Academic Success Week 09 - GI Embryology & Nitrogen Metabolism
- 1.
A 2 month old baby boy presents with a swollen umbilicus that has failed to heal properly. The umbilicus drains secretions and there is passage of fecal matter through the umbilicus at times. What is the most likely diagnosis?
- A.
Gastroschisis
- B.
Anal agenesis
- C.
Ileal diverticulum
- D.
Omphalocele
- E.
Intestinal volvulus
Correct Answer
C. Ileal diverticulumExplanation
The most likely diagnosis in this case is ileal diverticulum. This condition occurs when a small pouch or sac forms in the wall of the small intestine, in this case near the umbilicus. The symptoms described, such as a swollen umbilicus that fails to heal properly and the passage of fecal matter through the umbilicus, are consistent with ileal diverticulum. Gastroschisis and omphalocele usually present with visible protrusion of abdominal contents, while anal agenesis refers to the absence of an anus. Intestinal volvulus involves twisting of the intestines, which is not mentioned in the symptoms.Rate this question:
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- 2.
A five month old female infant presented at the pediatric unit due to yellow pigmentation of the skin which had developed on the 3rd day of life. Clinical examination showed jaundice with mild abdominal distention and hepatosplenomegaly and no ascites (fluid accumulation in abdominal cavity). The lungs and the heart were essentially normal. Stool was clay colored. Infection screen and hepatitis markers were negative. Bile salts and bile pigments were detected in the urine. What is the most likely diagnosis?
- A.
Duodenal stenosis
- B.
Pyloric stenosis
- C.
Extra hepatic biliary atresia
- D.
Neonatal hemochromatosis
- E.
Viral hepatitis
Correct Answer
C. Extra hepatic biliary atresiaExplanation
The most likely diagnosis in this case is extra hepatic biliary atresia. This is supported by the presence of jaundice, hepatosplenomegaly, clay-colored stool, and detection of bile salts and bile pigments in the urine. These findings suggest a blockage or absence of the bile ducts, leading to the accumulation of bilirubin in the liver and subsequent jaundice. Other options such as duodenal stenosis, pyloric stenosis, neonatal hemochromatosis, and viral hepatitis do not fit the clinical presentation and laboratory findings.Rate this question:
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- 3.
Periodontal ligaments are derived from
- A.
Ectoderm
- B.
Oral epithelium
- C.
Odontoblasts
- D.
Mesoderm
- E.
Neural crest
Correct Answer
D. MesodermExplanation
Periodontal ligaments are connective tissues that surround and support the teeth in the sockets of the jawbone. These ligaments are derived from the mesoderm, which is one of the three primary germ layers in the early development of an embryo. The mesoderm gives rise to various tissues and structures, including connective tissues, muscles, bones, and blood vessels. Since periodontal ligaments are a type of connective tissue, it is logical to conclude that they are derived from the mesoderm during embryonic development.Rate this question:
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- 4.
Which of the following events in the development of the abdominal cavity is affected by the rapid growth of the liver?
- A.
Formation of greater omentum
- B.
Formation of lesser sac
- C.
Physiological herniation of the midgut loop
- D.
Urorectal septum formation
- E.
Formation of pancreas
Correct Answer
C. pHysiological herniation of the midgut loopExplanation
The rapid growth of the liver affects the physiological herniation of the midgut loop. During development, the midgut loop temporarily herniates into the umbilical cord, allowing for proper positioning and rotation of the intestines. The rapid growth of the liver pushes the midgut loop back into the abdominal cavity, completing the process of physiological herniation. This event is essential for the proper development and positioning of the intestines in the abdominal cavity.Rate this question:
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- 5.
Prenatal ultrasound revealed polyhydramnios at 36 weeks, and at birth the infant had excessive fluids in its mouth and difficulty breathing. Which of the following is the most likely cause for these conditions?
- A.
Pyloric stenosis
- B.
Enterocystoma
- C.
Annular pancreas
- D.
Esophageal atresia with tracheoesophageal fistula
- E.
Meckel's diverticulum
Correct Answer
D. EsopHageal atresia with tracheoesopHageal fistulaExplanation
Esophageal atresia with tracheoesophageal fistula is the most likely cause for the conditions described. Esophageal atresia is a congenital condition where the esophagus does not properly develop, leading to a gap between the upper and lower parts of the esophagus. Tracheoesophageal fistula is an abnormal connection between the esophagus and the trachea. These conditions can result in excessive fluids in the mouth and difficulty breathing, which are consistent with the symptoms described in the question.Rate this question:
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- 6.
