Mass transport The blood systme and the passage of water through plants 2.0 / 5 based on 1 rating ? BiologyASAll boards Created by: Beth BrownCreated on: 24-05-11 13:21 Arteries Rapid blood flow Oxygenated blood High blood pressure Carries blood from the heart to the tissues Thick muscle layer - Arteries can be constricted and dialated to control volume of passing blood Thick elastic layer - elastic wall is streched in systole and spring back during diastole which helps to maintain high and smooth pressure surges Thick wall - to resist the vessel bursting No valves - blood does not flow backwards in the artery 1 of 6 Arterioles Blood flow slower than arteries Oxygenated blood Lower pressure Controls flow of blood (slows it down) Thicker muscle than artery - controls blood movement into the capillaries Elastic layer thinner than artery - becasue blood pressure is lower 2 of 6 Capillaries Very slow blood flow Both oxygenated and de-oxygenated blood Low blood pressure Exchanges metabolic materials between the blood and the cells of the body Extremley thin - diffusion distance is short Numerous and highly branched - large surface area for diffusion Narrow diameter - permeate tissues Narrow lumen - red blood cells are squeezed flat against side of capillary 3 of 6 Vein Slow blood flow De-oxygenated blood Very low blood pressure (due to valves) Transport blood from tissues to heart Thin muscle layer - constrictions and dialations cannot control blood flow Thin elastic layer - Low pressure of blood won't cause them to burst Thin wall - No need for thick wall - no risk of bursting Vavles throughout - to stop blood flowing backwards 4 of 6 Muscle layer Thickest = Arteriole Middle = Artery Thinnest = vein Reasons Muscle layer contration allows constrcition of the lumen in the arterioled. This contricts bloow flow and conrols blopd movement into the capillaries Smaller arteries can be constricted to controll the volume of blood passing through Constrction and dialation in the veins can't control bloow flow to the tissues 5 of 6 Elastic layer Thickest = Arteries Medium = Arterioles Thinnest = veins Reasons Thick elasitc in the artery helps to maintain high and smooth pressure surges by the beating of the heart Arterioles elastic layer is thinner than arteries because blood pressure is lower Thin in veins because they have a blood pressure so no risk of bursting 6 of 6
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