Dr Fadel NaimAss. Prof. Faculty of Medicine

IUG

Cardiovascular SystemCardiovascular SystemThe HeartThe Heart

Size of HeartSize of HeartSize of HeartSize of Heart

Average Size of Heart• 14 cm long• 9 cm wide

Location of HeartLocation of HeartLocation of HeartLocation of Heart

Inside thoracic cavityposterior to sternum medial to lungs anterior to vertebral columnapex tipped toward the left; base superior base lies beneath 2nd rib apex at 5th intercostal space lies upon diaphragm

Functions of the HeartFunctions of the HeartFunctions of the HeartFunctions of the Heart

Center of the cardiovascular system, the heart. Center of the cardiovascular system, the heart. Connects to Connects to blood vesselsblood vessels that transport blood between the that transport blood between the

heart and other body tissues. heart and other body tissues. – arteriesarteries carry blood away from the heart carry blood away from the heart– veins veins carry blood carry blood back to the heartback to the heart

Arteries Arteries carry blood carry blood high in oxygenhigh in oxygen.. – (except for the pulmonary arteries) (except for the pulmonary arteries)

VeinsVeins carry blood carry blood low in oxygenlow in oxygen.. – (except for the pulmonary veins)(except for the pulmonary veins)

Arteries and veins entering and leaving the heart are called Arteries and veins entering and leaving the heart are called the great vesselsthe great vessels..

Characteristics and Functions of the HeartCharacteristics and Functions of the HeartCharacteristics and Functions of the HeartCharacteristics and Functions of the Heart

Ensures the Ensures the unidirectionalunidirectional flow of blood through flow of blood through both the heart and the blood vessels. both the heart and the blood vessels.

Backflow of blood is prevented by Backflow of blood is prevented by valvesvalves within within the heart. the heart.

Acts like Acts like two independent, side-by-side pumpstwo independent, side-by-side pumps that work independently but that work independently but at the same rate. at the same rate. (double circuit)(double circuit)– one directs blood to the one directs blood to the lungslungs for for gas exchangegas exchange– the other directs blood to the other directs blood to body tissuesbody tissues for for nutrient nutrient

delivery delivery

Characteristics and Functions of the HeartCharacteristics and Functions of the HeartCharacteristics and Functions of the HeartCharacteristics and Functions of the Heart

Develops blood Develops blood pressure pressure through alternate through alternate cycles of heart wall contraction and cycles of heart wall contraction and relaxation. relaxation.

Minimum blood pressure is essential to Minimum blood pressure is essential to pushpush blood through blood vessels to the blood through blood vessels to the body tissues for nutrient and waste body tissues for nutrient and waste exchange.exchange.

Pulmonary & Systemic CircuitsPulmonary & Systemic CircuitsPulmonary & Systemic CircuitsPulmonary & Systemic Circuits

artery

vein

capillaries

Pulmonary and Systemic Circuits Pulmonary and Systemic Circuits Pulmonary and Systemic Circuits Pulmonary and Systemic Circuits

The pulmonary circuitThe pulmonary circuit consists of the consists of the chambers on the chambers on the right side of the heartright side of the heart (right atrium and ventricle) as well as the (right atrium and ventricle) as well as the pulmonary arteries and veins.pulmonary arteries and veins.– conveys blood conveys blood to the lungsto the lungs via pulmonary via pulmonary

arteriesarteries– to reduce carbon dioxide and replenish oxygen to reduce carbon dioxide and replenish oxygen

levels in the bloodlevels in the blood– Blood returns to the heart in pulmonary veinsBlood returns to the heart in pulmonary veins

Pulmonary and Systemic Circuits Pulmonary and Systemic Circuits Pulmonary and Systemic Circuits Pulmonary and Systemic Circuits

Blood returns to the Blood returns to the left side of the heartleft side of the heart, , where it then enters where it then enters the systemic circuitthe systemic circuit..

