PBL 3 Flashcards
what organ does the pancreas lie deep to?
deep to the stomach
what parts of the pancreas are retroperitoneal?
All of pancreas is retroperitoneal except for its tail.
what 5 parts is the pancreas composed of?
o Uncinate process o Head – lies within the C shaped concavity of the duodenum o Neck o Body o Tail
describe the uncinate process
Is a hook-like projection that arises from the lower part of the head. It extends medially to lie beneath the body of the pancreas
what do the acini (berry-like cluster of cells ) drain into?
drain into the centrally running main pancreatic duct.
what is the ampulla of vater?
sac like enlargement (of a duct) formed by union of the pancreatic duct and the common bile duct
where does the ampulla of vater open into the duodenum?
at the major duodenal papilla in the descending part of the duodenum
what surrounds the ampulla of vater?
the sphincter of Oddi - this is a collection of smooth muscle which controls the entry of secretions into duodenum.
what is minor duodenal papilla?
this is the opening of the accessory pancreatic duct into the descending second section of the duodenum.
what is the accessory pancreatic duct also called? does everyone have one?
duct of Santorini
no, only found in around 10% of people
what percentage of the pancreas is made up of exocrine function
Approximately 99% of the specialized cells of the pancreas
what are acinar cells? what shape are they and is found abundantly in them?
these are the secretory exocrine cells of the pancreas
they are pyramidal shaped cells, with abundant rough ER.
what are acini and what type of epithelium are they lined with?
acini are berry-like clusters of acinar cells that are lined with simple cuboidal epithelium.
what is the function of acinar cells?
to produce digestive enzymes. They travel down the pancreatic duct into the bile duct and are activated when they enter the duodenum.
what are ductal cells? what is their function? what stimulates them?
cells that line the pancreatic duct
They are responsible for secreting bicarbonate ions
They are stimulated by the hormone secretin
what is the endocrine portion of the pancreas known as?
the Islet of Langerhans
what cells are found in the Islet of Langerhans and what is their role?
Alpha cells – secrete glucagon
Beta cells – secrete insulin
Delta cells – secrete somatostatin
what is the arterial supply of the pancreas?
pancreatic branches of the splenic artery
what is the additional arterial supply to the head of the pancreas?
superior and inferior pancreaticoduodenal arteries
what is the origin of the superior and inferior pancreaticoduodenal arteries?
Superior = branch of gastroduodenal artery. Inferior = branch of Superior mesenteric artery.
what is the venous drainage of the pancreas?
Mainly splenic vein
what does the splenic vein merge with?
merges with the Superior mesenteric branches of the hepatic portal vein
what is the role of the small intestine?
It is the primary site of digestion and absorption of nutrients
describe features of the duodenum
primary site of chemical digestions using enzymes
Shortest part of SI (20 cm)
Contains Brunner’s glands which secrete alkali secretions
describe features of the jejunum
absorption of carbohydrates and proteins
has longer villi
describe role of ileum
absorbs vitamin B12, bile salts and other unabsorbed products of digestion
what are the 3 features which increase the surface area of the small intestine?
presence of circular folds (plicae circulares), villi and microvilli.
what are plicae circulares?
circular folds of a mucous membrane that form ridges and project into the lumen of the small intestine (do not lose their elasticity when the intestine is distended)
what are microvilli covered in?
a fuzzy coat known as the brush border which contains many digestive enzymes
what is found between the grooves of intestinal villi?
intestinal glands aka Crypts of Lieberkühn
what types of cells are found in the Crypts of Lieberkühn?
o Enterocytes/Absorptive cells o Goblet cells o Enteroendocrine cells o Paneth cells o Stem cells
what hormones are secreted by Enteroendocrine cells?
Secretin, cholecystokinin (CCK), gastric inhibitory protein (GIP), motilin
what is the role of paneth cells? how are they identified histologically?
They have a role in the gut’s defence. They secrete the enzyme lysozyme, which lyses bacteria and ruptures their cell walls.
They appear spotted and eosinophilic
what is the role of stem cells in the Crypt of Lieberkühn?
they are undifferentiated columnar epithelial cells which produce absorptive and goblet cells.
what type of epithelial cells are goblet and enterocytes/absorptive cells?
simple columnar epithelial cells
what is the role of enterocytes/absorptive cells?
responsible for the uptake of nutrients and produce digestive enzymes in the small intestine
what is the role of goblet cells?
They synthesise alkaline mucus to provide lubrication and prevent digestive enzymes from eroding the cell walls.
what is the arterial supply to the duodenum?
Proximal to the major duodenal papilla: supplied by the gastroduodenal artery which is a branch of the coeliac trunk
Distal to MDP and to the end of the duodenum: supplied by pancreatic duodenal artery
what is the arterial supply to the jejunum and ileum?
supplied by superior mesenteric artery and anastomoses arcades
what is the venous drainage of the small intestine?
the superior mesenteric vein
describe processes involved in meal-related motility in the small intestine
- Segmentation (mixing movements) – non-synchronised contractions of the circular smooth muscle in local segments.
- Peristaltic waves – movement of chyme through the intestinal lumen. Arises from duodenal bulb which generates its own BER of about 12/min. Involves the contraction of the longitudinal muscle layer while the inner muscle layer in an adjacent region is relaxed.
