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© 2012 Pearson Education, Inc.
21The Cardiovascular System: The Heart
PowerPoint® Lecture Presentations prepared bySteven BassettSoutheast Community College Lincoln, Nebraska
© 2012 Pearson Education, Inc.
Introduction
The blood must stay in motion to maintain homeostasis.
The heart keeps blood moving.
The volume of blood pumped by the heart can vary widely, between 5 and 30 liters per minute.
© 2012 Pearson Education, Inc.
An Overview of the Cardiovascular System
The heart is a small organ; your heart is roughly the size of your clenched fist. Two closed circuits:
Pulmonary circuit carries carbon dioxide—rich blood from the heart to the lungs and back
Systemic circuit transports oxygen-rich blood from the heart to the rest of the body and back
The heart has four muscular chambers: Right and left atria collect blood returning to heart Right and left ventricles discharge blood into vessels to leave
the heart. Left ventricle is considered the strongest chamber of the heart and creates
the highest pressure in the circulation. Right ventricle contains the “Moderator band”.
© 2012 Pearson Education, Inc.
Figure 21.2a Location of the Heart in the Thoracic Cavity
Anterior view of the open chest cavity showing the positionof the heart and major vessels relative to the lungs. Thesectional plane indicates the orientation of part (c).
Apex of heart
Parietal pericardium(cut)
Base ofheart
Diaphragm
Right lung
TracheaThyroid gland
First rib (cut)
Left lung
© 2012 Pearson Education, Inc.
An Overview of the Cardiovascular System
Pulmonary circuit Right atrium
Tricuspid valve Right ventricle
Pulmonary valve Pulmonary
trunk/pulmonary arteries.
Systemic circuit Left atrium
Mitral valve
Left ventricle Aortic valve Aorta
© 2012 Pearson Education, Inc.
CIRCULATIONS
© 2012 Pearson Education, Inc.
The Pericardium
The pericardium is the serous membrane lining the pericardial cavity, which surrounds the heart
Visceral pericardium (epicardium) covers the heart’s outer surface
Parietal pericardium lines the inner surface of the pericardial sac
© 2012 Pearson Education, Inc.
Figure 21.2b Location of the Heart in the Thoracic Cavity
Relationships between the heart and the pericardialcavity. The pericardial cavity surrounds the heartlike the balloon surrounds the fist (right).
Pericardialcavity containing
pericardial fluid
Cut edge ofparietal pericardium
Cut edge ofepicardium(visceral pericardium)
Fibrous attachmentto diaphragm
Air space(correspondsto pericardial
cavity)
Balloon
© 2012 Pearson Education, Inc.
Structure of the Heart Wall
Three distinct layers: Epicardium — covers the outside of the heart Myocardium — cardiac muscle, the thickest
layer of the heart. The muscular ridges in the inner surface of the atria
are called Pectinate muscles. Microscopic appearance of cardiac muscle shows
branched fibers and intercalated discs. Endocardium — lines the inside of the heart
© 2012 Pearson Education, Inc.
Figure 21.3de Histological Organization of Muscle Tissue in the Heart Wall
Diagrammatic three-dimensionalview of cardiac muscle cells
The structure of an intercalated disc
Cardiac muscle cell
Mitochondria
Intercalateddisc (sectioned)
Nucleus
Cardiac musclecell (sectioned)
Bundles ofmyofibrils
Intercalateddisc
Intercalateddisc
Z lines boundto opposing cell
membranes
Gap junction
Desmosomes
© 2012 Pearson Education, Inc.
Orientation and Superficial Anatomy of Heart
The heart lies slightly to the left of the midline. The heart sits at an oblique angle to the longitudinal axis of the body. The heart is rotated slightly toward the left. The heart has external sulci that mark internal boundaries.
© 2012 Pearson Education, Inc.
Figure 21.4 Position and Orientation of the Heart
Base of heart
Ribs
Apex of heart
Inferior border
Superiorborder
Rightborder Left
border
1 1
2 2
3 3
4 4
5 5
6 6
77
88
9 9
10 10
© 2012 Pearson Education, Inc.
Figure 21.5a Superficial Anatomy of the Heart, Part I
Anterior view of the heart and greatvessels
Fat inanteriorinterventricularsulcus
LEFTVENTRICLE
RIGHTVENTRICLE
RIGHTATRIUM
Fat incoronary
sulcus
Auricleof rightatrium
Superiorvena cava
Ascendingaorta
Brachiocephalic trunk
Left common carotid artery
Auricle ofleft atrium
Pulmonarytrunk
Left pulmonaryartery
Descendingaorta
Ligamentumarteriosum
Arch of aorta
Left subclavian artery
© 2012 Pearson Education, Inc.
