The heart!!!!!!

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The Heart
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 2.1
The Cardiovascular System
A closed system: heart and blood
vessels
 The heart pumps blood
 Blood vessels allow blood to circulate
A double system:
Pulmonary circuit
Systemic circuit
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 11.1
The Cardiovascular System
 Functions:
Delivery system for everything!
Supplies oxygen & nutrients to
tissues
Remove carbon dioxide and other
waste products
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 11.1
The Heart
 Location
 Thoracic cavity, between the lungs
 Pointed apex directed toward left hip
 2/3 to left of median plane
 Size: About the same as your fist
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 11.2a
Location and Orientation within the Thorax
Figure 18.2
The Heart: Did You Know…
 A blue whale’s heart may weight 1000
pounds (454,000 grams)
It’s the size of a VW beetle!
 An elephant heart may weigh 75
pounds
Heart rate about 10 bpm
 A mouse’s heart weighs ~ 10 grams
 Heart rate about 250 bpm
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 11.2a
The Heart: Coverings
 Pericardium – a double serous
membrane that encloses the heart &
protects it from continuous friction of the
moving sternum
 Average heart beat is 72 beats/minute.
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 11.3
The Heart: Coverings
The Heart: Coverings
 Pericardial cavity: between layers
Serous fluid fills the space
Fluid required for lubrication
Heart moves!!
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 11.3
Structure of the Heart – Coverings
Figure 18.3
The Heart: Chambers
 Right and left side are separate systems
 The septum is the wall that divides the
heart into 2 equal halves
 Four chambers
 Atria
 Thin walled upper chambers
 Receiving chambers
 Right atrium (-O2 blood)
 Left atrium (+O2 blood)
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 11.6
External Heart Anatomy
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 11.2a
Slide 11.5
The Heart: Chambers
 Ventricles
 Thick walled, lower chambers
 Pumping chambers
 Right ventricle:
to pulmonary circuit (-O2 blood)
has a thinner wall than the left because it
only has to pump blood to the lungs
 Left ventricle
To systemic circuit (+O2 blood)
Strongest chamber in the human heart
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 11.6
External Heart Anatomy
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 11.2a
Slide 11.5
The Heart: Valves
 Function: to direct blood flow
 Two pairs
 Atrioventricular valves – between atria and
ventricles
 Bicuspid (Mitral) valve (left)
 Tricuspid valve (right)
 “Active”: function with cardiac muscle
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 11.8
Heart Valves
Figure 18.5c
The Heart: Valves
 Semilunar valves between ventricle and
artery
 “Passive”: depend on blood pressure
 Pulmonary semilunar valve
RV to pulmonary trunk
 Aortic semilunar valve
LV to aorta
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 11.8
Heart Valves
Figure 18.5c
The Heart: Valves
 Valves open as blood is pumped
through
 AV valves held in place by chordae
tendineae (“heart strings”)
 Close to prevent backflow
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 11.9
Heart Valves
Fig. 12.7
Figure 18.5c
Operation of Heart Valves
Fig. 12.9
Figure 11.4
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 11.10
The Heart: Associated Great Vessels
 Great Arteries
Aorta
 Leaves left ventricle
 Supplies systemic circuit
Pulmonary trunk (artery)
 Leaves right ventricle
 Supplies pulmonary circuit
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 11.11
Great Arteries
The Heart: Associated Great Vessels
 Great Veins
Venae cavae (superior, inferior)
 Enter right atrium
 Drain systemic circuit
Pulmonary veins (four)
 Enter left atrium
 Drain pulmonary circuit
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 11.11
Great Vessels
Figure 18.5c
Coronary Circulation
 The heart muscle has its own blood
supply
Part of systemic circuit
 Coronary arteries (+O2 blood)
 Cardiac veins (-O2 blood)
 Blood returns to the right atrium via the
coronary sinus (-O2 blood)
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 11.12
Coronary Circuit, Anterior View
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 11.2a
Slide 11.5
Coronary Circuit, Posterior View
The Heart: Conduction System
 Intrinsic conduction system
(nodal system)
 Heart muscle cells contract without nerve
impulses
 Heart has an intrinsic rhythm (“built in”)
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 11.13a
The Heart: Conduction System
 Specialized cardiac muscle tissue
 Sinoatrial (SA) node
 Pacemaker
 Atrioventricular (AV) node
 Atrioventricular bundle (of His)
 Bundle branches (R and L)
 Purkinje fibers
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 11.13b
The Heart: conduction system
Fig. 12.15
Figure 11.5
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Heart Contractions
 Contraction is initiated by the sinoatrial
node: “pacemaker”
 Sits on top of the right atria
 Sends information to all muscle cells of
both atria
 Atria contract simultaneously
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 11.14a
The Heart: conduction system
Fig. 12.15
Figure 11.5
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Heart Contractions
 Impulse transmission
AV Node serves as “booster station”
Sits on top of the septum wall
Sends impulse through AV bundle,
along bundle branches (Bundle of
His)
Finally to Purkinje fibers
Ventricle muscles contract
simultaneously
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 11.14a
Heart: conduction system
Figure 11.5
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 11.14b
The Heart: Cardiac Cycle
 Atria contract simultaneously
 Atria relax, then ventricles contract
Systole = contraction of ventricles
Diastole = relaxation of ventricles
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 11.16
The Heart: Cardiac Cycle
 The SA Node or pacemaker of the heart is
where the heartbeat originates
 When the atria fill with blood, pressure in the
atria is greater than that of the ventricles,
which forces the tricuspid and bicuspid
valves to open
 When the ventricles contract, pressure inside
them increases sharply, causing the “A-V
valves” to close and the pulmonary and
aortic valves to open
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 11.16
Heart Sounds
• “Lub-dub” – sound of valves closing
• First sound “lub” – occurs as the ventricles contract
and the AV valves are closed
• Second sound “dub” – occurs as the ventricles
relax and the aortic and pulmonary valves are
closing
The Cardiac Cycle
Fig. 12.17
Figure 11.6
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 11.15
ECG
• Electrocardiogram is a
recording of the electrical
changes that occur during
the cardiac cycle
• P wave:
• Atrial depolarization which
leads to the contraction of the
atria.
• QRS complex:
• Depolarization of the
ventricles.
• Atrial repolarization.
• T wave:
• Ventricular repolarization or
gain of electrical charge.
Fig. 12.16
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