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13 Cards in this Set
- Front
- Back
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Blood Vessels: Constituents
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-Tunica Intima
-Tunica Media -Tunica Adventitia Made up of: endothelial cells, elastic fibres, collagen fibres and smooth muscle. |
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Endothelial Cells
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Single continuous layer that lines all of the vasculature.
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Elastic Fibres
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-Rubber like material that accounts for most of the stretch at normal pressures.
-Core of elastin surrounded by microfibrils. -arranged in concentric, cylindrical lamellae in arteries. |
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Collagen Fibres
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-Only stretches 3-4%
-Type 1 and Type III collagen molecules. -Not normally under tension |
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Vascular Smooth Muscle Cells
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Involved in active contraction.
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Arteries
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-Elasticated walled vessels that smooth out pulsatile outflow from the ventricles.
-stores energy during stretch, so that when artery relaxes artery contracts maintain blood flow. |
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Arterioles
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-Resistance Vessels.
-Provide TPR |
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Veins and Venules
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-Capacitance Vessels - 70% of blood flow
-Valves prevent backflow of blood. -Venous return aided by: 1. sympathetic activity 2.skeletal muscle pump 3.respiratory muscle pump |
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Capillaries
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-narrow, short and thin walled.
-Velocity of blood is low due to large cross sectional area. -Parallel vessels leads to low resistance. -Precapillary vessels, meta arterioles and precapillary sphincters control blood flow in capillary beds. |
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Changes aorta>precapillary sphincter
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-decreasing elastic fibres and collagen.
-increasing smooth muscle |
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venule>vena cava
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-elastic fibres and smooth muscle constant.
-increasing collagen |
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Resistance to flow
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1. Diameter of vessels most important - aggregate resistance more important than individual.
2. As pressure increases arteries increase in volume - muscular arteries = resistance vessels. 3. veins high compliance. Shift from oval to circle cross section when full - increase volume by 200%. Capacitance vessels. |
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Control of Arteriolar Tone
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1) External
-Nerves (ANS) - Hormones - circulating and local NO 2. Local Factors -Myogenic Response - vasoconstriction -metabolites - vasodilation |
