pelvic splanchinic nerves Inhibit secretion The pancreas also has a rich supply of afferent sensory fibers, which are responsible for the intense pain associated with advanced pancreatic cancer, as well as acute and chronic pancreatitis.

30. Developmental anomalies of pancreas Annular pancreas Annular part consists of thin, flat band of pancreatic tissue encircling 2 nd part of duodenum Growth of bifid ventral pancreatic bud around duodenum May cause obstruction of duodenum More seen in females 5/15/2024 33

31. P ortal annular pancreas : an anatomic variation due to aberrant fusion of the ventral and dorsal buds around the portal vein.

32. 5/15/2024 36 2. Pancreas D ivisum : most common type of anomaly(4-10% of the general population). Associated with recurrent pancreatitis. Three sub types; Type 1 (classic ) 70% : no connection at all. Type 2(absent ventral duct) 20-25% : minor papilla drains all of pancreas . Type 3(functional) 5-6% : filamentous or inadequate connection b/n dorsal and ventral ducts. Developmental anomalies cont,

33. 3. Ectopic(heterotopic) pancreas May arise anywhere in primitive foregut Most common sites are: Submucosa of gastric antrum 30% Proximal portion of the duodenum 30% Remaining duodenum 20% Other regions of small bowel 20% ( result in bowel obstruction caused by intussusception, bleeding, or ulceration. ) It is functional and subject to inflammatory and neoplastic changes, but majority of cases are asymptomatic.

34. Developmental anomalies cont, 4. Pancreatobiliary maljunction Junction of pancreatic and biliary ducts is detected outside duodenal wall Pancreatobiliary ductal junction is not controlled by sphincter mechanisms Often associated with choledochal cyst and gallbladder ca. 5/15/2024 38

35. Variations in the union of CBD and pancreatic duct The length of the common channel is variable. In 1/3 of patients, the bile duct and pancreatic duct remain distinct to the end of the papilla, 1/3 the two ducts merge at the end of the papilla 1/3 a true common channel is present for a distance of several millimeters. 5/15/2024 39

36. Physiology of Pancreas It is mainly composed of: 85% exocrine pancreas 10% extracellular matrix 4% blood vessels and the major ducts, only 2% of the gland is comprised of endocrine tissue.

37. Exocrine Pancreas The pancreas secretes nearly 500 – 800 ml/day of colorless, odorless, alkaline, isosmotic pancreatic juice The juice is a combination of acinar cell secretions( amylase, proteases and lipase) and duct cell secretions ( water, bicarbonate and electrolytes) 41

38. Exocrine Pancreas Structure A ) Acinus Functional units which produce and secrets digestive enzymes Composed of 15-100 pyramidal shaped cells called acinar cells Organized concentrically around a central lumen which is continuous with proximal end of intercalated duct B ) Centroacinar cells Present at the junction b/n acinus and the ductal cells of the intercalated duct

39. C ) The Ductal Network Two critical functions Transporting exocrine secretion from acini to duodenum Producing a solution rich in bicarbonate and electrolytes Draining pathway in the ductal network goes as Intercalated ducts then intralobular duct then interlobular ducts then main pancreatic duct finally into duodenum, via ampulla of Vater .

40. Exocrine Ductal System The centroacinar and intercalated duct cells secrete the water and electrolytes present in the pancreatic juice. The centroacinar cells contain the enzyme carbonic anhydrase, which is needed for bicarbonate secretion Biocarbonate secretion varies with pancreatic secretory rate (increases if the secretory rate increases)

41. Cont..

42. Phases of Pancreatic Secretion Cephalic Phase Gastric Phase Intestinal Phase Initiated by anticipation of food, smell, taste and chewing act Initiated when meal reaches the stomach and stimulated by gastric distention Begins with the entry of chyme and gastric acid juice in to duodenum Ach release by vagal nerve endings in pancreas Enzyme secretion with minimal water and bicarbonate secretion Release of Ach and Secretin Acinar type secretion 5-10% of total secretion of pancreatic enzymes 65-70% of total secretion of pancreatic enzymes 20% of total secretion of pancreatic enzymes

43. Regulation of Pancreatic Secretion Secretin : released from the duodenal mucosa in response to acidic chyme . major stimulant for bicarbonate secretion CCK : released from duodenal mucosal cells. stimulates bicarbonate secretion, but to a much lesser extent than secretin. Gastrin and acetylcholine : both stimulants of gastric acid secretion, are also weak stimulants of pancreatic bicarbonate secretion

44. Endocrine Pancreas Islets of Langerhans are functional units of endocrine pancreas with imp’t role in glucose homeostasis Nearly 1 millions distributed through out the gland 1-2% of organs mass At least five major cell types alpha cells secrete glucagon, β- cells secrete insulin, delta cells secrete somatostatin , epsilon cells that secrete ghrelin, and PP cells that secrete PP 5/15/2024 51

45. Islets cells distribution Cell types With in Islet Distribution (predominantly) Pancreatic distribution Beta Cells Central portion Through out Pancreas Delta Cells Peripheral portion Through out Pancreas Alpha Cells Peripheral portion Body and tail( Majority) Head and Uncinate process (few) PP cells Peripheral portion Head and Uncinate process (majority) Body and tail( few) E cells( Epsilon Cells) Peripheral portion -

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47. References Blumgarts surgery of the liver, biliary tract and pancreas 7 th edition Schwartz’s principle of surgery, 11 th edition Netter atlas of human anatomy, 6 th edition Grays anatomy, 41 st edition 5/15/2024 54

48. THANK YOU !!! 5/15/2024 55