BLOOD VESSELS

BLOOD VESSELS

1. TYPES OF BLOOD VESSELS

   • ARTERIES
     • blood AWAY from heart
     • ELASTIC ARTERIES
       • INACTIVE @ vasoconstriction
       • ALL 3 tunics
       • location
         • aorta
         • major branches
       • function
         • pressure resevoir
           • expand & recoils as blood ejects from <3
             • = continuous flow btwn HB
     • MUSCULAR ARTERIES
       • THICKEST tunic media
       • more S. muscle, less elastic tissue
       • ACTIVE @ vasoconstriction
     • ARTERIOLES
       • aka RESISTANCE arteries
         • change resistance in BLOODFLOW
       • smallest of all arteries
         • LARGE arterioles
           • all 3 tunics
         • SMALL arterioles
           • 1 layer s.muscle, endothelial surrounding
   • CAPILLARIES
     • CONTINUOUS CAPILLARIES
       • location
         • skin
         • muscle
         • lungs
         • brain
           • form blood brain barrier
         • cns
     • contact w/ tissue cells
     • endothelium walls and bound by tight junctions
     • FENESTRATED CAPILLARIES
       • location
         • where FILTRATION & ABSORPTION OCCUR
           • kidneys
           • intestines
       • contain "FENESTRATIONS"
         • "pores" like swiss cheese
           • increases permeability
     • SINUSOIDAL CAPILLARIES
       • location
         • liver
         • bone marrow
         • spleen
       • fewer tight junction, larger lumen
         • = blood flow is sluggish
         • = mod. of L. molecules & blood cells to pass
   • VEINS
     • blood TOWARDS heart
     • all 3 tunics
       • thinner walls, larger lumens
         • = good storage
     • formation begins @ cap. beds
       • formed when VENULES converge
         • = larger vein

2. GENERAL INFO

   • delivery system
     • start & end @ heart
   • structure
     • 3 tunics
       • intima
       • media
       • externa

3. BLOOD FLOW & REGULATION

   • BLOOD FLOW
     • vol. of blood flowing through ... @ a given time
     • ml/min
     • constant @ rest
     • CONTROL of blood flow
       • extrinsic controls
         • sympathetic NS & hormones control blood flow
         • ie. decrease blood flow to other organs (kidneys & digestive)
       • intrinsic controls
         • local, blood flow adjusted to local tissue needs
         • ie. skeletal muscle arterioles dilate increase blood flow to muscle
   • RESISTANCE
     • opposition to flow
     • measures friction that blood encounters
     • abrupt change in diameter
       • = increase resistance & disrupt flow & can = turbulence
   • BLOOD PRESSURE
     • force exerted by blood on bv wall
     • mm/Hg
     • pressure gradient = driving force
       • blood from high to low pressure
     • SYSTEMIC BP
       • pumping of heart
         • = generate blood flow
       • highest in aorta, declines throughout path
     • SYSTOLIC PRESSURE
       • pressure exerted @ aorta
         • ventricular contraction
     • DIASTOLIC PRESSURE
       • lowest lvl of aortic pressure
       • heart relaxes
     • CAPILLARY BP
       • range: 35mm @ beginning of cap. bed & 17mm @ end
       • LOW cap. pressure is favourable
         • high pressure can = rupture
         • & bc usually very permeable
     • VENOUS BP
       • changes little @ cardiac cycle
       • low pressure
       • if cut..@
         • vein
           • blood flows out smoothly
         • artery
           • blood will spurt
       • energy is lost as heat after each cycle
       • FACTORS aiding venous return
         • MUSCULAR PUMP
           • contraction SKELETAL muscle for blood back to HEART
         • RESPIRATORY PUMP
           • pressure changes during breathing move blood bk to heart
         • SYMPATHETIC VENOCONSTRICTION
           • under sympathetic control, smooth muscle contract blood bk to heart
     • Factors affecting BP
       • cardiac output
       • blood volume
       • peripheral resistance