1. Pancreas: Anatomy & Physiology
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2. Pancreas- Brief History
Pancreas – derived from the Greek pan, “all”, and kreas, “flesh”, probably referring to the organ’s homogenous appearance
Herophilus, Greek anatomist and Surgeon, first identified the pancreas in 335 – 280 BC
Ruphos, another Greek anatomist, gave pancreas its name after few hundred years
Wirsung discovered the pancreatic duct in 1642.
Pancreas as a secretory gland was investigated by Graaf in 1671.

3. Pancreas Gland with both exocrine and endocrine functions
6-10 inch in length (15-25 cm)
gram in weight
Location: retro-peritoneum, 2nd lumbar vertebral level
Extends in an oblique, transverse position
Parts of pancreas: head, neck, body and tail

4. Histology There are two distinct organ systems within the pancreas
The endocrine portion of the pancreas is served by structures called the islet of Langerhans
The islet of Langerhans have several distinct cell types
Alpha cells-produce glucagon and constitute approximate 25% of the total islet cell number
Beta cells-the insulin producing cells (majority of the cells)
Delta cells-produce somatostatin (smallest number)
The exocrine portion of the pancreas is made up of acini and ductal systems
Acinar cells contain zymogen

5. Anatomy
Is a retroperitoneal structure found posterior to the stomach and lesser omentum
It has a distinctive yellow/tan/pink color and is multilobulated
The gland is divided into four portions
The head
The neck
The body
The tail
The pancreas has an extensive arterial system arising from multiple sources
The venous drainage parallels arterial anatomy
The veins terminate in the portal vein
Multiple lymph nodes drain the pancreas
Neural function is controlled by duel sympathetic and parasympathetic innervation

6. Pancreas

8. Head of Pancreas Broadest part
Includes uncinate process: Lower part of the posterior surface of the head that wraps behind the superior mesenteric artery and superior mesenteric vein
Flattened structure, 2 – 3 cm thick
Attached to the 2nd and 3rd portions of duodenum on the right
Emerges into neck on the left
Border b/w head & neck is determined by GDA insertion
SPDA and IPDA anastamose b/w the duodenum and the rt. lateral border
Broadest part
Moulded into the C shaped concavity of duodenum
Lies over the inferior venacava, the right and left renal veins at the level of L2
Posterior surface is indented by the terminal part of the bile duct

9. Neck of Pancreas 2.5 cm in length
Lies in front of the superior mesenteric and portal veins
Posteriorly, mostly no branches to pancreas

11. Body of Pancreas Elongated structure
Anterior surface, separated from stomach by lesser sac
Posterior surface, related to aorta, lt. adrenal gland, lt. renal vessels and upper 1/3rd of lt. kidney
Splenic vein runs embedded in the post. Surface
Inferior surface is covered by tran. Mesocolon
Body passes across the left renal vein and aorta, left crus of diaphragm, left psoas muscle, lower pole of left suprarenal gland to the hilum of left kidney
Upper border crosses the aorta at the origin of the celiac trunk
Splenic artery passes to the left along the upper border
Lower border crosses the origin of the superior mesenteric artery

12. Pancreas

13. Tail of Pancreas Narrow, short segment
Lies at the level of the 12th thoracic vertebra
Lies in the lienorenal ligament along with splenic artery, vein, lymphatics
End of tail of pancreas touches the hilum of spleen
Anteriorly, close to splenic flexure of colon
May be injured during splenectomy (fistula)
Passes forward from the anterior surface of the left kidney at the level of hilum

14. Pancreatic Duct
Main duct (Duct of Wirsung) runs the entire length of pancreas
Joins Central Bile Duct at the ampulla of Vater
2 – 4 mm in diameter, 20 secondary branches
Lesser duct (Duct of Santorini) drains superior portion of head and empties separately into 2nd portion of duodenum
Drains the uncinate process and lower part of head

15. Pancreatic Physiology
Exocrine pancreas 85% of the volume of the gland
Extracellular matrix – 10%
Blood vessels and ducts - 4%
Endocrine pancreas – 1%

16. Histology-Exocrine Pancreas
2 major components
Acinar cells which secrete primarily digestive enzymes
Centroacinar or ductal cells which secrete fluids and electrolytes
Constitute 80% to 90% of the pancreatic mass
Acinar cells secrete the digestive enzymes
20 to 40 acinar cells coalesce into a unit called the acinus
Centroacinar cell (2nd cell type in the acinus) is responsible for fluid and electrolyte secretion by the pancreas
Duct system - network of conduits that carry the exocrine secretions into the duodenum

17. Histology-Endocrine Pancreas
Accounts for only 2% of the pancreatic mass
Nests of cells - islets of Langerhans
Four major cell types
Alpha (A) cells secrete glucagon
Beta (B) cells secrete insulin
Delta (D) cells secrete somatostatin
F cells secrete pancreatic polypeptide

18. Histology-Endocrine Pancreas
B cells are centrally located within the islet and constitute 70% of the islet mass
PP, A, and D cells are located at the periphery of the islet

19. Physiology – Exocrine Pancreas
Secretion of water and electrolytes originates in the centroacinar and intercalated duct cells
Pancreatic enzymes originate in the acinar cells
Final product is a colorless, odorless, and isosmotic alkaline fluid that contains digestive enzymes (amylase, lipase, and trypsinogen)
Alkaline pH results from secreted bicarbonate which serves to neutralize gastric acid and regulate the pH of the intestine
Enzymes digest carbohydrates, proteins, and fats

