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PANCREAS: Anatomy

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Anatomy & Physiology Dorothy Sparks, MD Dept. of Surgery Pancreas Continued Location: Retro-peritoneum, 2nd lumbar vertebral level Extends in an oblique ... – PowerPoint PPT presentation

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Title: PANCREAS: Anatomy


1
PANCREAS Anatomy Physiology
  • Dorothy Sparks, MD
  • Dept. of Surgery

2
Pancreas
  • Gland with both exocrine and endocrine functions
  • 6-10 inch in length
  • 60-100 gram in weight

3
Pancreas Continued
  • Location Retro-peritoneum, 2nd lumbar vertebral
    level
  • Extends in an oblique, transverse position
  • Parts of pancreas head, neck, body and tail

4
Embryology
  • 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)

5
Embryology of Pancreas
6
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7
Head 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

8
Neck 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

9
Pancreas
10
Body 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

11
Tail 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)

12
Pancreatic 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

13
Arterial 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

14
Arterial 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

16
Approx 25-27 variation in the arterial vascular
anatomy
17
Venous 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

19
Lymphatic Drainage
  • Rich periacinar network that drain into 5 nodal
    groups
  • Superior nodes
  • Anterior nodes
  • Inferior nodes
  • Posterior PD nodes
  • Splenic nodes

20
Innervation 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

21
Innervation 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

22
Histology-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

23
Histology-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

24
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

25
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

26
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)

27
Physiology 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

28
Bicarbonate 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

29
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 lt 3

30
Enzyme 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.

31
Enzymes
  • 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

32
Enzymes 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

33
Insulin
  • 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

34
Insulin
  • Major stimulants
  • Glucose, amino acids, glucagon, GIP, CCK,
    sulfonylurea compounds, ß-Sympathetic fibers
  • Major inhibitors
  • somatostatin, amylin, pancreastatin,
    a-sympathetic fibers

35
Glucagon
  • 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

36
Somatostatin
  • 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

37
Pancreatic Function Tests
  • Everything you ever wanted to know but were
    afraid to ask.

38
Secretin 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

39
Fecal 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

40
Paraaminobenzoic(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.

41
DIFFERENTIAL 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
42
Intravenous 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

43
Tolbutamide 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

44
Acute 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

45
Chr. Pancreatitis
  • Study of exocrine pancreatic function
  • CT- size, duct, stone, mass lesions
  • ERCP-Duct size, stenosis, obstruction, stones,
    therapeutic stenting

46
Pancreatic 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.

47
Work 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

48
Cystic 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

49
Functional 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

50
Gastrinoma
  • 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

51
VIPOMA
  • BMP- Hypokalemia, Metabolic acidosis
  • Elevated VIP levels- repeated testing required
  • Gastric acid levels- Achlorohydria
  • CT, EUS

52
Glucagonoma
  • Hyperglycemia
  • Hypoproteniemia
  • Glucagon levels
  • CT, EUS

53
Somatostatinoma
  • Hyperglycemia
  • Hypocholorohydria
  • Somatostatin levelgt100pgm/ml diagnostic
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