Anatomy of the Anatomy of the Cardiovascular Cardiovascular

SystemSystemChapter 18Chapter 18

pages 677 - 724pages 677 - 724

HeartHeart Location of the heartLocation of the heart

Lies in the mediastinumLies in the mediastinum ribs 2 through 6ribs 2 through 6 approximately two thirds approximately two thirds

of its mass is to the left of of its mass is to the left of the midlinethe midline

Apex lies on the Apex lies on the diaphragm, pointing to the diaphragm, pointing to the leftleft

Base lies just below the Base lies just below the second ribsecond rib

Boundaries of the heart Boundaries of the heart are clinically important are clinically important as an aid in diagnosing as an aid in diagnosing heart disordersheart disorders

Coverings of the heartCoverings of the heart PericardiumPericardium

Fibrous pericardiumFibrous pericardium tough, loose-fitting tough, loose-fitting

inextensible sacinextensible sac

Serous pericardiumSerous pericardium parietal layer lies parietal layer lies

inside fibrous inside fibrous pericardiumpericardium

visceral layer visceral layer (epicardium) (epicardium) adheres to outside adheres to outside of the heartof the heart

provides provides protection against protection against frictionfriction

Layers of the heartLayers of the heart EpicardiumEpicardium

outer layer of heart outer layer of heart wallwall

MyocardiumMyocardium thick, contractile thick, contractile

middle layer of heart middle layer of heart wallwall

compresses the heart compresses the heart cavities, and the cavities, and the blood within them,blood within them,with great force with great force

EndocardiumEndocardium delicate inner layer of delicate inner layer of

endothelial tissueendothelial tissue

Chambers of the heartChambers of the heart

Atria (2)Atria (2) ““receiving receiving

chamberschambers”” because they because they

receive blood receive blood from veinsfrom veins

Myocardial Myocardial wall of each wall of each atrium is not atrium is not very thickvery thick

Chambers of the heartChambers of the heart VentriclesVentricles

““pumping chamberspumping chambers”” because they push because they push

blood into the large blood into the large network of vesselsnetwork of vessels

Ventricular myocardium is Ventricular myocardium is very thickvery thick because great force because great force

must be generated to must be generated to pump blood a large pump blood a large distancedistance

myocardium of left myocardium of left ventricle is thicker than ventricle is thicker than the rightthe right

because it must push because it must push blood much furtherblood much further

Heart ValvesHeart ValvesAtrioventricular (AV) valvesAtrioventricular (AV) valves

prevent blood from flowing prevent blood from flowing back into the atria from the back into the atria from the ventricles when the ventricles when the ventricles contractventricles contract

Tricuspid valve (right AV Tricuspid valve (right AV valve)valve) guards the right guards the right

atrioventricular orificeatrioventricular orifice free edges of three flaps of free edges of three flaps of

endocardium are attached endocardium are attached to papillary muscles by to papillary muscles by chordae tendineaechordae tendineae

Bicuspid, or mitral, valve (left Bicuspid, or mitral, valve (left AV valve)AV valve) similar in structure to similar in structure to

tricuspid valve except only tricuspid valve except only two flaps presenttwo flaps present

Heart ValvesHeart Valves

Semilunar (SL) valvesSemilunar (SL) valves Half-moon shaped Half-moon shaped

valves that prevent valves that prevent back flow into the back flow into the heartheart

Pulmonary Pulmonary semilunar valvesemilunar valve at entrance of at entrance of

pulmonary arterypulmonary artery Aortic semilunar Aortic semilunar

valvevalve at entrance of aortaat entrance of aorta

Blood supply of heart Blood supply of heart tissuetissue Myocardial cells Myocardial cells

receive blood from receive blood from right and left right and left coronary arteriescoronary arteries

First branches to come off First branches to come off aortaaorta

Ventricles receive blood Ventricles receive blood from branches of both right from branches of both right and left coronary arteriesand left coronary arteries

Each ventricle receives Each ventricle receives blood only from a small blood only from a small branch of corresponding branch of corresponding coronary arterycoronary artery

Most abundant blood Most abundant blood supply goes to myocardium supply goes to myocardium of left ventricleof left ventricle

The right coronary artery The right coronary artery is dominant in is dominant in approximately 50% of all approximately 50% of all hearts and the left in about hearts and the left in about 20%; in approximately 20%; in approximately 30%, neither coronary 30%, neither coronary artery is dominantartery is dominant

http://www.youtube.com/watch?v=TS0Je1m9Q8A&feature=player_detailpage

Blood supply of heart Blood supply of heart tissuetissue

Veins of the Veins of the coronary circulationcoronary circulation As a rule, veins As a rule, veins

follow a course that follow a course that closely parallels that closely parallels that of coronary arteriesof coronary arteries

After going through After going through cardiac veins, blood cardiac veins, blood enters coronary enters coronary sinus to drain into sinus to drain into right atriumright atrium

