2 Types of Blood Vessels Arteries Capillaries Veins Blood vessels that carry blood away from the heartCapillariesmicroscopic blood vessels that allow exchanges between blood and tissueVeinsBlood vessels that carry blood to the heart
4 General Features of Blood Vessels Veins and arteries consist of three layersTunica intima: innermost layerTunica media: middle layerTunica adventia: outermost layer
5 Arteries THREE TYPES OF ARTERIES Elastic arteries Largest in diameter Thickest wallsMostly elastic tissueStretch when ventricles pump into themPrevents blood pressure from falling rapidlyMaintains blood flow when ventricles are relaxed
6 Arteries Muscular arteries Medium and smaller diameter Made up of a lot of smooth muscleControl blood flow to different regions of bodyVasoconstriction:Caused by contraction of smooth muscle in blood vesselsDecreases blood vessel diameter and blood flowVasodilation:Relaxation of smooth muscle in blood vesselsIncreases blood vessel diameter and blood flow
8 Arteries Small arteries Arterioles Smaller diameter Smaller walls Smallest arteriesTransport blood from small arteries to capillaries
9 Capillaries Structure Function Single layer of simple squamous epitheliumDiameter approximately the same as that of a red blood cell (7.5 micrometers)FunctionReceive blood from arteriolesBranches out to form networksRegulated by precapillary sphinctersGive up oxygen and nutrients to body tissuesTake up carbon dioxide and other waste products from body tissues.
13 Veins Venules Small Veins Medium Sized Veins Receive deoxygenated blood from capillariesDiameter a little larger than capillariesSmall VeinsReceive blood from venulesMedium Sized VeinsCollect blood from small veins and deliver it to large veins
15 VeinsValvesFound in veins that are larger than 2 millimeters in diameter.Allow blood to flow to the heart, but not backwardComposed of two cusps, or flapsSimilar in function to the semi-lunar valvesValve animation
19 Blood PressureBlood Pressure= measure of force blood exerts against the blood vessel walls.Systolic: Top number. Pressure in the arteries when the ventricles contract.Diastolic: Bottom number. Pressure in the arteries between beats when ventricles are resting.