physiology 3 -Pancreatic secretions Carbohydrate absorption Vitamin/mineral absorption Peyer patches Bile Flashcards
A patient with decreased α-amylase may have impaired digestion of what type of food material?
Starch
Proteases help digest protein. Name the major proteases secreted by the pancreas.
Trypsin, chymotrypsin, elastase, and carboxypeptidase
Are proteases secreted in active or inactive forms?
Inactive forms (called proenzymes or zymogens)
After being converted to its active form in the intestinal lumen, trypsin then does what?
It activates the other proenzymes as well as more trypsin molecules
For the pancreas, low flow of secretions results in high levels of ____, whereas high flow of secretions results in high levels of ____.
Cl-; HCO3-
Are pancreatic secretions hypotonic, isotonic, or hypertonic?
Isotonic
A man eats a large amount of popcorn at a movie. What critical enzyme is released in its active form to digest this?
α-amylase
Which of these sugars is/are not absorbed by enterocytes: glucose, galactose, fructose, sucrose?
Sucrose, a disaccharide (only monosaccharides are absorbed by enterocytes)
Glucose and galactose are taken up by this transporter, which is dependent on this ion.
Sodium-glucose linked transporter (SGTP1); sodium ion
____ is the transporter that takes up fructose in enterocytes via what method.
Glucose transporter 5 (GLUT-5); facilitated diffusion
All monosaccharides are transported from the enterocytes to the blood by what transporter?
Glucose transporter 2 (GLUT-2)
A patient with carbohydrate malabsorption might undergo which test to distinguish GI mucosal damage from other causes of malabsorption?
D-xylose absorption test
Iron is absorbed as this ionized form mainly in this part of the small intestine.
Fe2+ is absorbed in the duodenum
Folate is mainly absorbed in these parts of the small intestine.
Jejunum and ileum
A patient has resection of the ileum as part of surgery for Crohn disease. For which vitamin deficiency might he be at risk?
Vitamin B12 (absorbed in the ileum while bound to intrinsic factor)
A patient has severe Crohn disease requiring an extensive colectomy. Which vitamins/minerals is he at risk for deficiency?
Iron, Folate, and vitamin B12 are absorbed in the small bowel (think Iron Fist, Bro)
Peyer patches are made of which type of tissue: mucosal, lymphoid, or muscularis?
Lymphoid (Peyer patches are made of unencapsulated lymphoid tissue)
In what two layers of the gastrointestinal tract are Peyer patches found?
The lamina propria and the submucosa
What is the main action of M cells?
M cells take up antigens from the gut lumen for presentation to B cells and eventual creation of immunoglobulin A (IgA) antibodies
After stimulated B cells from Peyer patches have differentiated into plasma cells, what do they then secrete?
Immunoglobulin A, or IgA (Intragut Antibody)
After being secreted, immunoglobulin A (IgA) functions to bind what?
Intraluminal antigens (think IgA, the Intragut Antibody)
What must IgA receive before it can be transported through the epithelium and into the gut to deal with antigens?
Protective secretory component
What are the six components of bile?
Bile salts, phospholipids, cholesterol, bilirubin, water, and ions
What is the only means of cholesterol excretion from the body?
Via bile
Bile acid conjugation makes bile _____ (more/less) soluble by biding to which two amino acids?
More, glycine and taurine
In a patient who is unable to produce bile, what physiologic functions would be impaired?
Excretion of cholesterol, digestion and uptake of lipids and fat-soluble vitamins, & antimicrobial activity
A patient has defective cholesterol 7&945;-hydroxylase activity. Does this affect his ability to absorb vitamins in any way?
Yes, as this impairs the rate-limiting step of bile synthesis (one of bile’s functions is to assist with vitamin digestion and absorption)
In an experiment, bacteria within a Petri dish exposed to gallbladder secretions are noted to perish quickly. What is going on?
Bile has antimicrobial activity via bacterial membrane disruption
A patient with hemolytic anemia would be likely to have which abnormal result on liver function tests?
Unconjugated hyperbilirubinemia (bilirubin is a breakdown product of heme)
What is the essential structural difference between direct and indirect bilirubin?
Direct bilirubin is conjugated with glucuronic acid and is thus water soluble, whereas indirect bilirubin is not and is thus water insoluble
How is bilirubin excreted from the body?
Bilirubin is excreted in bile (it is excreted in urine as urobilin and stool as stercobilin)
What type of bilirubin is water soluble: direct or indirect? What type is water insoluble?
Direct bilirubin is water soluble; indirect bilirubin is water insoluble
Unconjugated bilirubin travels through the circulation bound to ____. This complex can be measured as ____.
Albumin; indirect bilirubin
A patient with impaired bile acid conjugation would develop which abnormality on liver function tests?
Conjugated (direct) hyperbilirubinemia
____ is excreted renally, giving ____ its classic yellow color.
Urobilin; urine
If exposed to conjugated bilirubin, colonic bacteria will produce what?
Urobilinogen
A patient taking antibiotics wipes out his gut flora. His urine is noted to be paler than usual. Why is this the case?
Bilirubin conversion into urobilinogen is impaired; reabsorbed urobilinogen is converted into urobilin, giving urine its yellow color
Of the urobilinogen that goes to the kidneys and liver, about ____% is excreted renally and ____% enters the enterohepatic circulation.
10; 90
A patient with an obstruction in stercobilin deposition has feces of what characteristic color?
Pale stools (obstruction inhibits its ability to be deposited in the gastrointestinal lumen, leading to pale stools)
Urobilinogen cannot be excreted in urine. What form is it excreted in feces, and in a normal patient, what color is the stool?
Excreted in feces as stercobilin, which causes the brown color of stool
In an experiment, tagged urobilinogen in the gut can be expected to be later found in which organ?
Liver, via enterohepatic circulation
Which enzyme catalyzes bilirubin conjugation?
UDP-glucuronosyltransferase
