11) Why do new red blood cells survive for only a few months?

A) The heart pumps red blood cells so often that their membranes deteriorate.

B) The oxygen that red blood cells carry damages their organelles.

C) Red blood cells do not have most organelles or a nucleus.

D) The hemoglobin that red blood cells carry is toxic.

12) Which of the following best describes High-Density Lipoproteins (HDLs)?

A) HDLs are transport proteins that carry lipids from tissues to the liver.

B) HDLs are transport proteins that carry lipids from the liver to tissues.

C) HDLs are large versions of the cholesterol molecule.

D) HDLs are critical components to the oxygen-carrying ability of red blood cells.

13) Which of the following is true of the relationship of red blood cells to the other formed elements?

A) Red blood cells make up about half of the formed elements.

B) Red blood cells make up over 99 percent of the formed elements.

C) Red blood cells are the only formed element not made in bone marrow.

D) Red blood cells are the most important formed element involved in blood clotting.

E) Red blood cells are the only formed element without a plasma membrane.

14) Which of the following best describes fibrinogen?

A) Fibrinogen is the connective tissue in the wall of an artery.

B) Fibrinogen is the protein portion of the hemoglobin molecule.

C) Fibrinogen is a transport lipoprotein that carries cholesterol.

D) Fibrinogen is a lipid found in platelets.

E) Fibrinogen is a plasma protein involved in clotting.

15) Which vessels are structurally suited for the central purpose of allowing substances to pass in and out of them through their entire lengths?

A) arterioles

B) veins

C) arteries

D) capillaries

E) semilunar valves

16) Veins always carry blood:

A) toward the heart.

B) toward the capillaries.

C) away from the lungs.

D) away from the heart.

17) People with high blood pressure often take medication to lower blood pressure. Some of these medications might do this by:

A) increasing the blood volume.

B) relaxing the smooth muscles in the arteries.

C) opening the valves in the veins.

D) increasing the number of platelets in the blood.

18) The outer layer of an artery or vein is composed of:

A) epithelium.

B) smooth muscle.

C) connective tissue.

D) cartilage.

19) What happens when the diameter of an artery decreases?

A) Its semilunar valves open.

B) Its epithelial cells stretch.

C) The heart rate decreases.

D) The blood pressure decreases.

E) The blood pressure increases.

20) Blood flow from the heart, to the lungs, and back to the heart is known as the:

A) pericardial circulation.

B) pulmonary circulation.

C) coronary circulation.

D) systemic circulation.