chapter 22 - heart
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13-1Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Chapter 22Heart
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Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
In thoracic cavity mediastinum Between the lungs
Between the sternum and vertebral column
Majority of heart is left of the bodys midline
Heart Location
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Heart Orientation
Cone-shaped; size of clenched fist Apex - directed anteriorly, inferiorly and to left
Base - directed posteriorly, superiorly and to right
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Heart Orientation
Rotated such that the right side is located
more anteriorly
the left side is located
more posteriorly.
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Pericardium
Fibrous pericardium tough, dense CT
protects
anchors heart to diaphragm
and major blood vessels restricts movement
prevents over-filling
Serous pericardium
thin delicate membrane contains
parietal layer-outer layer
pericardial cavity withpericardial fluid
visceral layer (epicardium)
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Fibrous
pericardium
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Layers of Heart Wall
Epicardium
visceral layer of serous
pericardium Myocardium
cardiac muscle layer isthe bulk of the heart
Endocardium
internal lining of heart
chambers
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Intercalated Disks-Junctions for cardiac
muscle cells
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Layers Associated with the Heart
Superficial
Deep
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Functions of the Heart
Center of the cardiovascular system Connects to blood vessels that transport blood
(oxygen, nutrients) to other body tissues
arteries carry blood away from the heart
veins carry blood back to the heart
Arteries carry blood high in oxygen.
(except for the pulmonary arteries)
Veins carry blood low in oxygen.
(except for the pulmonary veins)
Arteries and veins entering and leaving the heartare called the great vessels due to their relativelylarge diameter
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Functions of the Heart
Ensures the unidirectional flow of blood through boththe heart and the blood vessels. Valves prevent backflow of blood
Acts like two independent, side-by-side pumps that
work independently but at the same rate. one directs blood to the lungs for gas exchange the other directs blood to body tissues for nutrient delivery
Heart develops blood pressure through alternate cyclesof heart wall contraction and relaxation.
Minimum blood pressure is essential to push bloodthrough blood vessels to the body tissues for nutrientand waste exchange.
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Heart Structures
4 Heart Chambers Right ventricle, left ventricle, right atrium, left atrium
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Heart Structures Right & Left Atrium
Superior to the ventricles
Atrium chambers are covered by small flaps of tissuecalled auricles (little ear)
Right atrium Receives de-oxygenatedsystemic blood by way of the superior
vena cava and inferior vena cava.
Receives de-oxygenatedblood from the heart itself
(myocardium) by way of the coronary sinus Left atrium
Receives oxygenatedblood from the lungs by way of thepulmonary veins
Internally the 2 atria are separated by thin wall calledthe interatrial septum
Atria separated from ventricles by coronary sulcus13-17
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Heart Structures
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Heart Structures
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Heart Structures Right & Left Ventricles
Located inferior to the atrium
Internally the 2 ventricles are separated by theinterventricular septum
Externally the 2 ventricles are separated by the
anterior & posterior interventricular sulci
R ventricle receives blood from the R atrium Sends blood to lungs by way of pulmonary trunk and
pulmonary arteries
L ventricle receives blood from L atrium
Sends blood out to the rest of the body by way of the aorta
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Heart Structures
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Heart Structures
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Heart Structures Valves
Purpose is to help control blood flow
Atrio-ventricular valves (AV valves)
Right AV valve (Tricuspid valve)
Left AV valve (Bicuspid valve, mitral valve)
Semilunar valves Pulmonary semilunar valve
Aortic semilunar valves
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Heart Structures Atrio-ventricular Valves (AV valves)
Right AV valve
Located between R Atrium & R Ventricle
Left AV valve
Located between L Atrium & L Ventricle
Valves remain open as ventricles fill w/blood Valves close when ventricles contract to
prevent backflow into Atrium
Action of AV valves controlled by the papillary
muscles and chordae tendinae
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Heart Structures
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Heart Structures Semilunar Valves
Pulmonary semilunar valve
Located between Right Ventricle and Pulmonary
Trunk/Artery
Aortic semilunar valve
Located between Left Ventricle and Aorta
Valves remain open as ventricles contract
Valves close when ventricles relax
Prevents backflow into the Ventricles
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Figure 22.5
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Table 22.03
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Fig. 20.10(TE Art)
Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
3
4
8
7
75
66
2
1
10
11
12
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Aorta
Right
pulmonaryveins
Inferior
vena cava
Right AV
(tricuspid)valveRightventricle
Rightatrium
Superiorvena cava
Pulmonarytrunk
Leftpulmonary
artery
Left
pulmonaryveins
Aortic valve
Left AV(bicuspid)
valve
Left atrium
Leftventricle
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Practice at Home 1. Put each heart term (chamber, valve,
artery, vein) on a notecard
2. Rearrange notecards in the order which
blood flows through the heart
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Question Does the heart muscle tissue itself
(myocardium) ever receive any blood?
