Chapter 18

CHAPTER 18

The Cardiovascular System: The Heart:

Part A

HEART ANATOMY Approximately the size of a fist Location

In the mediastinum between second rib and fifth intercostal space

On the superior surface of diaphragmTwo-thirds to the left of the midsternal lineAnterior to the vertebral column, posterior

to the sternum Enclosed in pericardium, a double-walled

sacPLAY Animation: Rotatable heart

Copyright © 2010 Pearson Education, Inc. Figure 18.1a

Point ofmaximalintensity(PMI)

Diaphragm

(a)

Sternum2nd ribMidsternal line

Copyright © 2010 Pearson Education, Inc. Figure 18.1c

(c)

Superiorvena cava

Left lung

AortaParietalpleura (cut)

Pericardium(cut)

Pulmonarytrunk

DiaphragmApex ofheart

PERICARDIUMSuperficial fibrous pericardium

Protects, anchors, and prevents overfilling

PERICARDIUM Deep two-layered serous pericardium

Parietal layer lines the internal surface of the fibrous pericardium

Visceral layer (epicardium) on external surface of the heart

Separated by fluid-filled pericardial cavity (decreases friction)

Copyright © 2010 Pearson Education, Inc. Figure 18.2

Fibrous pericardiumParietal layer ofserous pericardiumPericardial cavityEpicardium(visceral layerof serouspericardium)MyocardiumEndocardium

Pulmonarytrunk

Heart chamber

Heartwall

PericardiumMyocardium

LAYERS OF THE HEART WALL1. Epicardium—visceral layer of the serous

pericardium

LAYERS OF THE HEART WALL2. Myocardium

Spiral bundles of cardiac muscle cells Fibrous skeleton of the heart:

crisscrossing, interlacing layer of connective tissue

Anchors cardiac muscle fibers Supports great vessels and valves Limits spread of action potentials

to specific paths

LAYERS OF THE HEART WALL3. Endocardium is continuous with

endothelial lining of blood vessels


Fibrous pericardiumParietal layer ofserous pericardiumPericardial cavityEpicardium(visceral layerof serouspericardium)MyocardiumEndocardium

Pulmonarytrunk

Heart chamber

Heartwall

PericardiumMyocardium

CHAMBERS Four chambers

Two atriaSeparated internally by the interatrial septum

Coronary sulcus (atrioventricular groove) encircles the junction of the atria and ventricles

Auricles increase atrial volume

CHAMBERS Two ventricles

Separated by the interventricular septum

Anterior and posterior interventricular sulci mark the position of the septum externally

Copyright © 2010 Pearson Education, Inc. Figure 18.4b

(b) Anterior view

Brachiocephalic trunk

Superior vena cava

Right pulmonaryarteryAscending aortaPulmonary trunk

Right pulmonaryveins

Right atriumRight coronary artery(in coronary sulcus)Anterior cardiac veinRight ventricle

Right marginal artery

Small cardiac vein

Inferior vena cava

Left common carotidarteryLeft subclavian artery

Ligamentum arteriosumLeft pulmonary artery

Left pulmonary veins

Circumflex artery

Left coronary artery(in coronary sulcus)

Left ventricle

Great cardiac veinAnterior interventricularartery (in anteriorinterventricular sulcus)Apex

Aortic arch

Auricle ofleft atrium

ATRIA: THE RECEIVING CHAMBERS

Walls are ridged by pectinate muscles

Vessels entering right atriumSuperior vena cava Inferior vena cavaCoronary sinus

Vessels entering left atriumRight and left pulmonary veins

VENTRICLES: THE DISCHARGING CHAMBERS

Walls are ridged by trabeculae carneae

Papillary muscles project into the ventricular cavities

Vessel leaving the right ventricle Pulmonary trunk

Vessel leaving the left ventricle Aorta

Copyright © 2010 Pearson Education, Inc. Figure 18.4e

AortaLeft pulmonaryarteryLeft atriumLeft pulmonaryveins

Mitral (bicuspid)valve

Aortic valvePulmonary valveLeft ventricle

Papillary muscleInterventricularseptumEpicardiumMyocardiumEndocardium

(e) Frontal section

Superior vena cavaRight pulmonaryarteryPulmonary trunkRight atriumRight pulmonaryveinsFossa ovalisPectinate musclesTricuspid valveRight ventricle

Chordae tendineaeTrabeculae carneaeInferior vena cava

PATHWAY OF BLOOD THROUGH THE HEART

The heart is two side-by-side pumpsRight side is the pump for the

pulmonary circuitVessels that carry blood to and from the lungs

Left side is the pump for the systemic circuitVessels that carry the blood to and from all body tissues


Oxygen-rich,CO2-poor bloodOxygen-poor,CO2-rich blood

Capillary bedsof lungs wheregas exchangeoccurs

Capillary beds of allbody tissues wheregas exchange occurs

Pulmonary veinsPulmonary arteries

PulmonaryCircuit

SystemicCircuit

Aorta and branches

Left atrium

HeartLeft ventricleRight atrium

Right ventricle

Venae cavae


Right atrium tricuspid valve right ventricle

Right ventricle pulmonary semilunar valve pulmonary trunk pulmonary arteries lungs

