GI Midterm Review

Question 1

A newborn becomes lethargic and drowsy 24 h after birth. Blood analysis shows hyperammonemia, coupled with orotic aciduria. This individual has an enzyme deficiency that leads to an inability to directly produce which of the following?
A. Carbamoyl phosphate
B. Ornithine
C. Citrulline
D. Argininosuccinate
E. Arginine

Answer 1

C. Citrulline
Given these symptoms, the defect is in the urea cycle and the elevated orotate suggests deficiency of ornithine transcarbamoylase.

Question 2

A newborn becomes lethargic and drowsy 24 h after birth. Blood analysis shows hyperammonemia, coupled with orotic aciduria. Considering the patient in question above, orotic acid levels are high in this patient due to which of the following?
A. Elevated ammonia
B. Elevated glutamine
C. Increased pyrimidine synthesis
D. Increased purine synthesis
E. Inhibition of carbamoyl phosphate synthetase I (CPS-I)

Answer 2

C. Increased pyrimidine synthesis

Given these symptoms, the defect is in the urea cycle and the elevated orotate suggests deficiency of ornithine transcarbamoylase.

In an OTC deficiency, the carbamoyl phosphate produced in the mitochondria leaks into the cytoplasm, leading to orotic acid synthesis as the regulated step of the pyrimidine synthesis pathway (CPSII step) is being bypassed.

Question 3

A newborn becomes lethargic and drowsy 24 h after birth. Blood analysis shows hyperammonemia, coupled with orotic aciduria. A potential treatment for
the patient is supplementation with which of the following?
A. Arginine and glutamine
B. Lysine and glutamine
C. Arginine and benzoate
D. Lysine and benzoate
E. Glutamine and phenylbutyrate

Answer 3

C. Arginine and benzoate

Given these symptoms, the defect is in the urea cycle and the elevated orotate suggests deficiency of ornithine transcarbamoylase (OTC).

Whenever there is a urea cycle defect, arginine becomes an essential amino acid (as its route of synthesis is the urea cycle). Benzoate, along with phenylbutyrate, is given to patients with urea cycle defects to conjugate with a nitrogen carrying molecule (benzoate conjugates with glycine while phenylbutyrate, after activation to phenylacetate, conjugates with glutamine), which is then excreted

Question 4

A 49-year-old male with a rare recessive condition is at high risk for deep vein thrombosis and stroke and has had replacement of ectopic lenses. He has a normal hematocrit and no evidence of megaloblastic anemia. He responds positively to pyridoxine administration. A mutation in the gene encoding which of the following is most likely to cause this disease?
A. Cystathionine b-synthase
B. Methionine Synthase
C. Fibrillin
D. Homogentisate oxidase
E. Branched chain α-ketoacid dehydrogenase
F. Methylmalonyl-CoA mutase

Answer 4

A. Cystathionine b-synthase

Homocysteine, the substrate for the enzyme, accumulates increasing the risk of deep vein thrombosis and ectopic lenses. Deficiency of Methionine Synthase would cause
homocystinuria, but would also predispose to megaloblastic anemia

Methionine would also be elevated in case of CBS deficiency

Question 5

A 12-year-old boy is brought to the pediatrician because of behavioral problems noted by the parents. Upon examination, the physician notices brittle and coarse hair, long, thin arms and legs (reminiscent of Marfan syndrome patients), scoliosis, pectus excavatum, displaced lens, and muscular hypotonia. Blood work is likely to show an elevation of which of the following metabolites?
A. Tyrosine
B. Phenylpyruvate
C. Cysteine
D. Orotate
E. Homocystine

Answer 5

E. Homocystine

The symptoms suggest homocystinuria, commonly caused by a mutation in CBS (cystathionine B-synthase) which presents with high levels of homocysteine and methionine

Question 6

An individual has been shown to have a deficiency in an intestinal epithelial cell amino acid transport system for leucine. However, the individual shows no symptoms of amino acid deficiency. This could be due to which of the following?
A. The body synthesizes leucine to compensate for the transport defect.
B. The kidney reabsorbs leucine and sends it to other tissues.
C. There are multiple transport systems for leucine.
D. Isoleucine takes the place of leucine in proteins.
E. Leucine is not necessary for bulk protein synthesis.

Answer 6

C. There are multiple transport systems for leucine.

Question 7

A strict vegan who has not consumed meat products for about 5 years slowly develops tiredness and lethargy and also occasional tingling of feet and lower extremities. An analysis of total folate indicate normal amounts. In which form will the folate be mostly found?
A. DHF
B. THF
C. Methyl-folate
D. Methylene-folate
E. Formyl-folate

Answer 7

C. Methyl-folate

People on a vegan diet may develop a Vitamin B12 deficiency because of paucity of this nutrient in vegan foods. A B12 deficiency may result in the “folate trap,” where much of the folate is “stuck” in the methyl folate form. This occurs because the B12-dependent reaction
that converts homocysteine to methionine is impaired

Question 8

A nutritional deficiency in which of the following may result in propionic acid accumulation?
A. Vitamin B6
B. Biotin
C. Folate
D. Vitamin B1
E. Vitamin B2

Answer 8

B. Biotin

Like the other carboxylases discussed (pyruvate carboxylase and acetyl CoA carboxylase) Propionic CoA carboxylase is a biotin-dependent enzyme

