Pancreas & Small Bowel Flashcards
What is the anatomical relationship of the pancreas and stomach?
Stomach: Separated from the pancreas by the lesser sac, the stomach and pylorus lie anterior and to the pancreas.
What is the anatomical relationship of the pancreas and duodenum?
The “C” shaped duodenum curves around and outlines the head of the pancreas. First part of the duodenum resides anteriorly; whereas the second part of the duodenum including the ampulla, resides laterally to the right of the pancreatic head.
What is the transverse mesocolon?
Transverse mesocolon: Attaches to the anterior surface of the pancreas.
What is the relationship of the common bile duct and the pancreas?
Common bile duct: Descends posteriorly to the head of the pancreas.
What is the anatomical relationship between the pancreas and spleen?
Spleen: Located posteriorly and laterally. Lienorenal ligament formed from the peritoneum, connecting the spleen to the tail of the pancreas.
What artery supplies the pancreas?
Superior mesenteric artery
Where is the superior mesenteric artery located in relation to the pancreas?
Lies behind the neck of the Pancras, and anterior to the uncinate process
The splenic and superior mesenteric arteries unite to form which vessel?
Unites to form the hepatic portal vein
Which plexus innervates the pancreas?
Coeliac plexus
What is the head of the pancreas?
Widest part of the pancreas lies within the C-shaped curve created by the duodenum and is connected via connective tissue
What is the uncinate process of the pancreas?
Projection arising from the lower part of the head, extending medially to lie beauty the body of the pancreas
What is the neck of the pancreas?
Located between the head & the body of the pancreas. Overlies the superior mesenteric vessels
What is the body of the pancreas?
Centrally located; crosses midline of the human body to lie behind the stomach, and to the left of the superior mesenteric vessels
What are the main exocrine pancreatic cells?
Acinar cells
What do the acinar cells secrete?
Acinar cells secrete enzyme-rich pancreatic juice into merging ducts.
What does the main pancreatic duct fuse with to form the hepatopancreatic duct?
Common bile duct
What is the accessory duct?
The duct of Santorini, traverses from pancreas directly into duodenum
What are the exocrine acini?
Clusters of secretory units associated to the ducts. They produce pancreatic digestive enzymes on the RER, moving to the Golgi complex forming condensing vacuoles -> Zymogens
What type of enzyme granule are released from pancreatic acinar cells?
Zymogen granules
What are pancreatic secretions secreted into?
Main pancreatic duct
How do pancreatic secretions enter the duodenum?
Main pancreatic duct fuses with the common bile duct, entering through the duodenum through the Ampulla of Vater
What molecule is released into the pancreatic secretions to control pH?
Bicarbonate ions, provide the optimum basic pH for digestive enzymes within the small intestine (lacks thick protective mucous barrier), neutralisation of acidic chyme
What are the endocrine cells of the pancreas?
Islets of Langerhans
alpha cells
beta cells
delta cells
What pancreatic polypeptides and hormone are released by pancreatic alpha cells?
Glucagon
What % of islet tissue is represented by alpha cells?
15-20%
What pancreatic hormone is released by beta cells?
Insulin
What % of islet tissue is represented by beta cells?
60-70%
What pancreatic hormone is secreted by delta cells?
Somatostatin
What % of islet cells are represented by delta cells?
5-10%
Which part of the pancreas has a greater distribution of islet cells?
Within the pancreatic tail.
What cells surround the islet cells?
The acini
Why are the islet cells highly vascular?
Ensures endocrine cells have proximal access for secretion
What granules secrete pancreatic secretions from acinI?
Apical secretion granules
What are the type of secretions released from acinar cells?
Low volume vicious enzyme rich
What are the type of secretions released from ductal cells?
High volume
Watery
Bicarbonate rich
What stimulates bicarbonate secretion from ductal cells?
Acidic chyme entry into the duodenum stimulates the release of secretion
What hormone stimulates acini secretion of pancreatic juice, and enhances secretin activity?
CCK
Which stages of gastric secretion does parasympathetic regulation play a role in?
