usmlebuzz
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Primordial germ cells that do not migrate to the proper place give rise to
A. mesotheliomas
B. normal but ectopic gonads
C. teratomas
D. streak gonads
E. hypospadias
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| rajeev
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hmmmm ... is it .. B ... normal but ectopic gonads ??
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| Yulia
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I think it's teratomas. Mesotheliomas and hypospadias are out of question... don't think ectopic gonads... streak gonads - sign of gonadal dysgenesis, germ cells are there initially, but die soon with inadequate support. I suppose teratomas could arise from germ cells "left behind" during migration.
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| rajeev
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hmmm, i thought of that one too .. the thing is .. with teratoma i was looking for 'totipotential cells '
in the Qn .. primordial germ cells migrate to the undifferentiated gonad at week 4 .. nothing else in the vignette to suggest any abnormality besides the delay .. 
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| aysha
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i think its " c"
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| Meghna
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it is C - teratomas. I just listened to it in Goljan audio.
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| usmlebuzz
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my source of question says
b.............. maybe because they are refering to germ cells :roll:
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| lionel
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B .....is it?
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| ManuNastai
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B
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| Ujk
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C
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| Jackofknives
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D is the best answer, C is the second best answer.
Explanation for D
In the sixth week of development primitive gonads must invade the genital ridges, if they fail to reach the ridges, the gonads do not develop. Hence, the primordial germ cells have an inductive influence on the development of the gonad into ovary or testis.
Thus failure of migration will result in hypogonadism, one form of it is streak gonades, which is NON functional.
B cannot be right due to the above explaination.
Explanation for C
Well nothing much to explain, it is documented that germ cells that do not migrate sucessfully to the gonadal ridges instead of becoming innate could also result in teratoma, but this is relative rarer in comparison to that derived from the remnants of the primitive streak during gastrulation.
Edited by Jackofknives on 05/04/07 - 01:41 PM
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| hedieh
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I also think D is the best answer.
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| doc179
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me too  ..D
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| virgola82
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C that's why teratomas are commonly found in the midline regions and mostly in the head
It's not D because it doesn't ask "What happen if migration completely fails" but rather asks "What happen if there are some cells among all that do not migrate?"
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| Jackofknives
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OK, this is from the 10th edition of Langman's embryo, more detailed than Kaplan and HY, almost as detailed as Gray's. I quote it word by word,
Langman's Embryology, 10th edition (newest), P353
"Teratoma - tumor containing derivatives from all three germ layers. They may arise from remnants of the primitive streak or fom germ cells that do not migrate successfully to the gonadal ridges. The most common ones are caudal teratomas arising in the buttocks region." AKA from primitive streak, it is so very very rare that primordial germ cells migrating too far and past the ridges to the caudal region.
It's almost a fact that if primordial germ cells don't migrate to the ridges, they become innate, hence the finding of streak gonades. I brought up hypogonadism to explain how I do not agree with option B.
Bottom line is, streak gonades is almost a guaranteed finding, teratoma is a rare finding.
Edited by Jackofknives on 05/10/07 - 06:54 AM
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| po
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was going for B,but now if I think undescended gonads are hyalinised and non functional and more appropriate for failure to migrate would be undescended than ectopic;I think there is some diff. betn 2.
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