Title: PANCREAS: Anatomy
1PANCREAS Anatomy Physiology
- Dorothy Sparks, MD
- Dept. of Surgery
2Pancreas
- Gland with both exocrine and endocrine functions
- 6-10 inch in length
- 60-100 gram in weight
3Pancreas Continued
- Location Retro-peritoneum, 2nd lumbar vertebral
level - Extends in an oblique, transverse position
- Parts of pancreas head, neck, body and tail
4Embryology
- Endodermal in origin
- Develops from ventral and dorsal pancreatic buds
- Ventral bud rotates posteriorly and becomes the
uncinate process and inferior head of pancreas - Dorsal bud becomes superior head, neck, body and
tail - Ventral bud duct fuses with dorsal bud duct to
become main pancreatic duct (Wirsung)
5Embryology of Pancreas
6(No Transcript)
7Head of Pancreas
- Includes uncinate process
- Flattened structure, 2 3 cm thick
- Attached to the 2nd and 3rd portions of duodenum
on the right - Merges into neck on the left
- Border between head neck is determined by GDA
insertion - SPDA and IPDA anastamose between the duodenum and
the rt. lateral border
8Neck of Pancreas
- 2.5 cm in length
- Straddles SMV and PV
- Superior border relates to the pylorus
- Superior mesenteric vessels emerge from the
inferior border - Posteriorly, SMV and splenic vein confluence to
form portal vein - Posteriorly, most often no branches to pancreas
9Pancreas
10Body of Pancreas
- Elongated, long 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
closer to the superior border - Inferior surface is covered by transverse
mesocolon
11Tail of Pancreas
- Narrow, short segment
- Lies at the level of the 12th thoracic vertebra
- Ends within the splenic hilum
- Lies in the splenophrenic ligament
- Anteriorly, related to splenic flexure of colon
- May be injured during splenectomy (fistula)
12Pancreatic Duct
- Main duct (Wirsung) runs the entire length of
pancreas - Joins CBD at the ampulla of Vater
- 2 4 mm in diameter, drains up to 20 secondary
branches - Ductal pressure is 15 30 mm Hg (vs. 7 17 in
CBD) thus preventing reflux and damage to panc.
duct - Lesser duct (Santorini) drains superior portion
of head and empties separately into 2nd portion
of duodenum
13Arterial Supply of Pancreas
- Variety of major arterial sources (Celiac, SMA
and Splenic) - Celiac ? Common Hepatic Artery ? Gastroduodenal
Artery ? Superior pancreaticoduodenal artery
which divides into anterior and posterior
branches - SMA ? Inferior pancreaticoduodenal artery which
divides into anterior and posterior branches
14Arterial Supply of Pancreas
- Anterior and posterior collateral arcade between
the superior and inferior PDA supply head - Body and tail supplied by splenic artery by about
10 branches - Three big branches from splenic are
- Dorsal pancreatic artery
- Pancreatica Magna (midportion of body)
- Caudal pancreatic artery (tail)
15- Arterial Supply of Pancreas
16Approx 25-27 variation in the arterial vascular
anatomy
17Venous Drainage of the Pancreas
- Follows arterial supply
- Anterior and posterior arcades drain head and the
body - Splenic vein drains the body and tail
- Major drainage areas are
- Suprapancreatic PV
- Retropancreatic PV
- Splenic vein
- Infrapancreatic SMV
- Ultimately, into portal vein
18- Venous Drainage of the Pancreas
19Lymphatic Drainage
- Rich periacinar network that drain into 5 nodal
groups - Superior nodes
- Anterior nodes
- Inferior nodes
- Posterior PD nodes
- Splenic nodes
20Innervation of Pancreas
- Sympathetic fibers from the splanchnic nerves
- Parasympathetic fibers from the vagus
- Both give rise to intrapancreatic periacinar
plexuses - Parasympathetic fibers stimulate both exocrine
and endocrine secretion - Sympathetic fibers have a predominantly
inhibitory effect
21Innervation of Pancreas
- Rich afferent sensory fiber network
- Ganglionectomy or celiac ganglion blockade
interrupt these somatic fibers (pancreatic pain) - However the origin of pancreatic pain is
difficult to explain anatomically
22Histology-Exocrine Pancreas
- 2 major components Acinar cells and Ducts
- They constitute 80 to 90 of the pancreatic mass
- 20 to 40 acinar cells coalesce into a unit
called the acinus - Acinar cells secrete the digestive enzymes
- Centroacinar cell (2nd cell type in the acinus)
is responsible for fluid and electrolyte
secretion by the pancreas
23Histology-Exocrine Pancreas
- Ductular system - network of conduits that carry
the exocrine secretions into the duodenum - Acinus ? small intercalated ducts ? interlobular
duct ? pancreatic duct - Interlobular ducts contribute to fluid and
electrolyte secretion along with the centroacinar
cells
24Histology-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
25Histology-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
26Physiology 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)
27Physiology Exocrine Pancreas
- 500 to 800 ml pancreatic fluid secreted per day
- 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
28Bicarbonate Secretion
- Centroacinar cells and ductular epithelium
secrete 20 mmol of bicarbonate per liter in the
basal state - Fluid (pH from 7.6 to 9.0) acts as a vehicle to
carry inactive proteolytic enzymes to the
duodenal lumen - Sodium and potassium concentrations are constant
and equal those of plasma - Chloride secretion varies inversely with
bicarbonate secretion
29Bicarbonate 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 lt 3
30Enzyme Secretion
- Acinar cells secrete isozymes
- amylases, lipases, and proteases
- Major stimulants
- Cholecystokinin, Acetylcholine, Secretin, VIP
- Synthesized in the endoplasmic reticulum of the
acinar cells and are packaged in the zymogen
granules - Released from the acinar cells into the lumen of
the acinus and then transported into the duodenal
lumen, where the enzymes are activated.
