<p>Hey, guys! I have 3 questions in the Cliffnotes exercises on the Animal Form and Function chapter. It's page 203 onwards if anybody is interested. </p>
<p>2) All of the following are examples of countercurrent exchange EXCEPT:</p>
<p>A. movement of blood through the legs of wading birds
B. movement of blood through the fins and tails of marine animals
C. the loop of Henle in the nephron
D. gas exchange in fish gills
E. gas exchange in human lungs</p>
<ul>
<li>The answer is E. I understand that extremities in animals like a moose or bird that stands on icy places would have countercurrent exchange in those places in order to keep the area warm. I also understand that fish use countercurrent exchange, because since water has much less oxygen than air, they need a very efficient system for oxygen/carbon dioxide transport. But why wouldn't a moose's lung for example have countercurrent exchange as well? I keep thinking about this and find no reason why it could be bad. </li>
</ul>
<p>9) In some areas of the human circulatory system, arteries branch into capillaries, merge into veins, then branch into capillaries a second time, before merging again into veins and returning to the heart. All of the following organs are found in such double capillary bed circuits EXCEPT:</p>
<p>A. the anterior pituitary gland
B. the glomerulus
C. the hypothalamus
D. the liver
E. the lungs</p>
<ul>
<li>The answer is E, and I have no idea why.</li>
</ul>
<p>18) Which of the following would be activated first
in response to a body cell that has been invaded by
a virus?</p>
<p>A. Cytotoxic T cells
B. Natural killer cells
C. Antibodies
D. Macrophages
E. Neutrophils</p>
<ul>
<li>The answer is A. I did this correct because since the question stated the word "activated," it would have to be either a B cell or a T cell and other leukocyts were nonspecific, then A was the only fit. The explanations in the book made no sense though: "As part of the cell-mediated immune response, cytotoxic T cells would attack the abnormal body cell first. Once the abnormal cell is lysed, nonspecific attacks by macrophages and other phagocytes would occur." I didn't read anything about order, though. </li>
</ul>
<p>Thanks in advance! :)</p>