The chorda tympani nerve, a derivative of the facial nerve, transmits taste fibers from the anterior two-thirds of the tongue to the brain. What is the best embryological reason for this anatomical pattern?
- A.
Contribution of the copula from pharyngeal arch II to the formation of the adult tongue
- B.
Contribution of the hypopharyngeal eminence from pharyngeal arch III to the formation of the adult tongue
- C.
A pretrematic branch from the nerve of pharyngeal arch II to arch I
- D.
A pretrematic branch from the nerve of pharyngeal arch III to arch II
- E.
A pretrematic branch from the nerve of pharyngeal arch IV to arch III
Correct Answer
C. A pretrematic branch from the nerve of pHaryngeal arch II to arch IExplanation
The best embryological reason for the anatomical pattern described is the contribution of the copula from pharyngeal arch II to the formation of the adult tongue. This suggests that the chorda tympani nerve, derived from the facial nerve, transmits taste fibers from the anterior two-thirds of the tongue to the brain because it is connected to the tongue through the copula, which is derived from pharyngeal arch II.Rate this question:
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- 7.
Meckel's diverticulum is a remnant of the
- A.
Ventral mesentery
- B.
Allantois
- C.
Lesser sac
- D.
Vitelline duct
- E.
Cloaca
Correct Answer
D. Vitelline ductExplanation
Meckel's diverticulum is a congenital abnormality that occurs when the vitelline duct, also known as the omphalomesenteric duct, fails to fully close during fetal development. The vitelline duct is a structure that connects the developing embryo to the yolk sac, allowing for nutrient transfer. In most cases, the vitelline duct obliterates and disappears by the 7th week of gestation. However, when it persists, it can lead to the formation of Meckel's diverticulum, a small pouch-like protrusion in the small intestine. Therefore, the correct answer is vitelline duct.Rate this question:
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- 8.
Which of the following structures is derived from hindgut?
- A.
Liver
- B.
Ascending colon
- C.
Descending colon
- D.
Appendix
- E.
Cecum
Correct Answer
C. Descending colonExplanation
The descending colon is derived from the hindgut. The hindgut is the last part of the embryonic gut tube and gives rise to the lower portion of the digestive tract, including the colon. The descending colon is the part of the colon that extends downward on the left side of the abdomen. It is responsible for reabsorbing water and electrolytes from the remaining indigestible food matter, forming stool, and storing it until it is ready to be eliminated from the body.Rate this question:
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- 9.
Which of the following structures is derived from the midgut?
- A.
Liver
- B.
Descending colon
- C.
Appendix
- D.
Gallbladder
- E.
Spleen
Correct Answer
C. AppendixExplanation
The appendix is derived from the midgut. During embryonic development, the midgut gives rise to the lower part of the small intestine, the ascending colon, and the appendix. The appendix is a small, finger-like pouch located at the junction of the small and large intestines. While its exact function is not well understood, it is believed to play a role in the immune system and may have some involvement in the digestion of certain types of food.Rate this question:
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- 10.
Appendix is derived from the
- A.
Dorsal mesentery
- B.
Ventral mesentery
- C.
Foregut
- D.
Hindgut
- E.
Midgut
Correct Answer
E. Midgut -
- 11.
Which of the following structures can be found at the free margin of falciform ligament?
- A.
Portal triad
- B.
Median umbilical ligament
- C.
Superior mesenteric artery
- D.
Round ligament of the liver
- E.
Cystic duct
Correct Answer
D. Round ligament of the liverExplanation
The round ligament of the liver can be found at the free margin of the falciform ligament. The falciform ligament is a fold of peritoneum that attaches the liver to the anterior abdominal wall and separates the right and left lobes of the liver. The round ligament of the liver is a remnant of the fetal umbilical vein, which carried oxygenated blood from the placenta to the liver. In adults, the round ligament of the liver is a fibrous cord that runs within the free margin of the falciform ligament.Rate this question:
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- 12.
Which of the following amino acids is both essential and glucogenic?
- A.
Alanine (Ala, A)
- B.
Methionine (Met, M)
- C.
Leucine (Leu, L)
- D.
Proline (Pro, P)
- E.
Lysine (Lys, K)
Correct Answer
B. Methionine (Met, M)Explanation
Methionine is both an essential and glucogenic amino acid. Essential amino acids are those that cannot be synthesized by the body and must be obtained from the diet. Glucogenic amino acids are those that can be converted into glucose through various metabolic pathways. Methionine fulfills both criteria as it is essential and can be converted into glucose when needed. Therefore, it is the correct answer to the question.Rate this question:
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- 13.