Question 9

A 6-month-old boy is brought to the office by his mother over concerns of a developmental delay and foul-smelling wet diapers. Pregnancy and birth history are unremarkable. The baby and his mother immigrated to the United States one month ago. On physical examination the patient has a social smile but does not hold his head up on his own or make babbling noises. Brisk reflexes are noted in the upper and lower extremities. Plasma tyrosine levels are low while ammonia levels are normal. Which of the following enzymes is most likely deficient in this patient?
A. Cystathionine β-synthase
B. Dihydrobiopterin reductase
C. Homogentisate oxidase
D. Tyrosinase
E. Methylmalonyl CoA mutase

Answer 9

B. Dihydrobiopterin reductase

The symptoms align with PKU. Classic PKU is caused by a deficiency in PAH, while variant form is caused by a deficiency in DHPR

Question 10

The co-factor, pyridoxal phosphate, promotes two distinct enzymatic reactions. Which combination is CORRECT?
A. Transamination reactions, and in the conversion of homocysteine to cysteine.
B. Oxidative deamination by glutamate dehydrogenase, and conversion of homocysteine to methionine.
C. Activation of carbamoyl phosphate synthase I and in the conversion of homocysteine to cysteine.
D. In the ATP-dependent conversion of glutamate to glutamine, and by phenylalanine hydroxylase in the conversion of phenylalanine to tyrosine.
E. Activation of S-adenosyl methionine synthase, and in carbon transfer reactions mediated by methyl tetrahydrofolate

Answer 10

A. Transamination reactions, and in the conversion of homocysteine to cysteine.

Question 11

The nitrogens in urea are most directly derived from which of the following compounds (choose best answer)?
A. Ornithine and carbamoyl phosphate
B. Ornithine and aspartate
C. Ornithine and glutamate
D. Carbamoyl phosphate and aspartate
E. Carbamoyl phosphate and alanine
F. Aspartate and glutamine

Answer 11

D. Carbamoyl phosphate and aspartate

Question 12

Your 56-year-old male patient presents with intense redness, heat, and pain over his right great toe at the metatarsophalangeal joint. Fluid from this joint shows bifringent crystals. This disease is caused by the degradation of an excessive amount of which of the following?
A. Adenine
B. Thymine
C. Uracil
D. Cytosine
E. Ribose-5-phosphate

Answer 12

A. Adenine. Gout is caused by uric acid crystallization into a joint and an intense inflammatory reaction to those crystals. Uric acid is an insoluble breakdown product of purines (adenine, hypoxanthine, or guanine).

Pyrimidines (thymine, uracil, and cytosine) breakdown to different water-soluble products that do not crystallize. Ribose-5-phosphate is also degraded to very water-soluble product

Question 13

A 6-month-old infant is seen by the pediatrician for developmental delay. Blood work shows megaloblastic anemia, although measurements of B12 and folate are in the high normal range. Urinalysis demonstrates, upon standing, the formation of a crystalline substance. Supplementation of the child’s diet with uridine reversed virtually all of the clinical problems. The crystalline substance was most likely composed of which of the following?
A. Uracil
B. Thymine
C. Orotate
D. Aspartate
E. Cytosine

Answer 13

C. Orotate. The child has hereditary orotic aciduria, a mutation in the UMP synthase that leads to orotic acid accumulation in the urine.

Treatment with uridine bypasses the block and allows UTP, CTP, and dTTP synthesis. Uridine treatment also has the beneficial effect of blocking further orotate production, as UTP inhibits carbamoyl phosphate synthetase II, the rate-determining step of pyrimidine production. As CPS-II is inhibited, less orotate is produced.

The megaloblastic anemia is the result of inadequate DNA synthesis in the red cell precursors due to the lack of dTTP and dCTP. The crystals are made of orotate, as that is the compound that is accumulating.

Question 14

Which ONE of the following statements about ribonucleotide reductase is CORRECT?
A. The amount of the enzyme in cells varies with the cell cycle.
B. It is postulated that the immunodeficiency observed with ADA results fromhigh levels of
dGTP shutting off the reduction of all ribonucleotides.
C. The enzyme requires NADH for regeneration.
D. The enzyme is critical for the reduction of the rings in the formation of purines.
E. The 3’OH of the ribose ring is reduced by this enzyme.

Answer 14

A. The amount of the enzyme in cells varies with the cell cycle.

The level of the enzyme corresponds with the need for DNA synthesis during S phase. ADA results in high levels of dATP. The enzyme uses NADPH for regeneration, not NADH. The enzyme has nothing to do with ring formation in purine biosynthesis, but reduces the 2’OH of the ribose

Question 15

Which ONE of the following statements about pyrimidine biosynthesis is CORRECT?
A. The level of purines in cells affects the rate of pyrimidine synthesis.
B. The committed step is the synthesis of 5’ phosphoribosylamine.
C. The final step in the pathway is the transfer of the ribose-5-P from PRPP.
D. Synthesis occurs solely in the cytoplasm.
E. IMP is the parent compound for UMP and CMP

Answer 15

A. The level of purines in cells affects the rate of pyrimidine synthesis.

ATP, a purine, does regulate pyrimidine synthesis. Formation of 5’phosphoribosylamine occurs in purine biosynthesis. Transfer of PRPP occurs onto an intermediate in the pathway. One enzyme in the pathway is in the outer face of the inner mitochondrial membrane

Question 16

The mucosal layer of the jejunum…
A. exhibits Brunner’s glands.
B. differs from that of the duodenum because it has a stratified squamous epithelium.
C. lacks a lamina propria.
D. lacks goblet cells.
E. exhibits a muscularis mucosae

Answer 16

E. exhibits a muscularis mucosae

Question 17

The lamina propria
A. lacks capillaries.
B. contains nerve fibers.
C. contains the cell bodies of the myenteric plexus.
D. lacks lymphocytes.
E. has all of the above features

Answer 17

B. contains nerve fibers.

Question 18

Paneth cells
A. are found throughout the stomach.
B. are found in the epithelium of villi of the small intestine.
C. produce lysozyme.
D. are restricted to the anal-rectal junction.
E. function as macrophages.

