Fill in the Blanks Fill in the Blanks: Blood Circulation and VesselsOnline version Learn about the blood circulation system and the different types of blood vessels in this Fill in the Blanks game. by Claire Rafferty 1 smooth artery vasodilation oxygen smooth stretch pressure metabolic vasoconstriction arteries high valves amino recoil glucose thin veins heart tissue fluid endothelium middle endothelium cells diameter thinner exchange of substances decreases smooth muscle carbon dioxide increases proteins The blood circulation carries blood from the , through to the tissues , and back through to the heart . Blood pressure with distance from the heart . All blood vessels have a central lumen lined by the . Compared to veins , arteries have thicker muscular walls . The outer layer of artery walls is made of connective tissue with elastic fibres . The middle layer of artery walls contains and elastic fibres . The contractions of the heart create surges of blood under . The elastic fibres in the artery walls allow them to and as these surges of blood pass . Contraction of the muscle in the layer of the artery wall reduces the of the lumen of the artery ; this is called . Vasoconstriction reduces the flow of blood into capillary beds . Relaxation of the smooth muscle of the middle layer of the wall causes the opposite effect ; this is called . Vasodilation the diameter of the lumen . Capillaries allow with the tissues . The wall of the capillary is very , consisting of a layer of and a surrounding layer of connective tissue . Compared to arteries , veins have walls with much less muscle . Veins contain which ensure blood only flows in one direction , back to the heart . In most capillaries , the escaping fluid consists of water with a variety of dissolved substances including , , hormones , acids and mineral ions . This escaping fluid becomes . Tissue fluid is similar to blood plasma but does not contain plasma . Tissue fluid returning to the capillaries carries with it and wastes for excretion . Lymph is returned to the veins near the heart .
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