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|SubCategory=Neurology | |SubCategory=Neurology | ||
|Prompt=A 23-year-old male was referred to a neurologist for the evaluation of progressive worsening vertigo and hearing loss that have started almost 4 months ago. Brain MRI showed bilateral cerebello-pontine angle masses. What is the embryological origin of the cells from which this patient’s masses arised? | |Prompt=A 23-year-old male was referred to a neurologist for the evaluation of progressive worsening vertigo and hearing loss that have started almost 4 months ago. Brain MRI showed bilateral cerebello-pontine angle masses. What is the embryological origin of the cells from which this patient’s masses arised? | ||
|Explanation=The patient presents with bilateral masses compressing CN VIII and causing hearing symptoms and vertigo. The bilateral nature of the masses, the age of the patient and the involvement of the CN VIII suggest a diagnosis of neurofibromatosis type II. Hence, the masses are more likely bilateral vestibular shwannoma. The embryological origin of shwannomas is the neural crest. | |Explanation=The patient presents with bilateral masses compressing [[CN VIII]] and causing hearing symptoms and [[vertigo]]]. The bilateral nature of the masses, the age of the patient and the involvement of the CN VIII suggest a diagnosis 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 embryological origin of shwannomas is the neural crest. | |||
|AnswerA=Mesoderm | |AnswerA=Mesoderm | ||
|AnswerAExp=The mesoderm forms the mesenchyme (connective tissue), mesothelium, non-epithelial blood cells and coelomocytes. Mesothelium | |AnswerAExp=The [[mesoderm]] forms the [[mesenchyme]] (connective tissue), [[mesothelium]], non-epithelial blood cells and coelomocytes. Mesothelium forms the [[muscles]] in a process known as myogenesis, septa (cross-wise partitions) and mesenteries (length-wise partitions); and forms part of the [[gonads]] (the rest being the gametes). | ||
|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 and the terminal part of the rectum (which are lined by involutions of the ectoderm), the lining cells of all the glands which open into the digestive tube, including those of the liver and pancreas | * GI: the entire alimentary canal except part of the mouth, [[pharynx]] and the terminal part of the rectum (which are lined by involutions of the ectoderm), 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 | ||
* Urinary system: Urinary bladder and part of the urethra | * 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) (along with glands, hair, and nails) | * Skin (only [[epidermis]]; dermis is derived from mesoderm) (along with 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 (as a side note, dentin and dental pulp are formed from ectomesenchyme which is derived from ectoderm (specifically neural crest cells and travels with mesenchmyal cells) | * Tooth enamel (as a side note, dentin and dental pulp are formed from ectomesenchyme which is derived from ectoderm (specifically neural crest cells and travels with mesenchmyal cells) | ||
* Epithelium of anterior pituitary | * Epithelium of [[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 the embryo. | * Apical ectodermal ridge inducing development of the limb buds of the 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]] | ||
* Posterior pituitary | * [[Posterior pituitary]] | ||
|AnswerE=Neural crest | |AnswerE=Neural crest | ||
|AnswerEExp=The neural crest gives rise to: | |AnswerEExp=The [[neural crest]] gives rise to: | ||
* Pigment cells in the skin | * Pigment cells in the [[skin]] | ||
* Ganglia of the autonomic nervous system | * Ganglia of the [[autonomic nervous system]] | ||
* Dorsal root ganglia | * Dorsal root ganglia | ||
* Facial cartilage | * Facial [[cartilage]] | ||
* Spiral septum of developing heart | * Spiral septum of developing [[heart]] | ||
* Ciliary body of the eye | * Ciliary body of the eye | ||
* Adrenal medulla | * Adrenal medulla | ||
|RightAnswer=E | |RightAnswer=E | ||
|Approved=No | |Approved=No | ||
}} | }} |
Revision as of 00:49, 27 August 2013
Author | [[PageAuthor::Rim Halaby, M.D. [1]]] |
---|---|
Exam Type | ExamType::USMLE Step 1 |
Main Category | MainCategory::Embryology |
Sub Category | SubCategory::Neurology |
Prompt | [[Prompt::A 23-year-old male was referred to a neurologist for the evaluation of progressive worsening vertigo and hearing loss that have started almost 4 months ago. Brain MRI showed bilateral cerebello-pontine angle masses. What is the embryological origin of the cells from which this patient’s masses arised?]] |
Answer A | AnswerA::Mesoderm |
Answer A Explanation | [[AnswerAExp::The mesoderm forms the mesenchyme (connective tissue), mesothelium, non-epithelial blood cells and coelomocytes. Mesothelium forms the muscles in a process known as myogenesis, septa (cross-wise partitions) and mesenteries (length-wise partitions); and forms part of the gonads (the rest being the gametes).]] |
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 and causing hearing symptoms and vertigo]. The bilateral nature of the masses, the age of the patient and the involvement of the CN VIII suggest a diagnosis 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 embryological origin of shwannomas is the neural crest. |
Approved | Approved::No |
Keyword | |
Linked Question | Linked:: |
Order in Linked Questions | LinkedOrder:: |