K.L. was born in Ville de Saguenay (Quebec), birth was uneventful. However, she failed to thrive. Suddenly at the age of 5 month her condition deteriorated rapidly and she was transferred to an emergency room. Organ function tests indicated failure of liver and kidney, attending physicians noticed a strong cabbage-like smell originating from her. The most likely diagnosis is
- A.
Hyperlysinemia
- B.
Cystinuria
- C.
Methylmalonic aciduria
- D.
Tyrosinemia I
- E.
Glycine cleavage enzyme deficiency
Correct Answer
D. Tyrosinemia IExplanation
The most likely diagnosis for K.L.'s condition is Tyrosinemia I. This is indicated by the symptoms of liver and kidney failure, as well as the presence of a strong cabbage-like smell. Tyrosinemia I is a rare genetic disorder that affects the body's ability to break down the amino acid tyrosine. This leads to a buildup of toxic substances in the body, which can cause liver and kidney damage. The symptoms typically appear in infancy and can be life-threatening if not treated promptly.Rate this question:
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- 14.
The presence of phenylpyruvate and phenylketones in a child's blood are indications of the genetic disorder Phenylketonuria. How does this compound accumulate? This is a disorder of phenyalanine metabolism which results from:
- A.
Too little product formation of a metabolic pathway
- B.
Too much substrate accumulation for an enzymatic reaction
- C.
An undersupply of tyrosine for protein translation
- D.
An oversupply of homogentisic acid
- E.
Modification of blood proteins by metabolic acids
Correct Answer
B. Too much substrate accumulation for an enzymatic reactionExplanation
In Phenylketonuria, there is a deficiency of the enzyme phenylalanine hydroxylase, which is responsible for converting phenylalanine into tyrosine. As a result, phenylalanine accumulates in the body, leading to the production of phenylpyruvate and phenylketones. This accumulation occurs because there is an excess of substrate (phenylalanine) for the enzymatic reaction catalyzed by phenylalanine hydroxylase. Therefore, the correct answer is "too much substrate accumulation for an enzymatic reaction."Rate this question:
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- 15.
Coconut protein is biologically inferior because it is lacking many essential amino acids. In your efforts to make transgenic coconuts with protein of high biological value, you should definitely ensure that your coconut protein has an adequate amount of:
- A.
Glutamine
- B.
Arginine
- C.
Phenylalanine
- D.
Tyrosine
- E.
Serine
Correct Answer
C. pHenylalanineExplanation
Coconut protein is considered biologically inferior because it lacks many essential amino acids. Phenylalanine is one of these essential amino acids that is missing in coconut protein. Therefore, in order to make transgenic coconuts with protein of high biological value, it is crucial to ensure that the coconut protein contains an adequate amount of phenylalanine.Rate this question:
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- 16.
High homocysteine levels are associated with an increased risk of atherosclerosis. A deficiency of which of the following enzymes would result in high blood levels of homocysteine (and also methionine)?
- A.
Tyrosine hydroxylase
- B.
Cystathionine synthase
- C.
Threonine dehydratase
- D.
Glutathione reductase
- E.
L-amino acid oxidase
Correct Answer
B. Cystathionine synthaseExplanation
A deficiency of cystathionine synthase would result in high blood levels of homocysteine (and also methionine). Cystathionine synthase is an enzyme that plays a crucial role in the conversion of homocysteine to cysteine. Without this enzyme, homocysteine cannot be properly metabolized and accumulates in the blood. This can lead to an increased risk of atherosclerosis, as high levels of homocysteine have been associated with damage to blood vessels and the development of plaque.Rate this question:
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- 17.
A negative nitrogen balance is most likely in:
- A.
A heavyweight boxer training for the world championship
- B.
A fast-growing teenager who eats 3500 calories of junk food every day
- C.
A political prisoner who went on a hunger strike
- D.
A woman who is 8 months pregnant
- E.
A patient who is recovering from successful cancer surgery and chemotherapy
Correct Answer
C. A political prisoner who went on a hunger strikeExplanation
A negative nitrogen balance occurs when the body excretes more nitrogen than it takes in. Nitrogen is an essential component of protein, which is necessary for growth and repair of body tissues. When a person goes on a hunger strike and does not consume enough protein, their body will start breaking down muscle tissue to obtain the necessary nitrogen. This results in a negative nitrogen balance. Therefore, a political prisoner who went on a hunger strike is most likely to have a negative nitrogen balance.Rate this question:
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- 18.
A 2-week-old infant presents with vomiting, lethargy and convulsions without evidence of an infectious process. Laboratory examination reveals hyperammonemia with alkalosis. Glutamine, citrulline and arginine are found elevated in the blood. The enzyme that is most likely deficient in this patient is:
- A.