Cephalic and gastric phases
Why is bicarbonate released by ductal cells?
Bicarbonate secretion counterbalances level of HCl secretion from parietal cells of body and fundus of stomach. Hydrogen ions enter the blood upon pancreatic bicarbonate secretion. Therefore, acidic blood draining from the pancreas neutralises the alkaline blood draining from the stomach, maintain the pH of venous blood that flows to the liver.
What does pancreatic juice comprise of?
Water, sodium bicarbonate, digestive enzymes
Which enzyme is inactivated by bicarbonate ions and alkaline environments?
Pepsin
What are the three main pancreatic enzymes?
Trypsin
Chymotrypsin
Carboxpeptidase
Where are pancreatic enzymes activated?
Activated within the duodenum
Which enzyme activates trypsinogen into trypsin?
Enteropeptidase/Enterokinase
How does pancreatitis occur in relation to enzymes?
Due to production of activated enzymes in the pancreas
Which two cells produce bicarbonate?
Ductal & centroacinar cells
Which enzyme catalyses the production of carbonic acid from water and carbon dioxide?
Carbonic anhydrase
Carbonic acid dissociates into which two ions?
Hydrogen ions
Bicarbonate ions
what happens to the hydrogen ions within pancreatic ductal cells?
Hydrogen ions are transported out of the pancreatic ductal cell exchanged for sodium ions by the Na+/H+ anti porter on the basolateral membrane into the blood
How are sodium ions removed out of the pancreatic ductal cell?
Na+/H+ ATPase
What junctions do sodium ions leave into the lumen?
Paracellular tight junctions
How does water move through paracellular tight junctions?
Water succeeds into the intercalated ducts via osmosis, due to the osmotic potential gradient
What is the fate of bicarbonate ions produced from the dissociation of carbonic acid in pancreatic ductal cells?
Bicarbonate ions are transported into intercalated ducts of the pancreas in exchange for chloride ions
How are intracellular chloride concentrations controlled?
Chloride ion channels facilitate the movement of chloride ions into the lumen of intercalated ducts
What is the bicarbonate anion exchanger on ductal cells?
Anion exchanger bicarbonate/chloride ions at the lumen
What ions and molecules move through the intercalated ducts into the pancreatic ducts?
Bicarbonate, sodium ions & water
Why is bicarbonate neutralisation important in the duodenum?
Neutralises acidic chyme from stomach, prevents damage to duodenal mucous, raises optimum pH range for pancreatic enzymes to be functional
Which glands also secrete alkaline fluid?
Brunner’s glands
Describe the extracellular concentrations of sodium ions in comparison to ductal cells?
High extracellular Na+ ions
Describe the extracellular concentrations of chloride ions in the lumen in comparison to the ductal cells
High chloride ions in lumen
What is the acidity of gastric venous blood?
Alkaline
Why its gastric venous blood alkaline?
The subsequent generated hydrogen ions within parietal cells contribute towards hydrochloric acid secretion, achieved through the exchanged of 𝐻𝐶𝑂3− into circulation
Why is pancreatic venous blood acidic?
The subsequent 𝑯𝑪𝑶𝟑− ions secreted into the pancreatic juice, thus results in acidic venous pancreatic blood, though hydrogen ion transfer into circulation
What is pancreatic amylase?
Carbohydrate digestion, brush border enzymes catalyses alpha-dextrin, hydrolysing glycosidic bonds, resulting in glucose removal
What does sucrose break into?
Fructose and glucose
What does maltase catalyse?
Catalyses the hydrolyses of maltose into 2 glucose molecule s
What does lactase catalyse?
Catalyses lactose into glucose & galactose
What granules are enzymes stored within the pancreatic acinar cells?
Zymogen granules
What is the role performed by gastric pepsin?
Proteins consist of polypeptides composed of amino acids by peptide linkages, digestion reduces polypeptide into their constituent amino acids.
HCl secretion from gastric parietal cells subsequently denatures proteins, enabling pepsin to hydrolyse protein into smaller polypeptides