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Lesson 20AS PE Anatomy &Physiology
James Barraclough
The Vascular System
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Starter
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Aims: Vascular System
Objectives:ALL learners will be able to understand:
Blood (functions/viscosity/vessels)Circulatory systemVenous return mechanism
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The Vascular (Circulation) System
Blood supports functioning of body
Blood vessels ensure sufficient blood & O reaches bodys tissues/muscles
Consists of cells & cell fragmentssurrounded by liquid called PLASMAAverage male has 5 6l
Average female has 4 5l
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Activity 1In pairs produce PowerPoint presentation
on following using key words as guidance:Khalifa & Aidan: functions of blood; bloodviscosity & double circulatory system Transportation, protection, homeostasis Resistance, training Pulmonary & systemic circulationJoe & Lamiko: blood vessels Arteries/arterioles, veins/venules, capillaries,
vasoconstriction/dilation, pre-capillarysphincters
Robin & Ali: venous return mechanism Muscle pump, pocket valves, respiratory pump,
smooth muscle, gravity
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Functions of Blood
Transporting nutrients e.g. Glucose (from liver tomuscles) & O Protection & fighting disease through interaction
with lymphatic system (contains cells/chemicalsvital to immune system)
Blood clots when blood vessel damage occurspreventing cell loss
Maintains HOMEOSTASIS including temperatureregulation (transports heat to bodys surface) &maintaining pH balance
Removes metabolites e.g. CO from muscles tolungs & lactic acid from muscles to liver
Transports enzymes, hormones & other chemicals(e.g. Drugs)ALL ESPECIALLY IMPORTANT DURING EXERCISE
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Blood Viscosity (Thickness)
More viscous = more resistant to flow More red blood cells = more capacity to transport
O BUT unless plasma is increased, viscosity may
also increase restricting blood flow Viscosity may also increase if plasma content
decreases due to dehydration Training = increase in total blood volume
blood plasma increases > blood cell volume =decrease in blood viscosity Therefore blood flow through vessels improved
as is O delivery to working muscles
http://images.google.co.uk/imgres?imgurl=http://upload.wikimedia.org/wikipedia/en/thumb/f/f6/Double_circulatory_system.jpg/150px-Double_circulatory_system.jpg&imgrefurl=http://en.wikipedia.org/wiki/Double_circulatory_system&usg=__OMJZBTVdO5z1-GNCqMlwidFFDck=&h=360&w=150&sz=10&hl=en&start=12&tbnid=tSq9Szkj-t_KnM:&tbnh=121&tbnw=50&prev=/images?q=double+circulatory+system&gbv=2&hl=en8/12/2019 As PE Lesson 20 Cir Syst 2013-14
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Double Circulatory SystemBlood flows through continuous network of blood vessel s
forming double circuit
Connects heart to lungs &heart to all other body tissues
Pulmonary circulation transports blood between lungs &heart
Pulmonary artery carries deoxygenated blood from RV tolungs where it is
re-oxygenated & unloads CO
Pulmonary vein carries oxygenated blood back to LA ofheart through pulmonary vein
http://images.google.co.uk/imgres?imgurl=http://upload.wikimedia.org/wikipedia/en/thumb/f/f6/Double_circulatory_system.jpg/150px-Double_circulatory_system.jpg&imgrefurl=http://en.wikipedia.org/wiki/Double_circulatory_system&usg=__OMJZBTVdO5z1-GNCqMlwidFFDck=&h=360&w=150&sz=10&hl=en&start=12&tbnid=tSq9Szkj-t_KnM:&tbnh=121&tbnw=50&prev=/images?q=double+circulatory+system&gbv=2&hl=enhttp://images.google.co.uk/imgres?imgurl=http://upload.wikimedia.org/wikipedia/en/thumb/f/f6/Double_circulatory_system.jpg/150px-Double_circulatory_system.jpg&imgrefurl=http://en.wikipedia.org/wiki/Double_circulatory_system&usg=__OMJZBTVdO5z1-GNCqMlwidFFDck=&h=360&w=150&sz=10&hl=en&start=12&tbnid=tSq9Szkj-t_KnM:&tbnh=121&tbnw=50&prev=/images?q=double+circulatory+system&gbv=2&hl=en8/12/2019 As PE Lesson 20 Cir Syst 2013-14
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Double Circulatory System
Blood returning to LA, pumped to LV &aorta then bodys tissues through network
of arteries
Veins return deoxygenated blood(now containing CO )
to RA through venae cavae
= SYSTEMIC CIRCULATION
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Blood VesselsVascular network through which blood flows to all
parts of body comprises:
Arteries
ArteriolesCapillariesVeinsVenules
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Arteries & Arterioles
Arteries - high pressure vessels carryingblood from heart to tissuesLargest artery is aorta (main arteryleaving heart)Aorta constantly subdivides & gets smallerConstant subdivision decreases diameterof vessel arteries, now become arterioles
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Structure of ArteriesArteries composed of 3 layers of tissue:
1 Outer fibrous layer tunica adventitia or tunica externa2 Thick middle layer tunica media3 Thin lining of cells to inside endothelium or tunica
intima
Tunica media comprised of smooth muscle & elastic tissue,
enables arteries & arterioles to alter diameter (stretch)Arteries tend to have more elastic tissue; arterioles havegreater amounts of smooth muscle; allows vessels toincrease diameter through vasodilation or decreasediameter through vasoconstrictionVasoconstriction & vasodilation mean vessels can regulateBP & ensure tissues receiving sufficient blood particularly during exercise
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Arteries & arterioles: 3 basicfunctions
1. Conduits carrying/controlling blood flowto tissues
2. Cushion & smooth out pulsate flow ofblood from heart
3. Help control BP
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Veins & VenulesVeins low pressure vessels returning bloodto heartStructure similar to arteries, althoughpossess less smooth muscle & elastictissueVenules are smallest veins & transportblood away from capillary bed into veinsVeins gradually increase in thicknessnearer to heart they get, until they reachlargest vein in body - venae cavae (entersRA)
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Veins & Venules
Thinner walls of veins often distend & allowblood to pool in themAlso allowed to happen as veins containpocket valves which close intermittently toprevent back flow of bloodExplains why up to 70% of total bloodvolume found in venous system at any time
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Venous Return Mechanism
Venous Return = blood returning to RA via veins c.70% of total blood volume in veins at rest Provides large reservoir of blood returned rapidly
to heart when needed Heart can only pump as much blood as receives
So cardiac output depends on venous return Rapid increase in venous return = significantlyincreased cardiac output (Starlings Law)
Several mechanisms aid process: Muscle pump during exercise muscular contractions
impinge & compress veins squeezing blood towards heart Pocket valves inside veins prevent backflow Respiratory pump during inspiration/expiration,
pressure changes occur in thoracic & abdominal cavitiesto compress veins & assist blood return to heart
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Venous Return MechanismMechanisms essential at start of exercise:
As exercise commences muscles contract tosqueeze vast blood reserves in veins backtowards heartStroke volume increases allowing optimal
delivery of nutrients to working muscles
Other factors aiding venous return:Smooth muscle in walls & surrounding veins
contract & help blood move back towards heartGravity helps blood return to heart fromupper body
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Homework
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Next Lesson
Blood pressure
