Ch. 19 The Cardiovascular System: Blood Vessels

Which statement does not accurately describe veins?

• (a) have less elastic tissue and smooth muscle than arteries

• (b) contain more fibrous tissue than arteries

• (c) most veins in the extremities have valves

• (d) always carry oxygenated blood

Answer explanation

Veins are included in both the systemic and the pulmonary circuit. The veins of the systemic circuit carry deoxygenated blood into the right heart and subsequently the lungs. The veins of the pulmonary circuit carry oxygenated blood into the left heart and subsequently the periphery.

Total peripheral resistance....

• (a) is inversely proportional to the length of the vascular bed

• (b) increases in anemia

• (c) decreases in polycythemia

• (d) is inversely related to the diameter of the arterioles

Answer explanation

As the diameter of the vessel increased, the TPR (total peripheral resistance) decreases. Resistance varies inversely with the fourth power of the vessel radius.

Ex: If the radius of the vessel doubles, the resistance drops to 1/16 of its original value.

Which of the following can lead to decreased venous return of blood to the heart?

• (a) an increase in blood volume

• (b) an increase in venous pressure

• (c) damage to the venous valves

• (d) increased muscular activity

Answer explanation

Venous return is the rate of blood flow to the heart. Venous valves prevent backward flow of blood. When your veins are damaged, the valves don't work properly, causing blood to flow backward and venous return decreases.

Arterial blood pressure increases in response to ...

• (a) increasing stroke volume

• (b) increasing heart rate

• (c) atherosclerosis

• (d) rising blood volume

• (e) all of these

Answer explanation

Increased stroke volume and increased blood volume increase blood pressure because a larger volume of blood is pumped into the arteries. Atherosclerosis reduces the elasticity of the arteries and their ability to stretch. This reduces their ability to adapt to the changes in blood volume and produces high BP. Increased heart rate also increases the volume of blood that is pumped into arteries.

Which of the following would not result in the dilation of the terminal arterioles and upstream arterioles in systemic capiallary beds?

• (a) a decrease in local tissue O₂ content

• (b) an increase in local tissue CO₂

• (c) a local increase in histamine

• (d) a local increase in pH

The structure of a capillary wall differs from that of a vein or an artery because ...

• (a) it has two tunics instead of three

• (b) there is less smooth muscle

• (c) it has a single tunic - only the tunica intima

• (d) none of these

Answer explanation

Capillary walls have a single tunica intima layer surrounded by a membrane.

The baroreceptors in the carotid sinus and aortic arch are sensitive to ...

• (a) a decrease in CO₂

• (b) changes in arterial pressure

• (c) a decrease in O₂

• (d) all of these

Answer explanation

Baroreceptors are mechanoreceptors, which means they respond to mechanical movement. The word root "baro-" comes form the Greek word baros which means "pressure or weight". These respond to changes in blood pressure.

The myocardium receives its blood supply directly from the ...

• (a) aorta

• (b) coronary arteries

• (c) coronary sinus

• (d) pulmonary arteries

Answer explanation

The myocardium is the muscular tissue of the heart. Like other issues in the body, the heart muscle needs oxygen-rich blood to function. Coronary arteries supply this blood.

Blood flow in the capillaries is steady despite the rhythmic pumping of the heart because of the …

• (a) elasticity of the large arteries

• (b) small diameter of capillaries

• (c) thin walls of the veins

• (d) venous valves

Answer explanation

Elastic arteries are those nearest the heart (aorta and pulmonary arteries) that contain much more elastic tissue in the tunica media than muscular arteries. This feature of the elastic arteries allows them to maintain a relatively constant pressure gradient despite the constant pumping action of the heart.

Which artery description matches the following: superior mesenteric, inferior mesenteric, celiac trunk?

• unpaired branch of abdominal aorta

• second branch of aortic arch

• branch of internal carotid

• branch of external carotid

• origin of femoral arteries

Answer explanation