GI: Digestion and Absorption 1 Flashcards
Name all of the peptide hormones that the duodenum secretes into the blood from endocrine cells in its mucosa.
Gastrin CCK Secretin Motilin Glucose- dependant insulino peptide (GIP) Glucagon-like peptide- 1 (GLP-1)
What cells secrete gastrin
G cells (remember this is also secreted in the stomach)
What cells secrete CCK?
I cells
What cells secrete secretin?
S cells
What cells secrete motilin?
M cells
What cells secrete GIP?
K cells
What secretes GLP-1?
L cells
What is the name of the digestive juice secreted in the small intestine?
Succus entericus
What mechnisms control the secretion of digestive juice in the small intestine?
Distention Gastrin CCK Secretin Parasympathetic nerve activity enhances
What is contained in secretin?
Mucus
Aqueous salt
No digestive enzymes
What is segmentation?
Mixing of chyme in the duodenum- moves back and forth
What muscle mediates segmentation?
Circular
What initiates segmentation?
BER established in duodenum
At threshold this activates segmentation which is cause primarily by distention of the duodenum
How is segmentation in the empty ileium triggered?
Gastrin release in stomach- gastroileal reflex
What is the purpose of segmentation?
Allows time for absorption
What enhances segmentation
parasympathetic stimulation
What is peristalsis in the duodenum?
Occurs after all of the absorption has taken place BETWEEN meals
Clears out all of the debris from the small intestine
What inhibitis peristalis in the duodenum?
Vagal activity and feeding
Gastrin
CCK
What triggers peristalsis in the duodenum
Motilin
What two types of secretions are there in the pancreas?
Endocrine- insulin and glucagon- into blood
Exocrine- digestive enzymes (aciner cells), aqueous Na HCO3 solution (duct cells) - secreted into the duodenum
Where are pancreatic zymogenes stored?
Aciner cells
Name the protease zymogens
trypsinogen
Chymotrypsinogen
Procarboxypeptidase
Name the enxymes which are already active in the pancreas
Pancreatic amylase
Pancreatic lipase
Where are pancreatic zymogens activated?
Duodenum
What activates trypsinogen?
Enterokinase and trypsin
What activates chymotrypsinogen and procarboxypeptidase?
Trypsin
Name the active form of the pancreatic proteases
Trypsin
Chymotrypsin
Carboxypeptidases
What is the purpose of the HCo3 solution secreted from pancreatic duct cells
Neutralises chyme to provide optiumum pH in duodenum for enzymes to work to break down food
Protect mucosa
What stimulates pancreatic juice secretion from the pancreas in the cephalic and gastric phases.
cephalic- vagal stimulation- aciner cells
gastric - distention evokes a vagovagal reflex- acinar and duct cells
Describe how acid in the duodenal lumen affects the release of the alkaline solution from the pancreas?
Increased acid in duodenum
Increase secretin from S cells
Stimulates pancreatic duct cells
Increase alkaline secretion
Describe how fat and protein in the duodenal lumen increase digestive enzyme release from pancreas
Fat and protein in duodenal lumen
Increased CCK release from I cells
Stimulation of pancreatic acinar cells
Increase digestive enzyme secretion
What stimulates contraction of the gall bladder smooth muscle?
Chyme in duodenum ie acid and fat an protein
What does fat and protein in the duodenal lumen cause to happen to the gall bladder?
Increases CCk release
Gall bladder contracts and spnincter of oddi opens
