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Vascular and Vascular and Lymphatic System Lymphatic System PathologyPathology

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Blood FlowBlood Flow

Systemic blood flow is a circuit :Systemic blood flow is a circuit : Heart Heart →→ArteriesArteries→→ Arterioles Arterioles→→

CapillariesCapillaries→→ Venules Venules→→ Veins Veins→→ HeartHeart

ArteryArtery – any vessels that carries – any vessels that carries blood away from the heart.blood away from the heart.

VeinVein – any vessels that carries – any vessels that carries blood toward the heartblood toward the heart

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Structure of blood Structure of blood vesselsvessels

Tunica intimaTunica intima– Endothelium and connective tissueEndothelium and connective tissue

Tunica mediaTunica media– Smooth muscle and elastic tissueSmooth muscle and elastic tissue

Tunica externa or tunica adventitiaTunica externa or tunica adventitia– Connective and elastic tissueConnective and elastic tissue

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ArteriesArteries

Large arteries are elastic (conducting) Large arteries are elastic (conducting) arteries – pressure reservoirsarteries – pressure reservoirs

Medium arteries are muscular Medium arteries are muscular (distributing) arteries – more smooth (distributing) arteries – more smooth musclemuscle

Contraction or relaxation of muscle Contraction or relaxation of muscle changes the size of the lumen, and so changes the size of the lumen, and so controls the blood pressure in the controls the blood pressure in the vessel.vessel.

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CapillariesCapillaries

Only a single layer of endothelium Only a single layer of endothelium and a basement membraneand a basement membrane

Connect arterioles and venulesConnect arterioles and venules Functional part of systemFunctional part of system True capillaries begin at a True capillaries begin at a

precapillary sphincter which precapillary sphincter which controls blood flow through the controls blood flow through the capillarycapillary

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VeinsVeins

Relatively thin; less elasticRelatively thin; less elastic Larger in diameter than arteriesLarger in diameter than arteries Have valves to prevent backflow Have valves to prevent backflow

of bloodof blood Flow to heart is assisted by Flow to heart is assisted by

contraction of skeletal musclescontraction of skeletal muscles

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Control of systemic Control of systemic circulationcirculation Nervous control – innervated by Nervous control – innervated by

sympathetic nervous system sympathetic nervous system ONLYONLY

Cardiac control center (primarily Cardiac control center (primarily in medulla oblongata)in medulla oblongata)

Heart has both Sympathetic and Heart has both Sympathetic and Parasympathetic innervations.Parasympathetic innervations.

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Baroreceptors and chemoreceptors:Baroreceptors and chemoreceptors:– Monitor pressureMonitor pressure

– Monitor blood levels of OMonitor blood levels of O22, CO, CO22 and H and H++

– Send information to cardiovascular Send information to cardiovascular center, which respondscenter, which responds

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ComplianceCompliance The increase in volume a vessel can The increase in volume a vessel can

accommodate for a given increase in accommodate for a given increase in pressure. pressure. – Depends on the ratio of elastic fibers to muscle Depends on the ratio of elastic fibers to muscle

fibers in the vessel wall.fibers in the vessel wall. Elastic arteries more compliant than muscular arteriesElastic arteries more compliant than muscular arteries Veins more compliant than either artery (blood Veins more compliant than either artery (blood

reservoirs)reservoirs)

Decreased compliance suggests an Decreased compliance suggests an increased stiffness of vessel wall.increased stiffness of vessel wall.

Determines the vessel’s response to Determines the vessel’s response to changes in pressure.changes in pressure.

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Blood pressureBlood pressure

Mean arterial pressure is the Mean arterial pressure is the average in pressure in the average in pressure in the arteries throughout the cardiac arteries throughout the cardiac cycle.cycle.

Depends on the compliance of the Depends on the compliance of the arteries and the amount of blood arteries and the amount of blood in the arterial system.in the arterial system.

