GI/Pancreas Flashcards
What is the difference between dog’s and cat’s esophagus?
Dog: 100% striated muscle
Cat: only upper 2/3 are striated muscle, the rest 1/3 is smooth muscle
What can cause the resting membrane potential less negative (more easily excitable) in GI tract? What can cause it to be more negative (harder to depolarize)?
Less negative
- stretch of the smooth muscle
- stimulation by acetylcholine released from the endings of parasympathetic nerves
- stimulation by several specific gastrointestinal hormones
More negative
- catecholamines
- stimulation of sympathetic nerves
What are the enteric nerve system composed of? And what are their functions?
Myenteric plexus - control the GI movement
Submucosal plexus - control the local blood flow and GI secretion
List 5 different enteric neurotransmitter/hormone substances
Substance P
Vasoactive intestinal peptide
Acetylcholine
Dopamine
Cholecystokinin
Somatostatin
Adenosine triphosphate
Norepinephrine
Serotonin
Nitric oxide
Which parts of the GI system dose vagus nerve innervated?
esophagus, stomach, small intestines, pancreas, first half of the large intestines
- The second half of large intestines and anus are innervated by pelvic nerves
Where is cholecystokinin secreted and what are its functions?
I cells of the duodenum, jejunum and ileum
It stimulates pancreatic enzymes and bicarb secretion, GB contractions, and inhibits gastric emptying
Where is gastrin secreted and what are its functions?
G cells in the gastric antrum
It stimulates gastric acid secretion and growth of the gastric mucosa
Where is motilin secreted and what is its functions?
M cells of stomach and upper duodenum during fasting
It increases GI motility
Why are the GI villi vulnerable to ischemia?
Because of the countercurrent blood flow of the arterioles and venules in the villi.
Most of the oxygenated blood (~80%) diffused from the arterioles to the venules without reaching the tip of the villi.
Fill out the blank about the gastric secretion.
True or False: Pepsinogen in the stomach can only become active in acidic environment.
True
Under acidic environment, pepsinogen is activated to form active pepsin and has proteolytic effect.
How does the body control gastric acid secretion?
Food goes down to antral end of the stomach → stimulates G cells secrete gastrin → gastrin reach the ECL cells in the oxyntic glands (gastric glands) → stimulates histamine release →histamine stimulate parietal cells secrete HCl
What are the pancreatic enzymes for proteins, carbohydrates and fat digestion?
Proteins: trypsin, chymotrypsin, carboxypolypeptidase
Carbohydrates: pancreatic amylase
Fat: pancreatic lipase, cholesterol esterases, phospholipase
What is the enzyme that activates the trypsinogen?
Enterokinase (secretes by the intestinal mucosa)
How does pancreas prevent self-digestive under normal condition?
The pancreatic cells that secrete proteolytic enzymes also secrete trypsin inhibitor at the same time to prevent activation of trypsin inside the pancreas
What are the three basic stimuli for pancreatic secretion?
Acetlycholine
Cholecystokinin
Secretin (make pancreas secretes lots of water and bicarbs by pancreatic duct epithelium)
True or False: only 50% of bile salts undergo enterohepatic circulation.
False
94% of bile salts go through enterohepatic circulation.
List the compositions of the bile
Water
Bile salt
Bilirubin
Cholesterol
Bicarb
Electrolytes
Fatty acids
Lecithin
What is the precursor of bile salt?
Cholesterol
What is the life span of an intestinal epithelial cell?
2-5 days
Where does the vomiting center locate?
Medulla oblongata of the brainstem
Muscarinic receptors
Where does the chemoreceptor trigger zone locate?
Area postrema of the floor of 4th ventricles (no BBB)
D2 receptors
5-HT3 receptors
What is the difference in the pathway of vestibular-induced vomiting between dogs and cats?
In dogs, the signal transmits from the vestibular system to the CRTZ zone and then to the vomiting center; in cats, the signal directly transmits from the vestibular system to the vomiting center
How can you determine intestinal dilation via x-rays in dogs and cats?
Dogs: diameter of the small intestine should be less than 1.6x of the height of L5 vertebral body at its narrowest point.
Cats: no bigger than 12mm or less than 2x of the height of L4 vertebral body