L5 Pancreatic Secretions and Spleen Flashcards
Which part of the Pancreas appears first?
Dorsal
Components of Dorsal Pancreas?
Body
Tail
Isthmus
Accessory pancreatic duct (Duct of Santorini)
Components of Ventral Pancreas?
Pancreatic head
Uncinate process
main pancreatic duct (Duct of Wirsung): becomes dominant after fusion
Condition in which the ductal systems of the dorsal and ventral buds do not fuse and the dorsal duct system remains well developed?
Pancreas Divisum
Endocrine cells of the pancreas that secrete insulin, glucagon other hormones into blood?
Islets of Langerhans
Exocrine cells of the pancreas that secrete Aqueous and Enzymatic components of pancreatic juice?
Pancreatic Acini / Duct cells
The Aqueous component of Pancreatic secretions comes from what cell?
Centro-Acinar Duct Cells
The Enzymatic component of Pancreatic Secretions come from what cell?
Acinar Cells
Role of Aqueous component of pancreatic secretions
High levels of Bicarbonate (HCO3-) neutralizes gastric acid in chyme
Release stimulated by hormone Secretin
What triggers the release of aqueous component of pancreatic secretions?
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
What is required to facilitate the accumulation of CL- in the lumen of the pancreatic duct to allow normal pancreatic bicarbonate secretion?
Apical CFTR Cl Channel is required for secretion of Bicarbonate
In Cystic Fibrosis, CFTR-dependent chloride conductance is reduced leading to decreased pancreatic secretions
2 Sources of bicarbonate secreted by pancreatic centroacinar duct cells?
1) Intracellular Carbonic Anhydrase Activity
2) Basolateral import of bicarbonate via HCO3/Na Symporter
What is the ionic concentration of pancreatic juice dependent on?
When flow rate is LOW: Bicarbonate secretion concentration is LOW
When flow rate is HIGH: Bicarbonate secretion concentration is HIGH
Constituents of Enzymatic Component of Pancreatic Secretions?
- 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)
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
Triacylglycerol hydrolase => 2 free fatty acids + monoglyceride
Cholesterol ester hydrolase => 1 free fatty acid + cholesterol
Phospholipase => 1 free fatty acid + lysophosphatide
3 Proteolytic Enzymes in pancreatic secretions and their functions?
What is Orlistat?
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
What is Olestra?
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
Controls of Intestinal Phase of Pancreatic Secretion?
Proportion of secretions?
- 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
Control of the Gastric Phase of Pancreatic Secretion?
Proportion of secretions?
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
Control of Cephalic Phase of pancreatic secretion?
Proportion of secretions?
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
Hormones that regulate pancreatic secretion?
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
What Causes Pancreatitis? Acute vs. Chronic?
Premature activation of Trypsin within the Pancreas
- Acute: Gall Stones
- Chronic: Alcohol/Infection
Diagnosis of Pancreatitis?
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
What is the largest accumulation of lymphoid tissue in the body?
Spleen
Functions/Histology of the Spleen?
- 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)
What Triggers Pancreatic Enzyme Secretion?
Intestinal Fatty Acids and Amino Acids => CCK Secretion by I Cells of Duodenum/Jejunum
