CARDIOVASCULAR SYSTEMBLOOD VESSELS General OrganizationGeneral Organization ArteriesArteries

Large (Elastic) ArteriesLarge (Elastic) Arteries Muscular (Distributing) ArteriesMuscular (Distributing) Arteries Arterioles (Small) ArteriesArterioles (Small) Arteries Precapillary (Terminal) ArteriolesPrecapillary (Terminal) Arterioles

CapillariesCapillaries VeinsVeins

VenulesVenules Medium VeinsMedium Veins Large VeinsLarge Veins

LymphaticsLymphatics

General Organization

Blood Vascular SystemPortal SystemLymph Vascular

System

Tissue Components

EndotheliumElastic elementsMuscular elementsConnective tissue

elements

Arteries - General Structural PlanTunica IntimaTunica MediaTunica

Adventitia

Arteriosclerosis

Tunica Intima

EndotheliumBasement membraneSubendothelial connective

tissueInternal elastic lamina (IEL)

Tunica Media

Smooth muscle Elastic fibers/lamina

Tunica Adventitia

External elastic lamina (EEL)

Connective tissueVasa vasorumSympathetic nerves

Arteriosclerosis - “Hardening of Art.”

AtherosclerosisMonckeberg’s Medical Calcific

SclerosisArteriolosclerosis

Myointimal Cells

Intimal smooth muscle cells

Potential of fibroblasts, macrophages & SM

Foam cells (lipophages)

BV CLASSIFICATIONS ArteriesArteries

Large (Elastic)Large (Elastic) Medium (Muscular)Medium (Muscular) Small (Arterioles)Small (Arterioles)

CapillariesCapillaries ContinuousContinuous Sinusoids Sinusoids Lymphatics Lymphatics

VeinsVeins Small (Venules)Small (Venules) MediumMedium Large (Cava)Large (Cava)

Large (Elastic) ArteriesTunica intimaTunica intima

thicker subendothelial c.t.thicker subendothelial c.t.poorly defined IELpoorly defined IEL

Tunica mediaTunica media - thickest, largely elastic - thickest, largely elasticTunica adventitiaTunica adventitia

EEL poorly definedEEL poorly definedvasa vasorumvasa vasorum

Muscular (Distributing) Arteries

Tunica intimaTunica intima - thin with prominent IEL - thin with prominent IELTunica mediaTunica media - largely smooth muscle - largely smooth muscleTunica adventitiaTunica adventitia

thick with prominent EELthick with prominent EELvasa vasorum, lymphatics, nervesvasa vasorum, lymphatics, nerves

Arterioles (Small Arteries)

Tunica intimaTunica intima - absence of IEL - absence of IEL Tunica mediaTunica media - gradual reduction in layers - gradual reduction in layersTunica adventitiaTunica adventitia - no EEL - no EEL

Precapillary (Terminal) Arterioles

MetarteriolesMetarteriolesno IELno IEL1-2 smooth muscle cells1-2 smooth muscle cellsserve as AV shuntsserve as AV shunts true capillaries are branchestrue capillaries are branches

Precapillary SphinctersPrecapillary Sphinctersguard openings of true capillariesguard openings of true capillaries

Capillaries - General Structural Plan

EndotheliumEndothelium Basement Memb.Basement Memb. PericytesPericytes Other CellsOther Cells

Endothelium

Cells elongated along capillary axisCells elongated along capillary axisAttached by both occluding (tight) and Attached by both occluding (tight) and

communicating (gap) junctionscommunicating (gap) junctionsOval or elongated nucleus (bulges into lumen)Oval or elongated nucleus (bulges into lumen)Contractile - cytoplasmic filamentsContractile - cytoplasmic filamentsPinocytotic vesicles and vacuolesPinocytotic vesicles and vacuoles

Basement Membranes

Continuous in blood vascular system Continuous in blood vascular system (prominent in brain as BBB)(prominent in brain as BBB)

Discontinuous in sinusoids and lymphaticsDiscontinuous in sinusoids and lymphaticsCollagen Type IVCollagen Type IVElastic fibersElastic fibers

Pericytes

Enclosed in own basement membraneEnclosed in own basement membraneDiscontinuous and irregularly spacedDiscontinuous and irregularly spacedParticularly numerous in brain (BBB)Particularly numerous in brain (BBB)Nucleus bulges away from lumenNucleus bulges away from lumen

Other Cells

Fixed macrophagesFixed macrophagesMast cells - secrete heparinMast cells - secrete heparinRare nerve fibersRare nerve fibers

Capillary FunctionBarrierBarrier

Endocapillary layerEndocapillary layerEndotheliumEndotheliumBasal lamina and pericytesBasal lamina and pericytesAdventitiaAdventitia

Exchange ForcesExchange ForcesHydrostaticHydrostaticOsmoticOsmoticConcentrationConcentration

Capillaries - Structural Types

True CapillariesTrue CapillariesContinuous capillariesContinuous capillariesFenestrated capillaries with diaphragmsFenestrated capillaries with diaphragmsFenestrated capillaries without diaphragmsFenestrated capillaries without diaphragms

SinusoidsSinusoids Lymphatic CapillariesLymphatic Capillaries

Venules (Small Veins)

Tunica intima - endothelial tubeTunica intima - endothelial tube Tunica mediaTunica media

PericytesPericytesIsolated smooth muscle cellsIsolated smooth muscle cells

Tunica Adventitia - minimalTunica Adventitia - minimal

Medium Veins

Tunica intima - thin, forms valvesTunica intima - thin, forms valves Tunica media - scattered smooth muscle Tunica media - scattered smooth muscle

Inner layer longitudinally arranged in large veinsInner layer longitudinally arranged in large veins Tunica adventitia - thick with longitudinal Tunica adventitia - thick with longitudinal

Large Veins

Tunica intima - slightly thicker than mediumTunica intima - slightly thicker than medium Tunica media - sparse smooth muscle cellsTunica media - sparse smooth muscle cells Tunica adventitia - thick with longitudinal Tunica adventitia - thick with longitudinal

bundles of smooth muscle cellsbundles of smooth muscle cells

Lymphatics Tunica intima & adventitia onlyTunica intima & adventitia only Discontinuous basement membraneDiscontinuous basement membrane Very frequent valvesVery frequent valves Anchoring filamentsAnchoring filaments Extensive vasa vasorumExtensive vasa vasorum LymphangionLymphangion Interposed lymph node filters Interposed lymph node filters Drain into veinsDrain into veins

BV CLASSIFICATIONS ArteriesArteries

Large Large ElasticElastic laminalamina MediumMedium >10 SM layers>10 SM layers Small (Arterioles)Small (Arterioles) <5 SM layers<5 SM layers

CapillariesCapillaries Continuous Continuous (Fenestrated & Non-Fenestrated)(Fenestrated & Non-Fenestrated) Sinusoids Sinusoids (Liver, spleen, lymph nodes, BM)(Liver, spleen, lymph nodes, BM) Lymphatics Lymphatics (Everywhere)(Everywhere)

VeinsVeins Small (Venules)Small (Venules) Thin wall, large lumenThin wall, large lumen MediumMedium Few layers of SM, “Few layers of SM, “ Large (Cava)Large (Cava) Long. SM in Adv.Long. SM in Adv.