Answer 18

C. produce lysozyme.

Question 19

A young male patient has self-medicated by taking substantial quantities of over-the-counter medications. You have concerns about the effect of the drugs on his liver. Which statement is the most true and relevant?
A. The liver is exposed to the highest level of toxins because it is the first organ to receive blood from the intestine.
B. A liver biopsy would show that cells in the centrolobular zone (zone 3) would be the most damaged.
C. The fixed hepatic macrophages would contain large numbers of phagosomes, evidence of their role in detoxification.
D. The drugs would be converted into bile salts and excreted.
E. The hepatic stellate cells (lipocytes) would be depleted of vitamin A and have few
lipid droplets.

Answer 19

B. A liver biopsy would show that cells in the centrolobular zone (zone 3) would be the most damaged.

Question 20

Which statement about hepatocyte function is correct?
A. In a well-fed individual, the perilobular/periportal region (zone 3) would have the highest amount of glycogen.
B. In a starved individual, the centrolobular zone (zone 1) would be the most active in glycolysis.
C. The cells in zone 1 are exposed to the highest concentrations of oxygen and nutrients in the blood coming from the intestine.
D. The bile flows in the bile ductules in the direction from zone 1 to zone 3.
E. The venous and arterial blood flow in opposite directions between zones 1 and 3.

Answer 20

C. The cells in zone 1 are exposed to the highest concentrations of oxygen and nutrients in the blood coming from the intestine.

Question 21

In relating the ultrastructure of the hepatocyte to cellular function…
A. Abundant rough endoplasmic reticulum is consistent with the hepatocyte being the major site of enzymes involved in lipid biosynthesis.
B. Abundant mitochondria are the sites of fatty acid and glucose metabolism.
C. Apolipoprotein synthesis is consistent with an extensive smooth endoplasmic reticulum.
D. The presence of peroxisomes is an indicator of the phagocytic activity of the hepatocyte.
E. The heterochromatic nucleus is indicative of the limited transcriptional activity by the hepatocyte.

Answer 21

B. Abundant mitochondria are the sites of fatty acid and glucose metabolism.

Question 22

Which of the following illustrates the liver’s function as an endocrine gland?
A. Secretion of bile
B. Receptor mediated endocytosis of HDL-cholesterol
C. Secretion of VLDL
D. Storage of vitamin A
E. Synthesis of albumin

Answer 22

C. Secretion of VLDL

Question 23

During an evaluation for swallowing problems, changes in pressure due to muscle contractions were recorded from the pharynx to the stomach. The results show strong contractions in the pharynx followed by a strong esophageal peristaltic wave over the entire length of the esophagus. This observation would most likely be described as a(n)…
A. abnormal primary esophageal wave.
B. normal primary esophageal wave.
C. abnormal secondary esophageal wave.
D. normal secondary esophageal wave.
E. inadequate evidence to make an evaluation

Answer 23

B. normal primary esophageal wave.

The normal primary esophageal (peristaltic) wave starts from the top to the end of the esophagus, and is strong.

Question 24

The loss of GI motility in a patient after an open abdominal surgery to remove gallbladder cancer is because of the activation of…
A. Colono-colonic reflex
B. Colonic-intestinal reflex
C. Ileal-gastric reflex
D. Intestino-intestinal reflex
E. Peritoneo-intestinal reflex

Answer 24

E. Peritoneo-intestinal reflex

Peritoneo-intestinal reflex, also called adynamic ileus, is activated by abdominal surgery or peritoneal irrigation

Question 25

Extensive loss of saliva may cause which of the following to be too low in the plasma? A. Na+ B. K+ C. Cl- D. Ca2+

Answer 25

B. K+ Saliva is rich in potassium, but low in sodium and chloride

Question 26

During a meal, pancreatic enzyme secretion is most likely mediated by… A. acetylcholine B. gastrin C. GIP D. secretin E. Somatostatin

Answer 26

A. acetylcholine Cephalic stimuli can activate the parasympathetic system, which controls pancreatic enzyme secretion. CCK would be the other major inducer, although not listed as an answer.

