GI Phys: Absorption & Large Intestine Flashcards
What sugars are produced in the breakdown of sucrose?
- Glucose
- Fructose
What sugars are produced in the breakdown of lactose?
- Glucose
- Galactase
What is trehalose?
A. Dimer of glucose and galactose B. Dimer of fructose and glucose C. Dimer of glucose D. Reduced form of glucose E. Oxidized form of glucose
C. a dimer of glucose
What glucose transporters are present in the apical membrane of small intestine epithelial cells?
- SGLT 1 (glucose & Galactose)
- GLUT 5 (Fructose)
What glucose transporters are present on the basolateral side of the small intestine epithelial cells?
-GLUT 2
What is insulin’s effect on glucose transporters in the intestinal epithelial cells? What are the implications for an individual with diabetes?
- Removes GLUT 2 from both apical and basolateral membranes
- lack of insulin in diabetic patients results in permanent glucose transporters in apical membrane, thus high rate of sugar absorption is maintained despite abnormally elevated blood glucose
What activates most carbohydrate digestion enzymes in the small intestine?
-Trypsin
What amino acid transporters are located on the apical side of the small intestine epithelial cells?
-Sodium AA/peptide symporters
What amino acid transporters are located on the basolateral side of the small intestine epithelial cells?
-Amino acid channel for facilitated diffusion
What is the advantage of absorbing di or tri peptides?
-If a transporter for an essential amino acid is defective or absent, that amino acid may still be absorbed by oligo carriers
Patients with a congenital absence of one of the
essential amino acid carriers do NOT become deficient
in that amino acid due to the fact that:
A. The amino acid is absorbed by passive diffusion
B. The amino acid can make use of other carriers
C. The amino acid is absorbed by facilitated diffusion
D. Peptides containing the amino acid are absorbed by
different carriers
E. The amino acid is an essential amino acid
D. Peptides containing the amino acid are absorbed by different carriers
What is the difference in absorption between fatty acids that are 14 to 18 carbons versus smaller chain fatty acids?
- fatty acids 14 to 18 carbons are packaged into chylomicrons and sent via lymphatic system
- Smaller fatty acids are more soluble and go directly into the blood stream and to the liver via portal vein
Small to medium chain fatty acids absorbed in the jejunum are delivered to the liver via the: A. Cystic artery B. Hepatic veins C. Hepatic artery D. Central veins E. Hepatic portal vein
E. Hepatic Portal Vein
What happens to indigestible carbs in the large intestine?
-Many are transformed into short-chain fatty acids by enzymes present in our microbiome, and are absorbed in the colon
What vitamin promotes Ca absorption?
-Vitamin D
How is calcium absorbed in the small intestine?
Transcellular:
- facilitated diffusion into cell
- pumped out via Na/Ca antiporter and H/Ca antiporter
Paracellular
-Passive diffusion
Active absorption only in the duodenum
How is iron absorbed in the small intestine?
- Fe binds transferrin, which binds to transferrin receptor on epithelial cell and endocytosed
- also absorbed as heme
Which part of the small intestine are folate, B12, and bile salts absorbed?
Folate: Jejunum
B12: Ileum
Bile acids: Ileum
What part of the small intestine absorbs iron?
-duodenum
A person who is obese and has high plasma cholesterol
levels is desperate to lose weight. Her physician suggests ileal bypass surgery and she undergoes the surgery successfully.
This person, while losing weight and lowering plasma
cholesterol, is also likely to:
A. Have high plasma LDL cholesterol levels
B. Develop anemia due to vitamin B12 deficiency
C. Develop anemia due to folate deficiency
D. Develop anemia due to iron deficiency
E. Develop deficiency of fat-soluble vitamins
B. Develop anemia due to vitamin B12 deficiency
Where is the majority of water reabsorbed in the GI tract?
-small intestine
During defecation or child birth (Valsalva maneuver),
we do what?
A. Contract thoracic cavity and expand abdominal cavity
B. We expand both thoracic and abdominal cavities
C. We contract both thoracic and abdominal cavities
D. We expand thoracic cavity and contract abdominal cavity
D. Expand thoracic cavity and contract abdominal cavity
What is the peritoneo-intestinal reflex?
-irritation of the peritoneum causes intestinal paralysis
What is the reno-intestinal reflex?
-irritation of the kidney causes intestinal inhibition
What is the vesico-intestinal reflex?
-irritation of the bladder causes intestinal inhibition
What is the somato-intestinal reflex?
-irriation of the skin over the abdomen causes intestinal inhibition
What is Hirschprung’s Disease?
- aganglionic megacolon
- no bowel movement in first 48 hrs of life
- gradual swelling of the abdomen
- Caused by a segment of the intestine that lacks normal nerve cells, error in neural crest migration
What is aldosterone’s effect on the Large intestine?
- stimulates sodium reabsorption
- increases potassium secretion
What is ADH’s effect on the large intestine?
-increase water reabsorption
How does the Cholera Toxin work?
- increasing cAMP, which adds more CFTR channels to luminal membrane
- increases Cl secretion leading to Na and water loss
What is osmotic diarrhea?
- happens in persons with lactose intolerance
- lactose not broken down, causes flow of water out of enterocytes into the lumen
What is secretory diarrhea?
- usually caused by bacteria or virus
- Tx = imodium
- Bacteria will increase cAMP, cGMP, or Ca in enterocytes
What is inflammatory diarrhea?
- caused by dysentery or ulcerative colitis
- damage to intestinal mucosa interferes with absorption of water
How does oral rehydration therapy work? What is it used to treat?
- Treatment for bacterial diarrhea
- dependent on the Na/Glucose transporter
- has lots of glucose, glucose will be absorbed and water will follow
Oral rehydration therapy saves millions of young children’s lives every year suffering from diarrhea.
This inexpensive and life-saving therapy is possible because of:
A. Sodium / Potassium ATPase pump on the apical membrane
B. Sodium / Glucose co-transporter
C. Glucose transporter on the basolateral side
D. Chloride channel (CFTR channel)
E. Fructose / GLUT 5 transporter
B. Sodium/Glucose co-transporter
Removal of distal ileum will increase bile acid: A. levels in hepatic venous outflow B. levels in the portal vein C. storage in the gall bladder D. synthesis by hepatocytes
D. Synthesis by hepatocytes
Most bile is absorbed in ileum for reuse. If we remove ileum, liver needs to make more bile.
Cholera toxin causes diarrhea by increasing which of the
second messengers?
A. Cyclic AMP / PKA B. Cyclic GMP / PKG C. IP3 / Calcium / CaM kinase D. Diacylglycerol / Phospholipase C E. Diacylglycerol / Protein Kinase C
A. Cyclic AMP/PKA
What does the puborectalis muscle do?
- keeps the inferior rectum bent
- prevents feces from passing
What is the nervous input to the external anal sphincter?
- from internal pudenal nerve
- S2-S4
What is the nervous input to the internal anal sphincter?
-Autonomic pelvic splanchnics
What does neuropeptide Y do? Where is it produced?
- promotes food intake
- made by beta cells of pancreas
Which of the following sphincters is NOT controlled by autonomic nervous system? A. Pyloric B. Lower Esophageal C. Internal anal D. External anal E. Ileo-Cecal
D. External Anal
During a marathon run,
the colon increases absorption of what?
A. Water B. Sodium C. Potassium D. Potassium, Sodium and Water E. Sodium and Water (excretes Potassium)
E. Sodium and Water (excretes potassium)
