Viraj's Weblog

So I just had a 2nd Anatomy exam and am fairly sure I got an A on it. I studied so many diagrams that were not even on the test. The only thing they put was a pelvis and baby skull, and we had to know all of the parts. There were 2 questions that got me a bit. One was similar to:

What are bones made of?
A. water, proteins, and calcium salts
B. hydroxyapatite
C. All of the above

It had to be either B or C, because I know that proteins, calcium salts, and hydroxyapatite are all part of bones. But the water part got to me. When I see such questions I think they are trick questions, and there are many compounds with water that are not liquid. Alas I picked B which I think is correct.

Usually when I take tests I also look for clues in one question that may help another. For example here was one:

From what are the skull bones formed?

A. endochondral tissue
B. dermal tissue
C. cartilage

Now I didn't have a good idea what endochondral tissue was, but then I thought about the etymology. endo of course means within. Chondro I knew had something to do with cartilage, because there are cells like chondrocytes, chondroblasts, and chondroclasts that all have to do with cartilage formation. So endochondral means within cartilage, and so neither A or C could be the answer. It had to be B. This then helped me with another question similar to:

Dermal tissue forms from neural crest cells. What are other aspects of dermal tissue?

A. also known as endochondral
B. used for bone replacement
C. preceded by a template of cartilage
D. not preceded by a template of cartilage
E. all of the above

Of course E is ruled out because C and D contradict each other (this professor likes to do that alot which is helpful). From previous questions I knew that endochondral is equivalent to cartilage, so it could not be A or C. So the only choices left were B and D. From the previous question I determined skull bones are formed from dermal tissue, so that hinted this was not used for bone replacement. I also knew a bit about fracture healing, and it involves cartilage. So the answer had to be D. Also 'neural crest' hints towards the skull question above.

So throughout the test, I am sort of learning things for other questions, and going back and forth. I know at this point that dermal tissue forms without cartilage and is the basis for the skull. Then I come across this question:

Which of the following bones form from dermal tissue?

A. clavicle
B. femur
C. humerus
D. all of the above

I can infer from previous questions that the limb bones definitely do not form from dermal tissue, because I know that a fracture of a limb involves cartilage formation. The only possible choice was the clavicle, which makes sense. The clavicle is a very weak bone and the whole pectoral girdle is very movable, so I imagined it forming within soft tissues.

Other than that the rest of the 54 questions were pretty painless.