In which of the following vessels does the vital exchange take place and also has the thinnest walls through which oxygen, nutrients, and wastes can pass?
A. Capillaries
B. Microvenules
C. Arterioles
D. Veins
A, capillaries. They are the thinnest of the vessels, being only one cell thick. For reference, they are 5-10 μm thick while micro venules are 12-35 μm thick. The exchange takes place in the capillary bed.