Several veins drain Several veins drain directly into right directly into right atriumatrium

Conduction system of Conduction system of the heartthe heart Key ComponentsKey Components

Sinoatrial nodeSinoatrial node hundreds of cells in right hundreds of cells in right

atrial wall near opening of atrial wall near opening of superior vena cavasuperior vena cava

Atrioventricular nodeAtrioventricular node small mass of special small mass of special

cardiac muscle in right cardiac muscle in right atrium along lower part of atrium along lower part of interatrial septuminteratrial septum

Atrioventricular bundleAtrioventricular bundle AV bundle originates in AV AV bundle originates in AV

node, extends by two node, extends by two branches down the two branches down the two sides of the interventricular sides of the interventricular septumseptum

Purkinje fibersPurkinje fibers extend out to papillary extend out to papillary

muscles and lateral walls of muscles and lateral walls of ventriclesventricles

Nerve supply of the Nerve supply of the heartheart Cardiac plexuses Cardiac plexuses

located near arch of located near arch of aorta, made up of the aorta, made up of the combination of combination of sympathetic and sympathetic and parasympathetic fibersparasympathetic fibers Most fibers end in the SA Most fibers end in the SA

node, but some end in node, but some end in the AV node and in the the AV node and in the atrial myocardiumatrial myocardium

Sympathetic nervesSympathetic nerves accelerator nervesaccelerator nerves

Vagus fibersVagus fibers inhibitory, inhibitory, or depressor, nervesor depressor, nerves

Blood Vessels Blood Vessels

ArteriesArteries Carry blood away Carry blood away

from heartfrom heart VeinsVeins

Carry Blood toward Carry Blood toward the heartthe heart

CapillariesCapillaries Carry blood to cells Carry blood to cells

of the bodyof the body

ArteriesArteries Elastic arteriesElastic arteries

Able to stretch Able to stretch without injurywithout injury

Accommodate surge Accommodate surge of blood when heart of blood when heart contracts and able to contracts and able to recoil when recoil when ventricles relaxventricles relax

aorta and its major aorta and its major branchesbranches

Muscular Muscular (distributing) (distributing) arteriesarteries Smaller in diameter Smaller in diameter

than elastic arteriesthan elastic arteries Muscular layer is Muscular layer is

thickthick brachial, gastricbrachial, gastric

Arterioles Arterioles (resistance (resistance vessels)vessels)

Smallest arteriesSmallest arteries Important in Important in

regulating blood regulating blood flow to end-organsflow to end-organs

MetarteriolesMetarterioles Short connecting Short connecting

vessel between vessel between true arteriole and true arteriole and 20 to 100 20 to 100 capillariescapillaries

Encircled by Encircled by precapillary precapillary sphincterssphincters

CapillariesCapillariesTrue capillariesTrue capillaries

receive blood flowing from receive blood flowing from metarteriole with input metarteriole with input regulated by precapillary regulated by precapillary sphincterssphincters

Continuous Continuous capillariescapillaries

Continuous lining of Continuous lining of endothelial cellsendothelial cellsOpenings called intercellular Openings called intercellular clefts exist between adjacent clefts exist between adjacent endothelial cellsendothelial cells

Fenestrated Fenestrated capillariescapillaries

Have both intercellular clefts Have both intercellular clefts and and ““holesholes”” to facilitate to facilitate exchange functions exchange functions

SinusoidsSinusoidsLarge lumen and tortuous Large lumen and tortuous coursecourseAbsent or incomplete Absent or incomplete basement membranebasement membrane

VeinsVeins

VeinsVeins Carry blood toward Carry blood toward

the heartthe heart Act as collectors Act as collectors

and as reservoir and as reservoir vesselsvessels

capacitance vesselscapacitance vessels TypesTypes

VeinulesVeinules VeinsVeins

Blood Vessel LayersBlood Vessel Layers

Three Main layersThree Main layers Tunica adventitiaTunica adventitia

found in arteries found in arteries and veinsand veins

Tunica mediaTunica media found in arteries found in arteries

and veinsand veins Tunica intimaTunica intima

found in all blood found in all blood vesselsvessels

only layer present in only layer present in capillariescapillaries

Building Blocks of Blood Building Blocks of Blood VesselsVessels

Lining endothelial Lining endothelial cellscells Only lining found in Only lining found in

capillarycapillary Line entire vascular Line entire vascular

treetree Provide a smooth luminal Provide a smooth luminal

surfacesurface——protects against protects against intravascular coagulationintravascular coagulation

Capable of secreting a Capable of secreting a number of substancesnumber of substances

Capable of Capable of reproductionreproduction

Building Blocks of Blood Building Blocks of Blood VesselsVessels

Collagen fibersCollagen fibers Exhibit woven Exhibit woven

appearanceappearance Have only a limited Have only a limited

ability to stretch ability to stretch (2% to 3%) under (2% to 3%) under physiological physiological conditionsconditions

Function to Function to strengthen and strengthen and keep lumen of keep lumen of vessel openvessel open

