Circulatory system 1/ Blood flow (Heart and circulatory system) 2/ Blood vessels 3/ Vasoconstriction and vasodilation

Circulatory system 1/ Blood flow (Heart and circulatory system)

Vena cava Pulmonary artery Pulmonary vein Aorta

Right atrium Right ventricleLeft ventricle Left atrium

Right Atrio-Ventricular valve AV valve Semi-lunar valves Left Atrio- Ventricular valve AV valve

Aorta Pulmonary vein Carotid artery Coronary artery Hepatic artery Renal artery Portal vein Renal vein Hepatic vein Vena cava Jugular vein Pulmonary artery

What is the function of arteries? Arteries take the blood Away from the heart, What is the function of veins? Veins have Valves What happens as the blood moves away from the heart? A decrease in blood pressure Why do we need a heart made of two pumps? One side restores blood pressure after the blood has passed in the tiny capillaries of the organ tissues. The other sides restores blood pressure after the blood has passed in the tiny capillaries of the lungs. What does oxygenated blood means? Blood which contains a higher concentration of oxygen than other tissues. What does deoxygenated blood means? Blood which contains a low concentration of oxygen.

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Circulatory system 1/ Blood flow (Heart and circulatory system) 2/ Blood vessels

Outer layer of connective tissue containing elastic fibres Thick layer of smooth muscles and elastic fibres Thin layer of smooth muscles and elastic fibres Outer layer of connective tissue containing elastic fibres Endothelium:

Arteries carry blood away from the heart Arteries have an outer layer of connective tissue containing elastic fibres and a middle layer containing 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. The smooth muscle in the walls of arterioles (small arteries) can contract or relax causing vasoconstriction or vasodilation to control blood flow. During strenuous exercise arterioles leading to working muscles vasodilate increasing blood flow. At the same time arterioles leading to abdominal organs vasocontract reducing blood flow. Veins carry the blood towards the heart. Veins have an outer layer of connective tissue containing elastic fibres. They have a much thinner muscular wall than arteries. Blood flows along veins at lower pressure than arteries. The lumen of a vein is wider than that of an artery. Valves are present in veins to prevent the back flow of blood. Capillaries merge together to form venules which again merge to form veins which carry the blood back to the heart. Capillaries form a dense network, they allow exchange of substances with tissues. They are only one cell thick so they allow quick and efficient exchange of materials. Arteries function? Arteries structure? Function of elastic fibres ? What is the effect of contraction or relaxation of smooth muscles in the walls of the arterioles? How do arterioles react to strenuous exercise? Function of veins? Structure of veins? How is a vein’s muscular wall compared to that of arteries? How is blood pressure in veins compared to arteries? How is the lumen of veins compared to arteries? What structure feature of veins is missing in arteries? What is its function? What are venules? Function of capillaries? Structure of capillaries and how It helps its function?

Circulatory system 1/ Blood flow (Heart and circulatory system) 2/ Blood vessels 3/ Vasoconstriction and vasodilation

What is vasodilation and vasoconstriction? The smooth muscle in the walls of arterioles (small arteries) can contract or relax causing vasoconstriction or vasodilation. What is the purpose of vasodilation and vasoconstriction? This process allows the control of blood flow to follow changing demands of the body’s tissues to be met.

Give 2 examples of circumstances during which vasoconstriction and vasodilation take place and describe the pattern of dilation and contractions. During exercise Regulate body temperature

During exercise, how is the blood flow changed by vasodilation and vasoconstriction? – During strenuous exercise arterioles leading to working muscles vasodilate increasing blood flow. – At the same time arterioles leading to abdominal organs vasocontract reducing blood flow. To regulate body temperature, how is the blood flow changed by vasodilation and vasoconstriction? – When we are too hot, blood vessels supplying blood to the skin can swell or dilate (vasodilation). This allows more warm blood to flow near the surface of the skin, where the heat can be lost to the air. – When we are too cold the blood vessels supplying warm blood to the skin become narrow or constrict (vasoconstriction). This reduces the flow of warm blood near the surface of the skin, and reduces heat loss. – A very common mistake in exams is to write that the blood vessels move up and down in the skin. The blood vessels do not move during vasodilation and vasoconstriction.