31Enzymes
- Amylase
- only digestive enzyme secreted by the pancreas in
an active form - functions optimally at a pH of 7
- hydrolyzes starch and glycogen to glucose,
maltose, maltotriose, and dextrins - Lipase
- function optimally at a pH of 7 to 9
- emulsify and hydrolyze fat in the presence of
bile salts
32Enzymes of Pancreas
- Proteases
- essential for protein digestion
- secreted as proenzymes and require activation for
proteolytic activity - duodenal enzyme, enterokinase, converts
trypsinogen to trypsin - Trypsin, in turn, activates chymotrypsin,
elastase, carboxypeptidase, and phospholipase - Within the pancreas, enzyme activation is
prevented by an antiproteolytic enzyme secreted
by the acinar cells
33Insulin
- Synthesized in the B cells of the islets of
Langerhans - 80 of the islet cell mass must be surgically
removed before diabetes becomes clinically
apparent - Proinsulin, is transported from the endoplasmic
reticulum to the Golgi complex where it is
packaged into granules and cleaved into insulin
and a residual connecting peptide, or C peptide
34Insulin
- Major stimulants
- Glucose, amino acids, glucagon, GIP, CCK,
sulfonylurea compounds, ß-Sympathetic fibers - Major inhibitors
- somatostatin, amylin, pancreastatin,
a-sympathetic fibers
35Glucagon
- Secreted by the A cells of the islet
- Glucagon elevates blood glucose levels through
the stimulation of glycogenolysis and
gluconeogenesis - Major stimulants
- Aminoacids, Cholinergic fibers, ß-Sympathetic
fibers - Major inhibitors
- Glucose, insulin, somatostatin, a-sympathetic
fibers
36Somatostatin
- Secreted by the D cells of the islet
- 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
37Pancreatic Function Tests
- Everything you ever wanted to know but were
afraid to ask.
38Secretin Test
- Overnight fast
- Double lumen tube
- Basal secretion
- 2u/kg of Secretin
- Four 20 min collections of secretions
- Test for volume, bicarbonate, amylase
- Useful for diagnosing gastrinomas
39Fecal fat test
- Distinguish between pancreatic dysfunction and
intestinal malabsorption - In Pancreatic disease when lipase secretion is
reduced by 90- 24-hour fecal fat content is
elevated to more than 20 g. - Intestinal dysfunction - Steatorrhea with low
levels of fecal fat - Use- Efficacy of pancreatic enzyme replacement
40Paraaminobenzoic(PABA) acid test
- Noninvasive test of pancreatic insufficiency
- N-benzoyl-l-tyrosyl-PABA is cleaved by
chymotrypsin to form PABA. - PABA is absorbed from the small intestine
excreted in the urine - One gram of BT-PABA in 300 mL of water is given
orally, and urine collections are obtained for 6
hours. - Patients with chronic pancreatitis excrete less
than 60 of the ingested dose of BT-PABA.