Question 27

Which of the following is mainly responsible for the secretion of a large volume of fluid from the pancreas 3 hours after a meal? A. Acetylcholine B. CCK C. Gastrin D. GRP E. Secretin

Answer 27

E. Secretin During the intestinal phase, in response to H+ from the stomach, secretin is produced during the intestinal phase to induce ductular secretion

Question 28

Cholecystokinin acts in an endocrine manner by: A. Promoting gastric distension B. Crossing the blood brain barrier to induce satiety C. Stimulating pancreatic enzyme secretion D. Inhibiting pancreatic bicarbonate secretion E. Being stimulated by carbohydrate digestion product

Answer 28

C. Stimulating pancreatic enzyme secretion

Question 29

Which of the following GI peptides is secreted in response to the presence of the digestive products of all three macronutrients (carbohydrates, fats and proteins) in the duodenum and jejunum, and leads to an increase in insulin secretion? A. CCK B. Gastrin C. GIP D. Motilin E. Secretin

Answer 29

C. GIP

Question 30

Inhibition of sodium transport has the least effect on absorption of which of the following? A. Monoglycerides B. Galactose C. Glucose D. Dipeptides E. Vitamin C (ascorbic acid)

Answer 30

Monoglycerides are absorbed by diffusion whereas all the rest are transported in a Na-dependent manner.

Question 31

In the normal individual, most of the water absorption occurs in the… A. stomach. B. lumen C. colon D. small intestine. E. pancreas

Answer 31

D. small intestine. Absorption of water is osmotically induced. Osmotically active particles are absorbed mainly throughout the small intestine.

Question 32

One of the many important roles cholesterol plays in the body is as the precursor to the bile acids and salts. A number of structural modifications are carried out in their synthesis in the liver and during their function in the intestine. Which ONE of the following statements CORRECTLY describes one of these changes? A. To improve the amphipathicity of the bile acids, the liver adds the amino acids glycine or phenylalanine to the four-ring structure derived from cholesterol. B. Bile acid synthesis includes the addition of hydroxyl groups at some positions on the parent cholesterol molecule while carbon atoms are removed elsewhere. C. Conversion of primary bile acids and salts into secondary bile acids and salts takes place in the bile duct. D. Bile salts are converted into bile acids by enzymes in the portal vein. E. Primary bile acids are synthesized from endogenous cholesterol while secondary bile acids are synthesized from dietary cholesterol

Answer 32

B. Bile acid synthesis includes the addition of hydroxyl groups at some positions on the parent cholesterol molecule while carbon atoms are removed elsewhere. Conversion of cholesterol to the amphipathic bile acids involves the addition of one or two hydroxyl groups and the shortening of the so-called hydrocarbon “tail” by three carbon atoms. The amino acids that are added to the bile acids are glycine and taurine. The conversion of primaries to secondaries occurs in the intestine, via bacterial enzyme action. No distinction is made in the synthesis of the bile acids as to the endogenous or dietary source of the cholesterol precursor.

Question 33

Which of the following would be MOST likely be the result of resection of the ileum? A. Increased absorption of Vitamin A B. Decreased solubility of cholesterol in bile C. Increased digestion of lipids D. Decreased water content of the feces

Answer 33

B. Decreased solubility of cholesterol in bile Ileal resection leads to decreased enterohepatic circulation of bile salts. As a result, the concentration of bile salts in the bile is also reduced, decreasing cholesterol solubility in bile

Question 34

Which ONE of the following statements about de novo cholesterol synthesis is CORRECT? A. The HMG CoA synthase isozyme that is used to synthesize the HMG CoA that serves as a precursor to cholesterol is located in the mitochondria. B. NADH is the source of the reducing equivalents required for cholesterol synthesis. C. Compared to a diet containing 150 mg cholesterol per day, consumption of 1500 mg cholesterol per day will lead to a decrease in HMG CoA reductase activity. D. ATP is not required for the production of cholesterol.

Answer 34

C. Compared to a diet containing 150 mg cholesterol per day, consumption of 1500 mg cholesterol per day will lead to a decrease in HMG CoA reductase activity. Chylomicron remnants (containing dietary cholesterol) internalized by liver cells, and low density lipoproteins internalized by cells of the liver and peripheral tissues, provide cholesterol, which causes a decrease in transcription of the HMG CoA reductase gene, leading to a decrease in de novo cholesterol synthesis.

Question 35

HMG CoA reductase is the regulatory enzyme in the pathway of cholesterol biosynthesis. Which ONE of the following statements regarding this enzyme is INCORRECT? A. Cholic acid is an inhibitor of this enzyme. B. Insulin signaling stimulates the activity of this enzyme by means of a phosphatase. C. The statin class of drugs are competitive inhibitors of the enzyme D. Cholesterol levels influence the rate of HMG CoA reductase mRNA synthesis.

Answer 35

A. Cholic acid is an inhibitor of this enzyme. Cholic acid (a precursor to the bile salts) is an inhibitor of the 7-alpha hydroxylase involved in bile acid synthesis, but has no allosteric effects on HMG CoA reductase

Question 36

A feature of the process of heme degradation is the lack of solubility this molecule has in aqueous solutions. Which ONE of the following statements CORRECTLY describes one of the means by which the system of organs, cells and enzymes that is responsible for heme degradation and excretion manages this low solubility in a healthy individual? A. Covalent attachment to CoA groups enhances the solubility of heme breakdown intermediates. B. Bilirubin is converted to its diglucuronide form by intestinal bacteria. C. Bilirubin diglucuronide is transported in the blood stream in association with albumin. D. Acidic derivatives of glucose are covalently attached to bilirubin prior to its export in the bile. E. Biliverdin is bound to albumin while it is being covalently modified in cells of the liver.

