5Tunics Tunica intima Endothelium lines lumen of all vessels Tunica mediaSmooth muscle and sheets of elastinSympathetic vasomotor nerve fibers control vasoconstriction and vasodilation of vessels: Influence blood flow and blood pressureTunica externaCollagen fibers protect & reinforce; anchor to surrounding structuresContains nerve fibers, lymphatic vesselsVasa vasorum of larger vessels nourishes external layer
6(depending on size & shape): Types of Arteries(depending on size & shape):ElasticMuscularArterioles
7Arterial System: Elastic Arteries Large thick-walled arteries with elastin in all three tunicsAorta and its major branchesLarge lumen offers low resistanceAct as pressure reservoirs—expand and recoil as blood ejected from heartSmooth pressure downstream
8Arterial System: Muscular Arteries Distal to elastic arteriesDeliver blood to body organsThick tunica media with more smooth muscleActive in vasoconstriction
9Arterial System: Arterioles Smallest arteriesLead to capillary bedsControl flow into capillary beds via vasodilation and vasoconstriction of the arterioles (influenced by hormones and other chemicals)
10CapillariesMicroscopic blood vesselsWalls of thin tunica intimaPericytes help stabilize their walls and control permeabilityDiameter allows only single RBC to pass at a time
11Provide direct access to almost every cell Functions CapillariesIn all tissues except for cartilage & epithelia (receive nutrients from nearby blood vessels), cornea & lens of eye (receive nutrients from aqueous humor)Provide direct access to almost every cellFunctionsExchange of gases, nutrients, wastes, hormones, etc., between blood and interstitial fluidThree structural typesContinuous capillariesFenestrated capillariesSinusoid capillaries (sinusoids)
12Continuous Capillaries Tight junctions connect endothelial cellsIntercellular clefts allow passage of limited passage of fluids and small solutesContinuous capillaries of brain uniqueTight junctions complete, forming blood brain barrierContinuous capillary. Least permeable, and mostcommon (e.g., skin, muscle).PericyteRed bloodcell in lumenIntercellularcleftEndothelialcellBasementmembraneTight junctionPinocytoticvesiclesEndothelialnucleus
13Fenestrated Capillaries Some endothelial cells contain pores (fenestrations)More permeable than continuous capillariesFunction in absorption or filtrate formation (small intestines, endocrine glands, and kidneys)PinocytoticvesiclesRed bloodcell in lumenFenestrations(pores)IntercellularcleftEndothelialcellnucleusBasement membraneTight junctionFenestrated capillary. Large fenestrations (pores)increase permeability. Occurs in areas of activeabsorption or filtration (e.g., kidney, small intestine).
14Sinusoid CapillariesFewer tight junctions; usually fenestrated; larger intercellular clefts; large lumensLarge molecules and blood cells pass between blood and surrounding tissuesFound only in the liver, bone marrow, spleen, adrenal medullaIn the liver, hepatic macrophages in lining to destroy bacteriaEndothelialcellRed bloodcell in lumenLargeintercellularcleftNucleus ofendothelialIncompletebasementmembraneSinusoid capillary. Most permeable. Occurs in speciallocations (e.g., liver, bone marrow, spleen).Tight junction
15Capillary Beds: Two Types of Vessels Def.: Interwoven networks of capillaries – blood flows thru arterioles-> venules (microcirculation)Capillary Beds: Two Types of VesselsVascular shunt (metarteriole—thoroughfare channel)Directly connects terminal arteriole and postcapillary venuleTrue capillaries10 to 100 exchange vessels per capillary bedBranch off metarteriole or terminal arteriole
16Blood Flow Through Capillary Beds Vascular shuntPrecapillary sphinctersMetarterioleThoroughfarechannelTrue capillaries normally branch from metarteriole and return to thoroughfare channelPrecapillary sphincters regulate blood flow into true capillariesBlood may go into true capillaries or to shuntRegulated by local chemical conditions and vasomotor nervesExample: Eating and relaxing – blood flow in the digestive system; abdominal cramps and indigestion when running and eating!!!TruecapillariesTerminal arteriolePostcapillary venuleSphincters open—blood flows through true capillaries.Terminal arteriolePostcapillary venuleSphincters closed—blood flows through metarteriole – thoroughfarechannel and bypasses true capillaries.