The systemic circuit consists of the The systemic circuit consists of the chambers on the left side of the heartchambers on the left side of the heart (left (left atrium and ventricle), along with atrium and ventricle), along with all the all the other named blood vessels.other named blood vessels.– carries blood to all the carries blood to all the peripheral organsperipheral organs and and

tissuestissues of the bodyof the body

Pulmonary and Systemic CircuitsPulmonary and Systemic CircuitsPulmonary and Systemic CircuitsPulmonary and Systemic Circuits

OxygenatedOxygenated blood from the left side of the heart is pumped blood from the left side of the heart is pumped into the into the aortaaorta– the largest systemic artery in the bodythe largest systemic artery in the body– then into smaller systemic then into smaller systemic arteriesarteries..

Gas exchange in tissues occurs from Gas exchange in tissues occurs from capillaries.capillaries. Systemic Systemic veinsveins then carry deoxygenated blood (high in then carry deoxygenated blood (high in

carbon dioxide) and waste products. carbon dioxide) and waste products. Most veins Most veins merge and drain into the superior and inferior merge and drain into the superior and inferior

venae cavaevenae cavae– drain blood into the drain blood into the rightright atrium. atrium.

There, the blood enters the pulmonary circuit, and the There, the blood enters the pulmonary circuit, and the cycle cycle repeats .repeats .

PericardiumPericardiumPericardiumPericardium

Fibrous, serous sacFibrous, serous sac– Contains the heartContains the heart– In the mediastinumIn the mediastinum– Held in place by connective Held in place by connective

tissuetissue» The external wall of the great The external wall of the great

vessels’ superior to the heartvessels’ superior to the heart» diaphragm inferior. diaphragm inferior.

Restricts heart movementsRestricts heart movements Prevents the heart fromPrevents the heart from

overfillingoverfilling with blood. with blood.

PericardiumPericardiumPericardiumPericardium

Outer portionOuter portion– tough, dense connective tissuetough, dense connective tissue– called the called the fibrous pericardiumfibrous pericardium..– attached to both the attached to both the

sternum and the sternum and the diaphragm diaphragm

Inner portionInner portion– thin, double-layered serous thin, double-layered serous

membranemembrane– called the called the serous pericardium.serous pericardium.

» parietal layer parietal layer » visceral layervisceral layer

PericardiumPericardiumPericardiumPericardium

Heart Wall StructureHeart Wall StructureHeart Wall StructureHeart Wall Structure

ThreeThree distinctive layers: distinctive layers: – external external epicardiumepicardium

– middle myocardium middle myocardium

– internal endocardiuminternal endocardium

EpicardiumEpicardium– outermost heart layeroutermost heart layer

– also known as the visceral layer of serous pericardium. also known as the visceral layer of serous pericardium.

– Simple squamous epithelium underlined by fat Simple squamous epithelium underlined by fat

As we age, more fat is deposited in the epicardiumAs we age, more fat is deposited in the epicardium– this layer becomes thicker and more fatty.this layer becomes thicker and more fatty.

Heart Wall StructureHeart Wall StructureHeart Wall StructureHeart Wall Structure

MyocardiumMyocardium– middle layermiddle layer of the heart wall of the heart wall– composed chiefly of cardiac composed chiefly of cardiac

muscle tissue.muscle tissue.– thickest of the three heart wall thickest of the three heart wall

layers. layers. – lies lies deep to the deep to the

epicardium and superficial epicardium and superficial to the endocardium to the endocardium

EndocardiumEndocardium– covers covers internal surfaceinternal surface of the of the

heart and the external surfaces heart and the external surfaces of the heart valvesof the heart valves

– thin endotheliumthin endothelium– areolar CT under the areolar CT under the

endotheliumendothelium

Functions of the Fibrous Functions of the Fibrous Skeleton of the HeartSkeleton of the Heart

Functions of the Fibrous Functions of the Fibrous Skeleton of the HeartSkeleton of the Heart

Located Located between the atria and the ventriclesbetween the atria and the ventricles Formed from Formed from dense irregular connective tissue.dense irregular connective tissue.

