BLOOD VESSELS BLOOD VESSELS Arteries take blood away

BLOOD VESSELS

BLOOD VESSELS Arteries take blood away from the heart.

BLOOD VESSELS Arteries take blood away from the heart. Artery walls are thickened with connective tissue to withstand blood pressure, yet elastic enough to expand contract to even out pressure from each heart beat.

BLOOD VESSELS Arteries take blood away from the heart. Artery walls are thickened with connective tissue to withstand blood pressure, yet elastic enough to expand contract to even out pressure from each heart beat. When arteries lose their elasticity (eg. Because of poor diet, or from disease) high blood pressure develops, which puts strain on the heart, affects kidneys and can even cause arteries to burst.

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BLOOD VESSELS Arteries divide into smaller vessels called arterioles, which supply blood to capillaries.

BLOOD VESSELS Arteries divide into smaller vessels called arterioles, which supply blood to capillaries. Capillaries are the smallest blood vessels; their walls are only one cell thick, allowing rapid exchange of materials between the blood and individual cells.

BLOOD VESSELS Arteries divide into smaller vessels called arterioles, which supply blood to capillaries. Capillaries are the smallest blood vessels; their walls are only one cell thick, allowing rapid exchange of materials between the blood and individual cells. Blood enters capillaries under pressure, forcing fluid and useful materials out of capillaries to surrounding cells.

BLOOD VESSELS Arteries divide into smaller vessels called arterioles, which supply blood to capillaries. Capillaries are the smallest blood vessels; their walls are only one cell thick, allowing rapid exchange of materials between the blood and individual cells. Blood enters capillaries under pressure, forcing fluid and useful materials out of capillaries to surrounding cells. Fluid containing waste products or cell secretions is drawn into the venule end of a capillary by osmosis and diffusion.

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VEINS The reduction in the volume of blood fluid, and friction between blood cells and capillary walls, causes blood pressure to drop, so that blood flowing through veins is of very low pressure.

VEINS The reduction in the volume of blood fluid, and friction between blood cells and capillary walls, causes blood pressure to drop, so that blood flowing through veins is of very low pressure. Veins carry blood back to the heart – they have thinner walls than arteries.

VEINS The reduction in the volume of blood fluid, and friction between blood cells and capillary walls, causes blood pressure to drop, so that blood flowing through veins is of very low pressure. Veins carry blood back to the heart – they have thinner walls than arteries. The lumen (in picture) of a vein is wider than that of an artery – valves are present in veins.

VEINS The reduction in the volume of blood fluid, and friction between blood cells and capillary walls, causes blood pressure to drop, so that blood flowing through veins is of very low pressure. Veins carry blood back to the heart – they have thinner walls than arteries. The lumen (in picture) of a vein is wider than that of an artery – valves are present in veins.

VEINS The reduction in the volume of blood fluid, and friction between blood cells and capillary walls, causes blood pressure to drop, so that blood flowing through veins is of very low pressure. Veins carry blood back to the heart – they have thinner walls than arteries. The lumen (in picture) of a vein is wider than that of an artery – valves are present in veins. Blood moves through veins towards the heart by: - The squeezing of muscles against the walls of veins

VEINS The reduction in the volume of blood fluid, and friction between blood cells and capillary walls, causes blood pressure to drop, so that blood flowing through veins is of very low pressure. Veins carry blood back to the heart – they have thinner walls than arteries. The lumen (in picture) of a vein is wider than that of an artery – valves are present in veins. Blood moves through veins towards the heart by: - The squeezing of muscles against the walls of veins - Gravity - Pressure in the chest cavity during inspiration ‘pulling’ blood into the heart.

VEINS The reduction in the volume of blood fluid, and friction between blood cells and capillary walls, causes blood pressure to drop, so that blood flowing through veins is of very low pressure. Veins carry blood back to the heart – they have thinner walls than arteries. The lumen (in picture) of a vein is wider than that of an artery – valves are present in veins. Blood moves through veins towards the heart by: - The squeezing of muscles against the walls of veins - Gravity - Pressure in the chest cavity during inspiration ‘pulling’ blood into the heart. - Some (very low) blood pressure helping push blood through the veins.