Structure of arteries veins and capilaries

Question 1

describe blood circulation from the heart

Answer 1

Blood circulates from the heart through arteries to the capillaries then to the veins and back to the heart. There is a decrease in pressure as blood moves away from the heart.

Question 2

describe arteries

Answer 2

Arteries have an outer layer of connective tissue containing elastic fibres and a middle layer of smooth muscle with more elastic fibres. The elastic walls of the arteries stretch and recoil to accommodate the surge of blood after each contraction of the heart.

Question 3

describe how smooth muscle controls blood flow

Answer 3

The smooth muscle surrounding arteries can contract causing vasoconstriction and can relax causing vasodilation. This controls blood flowing within the arteries.

Question 4

describe capillaries

Answer 4

Capillaries form dense networks around body tissues and have very thin walls to allow efficient exchange of materials.

Question 5

describe veins

Answer 5

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 6

describe pressure filtration

Answer 6

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

Tissue fluid 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. Much of the tissue fluid returns to the blood.

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.

Excess tissue fluid is absorbed by lymphatic vessels and return it as lymph to the circulatory system.