41DIFFERENTIAL DIAGNOSIS OF INTESTINAL AND
PANCREATIC STEATORRHEA
Parameter Intestinal steatorrhea Pancreatitis
Fecal fat lt20 g monoglycerides and diglycerides soapy consistency gt20 g tnglycendes only seepage
D-Xylose Low Normal
Secretion test Normal Abnormal
Small-bowel series Abnormal Normal
Small-bowel biopsy Abnormal Normal
Lunch meal Normal Abnormal
PABA test Normal Abnormal
PP response to test meal Normal Low
Treatment with pancreatic enzymes No change Improvement
42Intravenous arginine test
- Arginine stimulates the secretion of islet
hormones - Diagnosis of hormone-secreting tumors
- Overnight fast, and given a 30-minute infusion of
0.5 g of arginine per kilogram. - Blood samples are taken every 10 minutes
- Radioimmunoassays are performed for the specific
hormones in question. - This test is particularly useful for the
diagnosis of glucagon-secreting tumors - Elevations of plasma glucagon to above 400 pg/mL
usually indicate a glucagonoma
43Tolbutamide response test
- Useful in detecting hormone-secreting tumors.
- Sulfonylurea stimulates insulin secretion.
- Overnight fasting, basal blood samples are drawn.
- One gram of sodium tolbutamide is given
intravenously - Blood glucose level is monitored for 1 hour.
- Blood samples for radioimmunoassay of insulin or
other suspected hormones, such as somatostatin
obtained. - In normal patients, the blood glucose level falls
to 50 of basal values after 30 minutes. - Sustained hypoglycemia with hypersecretion of
insulin is consistent with an insulinoma. - In the case of a somatostatinoma, somatostatin
levels are more than twice as high as the
prevailing normal values for the particular
somatostatin radioimmunoassay
44Acute pancreatitis
- Blood Investigations CBC,LFT, serum calcium,
serum amylase and lipase, ABG - Chest Xray (for exclusion of perforated viscus)
- Abdominal Xrays (for detection of "sentinel
loop", gallstones which are radioopaque in 10) - CT abdomen
- U/S abdomen
- MRI/MRA
45Chr. Pancreatitis
- Study of exocrine pancreatic function
- CT- size, duct, stone, mass lesions
- ERCP-Duct size, stenosis, obstruction, stones,
therapeutic stenting
46Pancreatic neoplasm's
- CBC, LFT, Amylase, Lipase
- Ca-19-9- 80 accurate, prognosis and f/u
- Genetic testing- Genetic syndrome associated with
hereditary pancreatic cancer-(Peutz-Jeghers,
Hereditary pancreatitis, FAMMM, HNPCC) - Genetic Mutations-DPC4 gene(18Q)-missing in 90
of pancreatic cancers. K-ras mutations common.
Also changes in p53 and p16 tumor suppressor
genes.
47Work up of Pancreatic Neoplasm
- CAT scan - Spiral CT- Cuts taken through pancreas
both in a arterial phase and a portal venous
phase - Local disease and metastatic disease
- MRCP-Non invasive, assess biliary tract in a
jaundiced pt - ERCP-90 accurate, in pts whom no mass is seen,
brushings for biopsy - U/S
- EUS- Detect early lesions lt2cm, L.N assessment,
vascular involvement, FNAC
48Cystic neoplasms
- CT scan
- Serous mutilocular ,central calcification,
- Mucinous- more common in body and tail, 30
malignant potential, needs to be resected - ERCP- IPMN, common in the head and mucin secreted
from the ducts
49Functional endocrine neoplasms Insulinomas
- Monitored fast test
- Insulin to glucose ratio gt0.4 (N lt0.3)
- Elevated C-peptide and pro-insulin levels
- CT, EUS
- STS (Somatostatin receptor scintigraphy-
Octreotide scan)- Local tumors-75,
metastatic-65, significant false negatives - Visceral angiography- not performed anymore
- Selective arterial calcium stimulation test(GDA,
splenic, Inferior Panc. Duo. Art) - Intraop ultrasound
50Gastrinoma
- Serum gastrin- Fasting gastringt200pgm/ml
- gt1000pgm.ml pathgnomonic
- Gastric acid analysis-Basal Acid Outputgt15mEq/hr
(Non-ulcerogenic causes - Atrophic gastritis,
Pernicious anemia, Vagotomy) - Secretin Stimulation test- Increase by 200 pgm/ml
above the basal level - CT, EUS
- SRS- more sensitive than in Insulinoma
- Selective arterial secretin stimulation test
- Intra-op ultrasound
51VIPOMA
- BMP- Hypokalemia, Metabolic acidosis
- Elevated VIP levels- repeated testing required
- Gastric acid levels- Achlorohydria
- CT, EUS
52Glucagonoma
- Hyperglycemia
- Hypoproteniemia
- Glucagon levels
- CT, EUS
53Somatostatinoma
- Hyperglycemia
- Hypocholorohydria
- Somatostatin levelgt100pgm/ml diagnostic