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Blood pressureBlood pressure

BP = Cardiac Output * Total BP = Cardiac Output * Total Peripheral ResistancePeripheral Resistance

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Lymphatic SystemLymphatic System A vascular system that runs “parallel” A vascular system that runs “parallel”

to the blood vascular systemto the blood vascular system Flow does not circulate – begins in Flow does not circulate – begins in

tissuetissue Returns to venous system at Returns to venous system at

subclavian veinssubclavian veins Fluid in vessels is lymph – mostly Fluid in vessels is lymph – mostly

water and proteinswater and proteins Interstitial fluidInterstitial fluid→→ lymphatic lymphatic

capillariescapillaries→→ lymphatic vessels lymphatic vessels→→ lymphatic trunkslymphatic trunks→→ lymphatic ducts lymphatic ducts

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Lymph nodesLymph nodes Lie along lymphatic vesselsLie along lymphatic vessels Contain lymphocytes that filter Contain lymphocytes that filter

lymph and eliminate lymph and eliminate microbes/damaged cells/ toxinsmicrobes/damaged cells/ toxins

Biological filtrationBiological filtration

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Diseases of Arteries Diseases of Arteries and Veinsand Veins Thrombus- “clotting” in an Thrombus- “clotting” in an

unbroken vesselunbroken vessel– Maintains a point of attachmentMaintains a point of attachment– Organized differently than a clotOrganized differently than a clot– usually due to damage to usually due to damage to

endothelium and exposure of endothelium and exposure of collagen in the basement collagen in the basement membranemembrane

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Arterial thrombusArterial thrombus

Forms where blood is moving Forms where blood is moving rapidly – see alternating lines of rapidly – see alternating lines of platelets and red cells trapped in platelets and red cells trapped in fibrinfibrin

Lines of ZahnLines of Zahn

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Venous thrombusVenous thrombus

Forms differently due to Forms differently due to decreased blood flow decreased blood flow

Mixed regionMixed region at site of at site of attachmentattachment

More blood clotting forms a More blood clotting forms a downstream downstream red capred cap

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Factors that predispose to Factors that predispose to thrombosisthrombosis

Endothelial damageEndothelial damage– Bacterial damageBacterial damage– Damage to the myocardiumDamage to the myocardium– Wear and tear – Wear and tear – hemodynamic hemodynamic

stressstress Hypertension increases thisHypertension increases this ArteriosclerosisArteriosclerosis

– InflammationInflammation– Tumors and irritation by their productsTumors and irritation by their products

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Factors that predispose to Factors that predispose to thrombosisthrombosis Flow abnormalitiesFlow abnormalities

– Increases platelet contact with endotheliumIncreases platelet contact with endothelium– Reduction in flow:Reduction in flow:

Arterial:Arterial:– Cardiac damage and decreased Cardiac damage and decreased

pumping actionpumping action– Increased blood viscosityIncreased blood viscosity

Venous:Venous:– Physical inactivityPhysical inactivity– Varicose veinsVaricose veins

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– Turbulence:Turbulence:Damaged heart valvesDamaged heart valvesCongenital heart defectsCongenital heart defectsCompression of the vesselCompression of the vesselWeakened arterial wall - Weakened arterial wall - aneurysmaneurysm

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Other Causes Other Causes AgingAging ImmobilizationImmobilization Injury to vessel endotheliumInjury to vessel endothelium Increased clotting responseIncreased clotting response

Effects:Effects: Decreased venous emptyingDecreased venous emptying Increased venous pressuresIncreased venous pressures EdemaEdema PainPain

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Sequelae of ThrombosisSequelae of Thrombosis

1 Resolution – 1 Resolution –

Anticoagulation system Anticoagulation system

Fibrolytic systemFibrolytic system

Moderate exercise increases Moderate exercise increases thrombus resolutionthrombus resolution

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2 Organization2 Organization

The thrombus is digested by The thrombus is digested by phagocytes and replaced by phagocytes and replaced by connective tissue – incorporating connective tissue – incorporating the thrombus into the vessel wall.the thrombus into the vessel wall.

May recanalize – small channels May recanalize – small channels open up and restore blood flowopen up and restore blood flow

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3 Propagation – 3 Propagation –

Thrombus extends further down Thrombus extends further down the vessel, usually a vein.the vessel, usually a vein.

Initial thrombus acts as a site for Initial thrombus acts as a site for further platelet adherence.further platelet adherence.

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Propagation

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4 Infarction –4 Infarction –

an infarct is an area of necrosis an infarct is an area of necrosis caused by ischemia and hypoxia.caused by ischemia and hypoxia.