– separatesseparates the atria and ventricles the atria and ventricles– anchors heart valvesanchors heart valves by forming supportive rings at their by forming supportive rings at their

attachment points attachment points – provides provides electrical insulationelectrical insulation between atria and ventricles between atria and ventricles

» ensures that muscle impulses are not spread randomly throughout the ensures that muscle impulses are not spread randomly throughout the heartheart

» prevents all of the heart chambers from beating at the same time prevents all of the heart chambers from beating at the same time

Provides a Provides a rigid frameworkrigid framework for the attachment of cardiac for the attachment of cardiac muscle tissue.muscle tissue.

External Anatomy of the HeartExternal Anatomy of the HeartExternal Anatomy of the HeartExternal Anatomy of the Heart Chambers:Chambers:

– four hollow chambers:four hollow chambers: » two smaller two smaller atriaatria

» two larger two larger ventricles.ventricles.

AtriaAtria– thin-walled,thin-walled, located located superiorly.superiorly.

– anterior part of each atrium is a wrinkled, flaplike extension anterior part of each atrium is a wrinkled, flaplike extension called an called an auricleauricle

Atria receive bloodAtria receive blood through both circulatory circuits. through both circulatory circuits.– right atriumright atrium receives blood from the systemic circuit receives blood from the systemic circuit – left atriumleft atrium receives blood receives blood from the pulmonary circuit from the pulmonary circuit

External Anatomy of the HeartExternal Anatomy of the HeartExternal Anatomy of the HeartExternal Anatomy of the Heart

Blood that enters an atrium is passed to the Blood that enters an atrium is passed to the ventricleventricle on the on the same sidesame side of the heart. of the heart.

VentriclesVentricles– the the inferiorinferior chambers. chambers.– Two large arteries, the Two large arteries, the pulmonary trunkpulmonary trunk and the and the aorta aorta exit exit

the heart at the the heart at the basal basal surface. surface. The The pulmonary trunkpulmonary trunk carries blood from the carries blood from the right right

ventricle into the pulmonary circuit.ventricle into the pulmonary circuit. The The aorta aorta conducts blood from the conducts blood from the left ventricle into left ventricle into

the systemic circuitthe systemic circuit

External Anatomy of the HeartExternal Anatomy of the HeartExternal Anatomy of the HeartExternal Anatomy of the Heart

Atria are separated from the ventricles Atria are separated from the ventricles externally by externally by coronary sulcus (or coronary sulcus (or atrioventricular sulcus)atrioventricular sulcus)– extends around the extends around the circumference circumference of the heart. of the heart.

On both the anterior and posterior surfaces of On both the anterior and posterior surfaces of the heart, the the heart, the anterior interventricular sulcus anterior interventricular sulcus and the posterior interventricular sulcusand the posterior interventricular sulcus are are located located between the left and right ventricles. between the left and right ventricles.

These sulci extend inferiorly from the These sulci extend inferiorly from the coronary sulcuscoronary sulcus toward the heart toward the heart apex. apex.

Internal Anatomy of the Internal Anatomy of the HeartHeart

Internal Anatomy of the Internal Anatomy of the HeartHeart

There are There are fourfour heart chambers: heart chambers:– right atriumright atrium

– right ventricle right ventricle

– left atrium left atrium

– left ventricleleft ventricle

Each plays a role in the continuous process of blood Each plays a role in the continuous process of blood circulation.circulation.

Valves Valves permit the passage of blood permit the passage of blood in one direction and in one direction and prevent its backflow. prevent its backflow.

Left vs. Right VentricleLeft vs. Right VentricleLeft vs. Right VentricleLeft vs. Right Ventricle

Left: high pressure Left: high pressure pump - Right: low pump - Right: low pressure pump pressure pump right right chamber is thinner chamber is thinner walled than leftwalled than left

Ventricles separated by Ventricles separated by interventricular septuminterventricular septum

Structure and Function of ValvesStructure and Function of Valves

= Mitral valve

4 sets of valves

Prevent backflow of blood

Close passively under blood pressure

Heart sounds produced by valve closure

Function of the Heart ValvesFunction of the Heart ValvesFunction of the Heart ValvesFunction of the Heart Valves

picture taken from R ventricle, looking toward R atrium

Support for AV valves: Support for AV valves:

valves are restrained by chordae tendinae which are in turn attached to papillary muscles (prevention of backflow!)

