2.5 Structure & Function of Arteries, Capillaries & Veins

Question 1

How does blood circulate?

Answer 1

Blood circulates from the heart through the arteries to the capillaries then to
the veins and back to the heart.

Question 2

Blood Pressure

Answer 2

There is a decrease in blood pressure as blood moves away from the heart.

Question 3

The endothelium lining the central lumen of blood vessels…

Answer 3

is surrounded by layers of tissue (in arteries and veins).

Question 4

Structure of an Artery

Answer 4

Arteries have an outer layer of connective tissue containing elastic fibres and a middle layer containing smooth muscle with more elastic fibres.

Question 5

Elastic Walls of the Arteries

Answer 5

Stretch and recoil to accommodate the surge of blood after each contraction of the heart.

Question 6

Control of Blood Flow

Answer 6

To control blood flow, the smooth muscle surrounding arteries can contract
causing vasoconstriction (narrowing of blood vessels to slow or block blood flow) or relax causing vasodilation (widening of blood vessels to allow more blood flow and lowering blood pressure).

Question 7

Capillaries

Answer 7

Allow exchange of substances with tissues through their thin walls.

Question 8

Structure of Veins

Answer 8

Veins have an outer layer of connective tissue containing elastic fibres but a
much thinner muscular wall than arteries. They contain valves to prevent the backflow of blood.

Question 9

Tissue Fluid

Answer 9

The fluid between your capillaries and your cells. It supplies cells with glucose, oxygen and other substances. Carbon dioxide and other metabolic wastes
diffuse out of the cells and into the tissue fluid to be excreted.

Question 10

At the Artery End

Answer 10

Pressure filtration causes plasma to pass through capillary walls into the tissue fluid surrounding the cells.

Question 11

At the Vein End

Answer 11

Most of the tissue fluid returns to the blood.

Question 12

Tissue Fluid not Returned to Blood

Answer 12

Tissue fluid which does not return to the blood is absorbed by lymphatic vessels and returned as lymph to the circulatory system.

Question 13

Tissue Fluid and Blood Plasma

Answer 13

Tissue fluid and blood plasma are similar in composition, with the exception of
plasma proteins, which are too large to be filtered through the capillary walls.