Answer 36

D. Acidic derivatives of glucose are covalently attached to bilirubin prior to its export in the bile.

Question 37

Which ONE of the following statements regarding the first steps in the breakdown of red blood cell components, in cells of the reticuloendothelial (RE) system of a healthy individual, is CORRECT? A. At an early stage in the degradation of the globin tetramer, the heme ring is released intact into the circulation, with the iron quickly changing to the Fe+3 state. B. The first chemical change in heme ring breakdown is the opening of the ring structure, with the conversion of Fe+2 to Fe+3. C. Macrophages covalently attach a pair of glucuronic acid residues to the newly linearized porphyrin ring structure. D. Biliverdin is transported to the liver via attachment to albumin. E. The amino acids derived from globin tetramer protein degradation are secreted in the urine.

Answer 37

B. The first chemical change in heme ring breakdown is the opening of the ring structure, with the conversion of Fe+2 to Fe+3.

Question 38

Complete the following sentence so that it is CORRECT: “The catabolism of hemoglobin...” A. occurs in red blood cells. B. involves the complete oxidative breakdown of the porphyrin ring to CO2, H20 and NH3. C. results in the liberation of carbon monoxide. D. results in the formation of protoporphyrinogen. E. is inhibited by hemin.

Answer 38

C. results in the liberation of carbon monoxide.

Question 39

During the process of heme degradation, urobilinogen is formed in the: A. Spleen B. Liver C. Urinary tract D. Bowel E. Kidney

Answer 39

D. Bowel

Question 40

Which ONE of the following is an INCORRECT statement about the bile acids and salts? A. Bile salts facilitate the absorption of fat-soluble vitamins from the intestine. B. Bile salts are converted to bile acids by the addition of glycine or taurine. C. A deficiency of bile salts can lead to cholelithiasis (gall bladder disease). D. Bacteria in the intestine can convert cholic acid into deoxycholic acid, and chenodeoxycholic acid into lithocholic acid. E. Bile is stored and concentrated in the gall bladder.

Answer 40

B. Bile salts are converted to bile acids by the addition of glycine or taurine. Bile acids are converted into bile salts by the addition of glycine or taurine

Question 41

A 50 year old patient who had ileal resection mentioned that she can eat some eggs and bacon for breakfast and feels fine but other than breakfast, she has diarrhea after lunch and dinner. What could explain this? A. carbohydrate maldigestion and malabsorption B. protein maldigestion and malabsorption C. lipid maldigestion and malabsorption D. pancreatic insufficiency

Answer 41

C. lipid maldigestion and malabsorption Bile salt synthesis during the night (interdigestive period) results in sufficient bile to be made and stored in the gallbladder to aid in the digestion of the lipids consumed in the breakfast. However, because of the ileal resection, reabsorption of bile is impaired, and so bile available for digestion/absorption of meals later in the day is deficient, causing the diarrhea.

Question 42

An individual has overdosed on his heart medicine (digitalis intoxication) and the GI tract is being affected as evidenced by watery diarrhea. This poisoning of the Na+K+ ATPase most likely leads to a reduction in the absorption of which of the following? A. Free fatty acids B. Glucose C. Iron D. Cl-

Answer 42

B. Glucose Glucose is co-transported with Na+ via SGLT1. The Na+K+ ATPase provides the engine that drives the absorption of Na+-dependent transporters.

Question 43

Water is absorbed in the jejunum, ileum, and colon and excreted in the feces. Arrange these in order of the amount of water absorbed or excreted from greatest to smallest. A. Colon, jejunum, ileum, feces B. Feces, colon, ileum, jejunum C. Jejunum, ileum, colon, feces D. Colon, ileum, jejunum, feces E. Feces, jejunum, ileum, colon

Answer 43

C. Jejunum, ileum, colon, feces

Question 44

Compared to hepatic bile, gallbladder bile contains a reduced concentration of which of the following? A. Bile acids B. Chloride ions C. Protons D. Glucose E. Calcium ions

Answer 44

B. Chloride ions

Question 45

A patient is referred to a gastroenterologist because of persistent difficulties with swallowing. Endoscopic examination reveals that the lower esophageal sphincter fails to fully open as the bolus reaches it, and a diagnosis of achalasia is made. During the examination, or in biopsies taken from the sphincter region, a decrease would be expected in which of the following? A. Esophageal peristalsis B. Expression of neuronal NO synthase C. Acetylcholine receptors D. Substance P release E. Contraction of the crural diaphragm

Answer 45

B. Expression of neuronal NO synthase

Question 46

A 40-year-old woman comes to her primary care clinician complaining of severe, episodic abdominal pain that is particularly intense after she ingests a fatty meal. An imaging procedure reveals that her gallbladder is acutely dilated, and a diagnosis of cholelithiasis is made. A gallstone lodged in which location will also increase her risk of pancreatitis? A. Left hepatic duct B. Right hepatic duct C. Cystic duct D. Common bile duct E. Sphincter of Oddi

Answer 46

E. Sphincter of Oddi

Question 47

A surgeon is studying new methods of liver transplantation. She performs a complete hepatectomy in an experimental animal. Before the donor liver is grafted, a rise in the blood level of which of the following would be expected? A. Glucose B. Fibrinogen C. 25-Hydroxycholecalciferol D. Conjugated bilirubin E. Estrogens

Answer 47

E. Estrogens

Question 48

The symptoms of the dumping syndrome (discomfort after meals in patients with intestinal short circuits such as anastomosis of the jejunum to the stomach) are caused in part by A. increased blood pressure. B. increased secretion of glucagon. C. increased secretion of CCK. D. hypoglycemia. E. hyperglycemia.