Arginase
- B.
Carbamoyl-phosphate synthetase I
- C.
Arginosuccinate lyase
- D.
Ornithine transcarbamoylase
- E.
Arginosuccinate synthetase
Correct Answer
A. ArginaseExplanation
In this scenario, the infant is presenting with symptoms of hyperammonemia, which is an excess of ammonia in the blood. The elevated levels of glutamine, citrulline, and arginine in the blood suggest a urea cycle disorder. The urea cycle is responsible for converting ammonia into urea, which can be excreted by the body. Deficiency of the enzyme arginase, which is involved in the final step of the urea cycle, can lead to the accumulation of arginine and hyperammonemia. Therefore, arginase is the most likely enzyme deficient in this patient.Rate this question:
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- 19.
A newborn with acute encephalopathy is found to have hypoglycemia and ketonuria. Plasma leucine, isoleucine and valine are markedly elevated, but plasma ammonia is normal. This is most likely a case of:
- A.
Ornithine transcarbamoylase deficiency
- B.
Long-chain acyl-CoA dehydrogenase deficiency
- C.
Methylmalonic acidemia
- D.
Vitamin B12 deficiency
- E.
Maple syrup urine disease
Correct Answer
E. Maple syrup urine diseaseExplanation
Maple syrup urine disease (MSUD) is a rare genetic disorder characterized by the inability to break down the amino acids leucine, isoleucine, and valine. This results in the accumulation of these amino acids in the blood and urine, leading to the characteristic sweet-smelling urine. Symptoms of MSUD include encephalopathy, hypoglycemia, and ketonuria. In this case, the markedly elevated plasma levels of leucine, isoleucine, and valine, along with the presence of hypoglycemia and ketonuria, suggest a diagnosis of Maple syrup urine disease.Rate this question:
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- 20.
A nurse notices that the urine produced by a newborn infant has the odor of maple syrup. Which of the following pathways is most likely defective?
- A.
Metabolism of branched-chain amino acids
- B.
Metabolism of aromatic amino acids
- C.
Metabolism of sulfur-containing amino acids
- D.
Transformation of carbohydrates to amino acids
- E.
One-carbon transfer reactions
Correct Answer
A. Metabolism of branched-chain amino acidsExplanation
The correct answer is metabolism of branched-chain amino acids. The odor of maple syrup in urine is a characteristic symptom of maple syrup urine disease (MSUD), which is caused by a defect in the metabolism of branched-chain amino acids (leucine, isoleucine, and valine). In individuals with MSUD, these amino acids build up in the body, leading to a sweet-smelling urine. Defects in the metabolism of aromatic amino acids, sulfur-containing amino acids, transformation of carbohydrates to amino acids, or one-carbon transfer reactions would not result in the specific symptom of maple syrup odor in urine.Rate this question:
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- 21.
A 1-year-old child with mental retardation has a deficiency of dihydrobiopterin reductase. This enzyme deficiency leads to an increased blood level of:
- A.
Tyrosine
- B.
Methionine
- C.
Glucocerebroside
- D.
Glycine
- E.
Phenylalanine
Correct Answer
E. pHenylalanineExplanation
A deficiency of dihydrobiopterin reductase leads to an increased blood level of phenylalanine. Dihydrobiopterin reductase is an enzyme that is involved in the synthesis of tetrahydrobiopterin (BH4), which is required for the conversion of phenylalanine to tyrosine. Without sufficient BH4, phenylalanine cannot be converted to tyrosine, resulting in its accumulation in the blood. This can lead to a condition called phenylketonuria (PKU), characterized by intellectual disability and other neurological symptoms. Therefore, in a 1-year-old child with mental retardation and a deficiency of dihydrobiopterin reductase, an increased blood level of phenylalanine would be expected.Rate this question:
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- 22.
A.B. is transferred into the emergency room of a local hospital. Upon investigation high levels of glutamate:oxaloacetate transaminase (GOT) and glutamate:pyruvate transaminase (GPT) are found in his serum. His problems probably involve the following organ:
- A.
Heart
- B.
Brain
- C.
Liver
- D.
Muscle
- E.
Lungs
Correct Answer
C. LiverExplanation
High levels of glutamate:oxaloacetate transaminase (GOT) and glutamate:pyruvate transaminase (GPT) in the serum indicate liver damage. These enzymes are primarily found in the liver, and their elevated levels suggest liver dysfunction or injury. The liver is responsible for metabolizing and detoxifying various substances, including amino acids like glutamate. Therefore, the abnormal levels of these transaminases point to liver-related problems rather than issues with the heart, brain, muscle, or lungs.Rate this question:
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