Ap exocrine

Question 1

Pancreas

Answer 1

• Located beneath stomach
• Has both exocrine & endocrine functions
• Exocrine pancreas secretes pancreatic juice into duodenum through pancreatic duct(s)
• —Enzymes in pancreatic juice aid digestion of food
• —Bicarbonate helps to neutralize chyme (partly digested food) entering duodenum

-Endocrine pancreas

—Islets of Langerhans:

¢Secrete insulin and glucagon.

Question 2

Pancreatic enzymes secreted by acinar cells in active form:

Answer 2

lipase, amylase, deoxyribonuclease & ribonuclease

Question 3

Enzymes secreted as inactive proenzymes or zymogens:

Answer 3

trypsinogen, chymotrypsinogen, proelastase and procarboxypeptidase

Trypsinogen is converted to the active form trypsin by an enzyme found in the intestinal brush border called enterokinase (EN).

Trypsin then converts the remaining proenzymes into active enzymes

Question 4

Pancreatic enzymes aid in

Answer 4

tPancreatic enzymes aid in he digestion and absorption of fats, carbohydrates, and proteins.

• Proteins: Trypsin, chymotrypsin, elastase & carboxypeptidase
• Carbohydrates: Pancreatic amylase
• Fat: Pancreatic lipase, cholesterol esterase & phospholipaseA2
• Nucleic Acids: Ribonuclease & deoxyribonuclease

Secretion in zymogen form precludes digestion of pancreas by its own enzymes

Acinar cells also generate & secrete trypsin inhibitor to prevent self-digestion

Question 5

Outline how bicarbonate & water are secreted by pancreatic ductal cells

Answer 5

-Acidity of chyme entering duodenum triggers release of secretin

• —Secretin release proportional to degree of chyme acidity (pH 3.0–5.0)
• —Bicarbonate content of pancreatic juice adjusted to neutralize acidity

-Secretin stimulates ductal epithelium

—↑ bicarbonate & water secretion – pancreatic juice now able to flow freely

Question 6

Describe the mechanisms for regulation of pancreatic secretion

Answer 6

In the intestinal phase, pancreatic response is regulatedprimarily by the hormones secretin and CCK, and by neural influences including the enteropancreatic reflex which is mediated by the enteric nervous system and amplifies the pancreatic secretory response.Sep 14, 2

Question 7

Regulation of Pancreatic Secretion

Answer 7

¢Vagal stimulation (ACh) arises in anticipation of chyme entering duodenum

• —Presence of chyme in duodenum triggers release of CCK
• Acidity of chyme entering duodenum triggers release of secretin
• —Secretin release proportional to degree of chyme acidity (pH 3.0–5.0)
• —Bicarbonate content of pancreatic juice adjusted to neutralize acidity
• CCK & secretin both enter bloodstream & circulate to reach pancreas
• Acetylcholine (vagal stimulation) & cholecystokinin(CCK) stimulate acinar cells

—↑ digestive enzymes – stored in acini & ducts

-Secretin stimulates ductal epithelium

—↑ bicarbonate & water secretion – pancreatic juice now able to flow freely

-Total volume of pancreatic juice secreted typically 1,000–1,500 ml each day

Question 8

Acute Pancreatitis

Answer 8

• Characterized by acute escape of activated digestive enzymes from pancreatic ducts
• —Results in autodigestion of pancreatic tissues & inflammatory response
• Common cause of upper abdominal pain, nausea & fever
• —Significant fatality rate (-5%) for severe cases of acute pancreatitis

¢Etiologic factors:

—Metabolic: alcohol, hyperlipoproteinemia, hypercalcemia, drugs (e.g. thiazides)

—Mechanical: gallstones, traumatic & perioperative injury

—Vascular: shock, atheroembolism, polyarteritis nodosa

—Infections: mumps, mycoplasma, ascaris

—Heriditary : Cystic fibrosis, familial pancreatitis

Question 9

……… and …….may be useful as diagnostic indicators foracute pancreatitis

Answer 9

serum amylase & serum lipase

Question 10

Chronic Pancreatitis

Answer 10

• Relapsing disorder that ultimately causes pancreatic insufficiency
• Chronic inflammation leading to destruction of acini& stenosis of ducts
• —Fibrosis of gland & calcification typically follow
• Leads to impaired exocrine function
• —May also compromise endocrine function
• Etiologic factors:
• —Chronic alcoholism most common causative factor (70–80%)
• —Long-term obstruction of pancreatic duct & chronic hypercalcemia

Question 11

Pathogenesis of Chronic Pancreatitis

(Putative mechanism)

Answer 11

Protein hypersecretion from acinar cells → ductal plugs

Alcohol exacerbates problem by suppressing secretion of lithostathines

Peptides that normally inhibit formation of protein plugs & stones

Calcium carbonate crystalizes to form calculi (stones) → promote fibrosis

Fibrosis restricts flow through duct & leads to atrophy of acinarcells

Question 12

Exocrine Pancreatic Insufficiency

Answer 12

• A consequence of chronic pancreatitis
• —Other causes include cystic fibrosis, pancreatic cancer etc
• Symptoms: diarrhea, steatorrhea, weight loss etc
• Diagnosis: difficult due to generic GI symptoms
• —Three main tests that help diagnose
• Fecal elastase test
• Fecal fat test
• Direct pancreatic function test
• Directly collecting pancreatic secretions from small intestine
• Most accurate but complex procedure

Question 13

Pancreatic Carcinoma

Answer 13

• Malignant epithelial neoplasm
• 4th most frequent cause of death from cancer in the U.S

-Etiology: Strong association with smoking

• —other risk factors include - high intake of saturated fats, chronic pancreatitis, D.mellitus etc
• —associated with genetic syndromes like cystic fibrosis

Clinical features:

• —Usually silent until its extension impinges on other structures
• —Pain is usually the first symptom
• —Obstructive jaundice

Question 14

Pancreatic cancer…cont’d

Answer 14

Poor prognosis due to the advanced stage of disease by the time of presentation