Answer 48

D. hypoglycemia.

Question 49

In Hartnup disease (a defect in the transport of neutral amino acids), patients do not become deficient in these amino acids due to the activity of A. PepT1. B. brush border peptidases. C. Na+, K+ ATPase. D. cystic fibrosis transmembrane conductance regulator (CFTR). E. trypsin.

Answer 49

A. PepT1.

Question 50

Maximum absorption of short-chain fatty acids produced by bacteria occurs in the A. stomach. B. duodenum. C. jejunum. D. ileum. E. colon.

Answer 50

E. colon.

Question 51

In infants, defecation often follows a meal. The cause of colonic contractions in this situation is A. histamine. B. increased circulating levels of CCK. C. the gastrocolic reflex. D. increased circulating levels of somatostatin. E. the enterogastric reflex.

Answer 51

C. the gastrocolic reflex.

Question 52

A patient suffering from severe ulcerative colitis undergoes a total colectomy with formation of a stoma. After a full recovery from surgery, and compared to his condition prior to surgery, which of the following would be expected to be decreased? A. Ability to absorb lipids B. Ability to clot the blood C. Circulating levels of conjugated bile acids D. Urinary urea E. Urinary urobilinogen

Answer 52

E. Urinary urobilinogen

Question 53

state the secretion site and action of cholecystokinin

Answer 53

secretion site: **I cells** (small intestine) actions: decrease gastric motility/acid, **increase gallbladder contraction/ sphincter of Oddi relaxation**, **increase pancreatic enzyme/bicarbonate secretion**

Question 54

state the secretion site and action of secretin

Answer 54

secretion site: **S cells** (small intestine) actions: **increase pancreatic bicarbonate secretion**, decrease gastric acid secretion

Question 55

state the secretion site and action of somatostatin

Answer 55

secretion site: **D cells** (pancreatic islets, gut mucosa) actions: decrease secretion of GI hormones

Question 56

state the secretion site and action of GIP

Answer 56

aka glucose-dependent insulinotropic peptide (aka gastric inhibitory peptide) secretion site: **K cells** (small intestine) actions: **increase insulin release**, decrease gastric motility/acid secretion

Question 57

gastroileal reflex

Answer 57

entry of food into empty stomach results in relaxation of ileo-cecal sphincter leading to emptying of ileum

Question 58

gastrocolic reflex/ Duodenocolic reflex

Answer 58

entry of food into empty stomach or chyme into the duodenum results in increase of propulsive movement in the colon

Question 59

colonocolonic reflex

Answer 59

distention of one part of the colon leads to relaxation of other parts Causes decreased resistance and increased propulsive movement

Question 60

duodenogastric reflex

Answer 60

Duodenal distention causes decreased gastric emptying

Question 61

ileogastric reflex

Answer 61

ileal distention leads to decreased gastric emptying

Question 62

intestino-intestinal reflex

Answer 62

over distention of a segment of intestine caused by intestinal obstruction results in generalized inhibition of intestinal muscle activity Example – strictures, adhesion, cancer, IBS, etc.

Question 63

colonic-intestinal reflex

Answer 63

over distention in the colon caused by obstruction results in a generalized inhibition of intestinal muscle activity Example – strictures, adhesions, cancer, IBS, etc.

Question 64

peritoneo-intestinal reflex

Answer 64

aka **adynamic ileus**: handling of the intestine during abdominal surgery or peritoneal irrigation results in a generalized inhibition of intestinal muscle activity

Question 65

where do the following occur along the GI tract? a. Na+/H+ absorption b. Na+/solute absorption c. coupled Na+/Cl- absorption d. Na+ channel absorption

Answer 65

a. Na+/H+ absorption - duodenum + jejunum b. Na+/solute absorption - duodenum + jejunum + ileum c. coupled Na+/Cl- absorption - ileum + colon d. Na+ channel absorption - rectum

Question 66

A child lacking Cl-/HCO3 exchanger is diagnosed with congenital chloridorrhea. What are the findings? a. diarrhea or constipation b. fill in acid-base disturbance

Answer 66

—> diarrhea + metabolic alkalosis due to inability to absorb Cl- and secrete HCO3-

Question 67

cystinuria vs Hartnup disease

Answer 67

cystinuria: defect in **dibasic** AA transporters —> impaired uptake of **cystine, ornithine, arginine, lysine (COAL)** + cystine kidney stones Hartnup disease: defect in **neutral** AA transporters —> impaired uptake of **tryptophan**, serine, threonine, glutamine, tyrosine + **Pellagra-like symptoms** requiring niacin supplements

Question 68

Pellagra-like symptoms + tryptophan detected in urine

Answer 68

**Hartnup disease**: defect in **neutral** AA transporters —> impaired uptake of **tryptophan**, serine, threonine, glutamine, tyrosine + **Pellagra-like symptoms** requiring niacin supplements many patients won’t have symptoms due to redundancy with other transporters (esp. PEPT1)

Question 69

many patients with deficiency of AA transporters (cystinuria, Hartnup) won’t have symptoms due to redundancy with other transporters, especially _____

Answer 69

**PEPT1** - sequence-independent di/tri-peptide transporter

Question 70

frequent kidney stones + urine smells like rotten eggs

Answer 70

**cystinuria**: AR defect in transporter of basic amino acids (COAL: cystine, ornithine, arginine, lysine) —> cystine kidney stones + urine smells like rotten eggs