Lungs pulmonary veins left atriumLeft atrium bicuspid valve left ventricleLeft ventricle aortic semilunar valve

aorta systemic circulation Systemic circulation vena cavae Right atrium


Equal volumes of blood are pumped to the pulmonary and systemic circuits

Pulmonary circuit is a short, low-pressure circulation

Systemic circuit blood encounters much resistance in the long pathways

Anatomy of the ventricles reflects these differences


Rightventricle

Leftventricle

Interventricularseptum

CORONARY CIRCULATION The functional blood supply to the

heart muscle itself

Arterial supply varies considerably and contains many anastomoses (junctions) among branches

Collateral routes provide additional routes for blood delivery

CORONARY CIRCULATION Arteries

Right and left coronary (in atrioventricular groove), marginal, circumflex, and anterior interventricular arteries

Veins Small cardiac, anterior cardiac, and

great cardiac veins


Rightventricle

Rightcoronaryartery

Rightatrium

Rightmarginalartery Posterior

interventricularartery

Anteriorinterventricularartery

Circumflexartery

Leftcoronaryartery

Aorta

Anastomosis(junction ofvessels)

Leftventricle

Superiorvena cava

(a) The major coronary arteries

Left atrium

Pulmonarytrunk


Superiorvena cava

Anteriorcardiacveins

Small cardiac veinMiddle cardiac vein

GreatcardiacveinCoronarysinus

(b) The major cardiac veins

Copyright © 2010 Pearson Education, Inc. Figure 18.4d

(d) Posterior surface view

AortaLeft pulmonaryarteryLeft pulmonaryveinsAuricle of leftatriumLeft atriumGreat cardiacveinPosterior veinof left ventricleLeft ventricle

Apex

Superior vena cavaRight pulmonary arteryRight pulmonary veins

Right atrium

Inferior vena cava

Right coronary artery(in coronary sulcus)

Coronary sinus

Posteriorinterventricularartery (in posteriorinterventricular sulcus)Middle cardiac veinRight ventricle

HOMEOSTATIC IMBALANCES Angina pectoris

Thoracic pain caused by a fleeting deficiency in blood delivery to the myocardium

Cells are weakened Myocardial infarction (heart attack)

Prolonged coronary blockageAreas of cell death are repaired with

noncontractile scar tissue

HEART VALVESEnsure unidirectional blood flow through

the heartAtrioventricular (AV) valves

Prevent backflow into the atria when ventricles contract

Tricuspid valve (right)Mitral valve (left)

Chordae tendineae anchor AV valve cusps to papillary muscles

HEART VALVESSemilunar (SL) valves

Prevent backflow into the ventricles when ventricles relax

Aortic semilunar valvePulmonary semilunar valve


Pulmonary valveAortic valveArea of cutaway

Mitral valveTricuspid valve

Myocardium

Tricuspid(right atrioventricular)valveMitral(left atrioventricular)valveAorticvalve

Pulmonaryvalve

(b)

Pulmonary valveAortic valveArea of cutawayMitral valveTricuspid valve

Myocardium

Tricuspid(right atrioventricular)valve

(a)

Mitral(left atrioventricular)valveAortic valvePulmonaryvalveFibrous

skeletonAnterior


Pulmonary valveAortic valveArea of cutaway

Mitral valveTricuspid valve

Myocardium

Tricuspid(right atrioventricular)valveMitral(left atrioventricular)valveAorticvalve

Pulmonaryvalve

(b)

Copyright © 2010 Pearson Education, Inc. Figure 18.8c

Pulmonaryvalve

AorticvalveArea ofcutawayMitralvalve

Tricuspidvalve

Chordae tendineaeattached to tricuspid valve flap

Papillarymuscle

(c)

Copyright © 2010 Pearson Education, Inc. Figure 18.8d

PulmonaryvalveAortic valveArea of cutawayMitral valveTricuspidvalve

Mitral valveChordaetendineae

Interventricularseptum

Myocardiumof left ventricle

Opening of inferiorvena cavaTricuspid valve

Papillarymuscles

Myocardiumof rightventricle

(d)


1 Blood returning to theheart fills atria, puttingpressure againstatrioventricular valves;atrioventricular valves areforced open.

1 Ventricles contract, forcingblood against atrioventricularvalve cusps.

2 As ventricles fill,atrioventricular valve flapshang limply into ventricles.

2 Atrioventricular valvesclose.

3 Atria contract, forcingadditional blood into ventricles.

3 Papillary musclescontract and chordaetendineae tighten,preventing valve flapsfrom everting into atria.

(a) AV valves open; atrial pressure greater than ventricular pressure

(b) AV valves closed; atrial pressure less than ventricular pressure

Direction ofblood flowAtrium

Ventricle

Cusp ofatrioventricularvalve (open)

Chordaetendineae

Papillarymuscle

Atrium

Blood inventricle

Cusps ofatrioventricularvalve (closed)


As ventriclescontract andintraventricularpressure rises,blood is pushed upagainst semilunarvalves, forcing themopen.

As ventricles relaxand intraventricularpressure falls, bloodflows back fromarteries, filling thecusps of semilunarvalves and forcingthem to close.

(a) Semilunar valves open

(b) Semilunar valves closed

AortaPulmonarytrunk

MICROSCOPIC ANATOMY OF CARDIAC MUSCLE

Cardiac muscle cells are striated, short, fat, branched, and interconnected

Numerous large mitochondria (25–35% of cell volume)

Intercalated discs: junctions between cells anchor cardiac cells

Heart muscle behaves as a functional syncytium


Nucleus

DesmosomesGap junctions

Intercalated discs Cardiac muscle cell

(a)

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Chapter 18