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Circulatory System: How the blood from the heart is circulated throughout the body. General blood flow through the body after it leaves the heart follows a mapping system. From the heart → it flow... s through arteries → capillaries and comes back to the heart via the veins. BLOOD VESSELS IN THE CIRCULATORY SYSTEM Arteries: Referred to as Efferent Blood Vessels in the circulatory system. → They always carry blood away from the heart. → Typically carry oxygenated blood. (except in the pulmonary artery) 1.) Conducting arteries: Very large arteries typically exit from the heart. → They have the need/ability to expand when the heart beats so they withstand the splurge. So, with every heartbeat, blood surges out of the heart into these large vessels. ∆ To do this, they must have a layer of elastic tissue that gives it the ability to stretch and recoil when the heart is relaxing. [EXAMPLE]: Aorta & Pulmonary Trunk Atherosclerosis: When arteries age and stiffen because plaque builds up in the arteries, they lose that elasticity and the ability to stretch when blood surges into them. ∆ It results in an increase in pressure in those vessels which can lead to an aneurysm. Aneurysm: A weak point in an artery and with each heartbeat, that little thin walled area will pulsate and it can further and further weaken and eventually rupture which can lead to death or stroke. 2.) Distributing arteries or Medium or Muscular Arteries: They are direct branches from the conducting arteries with a very thick muscular wall (up to 40 layers of smooth muscle). ∆ The muscular wall in a distributing artery makes up 75% of the arterial wall itself. [EXAMPLE] : Brachial artery, Femoral artery (named for the area where they are distributing their blood). 3.) Resistance A rteries or Small Arteries: Too many to name 4.) Metarterioles: Very short vessels that will link the arteriole system to the capillaries. AFTER BLOOD FLOWS THROUGH THE ARTERIAL SYSTEM, IT THEN FLOWS INTO A SERIES OF CAPILLARY BEDS. 5.) Capillaries: Known as the exchange vessels because they have very thin walls that exchange oxygen, glucose, and other nutrients in the body. → They connect the smallest arteries to the smallest veins. Veins: Afferent blood vessels because they bring blood back to the heart, they typically carry deoxygenated blood (except the pulmonary vein). → They are called Capacitance Vessels because they typically control a large amount of volume. → Can stretch more easily than arteries and have thin, flaccid walls and can therefore accommodate a larger volume of blood. Comparing Arteries to Veins: ∆ In a resting person, about 11% of the blood is found in the Arteries while 54% is found in the Veins. ∆ Veins are subject to much lower blood pressure because they are further away from the heart. Because of that, they can have thinner walls compared to the arteries that need more muscular support. ∆ In the Arteriole System, we go from large to small vessels and the Venous System is opposite. 6.) Post C apillary V ein: Very small veins called venules. 7.) Muscular Venules: Very small and too numerous to name. 8.) Medium V eins: They drain blood from specific areas of the body, organs and muscles. [EXAMPLE] :Radial and Ulnar Veins (drain blood out of the forearm) *Unique: They contain valves.* Valves: Flaps of tissue that extend into the lumen and point upwards towards the heart. → Because veins have a very low blood pressure, they don’t have the strength to pump the blood back to the heart against the pull of gravity. → Skeletal muscles that surround the veins also help to pump the blood [Show More]

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