Download Ch 11 The Heart

Chapter 11
The Cardiovascular System
The Cardiovascular System
 A closed system of the
heart and blood
vessels
-heart pumps blood
-blood vessels - circulate
to all parts of body
 Deliver oxygens &
nutrients and to
remove carbon dioxide
& waste products
The Heart
 In thorax between lungs
 Pointed apex toward left hip
 Size of fist
Figure 18.1a Location of the heart in the
mediastinum.
Midsternal line
2nd rib
Sternum
Diaphragm
(a)
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Point of
maximal
intensity
(PMI)
Heart Coverings & Wall Layers
Pericardium – double Three layers
serous membrane
 Visceral - next to heart
 Parietal -
1.Epicardium- Outside
 visceral pericardium
 Connective tissue
outside layer
2.Myocardium- Middle
 Serous fluid fills space
between the layers
 Mostly cardiac muscle
3.Endocardium - Inner
 Endothelium
Figure 18.2 The pericardial layers and
layers of the heart wall.
Pulmonary
trunk
Pericardium
Myocardium
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Fibrous pericardium
Parietal layer of
serous pericardium
Pericardial cavity
Epicardium
(visceral layer Heart
of serous
wall
pericardium)
Myocardium
Endocardium
Heart chamber
External Heart Anatomy
Figure 11.2a
The Heart: Chambers
 Right and left act as
separate pumps
 Four chambers
2 Atria - Receiving
- Right atrium
- Left atrium
2 Ventricles - Discharging
- Right ventricle
- Left ventricle
Septum - divides the right
from left side of the heart.
Figure 18.6 Anatomical differences
between the right and left ventricles.
Left
ventricle
Right
ventricle
Interventricular
septum
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The Heart: Associated Great Vessels
 Aorta - Leaves left
ventricle
 Pulmonary arteries
- Leave right ventricle
 Vena cava - Enters
right atrium
 Pulmonary veins
(four) - Enter left
atrium
The Heart: Valves
 Allow blood to flow in only one direction
 Four valves
2 Atrioventricular valves – between atria & ventricles
 Bicuspid valve (left)
 Tricuspid valve (right)
2 Semilunar valves - between ventricle & artery
 Pulmonary semilunar valve
 Aortic semilunar valve
 Held in place by chordae
tendineae (“heart strings”)
Pulmonary valve
Aortic valve
Area of cutaway
Mitral valve
Tricuspid valve
Myocardium
Tricuspid
(right atrioventricular)
valve
Mitral
(left atrioventricular)
valve
Aortic valve
Fibrous
skeleton
(a)
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Pulmonary
valve
Anterior
Figure
18.8b
Heart
valves.
Myocardium
Tricuspid
(right atrioventricular)
valve
Mitral
(left atrioventricular)
valve
Aortic
valve
Pulmonary
valve
Pulmonary valve
Aortic valve
Area of cutaway
Mitral valve
Tricuspid valve
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(b)
Figure 18.8c Heart valves.
Chordae tendineae
attached to tricuspid valve flap
(c)
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Papillary
muscle
Pulmonary
valve
Aortic
valve
Area of
cutaway
Mitral
valve
Tricuspid
valve
Opening of inferior
vena cava
Tricuspid valve
Mitral valve
Chordae
tendineae
Myocardium
of right
ventricle
Myocardium
of left ventricle
Papillary
muscles
(d)
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Interventricular
septum
Pulmonary
valve
Aortic valve
Area of
cutaway
Mitral valve
Tricuspid
valve
Operation of Heart Valves
1 Blood returning to the
2 As ventricles fill,
3 Atria contract, forcing
heart fills atria, putting
pressure against
atrioventricular valves;
atrioventricular valves are
forced open.
atrioventricular valve flaps
hang limply into ventricles.
additional blood into
ventricles.
Direction of
blood flow
Atrium
Cusp of
atrioventricular
valve (open)
Chordae
tendineae
Ventricle
Papillary
muscle
(a) AV valves open; atrial pressure greater than ventricular pressure
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1 Ventricles contract, forcing blood
against atrioventricular valve cusps.
2 Atrioventricular valves close.
Atrium
Cusps of
atrioventricular
valve (closed)
Blood in
ventricle
3 Papillary muscles contract and
chordae tendineae tighten, preventing
valve flaps from everting into atria.
