Bio 118 Test #4 Notes

Bio 118 Test #4 Notes - The Vascular System 161 Follow the...

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The Vascular System: 161. Follow the trail of a single blood cell through the vascular system – what are the components of the arterial and venous vasculature? What are the major veins and arteries entering and leaving the heart? - Blood trail: Collateral arteries Arteriole Capillaries Small Venule Venule Vein - the walls of arteries and veins contain three distinct layers - The tunica intima is the innermost layer of a blood vessel. It includes the endothelial lining of the vessel and an underlying layer of connective tissue dominated by elastic fibers - The tunica media, the middle layer, contains smooth muscle tissue in a framework of collagen and elastic fibers. When these smooth muscles contract, vessel diameter decreases; when they relax, vessel diameter increases - the outer tunica externa forms a sheath of connective tissue around the vessel. Its collagen fibers may intertwine with those of adjacent tissues, stabilizing and anchoring the blood vessel. - Blood goes into the heart through the Superior vena cava and the pulmonary veins. It goes out through the aorta and the pulmonary arteries. Blood goes into the heart through the major veins and leaves the heart through the major arteries. 162. How does pressure act on blood (or any fluid) to produce movement? - any fluid will move from an area of higher pressure to lower pressure, or, down a pressure gradient 163. What are the three types of resistance that opposes blood movement through the vasculature? - Total peripheral resistance: the resistance of the entire cardiovascular system. The greatest pressure difference (~65 mm Hg) within the cardiovascular system occurs in the arterial network because of the high resistance of the arterioles - Vascular resistance is the strongest opposing force: this is friction of blood against the inside of blood vessels. This friction increases with decreasing blood vessel diameter (the constriction of blood vessels) - Viscocity (resistance): this can be considered as a fluid’s friction against itself, and will increase as a fluid’s thickness increases (the more RBC, the thicker the blood) - Turbulence (resistance): This is a disorderly movement of fluid; energy is wasted in forming swirls and eddies. 164. Consider the graph on page 420. Why does blood pressure fall as it travels away from the heart? Why does blood pressure oscillate in the arterial system, but smooth’s out by the time it reaches the capillaries?
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- The average pressure declines as a result of friction between the blood and the vessel walls. The pulse pressure fades because arteries are elastic tubes rather than solid pipes. Much as a balloon’s walls expand upon the entry of air, the elasticity of the arteries allows them to expand with blood during systole. When diastole begins and blood pressures fall, the arteries recoil to their original dimensions. Because the aortic semilunar valve prevents the return of blood to the heart, arterial recoil adds an extra
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Bio 118 Test #4 Notes - The Vascular System 161 Follow the...

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