L5 Pancreatic Secretions and Spleen

Question 1

Which part of the Pancreas appears first?

Answer 1

Dorsal

Question 2

Components of Dorsal Pancreas?

Answer 2

Body

Tail

Isthmus

Accessory pancreatic duct (Duct of Santorini)

Question 3

Components of Ventral Pancreas?

Answer 3

Pancreatic head

Uncinate process

main pancreatic duct (Duct of Wirsung): becomes dominant after fusion

Question 4

Condition in which the ductal systems of the dorsal and ventral buds do not fuse and the dorsal duct system remains well developed?

Answer 4

Pancreas Divisum

Question 5

Endocrine cells of the pancreas that secrete insulin, glucagon other hormones into blood?

Answer 5

Islets of Langerhans

Question 6

Exocrine cells of the pancreas that secrete Aqueous and Enzymatic components of pancreatic juice?

Answer 6

Pancreatic Acini / Duct cells

Question 7

The Aqueous component of Pancreatic secretions comes from what cell?

Answer 7

Centro-Acinar Duct Cells

Question 8

The Enzymatic component of Pancreatic Secretions come from what cell?

Answer 8

Acinar Cells

Question 9

Role of Aqueous component of pancreatic secretions

Answer 9

High levels of Bicarbonate (HCO3-) neutralizes gastric acid in chyme

Release stimulated by hormone Secretin

Question 10

What triggers the release of aqueous component of pancreatic secretions?

Answer 10

Release stimulated by hormone Secretin

S- cells perceive a change in pH as chyme enters the duodenum => Release secretin => Inhibits gastric motility and stimulates the secretion of Aqueous component from duct cells w/ bicarbonate to neutralize acid

Question 11

What is required to facilitate the accumulation of CL- in the lumen of the pancreatic duct to allow normal pancreatic bicarbonate secretion?

Answer 11

Apical CFTR Cl Channel is required for secretion of Bicarbonate

In Cystic Fibrosis, CFTR-dependent chloride conductance is reduced leading to decreased pancreatic secretions

Question 12

2 Sources of bicarbonate secreted by pancreatic centroacinar duct cells?

Answer 12

1) Intracellular Carbonic Anhydrase Activity
2) Basolateral import of bicarbonate via HCO3/Na Symporter

Question 13

What is the ionic concentration of pancreatic juice dependent on?

Answer 13

When flow rate is LOW: Bicarbonate secretion concentration is LOW

When flow rate is HIGH: Bicarbonate secretion concentration is HIGH

Question 14

Constituents of Enzymatic Component of Pancreatic Secretions?

Answer 14

• Amylase
• DNAase/RNAase
• Elastase
• 3 Lipases (Triacylglycerol hydrolase, Cholesterol Hydrolase, Phospholipase)
• 3 Proteolytic Enzymes (Trypsinogen, Chymotrypsinogen,
  Procarboxypeptidase)
• Trypsin inhibitor (keeps proteolytic enzymes inactive until in intestine)

Question 15

3 Lipases within pancreatic secretions from acinar cells and their functions

_____=> 2 free fatty acids + monoglyceride

_____ => 1 free fatty acid + cholesterol

_____=> 1 free fatty acid + lysophosphatide

Answer 15

Triacylglycerol hydrolase => 2 free fatty acids + monoglyceride

Cholesterol ester hydrolase => 1 free fatty acid + cholesterol

Phospholipase => 1 free fatty acid + lysophosphatide

Question 16

3 Proteolytic Enzymes in pancreatic secretions and their functions?

Answer 16

Question 17

What is Orlistat?

Answer 17

Orlistat is a lipase inhibitor used as a treatment for obesity. It prevents the hydrolyzation of triglycerides into fatty acids => dietary lipids cannot be absorbed in the gut

Question 18

What is Olestra?

Answer 18

Olestra is a synthetic “fat” composed 7-8 fatty acids attached to a sugar backbone. It is inaccessible to lipases and cannot be broken down into fatty acids => Passes through the GIT unabsorbed

Question 19

Controls of Intestinal Phase of Pancreatic Secretion?

Proportion of secretions?

Answer 19

• Products of protein and fat digestion in duodenum => Secretion of CCK by I-Cells (Duodenum/Jejunum) => Enzyme-rich secretions by Pancreatic Acinar Cells and Vagal sensory Activation
• Low pH in Duodenum => Secretion of Secretin by S-Cells => Secretion of Bicarbonate-rich fluid by Pancreatic Duct Cells
• >70% of secretions

Question 20

Control of the Gastric Phase of Pancreatic Secretion?

Proportion of secretions?

Answer 20

Distention of stomach=> Vago-Vagal Reflex => Secretion of Gastrin by G-Cells and ACh from nerve endings => Enzyme-rich secretions by Pancreatic Acinar Cells

<10% of secretions

Question 21

Control of Cephalic Phase of pancreatic secretion?

Proportion of secretions?

Answer 21

Sight/Smell/Taste of food => Parasympathetic vagal activity => Secretion of ACh by nerve endings and Secretion of Gastrin by G-Cells=> Enzyme-rich secretions by Pancreatic Acinar Cells

<20% of Secretions

Question 22

Hormones that regulate pancreatic secretion?

Answer 22

Gastrin released from G- Cells due to distention of stomach/vagal stimulation => Enzyme-rich secretions by Pancreatic Acinar Cells

Secretin released by S-cells when acid is in the Duodenum => Secretion of Bicarbonate rich fluid by Duct Cells

CCK is released by I-Cells when fat/protein is in Duodenum/Jejunum => Enzyme-rich secretions by Pancreatic Acinar Cells / Bicarbonate rich fluid by Duct Cells

Question 23

What Causes Pancreatitis? Acute vs. Chronic?

Answer 23

Premature activation of Trypsin within the Pancreas

• Acute: Gall Stones
• Chronic: Alcohol/Infection

Question 24

Diagnosis of Pancreatitis?

Answer 24

Measurement of serum lipases is a more reliable indicator (High sensitivity, low false negative rate)

Raised enzyme levels could also be due to renal disease (reduced clearance) => Normalize enzyme values to creatinine to rule out

Question 25

What is the largest accumulation of lymphoid tissue in the body?

Answer 25

Spleen

Question 26

Functions/Histology of the Spleen?

Answer 26

• Filters Blood
• Protection against blood-borne antigens
• Produces antibodies + activated lymphocytes
• Iron homeostasis (Heme – metabolism to bilirubin)

White Pulp (20% ) - Lymphoid cells

Red Pulp (80%)- Splenic Sinusodis (RBC removal and iron recycling)

Question 27

What Triggers Pancreatic Enzyme Secretion?

Answer 27

Intestinal Fatty Acids and Amino Acids => CCK Secretion by I Cells of Duodenum/Jejunum