Figure 21.5b Superficial Anatomy of the Heart, Part I
Posterior view of the heart and greatvessels
LEFTVENTRICLE
Fat incoronary
sulcus
Coronarysinus
Left pulmonary artery
Left pulmonary veins
RIGHTVENTRICLE
LEFTATRIUM
RIGHTATRIUM
Arch of aorta
Right pulmonaryartery
Superiorvena cava
Right pulmonaryveins (superiorand inferior)
Inferiorvena cava
Fat in posteriorinterventricular sulcus
© 2012 Pearson Education, Inc.
Orientation and Superficial Anatomy of Heart
• The left and right atria• Positioned superior to the coronary sulcus• Both have thin walls• Both consist of expandable extensions called
auricles
• The left and right ventricles• Positioned inferior to the coronary sulcus• Much of the right ventricle forms the
diaphragmatic surface
© 2012 Pearson Education, Inc.
Figure 21.6a Superficial Anatomy of the Heart, Part II
In this photo, the pericardial sac has beencut and reflected to expose the heart andgreat vessels.
Parietal pericardium fused to diaphragm
RIGHTVENTRICLE
RIGHTATRIUM
LEFTVENTRICLE
Marginal branchof right
coronary artery
Coronary sulcus
Right coronaryartery
Auricle ofright atrium
Superiorvena cava
Parietalpericardium
Ascendingaorta
Fibrouspericardium
Pulmonary trunk
Auricle ofleft atrium
Anteriorinterventricularsulcus
© 2012 Pearson Education, Inc.
Diagrammatic frontal section through the relaxed heart shows the majorlandmarks and the path of blood flow through the atria and ventricles (arrows).
Inferior vena cava
RIGHT VENTRICLE
Papillary muscle
Chordae tendineae
Cusp of right AV(tricuspid) valve
Conus arteriosus
Pectinate muscles
RIGHT ATRIUM
Opening ofcoronary sinus
Ascendingaorta
Rightpulmonary
arteries
Fossa ovalis
Superiorvena cava
Brachiocephalictrunk
Aortic arch
LEFTATRIUM
Left common carotid artery
Left subclavian artery
Ligamentum arteriosum
Pulmonary trunk
Pulmonary valve
Left pulmonaryarteries
Left pulmonaryveins
Interatrial septumAortic valve
Cusp of left AV(mitral) valve
LEFT VENTRICLE
Interventricularseptum
Trabeculaecarneae
Moderatorband
Descendingaorta
Figure 21.7b Sectional Anatomy of the Heart, Part I
© 2012 Pearson Education, Inc.
Cardiac cycle
All of the electrical and mechanical events that take place during one heart beat are referred to as one cardiac cycle.
Systole — contraction Atrial systole Ventricular systole
Blood is pushed out of the heart. AV valves are closed
Diastole — relaxation, when the chambers of the heart fill. Atrial diastole
RA receives blood from SVC and IVC. LA receives blood from pulmonary veins.
© 2012 Pearson Education, Inc.
Figure 21.9a Valves of the Heart
Transverse Sections, Superior View, Atria and Vessels Removed Frontal Sections Through Left Atrium and Ventricle
POSTERIOR
ANTERIOR
RIGHTVENTRICLE
LEFTVENTRICLE
Fibrousskeleton
Left AV (bicuspid)valve (open)
Aortic valve(closed)
Pulmonaryvalve (closed)
Right AV(tricuspid)
valve (open)Ve
ntr
icu
lar
Dia
sto
le
When the ventricles are relaxed, the AV valves are open andthe semilunar valves are closed. The chordae tendineae areloose, and the papillary muscles are relaxed.
Aortic valve(closed)
Pulmonaryveins
LEFTATRIUM
Left AV(bicuspid)valve (open)
Chordaetendineae(loose)
Papillarymuscles(relaxed)
LEFT VENTRICLE(dilated)
Aortic valve closed
© 2012 Pearson Education, Inc.
Figure 21.9b Valves of the Heart
Ve
ntr
icu
lar
Sy
sto
le
When the ventricles are contracting, the AV valvesare closed and the semilunar valves are open. Inthe frontal section notice the attachment of the leftAV valve to the chordae tendineae and papillarymuscles.
RIGHTVENTRICLE
Right AV(tricuspid) valve
(closed)
Fibrousskeleton
Left AV(bicuspid) valve
(closed)LEFTVENTRICLE
Aortic valve(open)
Pulmonaryvalve (open)
Aortic valve open
Transverse Sections, Superior View, Atria and Vessels Removed Frontal Sections Through Left Atrium and Ventricle
LEFTATRIUM
Aorta
Aortic sinus
Aortic valve(open)
Left AV(bicuspid)valve (closed)
Chordaetendineae(tense)
Papillarymuscles(contracted)
Left ventricle(contracted)
© 2012 Pearson Education, Inc.
Blood supply to the heart
• The heart muscle is receiving its own blood from right and left coronary arteries.
• Coronary arteries are originating from the base of the ascending aorta.
© 2012 Pearson Education, Inc.
