Conflicting bio examples

[baywatch123]

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So this is from Feralis' notes... and as I'm going through notes from bio destroyer and kaplan tests I found that some things overlap within the three germ layers... take respiratory for example, it is in both endoderm and mesoderm...

If we were to be tested on germ layers which one would be correct :S

a. Endoderm – epithelial lining of digestive & respiratory, parts of liver, pancreas, thyroid, and urinary bladder lining

b. Mesoderm – musculoskeletal, circulatory system, excretory system, gonads, connective tissue, portions of digestive & respiratory, notochord

c. Ectoderm – Nervous system (brain and spinal cord), integument (epidermis & hair / epithelium of nose, mouth, anal canal), sense structures (lens of eye, retina), teeth, neural tube

 

[KT Fletcher]

I noticed the conflicts you're talking about when I was studying too but I just figured that it meant not the ENTIRE respiratory was from the endoderm alone. I figure it's kind of like how the bones in general are derived from the mesoderm except the facial bones and teeth which are derived from the ectoderm (you should know this one, it was a germ layer favorite question throughout my practice). Or how technically my books say the respiratory TRACTS and lungs are the endoderm but the mesoderm includes PORTIONS of respiratory organs. In terms of other tissues that overlap I never saw a question about germ layers where it wasn't obvious. I'm sure test writers know that some structures overlap and wouldn't be so nitty gritty about the details so they stick with general structures. From my practices, what you have written here is more than sufficient to answer any of the types of questions you will see on the germ layers and I wouldn't get so wound up on the tight details if I were you. Though I will say, 9 times out of 10, if its involved in digestion I went with endoderm and I was never wrong when answered accordingly. The portions of it from the mesoderm I figure are not as important so I never saw it in question from destroyer nor kaplan.

 

[baywatch123]

ahh cool cool, thanks a lot