YES!!
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Blood Supply of Heart Left coronary artery (oxygenated blood)
Anterior interventicular artery Supplies anterior wall of both ventricles
Circumflex artery Supplies left atrium and left ventricle
Right coronary artery (oxygenated blood)Posterior interventricular artery
Supplies posterior walls of both ventricles
Right marginal artery Supplies right border of right ventricles
Coronary sinus Returns de-oxygenated blood to right atrium
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Fig. 20.11a(TE Art)
Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Rightcoronary
artery
Aortic arch
Left coronary
artery
*Coronary arteries
branch from the aorta
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Fig. 20.11b(TE Art)
Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Coronarysinus
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*Blood going to R. Atrium
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Heart itself is responsible for initiating heart beat Nervous system alters heart rate not start of heart beat
1. Intrinsic conduction system Autorhythmic cells
Non-contractile cells that initiate and distribute impulses Act as pacemaker for heart
2. Gap junctions
SA node
cluster of autorhythmic cells in wall of right atrium generates impulse which begins heart activity
75 beats/min spreads to atria and triggers atria contraction excitation spreads to AV node
Conduction System of Heart
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Conduction System of Heart
AV node Located on the floor of the right atrium
Causes 0.1s delay in the impulse from atria toventricle
Allows atria and ventricles to contract separately Acts as a backup pacemaker (40-60bpm)
Sends impulse to AV bundle
AV bundle (Bundle of His)
The connection between atria and ventricles Brings signal from atria to ventricles Divides into bundle branches & Purkinje fibers
triggers ventricles to contract Purkinje fibers in left ventricle due to larger size
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Rhythm of Conduction System
SA node fires spontaneously 60-100 (~75) times
per minute
AV node fires at 40-60 times per minute
If both nodes are suppressed, fibers in ventricles
themselves fire 20-40 times per minute
Artificial pacemaker needed if pace is too slow
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Timing of Atrial &
Ventricular Excitation
SA node setting pace since it is the fastest
In 50 msec excitation spreads through both atria
and down to AV node
100 msec delay at AV node - allows atria to fully
contract filling ventricles before ventricles contract
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Electrocardiogram (ECG or EKG) Terminology
ECG/EKG: recording of electrical activity of heart
Cardiac cycle: all heart processes which occur from thestart of one heartbeat to the start of the next heartbeat
Systole: contraction of a heart chamber
Diastole: relaxation of a heart chamber
Depolarization: cell membrane potential becomesmore positive (less negative)
Repolarization: cell membrane potential returns toresting potential
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Electrocardiogram (ECG or EKG)
P wave
atrial depolarization (wavefrom SA node through atria)
P to Q interval
atrial systole
QRS complex
ventricular depolarization
atrial repolarization (hidden)
S - T segment
ventricular systole
T wave
ventricular repolarization
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Auscultation
Stethoscope
Sounds of heartbeat are from turbulence in
blood flow caused by valve closure
first heart sound (lubb) is created with the closing
of the atrioventricular valves
second heart sound (dupp) is created with the
closing of semilunar valves
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Heart Sounds
Where to listen on chest wall for heart sounds.