WBR0138: Difference between revisions
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{{WBRQuestion | {{WBRQuestion | ||
|QuestionAuthor={{Rim}} | |QuestionAuthor={{Rim}} {{Alison}} | ||
|ExamType=USMLE Step 1 | |ExamType=USMLE Step 1 | ||
|MainCategory=Embryology | |MainCategory=Embryology | ||
Line 20: | Line 20: | ||
|MainCategory=Embryology | |MainCategory=Embryology | ||
|SubCategory=Neurology | |SubCategory=Neurology | ||
|Prompt=A 23-year-old male | |Prompt=A 23-year-old male is referred to a neurologist for evaluation of a progressively worsening vertigo and hearing loss that started almost 4 months ago. A brain MRI showed bilateral cerebello-pontine angle masses. Which of the following most likely is the embryological origin of the cells from which this patient’s masses arose? | ||
|Explanation=The patient presents with bilateral masses compressing [[CN VIII]] | |Explanation=The patient presents with bilateral masses, compressing [[CN VIII]], which results in hearing loss and [[vertigo]]. The bilateral nature of the masses, the age of the patient, and the involvement of the [[CN VIII]] are all characteristic of [[neurofibromatosis type II]]. Hence, the masses are more likely bilateral vestibular [[shwannoma]]. The embryological origin of shwannomas is the [[neural crest]]. | ||
|AnswerA=Mesoderm | |AnswerA=Mesoderm | ||
|AnswerAExp=The [[mesoderm]] gives rise to: | |AnswerAExp=The [[mesoderm]] gives rise to: | ||
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|AnswerB=Endoderm | |AnswerB=Endoderm | ||
|AnswerBExp=The [[endoderm]] gives rise to: | |AnswerBExp=The [[endoderm]] gives rise to: | ||
* GI: the entire alimentary canal except part of the mouth, [[pharynx]] | * GI: the entire alimentary canal except for part of the mouth, [[pharynx]], the terminal part of the rectum (which are lined by involutions of the ectoderm), and the lining cells of all the glands which open into the digestive tube, including those of the liver and pancreas. | ||
* Respiratory: the trachea, bronchi, and alveoli of the lungs | * Respiratory: the trachea, bronchi, and alveoli of the lungs | ||
* Endocrine: the lining of the follicles of the [[thyroid]] gland and [[thymus]] | * Endocrine: the lining of the follicles of the [[thyroid]] gland and [[thymus]] | ||
* Auditory system: epithelium of the auditory tube and tympanic cavity | * Auditory system: epithelium of the auditory tube and tympanic cavity | ||
* Urinary system: | * Urinary system: urinary bladder and part of the [[urethra]] | ||
|AnswerC=Surface ectoderm | |AnswerC=Surface ectoderm | ||
|AnswerCExp=The surface [[ectoderm]] gives rise to: | |AnswerCExp=The surface [[ectoderm]] gives rise to: | ||
* Skin (only [[epidermis]]; dermis is derived from mesoderm) | * Skin (only [[epidermis]]; dermis is derived from mesoderm), glands, hair, and nails | ||
* Epithelium of the mouth and nasal cavity salivary glands, and glands of mouth and nasal cavity | * Epithelium of the mouth and nasal cavity, salivary glands, and glands of mouth and nasal cavity | ||
* Tooth enamel ( | * Tooth enamel (although dentin and dental pulp are derived from ectoderm) | ||
* Epithelium of [[anterior pituitary]] | * Epithelium of the [[anterior pituitary]] | ||
* [[Lens]], [[cornea]], [[lacrimal gland]], tarsal glands and the conjunctiva of the eye | * [[Lens]], [[cornea]], [[lacrimal gland]], tarsal glands, and the conjunctiva of the eye | ||
* Apical ectodermal ridge inducing development of the limb buds of | * Apical ectodermal ridge-inducing development of the limb buds of an embryo | ||
* Sensory receptors in epidermis | * Sensory receptors in epidermis | ||
|AnswerD=Neuroectoderm | |AnswerD=Neuroectoderm | ||
|AnswerDExp=The [[neuroectoderm]] gives rise to: | |AnswerDExp=The [[neuroectoderm]] gives rise to: | ||
* [[Brain]] (rhombencephalon, mesencephalon and prosencephalon) | * [[Brain]] (rhombencephalon, mesencephalon, and prosencephalon) | ||
* [[Spinal cord]] and motor neurons | * [[Spinal cord]] and motor neurons | ||
* [[Retina]] | * [[Retina]] | ||
Line 59: | Line 59: | ||
* Dorsal root ganglia | * Dorsal root ganglia | ||
* Facial [[cartilage]] | * Facial [[cartilage]] | ||
* Spiral septum of developing [[heart]] | * Spiral septum of the developing [[heart]] | ||
* Ciliary body of the eye | * Ciliary body of the eye | ||
* Adrenal medulla | * Adrenal medulla | ||
|EducationalObjectives=The embryological origin of shwannomas | |EducationalObjectives= The neural crest is the embryological origin of shwannomas. | ||
|RightAnswer=E | |RightAnswer=E | ||
|WBRKeyword=Embryology, Neural crest, Schwannoma, Brain tumor, Cancer, Neurofibromatosis | |WBRKeyword=Embryology, Neural crest, Schwannoma, Brain tumor, Cancer, Neurofibromatosis | ||
|Approved= | |Approved=Yes | ||
}} | }} |
Revision as of 18:28, 9 July 2014
Author | [[PageAuthor::Rim Halaby, M.D. [1] (Reviewed by Alison Leibowitz)]] |
---|---|
Exam Type | ExamType::USMLE Step 1 |
Main Category | MainCategory::Embryology |
Sub Category | SubCategory::Neurology |
Prompt | [[Prompt::A 23-year-old male is referred to a neurologist for evaluation of a progressively worsening vertigo and hearing loss that started almost 4 months ago. A brain MRI showed bilateral cerebello-pontine angle masses. Which of the following most likely is the embryological origin of the cells from which this patient’s masses arose?]] |
Answer A | AnswerA::Mesoderm |
Answer A Explanation | [[AnswerAExp::The mesoderm gives rise to:
|
Answer B | AnswerB::Endoderm |
Answer B Explanation | [[AnswerBExp::The endoderm gives rise to:
|
Answer C | AnswerC::Surface ectoderm |
Answer C Explanation | [[AnswerCExp::The surface ectoderm gives rise to:
|
Answer D | AnswerD::Neuroectoderm |
Answer D Explanation | [[AnswerDExp::The neuroectoderm gives rise to:
|
Answer E | AnswerE::Neural crest |
Answer E Explanation | [[AnswerEExp::The neural crest gives rise to:
|
Right Answer | RightAnswer::E |
Explanation | [[Explanation::The patient presents with bilateral masses, compressing CN VIII, which results in hearing loss and vertigo. The bilateral nature of the masses, the age of the patient, and the involvement of the CN VIII are all characteristic of neurofibromatosis type II. Hence, the masses are more likely bilateral vestibular shwannoma. The embryological origin of shwannomas is the neural crest. Educational Objective: The neural crest is the embryological origin of shwannomas. |
Approved | Approved::Yes |
Keyword | WBRKeyword::Embryology, WBRKeyword::Neural crest, WBRKeyword::Schwannoma, WBRKeyword::Brain tumor, WBRKeyword::Cancer, WBRKeyword::Neurofibromatosis |
Linked Question | Linked:: |
Order in Linked Questions | LinkedOrder:: |