- Pendular contractions
- Villus movements – contraction of the muscularis mucosae, micro mixing at the surface of the mucosa
what digestive enzymes are secreted as zymogens?
o Trypsinogen o Chymotrypsinogen o Carboxypeptidase o Elastase o Phospholipase
what activates Trypsinogen?
is activated via the duodenal enzyme enterokinase into its active form trypsin.
what activates Chymotrypsinogen ?
activated by either duodenal enterokinase or trypsin into its active form (chymotrypsin)
what digestive enzymes are secreted in active forms?
o Pancreatic lipase
o Nucleases (ribonucleases, deoxyribonucleases)
o Pancreatic amylase
what is the role of pancreatic lipase?
degrades triglycerides into 2 fatty acids and a monoglyceride
what is the role of Nucleases?
split nucleases into nucleotides
describe the protein digestion that occurs in the small intestine?
o Proteolytic enzymes, including trypsin and chymotrypsin, are secreted by the pancreas and cleave proteins into smaller peptides.
o Carboxypeptidase, which is a pancreatic brush border enzyme, takes off terminal amino acid from protein
o Aminopeptidase and dipeptidase free the final amino acid products
describe the lipid digestion that occurs in the small intestine?
They are degraded into fatty acids and glycerol.
Pancreatic lipase breaks down the triglycerides into free fatty acids and monoglycerides. It works with the help of the bile salts secreted by the liver and the gall bladder.
Bile salts attach to triglycerides to help emulsify them and aid access by pancreatic lipase.
describe the carbohydrate digestion that occurs in the small intestine
Pancreatic amylase breaks down some polysaccharides into disaccharides. The enterocytes (cells of the intestinal lining) which cover the intestinal microvilli brush border contain 4 enzymes: sucrase, lactase, maltase, alpha-dextrinase. As the disaccharides come into contact with these enterocytes, the digestive enzymes hydrolyse them
describe the hydrolysis carried out by sucrase, lactase, maltase, alpha-dextrinase
- Lactase hydrolyses lactose into galactose and glucose.
- Sucrase hydrolyses sucrose into fructose and glucose.
- Maltase and alpha-dextrinase hydrolyse maltose and the glucose polymers into multiple glucose molecules
describe the hormonal stimulation of acinar cells to produce inactive pancreatic enzymes
I cells secrete CCK (cholecystokinin) to produce inactive pancreatic enzymes (zymogens) in response to the presence of fats and amino acids
describe the hormonal stimulation of ductal cells tin response to acidic chyme
S cells in the duodenum secrete secretin which causes bicarbonate to be released into the small intestine from the pancreas. This neutralizes the potentially harmful acid that comes from the stomach.
define chronic pancreatitis
inflammation of the pancreas that does not heal and leads to the permanent impairment of endocrine and exocrine functions.
list causes of chronic pancreatitis
Heavy alcohol use Repeated episodes of acute pancreatitis Autoimmune conditions Genetic mutations due to cystic fibrosis Blocked pancreatic or common bile duct Hereditary Idiopathic Hypercalcaemia
list clinical features of chronic pancreatitis
o Upper abdominal pain radiating to the back - which increases after eating or drinking
o Nausea and vomiting
o Steatorrhea – frequent, oily, foul-smelling stool, due to malabsorption
o Weight loss – due to malabsorption
o Diabetes type 1: can affect the ability of the pancreatic islets to produce insulin to regulate blood glucose levels. Can lead to type 1 diabetes.
o Jaundice if bile duct is blocked
how much destruction to acinar tissue must there be before symptoms of malabsorption present?
90% of acinar tissue
list the tests of pancreatic damage
Serum amylase (normal <100 U/L, low specificity)
Urine amylase (normal 30-600 U/L)
Serum lipase (normal 30-210 U/L, Higher clinical sensitivity and specificity than amylase)
list the tests of pancreatic function
– Direct/invasive and indirect function tests
– Faecal chymotrypsin
– Faecal elastase
what is the gold standard invasive/direct test of pancreatic function
Secretin-pancreozymin test - measures pancreatic enzymes e.g. trypsin in duodenum aspirate
what is the Lundh test?
an invasive/direct test which measures bicarbonate, amylase or trypsin activity following a meal
what do low levels of faecal chymotrypsin and elastase suggest?
Low values indicate pancreatic insufficiency.
what other diagnostic test can be used to check for chronic pancreatitis ?
Blood Glucose - may be elevated (due to endocrine insufficiency) CT Scan (contrast enhanced) - pancreatic calcifications, enlargement of the pancreas, ductal dilation and vascular problems Abdominal Ultrasound - structural/anatomical changes including inflammation, duct irregularity, irregularity of head/body, calcification. Abdominal X-Ray - pancreatic calcifications MRCP – dye injected into patient’s veins and MRI used.
describe the management of chronic pancreatitis
Lifestyle changes – avoiding alcohol
Stop smoking
Change diet – low fat, high protein, high calorie diet with fat-soluble vitamin supplements
Pancreatic enzyme supplements
Steroid medication to relieve the inflammation
Painkillers
Surgery
what surgical interventions can be used to treat chronic pancreatitis ?
– Endoscopic lithotripsy – involves using shock waves to break the stones into smaller pieces
– Pancreas resection – surgical removal of inflamed area of pancreas
– Total pancreatectomy – removal of the entire pancreas
what are reasons for poor dug compliance?
– Forgetfulness
– May stop taking medication once they start to see results
– Impatient with results and think it’s not working
– Side effects
– Difficulty swallowing pills
– Doesn’t understand the importance of taking it
what improvements can be made to improve drug compliance
– Maintain good communication and rapport with the patient to develop trust
– Ensure that information provided is clear and concise and that they understand reasons for taking it
– Check up on patient in follow up consultations to ensure they are taking their medication as advised
– Make sure they are well educated and informed about the medical condition and the benefits of the treatment
– Recommend ways to help them remember to take it if they are forgetful