More common in arteries than veins More common in arteries than veins due to blood flow patterns due to blood flow patterns

Collateral circulation and Collateral circulation and anastomosis prevent infarctionanastomosis prevent infarction

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Embolism – obstruction of vessel by Embolism – obstruction of vessel by matter circulating in blood streammatter circulating in blood stream

– Matter could be fat, air, infant’s Matter could be fat, air, infant’s cells, in addition to pieces of clot – cells, in addition to pieces of clot – thromboembolithromboemboli

– Thromboemoboli from the venous Thromboemoboli from the venous system tend to end up in the:system tend to end up in the:

lungs and liverlungs and liver

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Treatment Treatment

AnticoagulantsAnticoagulants Fibrinolytics – t-PasFibrinolytics – t-Pas Prophylactic aspirin therapyProphylactic aspirin therapy

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Arterial OcclusionsArterial Occlusions

Arteriosclerosis – abnormal thickening Arteriosclerosis – abnormal thickening and hardening of the arterial wallsand hardening of the arterial walls– Smooth muscle cells and collagen fibers Smooth muscle cells and collagen fibers

migrate into the tunica intima, causing migrate into the tunica intima, causing stiffening and thickening, narrowing the stiffening and thickening, narrowing the lumenlumen

– Can exacerbate high blood pressure, and Can exacerbate high blood pressure, and cause weakening and outpouching of cause weakening and outpouching of vessel wallsvessel walls

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AtherosclerosisAtherosclerosis

A form of arteriosclerosis where soft A form of arteriosclerosis where soft deposits of intra-arterial fat and deposits of intra-arterial fat and fibrin harden over time – atheromafibrin harden over time – atheroma

May see build up in skin – May see build up in skin – Xanthoma or arcus in cornea.Xanthoma or arcus in cornea.

In general, patients suffer few In general, patients suffer few symptoms unless > 60 % of blood symptoms unless > 60 % of blood supply is blockedsupply is blocked

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Progressive over yearsProgressive over years– Starts with some injury to endotheliumStarts with some injury to endothelium

Smoking, hypertension, hyperlipidemia, Smoking, hypertension, hyperlipidemia, diabetes, autoimmune disease, and diabetes, autoimmune disease, and infectioninfection

– Inflammation, release of enzymes by Inflammation, release of enzymes by macrophages causes oxidation of LDL, which macrophages causes oxidation of LDL, which is then consumed by macrophages – foam is then consumed by macrophages – foam cells – accumulate to form fatty streakscells – accumulate to form fatty streaks

– Fatty streaks of lipid material appear first as Fatty streaks of lipid material appear first as yellow streaks and spotsyellow streaks and spots

– Smooth muscle cells proliferate, and migrate Smooth muscle cells proliferate, and migrate over the streak forming a fibrous plaqueover the streak forming a fibrous plaque

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Fibrous plaque results in necrosis of Fibrous plaque results in necrosis of underlying tissue and narrowing of underlying tissue and narrowing of lumenlumen

Inflammation can result in Inflammation can result in ulceration and rupture of the plaque, ulceration and rupture of the plaque, resulting in platelet adherence to resulting in platelet adherence to the lesion = the lesion = complicated lesioncomplicated lesion

Can result in rapid thrombus Can result in rapid thrombus formation with complete vessel formation with complete vessel occlusion occlusion → → tissue ischemia and tissue ischemia and infarction infarction

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Clinical manifestationsClinical manifestations

Signs and symptoms of inadequate Signs and symptoms of inadequate perfusion – TIAs, often associated perfusion – TIAs, often associated with exercise or stresswith exercise or stress

When lesion becomes complicated, When lesion becomes complicated, can result in tissue infarctioncan result in tissue infarction– Coronary artery disease – Coronary artery disease –

myocardial ischemiamyocardial ischemia– In brain – major cause of strokeIn brain – major cause of stroke

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TreatmentTreatment

ExerciseExercise Smoking cessationSmoking cessation Control of hypertension and/ or Control of hypertension and/ or

diabetesdiabetes Reduce LDL cholesterol by diet or Reduce LDL cholesterol by diet or

medication or bothmedication or both

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Other arterial Other arterial problemsproblems Aneurism – dilation in the arterial wallAneurism – dilation in the arterial wall Most arise in aorta or major branches Most arise in aorta or major branches

as a result of atherosclerotic wall as a result of atherosclerotic wall damagedamage

Males over 50 at greatest risk for Males over 50 at greatest risk for aortic aneurysmsaortic aneurysms

Disturbs blood flow, predisposing to Disturbs blood flow, predisposing to thrombus formation - can release thrombus formation - can release thromoembolithromoemboli

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Asymptomatic until ruptureAsymptomatic until rupture– EmbolismEmbolism– DeathDeath

Treatment by surgical repairTreatment by surgical repair Aortic Dissection –bleeding into Aortic Dissection –bleeding into

vessel wall, separating vessel layersvessel wall, separating vessel layers– Men in 40-60 y.o. age group with Men in 40-60 y.o. age group with

hypertensionhypertension– Younger persons with connective tissue Younger persons with connective tissue

disease or congenital defectsdisease or congenital defects– Presents with pain – life threateningPresents with pain – life threatening

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Systemic HypertensionSystemic Hypertension A consistent increase in arterial blood A consistent increase in arterial blood

pressure caused by increased Cardiac pressure caused by increased Cardiac output or increased peripheral output or increased peripheral resistance or bothresistance or both

Leads to damage of vessel wallsLeads to damage of vessel walls If arteries constrict over a long time If arteries constrict over a long time

with increased pressure in vessel, the with increased pressure in vessel, the wall becomes thicker to withstand the wall becomes thicker to withstand the stress.stress.