Mitral Valve ProlapseMitral Valve ProlapseMitral Valve ProlapseMitral Valve Prolapse Most common cardiac variation (5-10% of Most common cardiac variation (5-10% of

population)population)

Mitral valve cusps do not Mitral valve cusps do not close properlyclose properly

Regurgitation during left Regurgitation during left ventricular systoleventricular systole

Not life threatening; Not life threatening; may be may be

lifestyle threateninglifestyle threatening

Blood flow pattern through the heartBlood flow pattern through the heartBlood flow pattern through the heartBlood flow pattern through the heart

1.1. Blood enters right atriumBlood enters right atrium2.2. Passes tricuspid valve into right ventriclePasses tricuspid valve into right ventricle3.3. Leaves by passing pulmonary semilunar valves into Leaves by passing pulmonary semilunar valves into

pulmonary trunk and to the lungs to be oxygenatedpulmonary trunk and to the lungs to be oxygenated4.4. Returns from the lung by way of pulmonary veins into the Returns from the lung by way of pulmonary veins into the

left atriumleft atrium5.5. From left atrium past bicuspid valve into left ventricleFrom left atrium past bicuspid valve into left ventricle6.6. Leaves left ventricle past aortic semilunar valves into Leaves left ventricle past aortic semilunar valves into

aortaaorta7.7. Distributed to rest of the bodyDistributed to rest of the body

Coronary Circulation Coronary Circulation Coronary Circulation Coronary Circulation

Left and right coronary arteries travel in the coronary Left and right coronary arteries travel in the coronary sulcus (atrioventricular groove) of the heart to supply sulcus (atrioventricular groove) of the heart to supply the heart wall. the heart wall. – the only branches of the ascending aorta the only branches of the ascending aorta

Located immediately superior to the aortic semilunar Located immediately superior to the aortic semilunar valve. valve.

The The right coronary arteryright coronary artery typically branches into the typically branches into the – marginal arterymarginal artery

» supplies the right border of the heartsupplies the right border of the heart

– posterior interventricular arteryposterior interventricular artery» supplies both the left and right ventriclessupplies both the left and right ventricles

Coronary Circulation Coronary Circulation Coronary Circulation Coronary Circulation

Left coronary arteryLeft coronary artery typically branches into the typically branches into the anterior interventricular arteryanterior interventricular artery.. – also called the left anterior descending arteryalso called the left anterior descending artery– supplies the anterior surface of both ventricles and most supplies the anterior surface of both ventricles and most

of the interventricular septumof the interventricular septum Circumflex arteryCircumflex artery..

– supplies the left atrium and ventricle supplies the left atrium and ventricle Arterial pattern can Arterial pattern can varyvary greatly greatly among individuals. among individuals.

Risk Factors for CADRisk Factors for CADRisk Factors for CADRisk Factors for CAD

High blood cholesterolHigh blood cholesterol High blood pressureHigh blood pressure SmokingSmoking ObesityObesity Diabetes mellitusDiabetes mellitus Type “A” personalityType “A” personality Sedentary lifestyleSedentary lifestyle

Angiogram of Coronary ArteriesAngiogram of Coronary ArteriesAngiogram of Coronary ArteriesAngiogram of Coronary Arteries

Myocardial Infarction (MI)Myocardial Infarction (MI)Myocardial Infarction (MI)Myocardial Infarction (MI) ~ 1.3 Mio MIs / year in US~ 1.3 Mio MIs / year in US Most commonly due to severe CAD (coronary Most commonly due to severe CAD (coronary

thrombosis)thrombosis) Ischemic tissue degenerates → nonfunctional area = Ischemic tissue degenerates → nonfunctional area =

infarctinfarct

THE ENDTHE ENDTHE ENDTHE END