Building Blocks of Building Blocks of Blood VesselsBlood Vessels Elastic fibersElastic fibers

Fibers can stretch over Fibers can stretch over 100% under 100% under physiological conditionsphysiological conditions

Play important role in Play important role in creating passive tension creating passive tension to help regulate blood to help regulate blood pressure throughout pressure throughout cardiac cyclecardiac cycle

Smooth muscle fibersSmooth muscle fibers Present in all segments Present in all segments

of vascular system of vascular system except capillariesexcept capillaries

Most numerous in elastic Most numerous in elastic and muscular arteriesand muscular arteries

Exert active tension in Exert active tension in vessels when contractingvessels when contracting

Circulatory routesCirculatory routes Systemic circulationSystemic circulation

Left sided pumpLeft sided pump blood flows from the blood flows from the

left ventricle of the left ventricle of the heart through blood heart through blood vessels to all parts of vessels to all parts of the bodythe body

except gas except gas exchange tissues exchange tissues of lungsof lungs

back to right atriumback to right atrium

Circulatory routesCirculatory routes

Pulmonary circulationPulmonary circulation Right Sided pumpRight Sided pump venous blood moves venous blood moves

from right atrium to from right atrium to right ventricle to right ventricle to pulmonary artery to pulmonary artery to lung arterioles and lung arterioles and capillaries capillaries

gases are exchangedgases are exchanged oxygenated blood oxygenated blood

returns to left atrium returns to left atrium via pulmonary veinsvia pulmonary veins

Systemic circulationSystemic circulation

Arterial anastomosis Arterial anastomosis open into other open into other

branches of the same branches of the same or other arteries or other arteries

Arteriovenous Arteriovenous anastomoses anastomoses shunts occur when shunts occur when

blood flows from an blood flows from an artery directly into a artery directly into a veinvein

Systemic circulationSystemic circulation

Superior Vena CavaSuperior Vena Cava Venous blood from Venous blood from

the head, neck, the head, neck, upper extremities, upper extremities, and thoracic cavityand thoracic cavity

except lungs except lungs Inferior vena cavaInferior vena cava

Venous blood from Venous blood from lower extremities lower extremities and abdomenand abdomen

Fetal circulationFetal circulation Two umbilicalTwo umbilical arteriesarteries

extensions of internal extensions of internal iliac arteries;iliac arteries;

carry fetal blood to carry fetal blood to placentaplacenta

PlacentaPlacenta attached to uterine wallattached to uterine wall where exchange of where exchange of

oxygen and other oxygen and other substances between the substances between the separated maternal and separated maternal and fetal blood occurs fetal blood occurs

Umbilical veinUmbilical vein returns oxygenated returns oxygenated

blood from placenta to blood from placenta to fetusfetus

enters body through enters body through umbilicus continues as umbilicus continues as ductus venosusductus venosus

Ductus venosus Ductus venosus continuation of continuation of

umbilical vein, drains umbilical vein, drains into inferior vena cavainto inferior vena cava

Foramen ovaleForamen ovale opening in septum opening in septum

between right and left between right and left atriaatria

Ductus arteriosusDuctus arteriosus small vessel small vessel

connecting pulmonary connecting pulmonary artery with descending artery with descending thoracic aortathoracic aorta

Diagram of Fetal Blood Diagram of Fetal Blood FlowFlow

Fetal circulationFetal circulation Changes in circulation at Changes in circulation at

birthbirth When umbilical cord is cut, the When umbilical cord is cut, the

two umbilical arteries, the two umbilical arteries, the placenta and the umbilical vein placenta and the umbilical vein no longer functionno longer function

Umbilical vein within the babyUmbilical vein within the baby’’s s body becomes the round ligament body becomes the round ligament of the liverof the liver

Ductus venosus becomes the Ductus venosus becomes the ligamentum venosum of the liverligamentum venosum of the liver

Foramen ovaleForamen ovale functionally closed shortly after a functionally closed shortly after a

newbornnewborn’’s first breath and s first breath and pulmonary circulation is establishedpulmonary circulation is established

structural closure takes structural closure takes approximately 9 monthsapproximately 9 months

Ductus arteriosusDuctus arteriosus contracts with establishment of contracts with establishment of

respiration, becomes ligamentum respiration, becomes ligamentum arteriosumarteriosum

Changes over timeChanges over time BirthBirth

change from placenta-dependent change from placenta-dependent systemsystem

Childhood to adulthoodChildhood to adulthood Exercise thickens myocardium Exercise thickens myocardium increases blood supplyincreases blood supply

Adulthood through later Adulthood through later adulthoodadulthood degenerative changesdegenerative changes

AtherosclerosisAtherosclerosis blockage or weakening of critical blockage or weakening of critical

arteriesarteries Heart valves and myocardial Heart valves and myocardial

tissue degenerate - reduces tissue degenerate - reduces pumping efficiencypumping efficiency