Results in narrowing of arterial lumenResults in narrowing of arterial lumen Leads to inflammatory responseLeads to inflammatory response

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Causes one in eight deaths Causes one in eight deaths worldwideworldwide

Third leading cause of death in Third leading cause of death in the worldthe world

Affects 50 million AmericansAffects 50 million Americans

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Primary hypertensionPrimary hypertension Also called essential or idiopathic Also called essential or idiopathic

hypertensionhypertension 92- 95 % of all cases92- 95 % of all cases No specific cause identifiedNo specific cause identified Can happen with retention of sodium Can happen with retention of sodium

and water and water →→ increased blood increased blood volume.volume.

Also low dietary potassium, calcium Also low dietary potassium, calcium and magnesium intakesand magnesium intakes

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Other risk factorsOther risk factors

SmokingSmoking– Nicotine is a vasoconstrictorNicotine is a vasoconstrictor

Greater than 3 alcoholic drinks/ dayGreater than 3 alcoholic drinks/ day– 2-4 drinks / week lowers blood 2-4 drinks / week lowers blood

pressurepressure

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Suspected causesSuspected causes

Interaction of genetics and Interaction of genetics and environmentenvironment

Overactivity of sympathetic nervous Overactivity of sympathetic nervous systemsystem

Overactivity of renin / angiotensin/ Overactivity of renin / angiotensin/ aldosterone systemaldosterone system

Salt and water retention by kidneysSalt and water retention by kidneys And othersAnd others

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Secondary Secondary hypertensionhypertension

Caused by a systemic disease Caused by a systemic disease process that raises peripheral process that raises peripheral resistance or cardiac output = 5 - resistance or cardiac output = 5 - 10 % of cases.10 % of cases.

Renal vascular diseaseRenal vascular disease Adrenocortical tumorsAdrenocortical tumors Adrenomedullary tumorsAdrenomedullary tumors Drugs ( oral contraceptives, Drugs ( oral contraceptives,

corticosteroids, antihistamines)corticosteroids, antihistamines)

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Complicated Complicated hypertensionhypertension

Sustained primary hypertension Sustained primary hypertension that damages the structure and that damages the structure and function of the vessels function of the vessels themselves.themselves.

Commonly affects heart, aorta, Commonly affects heart, aorta, kidneys, eyes, brain, and lower kidneys, eyes, brain, and lower extremities (target-organ extremities (target-organ damage).damage).

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Clinical manifestationsClinical manifestations None in early stages other than None in early stages other than

elevated BPelevated BP Some individuals never have Some individuals never have

symptoms; others become very ill symptoms; others become very ill and dieand die

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TreatmentTreatment

Modification of life styleModification of life style DrugsDrugs

– Diuretics, beta-blockers, angiotensin Diuretics, beta-blockers, angiotensin converting enzyme inhibitorconverting enzyme inhibitor

Compliance is often difficult – patients Compliance is often difficult – patients stop taking medication when they feel stop taking medication when they feel better – can get rebound effectsbetter – can get rebound effects

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Venous DisordersVenous Disorders

Varicose veins – dilations, can lead Varicose veins – dilations, can lead to valvular insufficiencyto valvular insufficiency

Can occur in superficial veins Can occur in superficial veins (saphenous) or deep veins(saphenous) or deep veins

Causes of secondary varicose veins:Causes of secondary varicose veins:– Deep vein thrombosisDeep vein thrombosis– Congenital defects and pressure on Congenital defects and pressure on

abdominal veinsabdominal veins

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TreatmentTreatment Prevention – little can be done after Prevention – little can be done after

valves become incompetentvalves become incompetent Avoid stressors, such as standing for Avoid stressors, such as standing for

long periodslong periods Elastic support stockingsElastic support stockings Sclerotherapy – injections of drugs to Sclerotherapy – injections of drugs to

induce fibrosis of vessel induce fibrosis of vessel Surgical removal - but only when Surgical removal - but only when

deep vein are open.deep vein are open.