GIT Phsiology Flashcards
What type of movements occur in the GI tract?
Propulsion and mixing.
Propulsive movements occur via peristalsis. The usual stimulus is distension but
also irritants and parasympathetic supply. Requires an active myenteric plexus.
It is directed towards the anus. Downstream gut typically relaxes to accommodate the bolus.
Mixing movements. Constricting type actions, produces mixing if against a
closed sphincter.
Name the layers of the bowel wall (outer to inner)
(1) Serosa (2) Longitudinal muscle layer (3) Circular muscle layer (4) Submucosa
(5) Mucosa
how many ml of endogenous secretions does the GIT make a day?
7000ml
what sets the basic electrical rhythm of the GIT?
• Basic electrical rhythm (BER) caused by interstitial cells of Cajal.
GI smooth muscle is excited intrinsically by slow waves and spikes.
how many spikes a min do each of these GIT organs have for peristalsis?
Stomach, duodenum, ileum, caecum, sigmoid.
(stomach 4/min, duodenum 12/min, ileum 8/min, caecum 2/min, sigmoid 8/min)
what factors make the GIT more excitable?
A number of factors make it more excitable (stretch, acetylcholine, parasympathetic supply and hormones)
which catecholamine always inhibits GIT activity?
NA
what are the names of the outer and inner plexi of the GIT? and what are they responsible for?
Outer, myenteric plexus (Auerbach’s plexus) which largely controls GI movement
– Inner, submucosal plexus (Meissner’s plexus) which largely controls secretion and local GI blood flow
which GI reflex go back to the sympathetic ganglia
To the prevertebral sympathetic ganglia (gastrocolic, enterogastric, colonoileal
reflexes)
where does the defecation reflex go to?
to the spnal cord or brain stem
what are the three basicmachanisms of adsorption?
– Active transport; energy is used to transport the substance
– Diffusion; a passive process via random movement
– Solvent drag; dissolved substances dragged across with a solvent
Name the functions of the liver
(a) Carbohydrate, protein and lipid metabolism
(b) Synthesis of plasma proteins
(c) Detoxification
(d) Immune modification
What is bile made of?
Water, bile salts (highest concentration after H2O), bilirubin, cholesterol, fatty
acids, lecithin and electrolytes (Na+, K+, Ca2+, Cl− and HCO3
−)
What is the function of bile?
Bile is needed for the absorption of fat as well as an excretory route for lipid
soluble waste products into the GIT
Name primary bile salts.
Primary bile salts are cholic acid and chenodeoxycholic acid
Where are bile salts absorbed?
94% are reabsorbed in the small intestine, largely in the terminal ileum
Name three causes of high blood ammonia.
High blood levels of ammonia can be due to liver dysfunction, portal hypertension with shunting or overproduction in the liver.
Name the exocrine enzymes released from the pancreas.
(a) Protein digestion: Trypsin (most abundant), chymotrypsin, elastase and
carboxypolypeptidases
(b) Fat: Pancreatic lipase, cholesterol esterase and phospholipase A
(c) Carbohydrate: Pancreatic amylase
what are the secondary bile salts which from in the GIT due to bacteria?
Secondary bile salts formed in colon due to bacteria
deoxycholic acid, lithocholic acid and ursodeoxycholic acid.
what is the role of bile salts in digestion?
– Emulsify large fat particles into minute particles
– Formation of micelles.
what percentage of bile salts are resorbed in the small intestine?
94%
what is bilirubin converted to in the gut?
urobilinogen
what is jaundice caused from?
Jaundice is due to an excess of bilirubin in the blood from excess production,
decreased uptake, impaired metabolism, or decreased secretion.
what does the liver convert ammonia to in the liver to be excreted in bowel and kidneys?
urea