20. Exocrine
The bulk of the pancreas is an exocrine gland secreting pancreatic fluid into the duodenum after a meal.
The principal stimulant of pancreatic water and electrolyte secretion – Secretin
Secretin is synthesized in the S cells of the crypts of Liberkuhn
Released into the blood stream in the presence of luminal acid and bile
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21. Bicarbonate Secretion
Bicarbonate is formed from carbonic acid by the enzyme carbonic anhydrase
Major stimulants
Secretin, Cholecystokinin, Gastrin, Acetylcholine
Major inhibitors
Atropine, Somatostatin, Pancreatic polypeptide and Glucagon
Secretin - released from the duodenal mucosa in response to a duodenal luminal pH < 3

22. Enzymes: Types and Secretion
Amylase
only digestive enzyme secreted by pancreas in active form
hydrolyzes starch and glycogen to glucose, maltose, maltotriose, and dextrins
Lipase
emulsify and hydrolyze fat in the presence of bile salts
Proteases
essential for protein digestion
secreted as proenzymes; require activation for proteolytic activity
duodenal enzyme, enterokinase, converts trypsinogen to trypsin
Trypsin, in turn, activates chymotrypsin, elastase, carboxypeptidase, and phospholipase
Released from the acinar cells into the lumen of the acinus and then transported into the duodenal lumen, where the enzymes are activated.
Ultimate result of all these actions is food digestion and absorption

23. Physiology – Endocrine Pancreas
Principal function is to maintain glucose homeostasis
Insulin and glucagon play a major role in glucose homeostasis
In addition endocrine pancreas secrete somatostatin, pancreatic polypeptide, c peptide, & amylin
pancreatic polypeptide – released internally to self-regulate pancreas activities
amylin – released with insulin; contributes to glycemic control

24. Insulin Synthesized in the beta cells of the islets of Langerhans
80% of the islet cell mass must be surgically removed before diabetes becomes clinically apparent
Insulin and C peptide are packaged into secretory granules and released together into the cytoplasm
95% belong to reserve pool and 5% stored in readily releasable pool
Thus small amount of insulin is released under maximum stimulatory conditions

25. Insulin Major stimulants Major inhibitors
Glucose, amino acids, glucagon, GIP, CCK, sulfonylurea compounds, β-Sympathetic fibers
Major inhibitors
somatostatin, amylin, pancreastatin, α-sympathetic fibers
Stimulation of Beta cells results in exocytosis of the secretory granules
Equal amount of insulin and c peptide are released into circulation
Insulin circulates in free form and has half life of 4-8 minutes
Liver predominantly degrades insulin
C peptide is not readily degraded in the liver
Half life of c peptide averages 35 minutes

26. Glucagon Secreted by the alpha cells of the islets of Langerhans
Major stimulants
Amino acids, Cholinergic fibers, β-Sympathetic fibers
Major inhibitors
Glucose, insulin, somatostatin, α-sympathetic fibers
Main physiological role
increase blood glucose level through stimulation of glycogenolysis and gluconeogenesis
Antagonistic effect on insulin action
Release is inhibited by hyperglycemia and stimulated by hypoglycemia

27. Somatostatin Secreted by the delta cells of the islets of Langerhans
Major Stimulants
High fat, protein rich , high carbohydrate meal
Generalized inhibitory effect
Inhibits the release of growth hormone
Inhibits the release of almost all peptide hormones
Inhibits gastric, pancreatic, and biliary secretion
Used to treat both endocrine and exocrine disorders

28. Diseases and Disorders
Acute Pancreatitis – Includes a broad spectrum of pancreatic disease
Varies from mild parenchymal edema to severe hemorrhagic pancreatitis associated with gangrene and necrosis
Chronic Pancreatitis
Is associated with alcohol abuse (most common), cystic fibrosis, congenital anomalies of pancreatic duct and trauma to the pancreas
Disruptions of the Pancreatic Duct
In adults, the most common cause is alcoholic pancreatitis
In children the most common cause is neoplasms. (tumors)
The fifth most common cause of cancer death
90% of patients die within the first year after diagnosis
Adenocarcinoma of the Body and Tail of Pancreas
Represents up to 30% of all cases of pancreatic carcinoma

29. Diseases and Disorders
Endocrine Tumors – Rare with an incidence of five per one million
Insulinoma: Most common endocrine tumor of the pancreas
Gastrinoma (Zollinger-Ellison Syndrome)
Identification of a islet cell tumor of the pancreas
Patient management is through control of gastric acid hypersecretion
Pancreatic Lymphoma
Involvement of pancreas with non-Hodgkin’s lymphoma is an unusual neoplasm
Pancreatic Trauma
Pancreas is injured in less than 2% of patients with abdominal trauma

30. Diseases and Disorders
Diabetes Mellitus
Group of diseases characterized by high levels of blood glucose resulting from defects in insulin production, insulin action, or both
Leads to Hyperglycemia, or high blood glucose (sugar)
Estimated 20.8 million in US ( 7% of population)
Estimated 14.6 million diagnosed (only 2/3)
Consists of 3 types:
1) Type 1 diabetes
2) Type 2 diabetes
3) Gestational diabetes
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31. Diabetes Mellitus Type 1 Diabetes (insulin-dependent diabetes)
cells that produce insulin are destroyed
results in insulin dependence
commonly detected before age 30
Type 2 Diabetes (non-insulin-dependent diabetes)
blood glucose levels rise due to
1) Lack of insulin production
2) Insufficient insulin action (resistant cells)
commonly detected after age 40
effects > 90% of persons with diabetes
eventually leads to beta cell failure (resulting in insulin dependence)
Gestational Diabetes
3-5% of pregnant women in the US develop gestational diabetes
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32. Conclusions Pancreas is a composite gland
Has exocrine and endocrine functions
Plays major role in digestion and glucose homeostasis
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