Duodenum and Pancreas Flashcards
What is the duodenum
Duodenum is a C-shaped part of the small intestine that curves around the pancreatic head
It is the most proximal part
What type of chyme enters the duodenum and what type exits the duodenum
Hypertonic, acidic chyme enters the duodenum. It has been partially digested
Isotonic, neutral chyme exits the duodenum and enters the jejunum
Describe why chyme is hypertonic when it enters the duodenum and what happens in the duodenum so that it becomes isotonic
Stomach is impermeable to water -> water cannot move into stomach to dilute chyme
Duodenum is relatively permeable to water -> hypertonic chyme draws water from ECF into the duodenum so the chyme becomes isotonic
What hormones are secreted by the duodenum in response to chyme and what do they cause
Secretin and CCK
Secretin acts on pancreas to stimulate release of aqueous bicarbonate component of pancreatic secretion
CCK acts on pancreas to stimulate release of enzymatic component of pancreatic secretion
CCK causes gallbladder contraction and relaxes sphincter of oddi
Describe the secretory unit of the pancreas
Pancreatic acini are the exocrine secretory unit of the pancreas. They contain:
Centroacinar cells - secrete bicarbonate
Acinar cells - secrete enzymes
Duct cells - secrete bicarbonate
What enzymes are produced by the pancreas
Amylase - active
Lipases - active
Proteases - inactive
Why are proteases released inactivated
Proteases are produced in an inactivated form and are stored in zymogen granules in acinar cells
This prevents the proteases from self-digesting the pancreas
Zygomens are converted to proteases inside the intestinal lumen
Describe tha flow of pancreatic secretions from the pancreas to the duodenum
Pancreatic secretions are released from acini and enter the terminal duct
Terminal ducts join, draining the secretions into the pancreatic duct
The pancreatic duct connects to the common bile duct and enters the duodenum at the ampulla of Vater