Question 71

intellectuality disability + eczema + musty odor of urine

Answer 71

**phenylketonuria**: AR defect in phenylalanine hydroxylase or DHPR

Question 72

hyperammonemia + hypertonia + intellectual disability + hyperglycemia

Answer 72

**methylmalonic acidemia mutase**: AR defect in methylmalonyl-CoA mutase/racemase or B12 reductase/ adenosyltransferase

Question 73

lens dislocation + thrombotic vascular disease + intellectual disability + marfanoid habitus

Answer 73

**homocystinuria**: AR defect in cystathionine beta-synthase or MTHFR or methionine synthase

Question 74

ochronosis + arthritis + cardiac valve involvement + coronary artery calcification

Answer 74

**alkaptonuria**: AR defect in homogentisic acid oxidase (breaks down tyrosine)

Question 75

what is the embryonic origin of the epithelial cells found within a peritoneal mesothelioma? a. ectoderm b. neural crest c. parietal mesoderm d. endoderm e. visceral mesoderm

Answer 75

c. parietal mesoderm parietal peritoneum is a serosal membrane made up of mesothelium (simple squamous epithelium) and loss connective tissue body cavity divides lateral plate mesoderm into parietal layer (lines body cavity wall) and visceral layer (covers intraperitoneal viscera) in the peritoneal cavity, parietal mesoderm gives rise to parietal peritoneum, and visceral mesoderm gives rise to visceral peritoneum

Question 76

a patient with esophageal varices due to liver cirrhosis and portal HTN has: a. additional varices in other regions where anastomoses occur between veins draining to the IVC and azygos vein b. reversal of blood flow in veins that drain to the hepatic portal vein c. dilation of submucosal esophageal veins that normally drain into inferior mesenteric vein d. increased blood volume exiting hepatic veins e. prolapse of veins within venous tributaries to hepatic portal vein

Answer 76

b. reversal of blood flow in veins that drain to the hepatic portal vein when portal circulation through liver is impeded due to portal HTN, blood from GI tract can still reach the IVC and right side of heart via collaterals these collaterals are possible bc the hepatic portal vein and its tributaries lack valves so blood can flow in reverse direction however, excess blood through collateral venous routes can cause hemorrhage from varices (abnormally dilated)

Question 77

which of the following distinguishes the jejunum? a. mesentery with little fat and fewer, larger vascular arcades with long vasa recta b. more Peyer's patches than the ileum c. omental/epiploic appendices d. more fat in mesentery e. taeniae coli and haustra f. thinner wall with fewer plicae circulares

Answer 77

a. mesentery with little fat and fewer, larger vascular arcades with long vasa recta large intestine has taenia coli, haustra, omental/epiploic appendices jejunum also has more plicae circulares (mucosal-submucosal folds)

Question 78

histological slide shows cells within wall of intestine with many small pink (eosinophilic) granules - what might these be?

Answer 78

Paneth cells - secrete lysozyme (bactericidal)

Question 79

what is the difference in the acini of the parotid gland vs salivary gland?

Answer 79

parotid - serous acini [note parotid looks similar to exocrine pancreas but lacks islets of Langerhans] salivary - mucous secreting [striated ducts resorb Na+ and Ca2+, making saliva hypotonic]

Question 80

which is a feature of the small intestine? a. a few ciliated goblet cells b. multinucleated stem cells in lamina propria c. absence of crypts of Lieberkuhn d. presence of enterocytes that synthesize transmembrane enzymes associated with the glycocalyx e. parietal cells

Answer 80

d. presence of enterocytes that synthesize transmembrane enzymes associated with the glycocalyx [stem cells are not multinucleated and are found within epithelium, not lamina propria]

Question 81

what is the most varied layer of the alimentary canal?

Answer 81

mucosal layer

Question 82

which of the following illustrates that hepatocytes are epithelial cells? a. abundant RER b. microvilli c. abundant mitochondria d. junctional complex surrounding the bile canaliculus e. abundant smooth ER

Answer 82

d. junctional complex surrounding the bile canaliculus epithelial tissue contain junctional complexes between adjacent cells none of the other choices are specific enough

Question 83

what are the derivates of foregut, midgut, and hindgut?

Answer 83

foregut: pharynx, esophagus, stomach, proximal duodenum, liver, gallbladder, pancreas [all the random stuff not directly connected] midgut: distal duodenum, jejunum, ileum, cecum, ascending colon, proximal 2/3 of transverse colon hindgut: distal 1/3 transverse colon, descending colon, sigmoid colon, rectum, proximal anal canal

Question 84

pain from bloating/distention of digestive organs derived from each of the following refers to where? a. foregut b. midgut c. hindgut

Answer 84

a. foregut - refers to epigastric region b. midgut - refers to umbilical region c. hindgut - refers to hypogastric region OR hindgut below pelvic pain line refers to posterior thighs distal anal canal refers to posterior thigh

Question 85

ligation of gastroduodenal artery will result in retrograde flow in the...

