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{{WBRQuestion
{{WBRQuestion
|QuestionAuthor={{Rim}}
|QuestionAuthor={{Rim}}, {{AJL}} {{Alison}}
|ExamType=USMLE Step 1
|ExamType=USMLE Step 1
|MainCategory=Physiology
|MainCategory=Physiology
Line 20: Line 20:
|MainCategory=Physiology
|MainCategory=Physiology
|SubCategory=Renal
|SubCategory=Renal
|Prompt=A researcher is studying the fate of bile salts following release into the gastrointestinal tract. At the level of the kidney, the researcher notes that after filtration, the amount of bile salts within one of the nephron segments increases rapidly.  According to the image below, which of the following nephron segments is responsible for the secretion of bile salts?
|Prompt=A researcher, studying the fate of bile salts following release into the gastrointestinal tract, notes that after filtration, at the level of the kidney, the amount of bile salts within one of the nephron segments increases rapidly.  Based on the image below, which of the following nephron segments is most likely responsible for the secretion of bile salts?


[[Image:Nephron.jpg|400px]]
[[Image:Nephron.jpg|400px]]
|Explanation=The [[proximal tubule]] is the most important nephron segment responsible for secretion of organic acids and bases.  As such, [[bile salts]], [[oxalate]], [[urate]], and [[catecholamines]] are all secreted mainly in the proximal tubule. Both filtration and secretion of these compounds play an important role in their renal excretion.
|Explanation=The [[proximal tubule]], the nephron segment responsible for secretion of organic acids and bases, secretes [[bile salts]], [[oxalate]], [[urate]], and [[catecholamines]]. Both filtration and secretion of these compounds play an important role in their renal excretion.
   
   
The proximal tubule is considered a site of major metabolic activity with numerous mitochondria to serve its metabolic function.
The [[proximal tubule]] is a site of major metabolic activity with numerous mitochondria.
 
|EducationalObjectives= The [[proximal tubule]], the nephron segment responsible for secretion of organic acids and bases, secretes [[bile salts]], [[oxalate]], [[urate]], and [[catecholamines]].
|References= First Aid 2014 page 221


Educational Objective:
The proximal tubule of the nephron is the most important segment for secretion of bile salts, oxalate, urate, and catecholamines.
|AnswerA=A
|AnswerA=A
|AnswerAExp=The proximal tubule of the nephron is the most important segment for secretion of bile salts.
|AnswerAExp=See explanation.
|AnswerB=B
|AnswerB=B
|AnswerBExp=Thin descending segment of loop of Henle is not the major site of bile salt secretion.  The thin descending loop of Henle has thin epithelial membranes that lacks brush borders.  Because it is considered a segment with minimal metabolic activity, few mitochondria are located in this site of nephron.
|AnswerBExp=The thin descending segment of [[loop of Henle]], with thin epithelial membranes lacking brush borders, is not the major site of bile salt secretion.  Because few mitochondria are located in this site of nephron, it is considered a segment with minimal metabolic activity.
|AnswerC=C
|AnswerC=C
|AnswerCExp=Thick ascending loop of Henle is not the major site of bile salt secretion. It has thick epithelial cells with high metabolic activity.  Reabsorption of major ions, such as sodium, potassium, and chloride, occurs at the level of thick ascending loop of Henle.
|AnswerCExp=The thick ascending [[loop of Henle]], which has thick epithelial cells with high metabolic activity, is not the major site of bile salt secretion. The reabsorption of crucial ions, such as sodium, potassium, and chloride, occurs at the thick ascending loop of Henle.
|AnswerD=D
|AnswerD=D
|AnswerDExp=The distal tubule is not the major site of bile salt secretion.  Its first part forms the macula densa, a part of the juxtaglomerular complex. The convoluted part of the distal tubules has reabsorptive capacity similar to that of the thick ascending loop of Henle.  The distal part of the distal tubules has similar functional characteristics as that of cortical collecting tubule.
|AnswerDExp=The distal tubule, with a  reabsorptive capacity similar to that of the thick ascending loop of Henle, is not the major site of bile salt secretion.  The functional characteristics resemble those of the cortical collecting tubule.
|AnswerE=E
|AnswerE=E
|AnswerEExp=The collecting duct is not the major site of bile salt secretion.  Collecting tubules contain principal cells and intercalated cells.
|AnswerEExp=The collecting duct is not the major site of bile salt secretion.  Collecting tubules contain principal cells and intercalated cells.
|RightAnswer=A
|RightAnswer=A
|Approved=No
|WBRKeyword= loop of Henle, kidney, bile salts, proximal tubule, nephron, secretion, metabolic
|Approved=Yes
}}
}}

Revision as of 13:07, 21 July 2014
Author [[PageAuthor::Rim Halaby, M.D. [1], Alison Leibowitz [2] (Reviewed by Alison Leibowitz)]]
Exam Type ExamType::USMLE Step 1
Main Category MainCategory::Physiology
Sub Category SubCategory::Renal
Prompt [[Prompt::A researcher, studying the fate of bile salts following release into the gastrointestinal tract, notes that after filtration, at the level of the kidney, the amount of bile salts within one of the nephron segments increases rapidly. Based on the image below, which of the following nephron segments is most likely responsible for the secretion of bile salts?

]]

Answer A AnswerA::A
Answer A Explanation AnswerAExp::See explanation.
Answer B AnswerB::B
Answer B Explanation [[AnswerBExp::The thin descending segment of loop of Henle, with thin epithelial membranes lacking brush borders, is not the major site of bile salt secretion. Because few mitochondria are located in this site of nephron, it is considered a segment with minimal metabolic activity.]]
Answer C AnswerC::C
Answer C Explanation [[AnswerCExp::The thick ascending loop of Henle, which has thick epithelial cells with high metabolic activity, is not the major site of bile salt secretion. The reabsorption of crucial ions, such as sodium, potassium, and chloride, occurs at the thick ascending loop of Henle.]]
Answer D AnswerD::D
Answer D Explanation AnswerDExp::The distal tubule, with a reabsorptive capacity similar to that of the thick ascending loop of Henle, is not the major site of bile salt secretion. The functional characteristics resemble those of the cortical collecting tubule.
Answer E AnswerE::E
Answer E Explanation AnswerEExp::The collecting duct is not the major site of bile salt secretion. Collecting tubules contain principal cells and intercalated cells.
Right Answer RightAnswer::A
Explanation [[Explanation::The proximal tubule, the nephron segment responsible for secretion of organic acids and bases, secretes bile salts, oxalate, urate, and catecholamines. Both filtration and secretion of these compounds play an important role in their renal excretion.

The proximal tubule is a site of major metabolic activity with numerous mitochondria.
Educational Objective: The proximal tubule, the nephron segment responsible for secretion of organic acids and bases, secretes bile salts, oxalate, urate, and catecholamines.
References: First Aid 2014 page 221]]

Approved Approved::Yes
Keyword WBRKeyword::loop of Henle, WBRKeyword::kidney, WBRKeyword::bile salts, WBRKeyword::proximal tubule, WBRKeyword::nephron, WBRKeyword::secretion, WBRKeyword::metabolic
Linked Question Linked::
Order in Linked Questions LinkedOrder::
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