17Venous System: Venules Formed when capillary beds uniteSmallest postcapillary venules: very porous; allow fluids and WBCs into tissuesConsist of endothelium and a few pericytesLarger venules have one or two layers of smooth muscle cells
18Veins Venules join to form veins Have thinner walls, larger lumens compared with corresponding arteriesThin tunica media; thick tunica externa of collagen fibers and elastic networksCalled capacitance vessels (blood reservoirs); contain up to 65% of blood supplyBlood pressure lower than in arteries (walls don’t burst!) =>Adaptations ensure return of blood to heart despite low pressureLarge-diameter lumens offer little resistanceVenous valves prevent backflow of bloodMost abundant in veins of limbsVenous sinuses: flattened veins with extremely thin walls (e.g., coronary sinus of the heart & dural sinuses of the brain)
20Circulatory Pathways: Blood Vessels of the Body Two main circulationsPulmonary circulation: short loop that runs from heart to lungs and back to heartSystemic circulation: long loop to all parts of body and back to heart
23Figure 19.20 Schematic flowchart showing an overview of the systemic circulation. Commoncarotid arteriesto head andsubclavianarteries toupper limbsCapillary beds ofhead andupper limbsSuperiorvena cavaAorticarchAortaRALARVLVAzygossystemThoracicaortaVenousdrainageArterialbloodInferiorvenacavaCapillary beds ofmediastinal structuresand thorax wallsDiaphragmAbdominalaortaCapillary beds ofdigestive viscera,spleen, pancreas,kidneysInferiorvenacavaCapillary beds ofgonads, pelvis, andlower limbs
24Figure 19.21a Major arteries of the systemic circulation. R. externalcarotid arteryR. internalcarotid arteryL. externalcarotid arteryL. internalcarotid arteryR. common carotid– right side of head and neckL. common carotid– left side of head and neckR. vertebralL. vertebralR. axillaryR. subclavian– neck andR. upper limbBrachiocephalic– head, neck, andR. upper limbL. subclavian– neck and L.upper limbL. axillaryAortic archArteries ofL. upperlimbArteries ofR. upperlimbAscending aorta– L. ventricle to sternal angleL. and R. coronaryarteriesThoracic aorta T5–T12 (diaphragm)L. ventricle of heartVisceral branchesParietal branchesMediastinal– posteriormedia-stinumEsophageal– esophagusBronchial– lungs andbronchiPericardial– pericardiumPosterior intercostals– intercostal muscles, spinalcord, vertebrae, pleurae, skinSuperior phrenics– posterior and superiordiaphragmDiaphragmAbdominal aorta T12 (diaphragm)–L4Visceral branchesParietal branchesGonadal– testes orovariesSuprarenal– adrenalglandsandRenal– kidneysSuperiorand inferiormesenterics– smallintestine– colonCeliac trunk– liver– gallbladder– spleen– stomach– esophagus– duodenumInferior phrenics– inferior diaphragmLumbars– posteriorabdominalwallMedian sacral– sacrum– coccyxR. common iliac– pelvis and R. lower limbL. common iliac– pelvis and L. lower limbArteries of R. lower limbArteries of L. lower limb
25Aorta Ascending artery Aortic Arch Descending aorta Major arteries of the systemic circulation.AortaAscending arteryAortic ArchDescending aortaLeft coronary arteryRight coronary arteryThoracic aortaAbdominal aortaLeft & right common iliac arteriesbrachiocephalicLeft common carotid arteryLeft subclavian arteryRight commoncarotid arteryRight subclavian artery
30Major arteries serving the brain (inferior view, right side Figure 19.22d Arteries of the head, neck, and brain.AnteriorCerebral arterialcircle(circle of Willis)Frontal lobeOptic chiasma• AnteriorcommunicatingarteryMiddlecerebralartery• Anteriorcerebral arteryInternalcarotidartery• PosteriorcommunicatingarteryMammillarybody• Posteriorcerebral arteryTemporallobeBasilar arteryVertebral arteryPonsOccipital lobeCerebellumPosteriorMajor arteries serving the brain (inferior view, right sideof cerebellum and part of right temporal lobe removed)
38Superior gluteal artery Figure 19.25b Arteries of the right pelvis and lower limb.Common iliac arteryInternal iliac arterySuperior gluteal arteryExternal iliac arteryDeep artery of thighLateral circumflexfemoral arteryMedial circumflexfemoral arteryObturator arteryFemoral arteryAdductor hiatusPopliteal arteryAnterior tibial arteryPosterior tibial arteryFibular arteryDorsalis pedis arteryArcuate arteryDorsal metatarsalarteriesAnterior view
39Figure 19.26b Major veins of the systemic circulation. Veins of the head and trunkDural venous sinusesVeins that drainthe upper limbExternal jugular veinVertebral veinSubclavian veinInternal jugular veinAxillary veinRight and leftbrachiocephalic veinsCephalic veinBrachial veinSuperior vena cavaBasilic veinGreat cardiac veinHepatic veinsSplenic veinMedian cubital veinHepatic portal veinUlnar veinRenal veinRadial veinSuperior mesenteric veinInferior mesenteric veinDigital veinsInferior vena cavaCommon iliac veinVeins that drainthe lower limbInternal iliac veinExternal iliac veinFemoral veinGreat saphenous vein (longest vein; issue from dorsal venous arch)Popliteal veinPosterior tibial veinAnterior tibial veinSmall saphenous veinDorsal venous archDorsal metatarsal veinsIllustration, anterior view. The vessels of the pulmonary circulation are not shown.
40Veins of the head and neck, right superficial aspect Figure 19.27b Venous drainage of the head, neck, and brain.Ophthalmic veinSuperficialtemporal veinFacial veinOccipital veinPosteriorauricular veinExternaljugular veinVertebral veinInternaljugular veinSuperior andmiddle thyroid veinsBrachiocephalicveinSubclavian veinSuperiorvena cavaVeins of the head and neck, right superficial aspect
41Brachiocephalic veins Internal jugular vein Right subclavian vein External jugular veinLeft subclavian veinAxillary veinBrachial veinSuperior vena cavaAzygos veinCephalic veinAccessory hemiazygosveinBasilic veinHemiazygos veinPosterior intercostalsInferior vena cavaMedian cubitalveinAscending lumbar veinMedianantebrachial veinBasilic veinCephalic veinUlnar veinRadial veinDeep venouspalmar archSuperficial venouspalmar archDigital veinsAnterior viewFigure 19.28b Veins of the thorax and right upper limb.
42Tributaries of the inferior vena cava. Figure 19.29b Veins of the abdomen.Inferior phrenicveinHepatic veinsInferior vena cavaLeft suprarenalveinRight suprarenalveinRenal veinsLeft ascendinglumbar veinRight gonadalveinLumbar veinsLeft gonadalveinCommon iliacveinExternal iliacveinInternal iliacveinTributaries of the inferior vena cava.Venous drainage of abdominal organs not drained by the hepatic portal vein.