A human red blood cell in an artery of the left arm is on its way to deliver oxygen to a cell in thumb. to travel from the arter
y in the arm to the left ventricle, this red blood cell must pass through:_________. a. one capillary beds
b. two capillary beds
c. three capillary beds
d. four capillary beds
e. five capillary beds
Our body contains miles of arteries and arterioles, yet these structures are nothing more than the vascular highways that provide a pathway for the blood. It's only when our blood reaches the tiny capillaries that nutrients and wastes can be exchanged. Capillaries are microscopic blood vessels that connect the arterioles with the venules. We'll discuss venules later in the lesson.
Capillaries are grouped together in capillary beds, which are simply a network of capillaries. Capillary beds are too small to see, but if you could see them, they would look like endless alleyways leading to virtually every tissue in our body. The rate of blood flow within a capillary bed is slow because there are so many different alleyways through which blood can travel. This slow speed limit, along with the very thin walls of the capillaries, means that capillary beds are an ideal place for the exchange of gases, nutrients, hormones, and wastes between the blood and tissue cells.
Hence, the right answer is option b "two capillary beds".
North America and Europe lie entirely north of the equator. Almost all of Asia, most of Africa, and a part of South America are above the equator. Not sure if South America counts as 'mostly' though. That's up to you.