Figure 21.10a Coronary Circulation
Coronary vessels supplying theanterior surface of the heart
Marginal branchof RCA
Anterior cardiacveins
Small cardiacvein
Atrialbranches
of RCA
LEFTVENTRICLERIGHT
VENTRICLE
RIGHTATRIUM
Aorticarch
Rightcoronary
artery(RCA)
Pulmonarytrunk
Brachiocephalictrunk
Left common carotidartery
Left subclavian artery
LEFT ATRIUM
Left coronaryartery (LCA)
Circumflexbranch of LCA
Diagonal branchof LCA
Anteriorinterventricularbranch of LCA
Great cardiacvein
© 2012 Pearson Education, Inc.
Figure 21.10b Coronary Circulation
Coronary vessels supplying theposterior surface of the heart
Marginalbranch of LCAPosterior vein
of left ventricle
Posteriorleft ventricularbranch of LCA
Circumflexbranch of LCA
Atrial branchof LCA
LEFTVENTRICLE
RIGHTVENTRICLE
LEFTATRIUM
RIGHTATRIUM
Coronarysinus
Small cardiacvein
Rightcoronaryartery (RCA)
Right marginalbranch of RCA
Middle cardiacvein
Posterior interventricularbranch of RCA
Great cardiac vein
© 2012 Pearson Education, Inc.
The Cardiac Cycle
• The cardiac cycle consists of alternate periods of contraction and relaxation• Contraction is systole
• Blood is ejected into the ventricles• Blood is ejected into the pulmonary trunk and the
ascending aorta
• Relaxation is diastole• Chambers are filling with blood
© 2012 Pearson Education, Inc.
Figure 21.11 The Cardiac Cycle
Cardiaccycle
370msec
100msec
0msec800
msec
Ventricular diastole—early:As ventricles relax, pressure in ventriclesdrops; blood flows back against cusps ofsemilunar valves and forces them closed.Blood flows into the relaxed atria.
Ventricular systole—second phase: As ventricular pressure risesand exceeds pressurein the arteries, thesemilunar valvesopen and bloodis ejected.
Ventricular diastole—late:All chambers are relaxed.Ventricles fill passively.
Ventricular systole—first phase:Ventricular contractionpushes AV valvesclosed but does notcreate enoughpressure to opensemilunar valves.
Atrial systole ends,atrial diastolebegins
Atrial systole begins:Atrial contraction forces a small amountof additional blood into relaxed ventricles.
Start
Atrial systole
Atrial diasto le
Ven
tric
ula
rdi
asto
le
Ven
tri c
ul a
rsy
sto
le
© 2012 Pearson Education, Inc.
Figure 21.12a The Conducting System of the Heart
The stimulus for contraction is generated by pacemaker cells atthe SA node. From there, impulses follow three different pathsthrough the atrial walls to reach the AV node. After a brief delay,the impulses are conducted to the bundle of His (AV bundle), andthen on to the bundle branches, the Purkinje fibers, and theventricular myocardial cells.
Purkinje fibersModerator band
Right bundle branch
Left bundle branch
AV bundle
Atrioventricular(AV) node
Internodalpathways
Sinoatrial(SA) node
© 2012 Pearson Education, Inc.
Figure 21.12b The Conducting System of the Heart
The movement of the contractile stimulus through theheart is shown in STEPS 1–5.
SA node activity andatrial activation begin.
SA node
Time 0
Stimulus spreads acrossthe atrial surfaces andreaches the AV node. AV node
Elapsed time 50 msec
Elapsed time 150 msec
AVbundle
Bundlebranches
There is a 100 msec delayat the AV node. Atrialcontraction begins.
The impulse travels along theinterventricular septum withinthe AV bundle and the bundlebranches to the Purkinje fibersand, via the moderator band,to the papillary muscles of theright ventricle.
ModeratorbandElapsed time 175 msec
Elapsed time 225 msec
The impulse is distributed byPurkinje fibers and relayedthroughout the ventricularmyocardium. Atrial contractionis completed, and ventricularcontraction begins.
Purkinjefibers
© 2012 Pearson Education, Inc.
The Cardiac Cycle
The ECG is a recording of the electrical events in the heart and reveals the condition of cunducting system of the heart.
P wave — atrial depolarization QRS complex — ventricular depolarization T wave — ventricular repolarization
© 2012 Pearson Education, Inc.
ECG
© 2012 Pearson Education, Inc.
Figure 21.13 The Autonomic Innervation of the Heart
Sympathetic Parasympathetic
Parasympatheticpreganglionicfiber
Synapses incardiac plexus
Parasympatheticpostganglionicfibers
Sympatheticpostganglionic fiber
Cardiac nerve
Sympatheticpreganglionic
fiber
Sympathetic ganglia(cervical ganglia and
superior thoracicganglia [T1–T4])
Spinal cord
Vagus (N X)
Medullaoblongata
Vagal nucleus
Cardioacceleratorycenter
Cardioinhibitorycenter