Answer 85

...right gastro-omental artery: branch of the gastroduodenal artery left gastro-omental artery is a branch of the splenic artery the R and L gastro-omental arteries anastomose... so blood would flow from L to R gastro-omental artery (even though R does not receive direct blood from gastroduodenal artery)

Question 86

lesion of the vagus nerve may result in loss of peristalsis of the: a. ascending colon b. descending colon c. sigmoid colon d. rectum

Answer 86

a. ascending colon vagus supplies parasympathetics to derivatives of foregut and midgut pelvic splanchnic supplies parasympathetics to derivatives of hindgut

Question 87

segment of intestine with fat on its mesenteric border and mesentery with short vasa recta and small, numerous vascular arcades describes the...

Answer 87

ileum [jejunum has arcades with fewer and longer vasa recta]

Question 88

large gallstone in cystic duct would cause pain to be carried by afferents in the: a. vagus nerve b. intercostal nerve c. lesser thoracic splanchnic nerves d. greater thoracic splanchnic nerves

Answer 88

d. greater thoracic splanchnic nerves foregut receives sympathetic innervation from greater splanchnic nerves and associated visceral pain is conveyed along the same pathway

Question 89

annular pancreas obstructs the...

Answer 89

second part of the duodenum

Question 90

rupture of which of the following could cause a retroperitoneal bleed? a. sigmoid colon b. jejunum c. ileum d. second part of duodenum

Answer 90

d. second part of duodenum

Question 91

adenocarcinoma of the sigmoid colon are made of cells derived from...

Answer 91

endoderm

Question 92

what carries visceral sensory pain above vs below the pelvic pain line?

Answer 92

above = sympathetics below = pelvic splanchnic nerves

Question 93

pulsatile bleeding from a vessel in the first portion of the duodenum is a branch of the...

Answer 93

... common hepatic artery: divides into proper hepatic and gastroduodenal artery (which supplies first portion of duodenum)

Question 94

patient with jaundice + dilation of gallbladder has obstruction where?

Answer 94

common bile duct obstruction of cystic duct would not prevent bile from reaching duodenum (can still pass from common hepatic to common bile duct)

Question 95

There is competition between: A. Digestion of sucrose and lactose. B. Transport of glucose and fructose into the enterocyte. C. Transport of glucose and galactose into the enterocyte.

Answer 95

C. Transport of glucose and galactose into the enterocyte. Both are absorbed by SGLT1 transporters

Question 96

Immunostaining for which of the following would most likely be positive in a biopsy from the colon? A. Motilin B. Secretin. C. Cholecystokinin. D. Gastrin E. Serotonin.

Answer 96

E. Serotonin. Much of the enteroendocrine cell population is concentrated in the proximal small intestine and cells become less frequent as you progress distally stopping all together as you enter the colon Exception to this is enterochromaffin, or serotonin secreting cells, which are distributed throughout the G.I. tract, including the colon

Question 97

Orotic aciduria = deficiency in which enzyme? What accumulates?

Answer 97

UMP synthase - orotate accumulates Supplement uridine to treat megaloblastic anemia

Question 98

What is NAG (N-acetyl glutamate) needed for?

Answer 98

Cofactor for carbamoyl phosphate I (urea cycle) Deficiency of NAGS (NAG synthase) is treated with synthetic NAG, benzoate and phenylacetate (treat hyperammonemia) + arginine (becomes limited)

Question 99

Why do NSAIDs cause stomach ulcers?

Answer 99

NSAIDs inhibit production of prostaglandins, which protects the stomach mucous membranes partly by stimulating the production of the protective mucus and bicarbonate in the stomach

Question 100

Colectomy would cause decrease in: A. Ability to absorb dietary lipids. B. Ability to absorb conjugated bile salts C. Ability to acquire, secondary bile acids.

Answer 100

C. Ability to acquire secondary bile acids. Secondary bile acids are made in the colon by gut bacteria, and passively absorbed and delivered to the liver through the portal vein

Question 101

Two week old girl found to have it elevated methionine concentration on screening. Which enzyme is most likely deficient?

Answer 101

Cystathionine b-synthase Most common cause of homocystinuria. CBS is involved in the conversion of homocysteine to assisting and deficiency is associated with elevated levels of methionine.

Question 102

57 year old patient with a 15 year history of type two diabetes mellitus presents with nausea bloating and early satiety. Evaluation reveals delayed gastric emptying. Increasing which of the following would be an appropriate therapeutic strategy? A. Secretin. B. Cholecystokinin. C. Acetylcholine. D. Vasoactive, intestinal peptide. E. Norepinephrine.

Answer 102

C. Acetylcholine. Enteric nerves act as postganglionic parasympathetic nerves in the G.I. tract. The principal postganglionic neurotransmitter is acetylcholine, which has prokinetic effects, increasing G.I. motility. The rest decrease peristaltic activity

Question 103

What is the function of colipase?

Answer 103

Allows pancreatic lipase to bind to the oil – water interface of lipids

Question 104

Defect in which of the following could cause seizures, elevated ammonium, elevated glutamine and alanine, but no increase in orotic acid or citrulline?

Answer 104

Carbamoyl phosphate synthetase I (CPS-I)

Question 105

Which of the following will occur in an individual with the ileum removed? A. Increased stomach emptying rate B. Increased small intestine transient time. C. Increase the number of ECA in the stomach.

Answer 105

A. Increased stomach emptying rate Removal of terminal ileum eliminates the ileo-gastric reflux, which inhibits gastric emptying

Question 106

Which amino acid is present in the highest concentration in serum?

Answer 106

Glutamine – plays special role in the transport of amino groups from non-hepatic tissues to the liver