(b) AV valves closed; atrial pressure less than ventricular pressure
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Figure 18.10a The semilunar valves.
Aorta
Pulmonary
trunk
As ventricles
contract and
intraventricular
pressure rises,
blood is pushed up
against semilunar
valves, forcing them
open.
(a) Semilunar valves open
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Figure 18.10b The semilunar valves.
As ventricles relax
and intraventricular
pressure falls, blood
flows back from
arteries, filling the
cusps of semilunar
valves and forcing
them to close.
(b) Semilunar valves closed
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Pathway of Blood Through the Heart
• Right atrium  tricuspid valve  right ventricle
• Right ventricle  pulmonary semilunar valve 
pulmonary trunk  pulmonary arteries  lungs
PLAY
Animation: Rotatable heart (sectioned)
Pathway of Blood Through the Heart
• Lungs  pulmonary veins  left atrium
• Left atrium  bicuspid valve  left ventricle
• Left ventricle  aortic semilunar valve  aorta
• Aorta  systemic circulation
PLAY
Animation: Rotatable heart (sectioned)
Figure 18.19 Aortic
Areasvalve
of sounds
the thoracic
surface
heard
in 2nd intercostal space at
where the heart
can be best detected.
rightsounds
sternal margin
Pulmonary valve
sounds heard in 2nd
intercostal space at left
sternal margin
Mitral valve sounds
heard over heart apex
(in 5th intercostal space)
in line with middle of
clavicle
Tricuspid valve sounds typically
heard in right sternal margin of
5th intercostal space
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• Mitral Regurgitation
• Aortic Stenosis
Current Event
• Causes of elevated cholesterol levels in our blood
and typical medical methods to reduce high
cholesterol. Then focus on if/how
hypercholesterolemia can be controlled without
the use of drugs. Be very specific about how it
can be done if it is possible.
Coronary Circulation
 Blood in heart doesn’t
nourish the heart
 Heart’s nourishing
circulatory system
- Coronary arteries
- Come off the aorta
- Cardiac veins
- Blood empties into
the right atrium via
the coronary sinus
Figure 18.7a Coronary circulation.
Aorta
Superior
vena cava
Anastomosis
(junction of
vessels)
Right
atrium
Pulmonary
trunk
Left atrium
Left
coronary
artery
Circumflex
artery
Right
coronary
artery
Left
ventricle
Right
ventricle
Anterior
Right
interventricular
artery
marginal
Posterior
artery
interventricular
artery
(a) The major coronary arteries
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Figure 18.7b Coronary circulation.
Superior
vena cava
Anterior
cardiac
veins
Great
cardiac
vein
Coronary
sinus
Small cardiac vein
Middle cardiac vein
(b) The major cardiac veins
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Coronary Circulation Pattern
Aorta
Coronary Arteries
Myocardium
Coronary Circulation Pattern
Aorta
Coronary Arteries
Myocardium
Cardiac Veins
Coronary Sinus
Right Atrium
•Collateral Circulation
• Most organs receive blood from more than one arterial
branch.
• Arterial anastomosis - where arteries supplying the same
area join.
• Embolism
• Angina pectoris
• Myocardial Infarction (MI)
• Coronary bypass surgery
•
Open Heart Surgery
•
Coronary artery disease (Adam)
•
Atherosclerosis
Heart Dissection (Lab Manual pg 306)
• Heart Dissection I
• Heart Dissection II
The Heart: Cardiac Cycle
 Cardiac cycle – events of one heart beat
 Terms: Systole = contraction
 Atria contract simultaneously
 Atria relax, then ventricles contract
Diastole = relaxation
Phases of the Cardiac Cycle
1. Ventricular filling—takes place in mid-to-late
diastole
•
AV valves are open
•
80% of blood passively flows into ventricles
•
Atria contract occurs, delivering the remaining 20%
Phases of the Cardiac Cycle
2. Ventricular systole
•
Atria relax and ventricles begin to contract
•
Rising ventricular pressure results in closing of AV valves
•
In ejection phase, ventricular pressure exceeds pressure in
the large arteries, forcing the SL valves open
Phases of the Cardiac Cycle
3. Early diastole
•
Ventricles relax
•
Backflow of blood in aorta and pulmonary trunk
closes SL valves.
The Heart: Conduction System
 Intrinsic conduction system (nodal system)
 Heart muscle cells contract, without nerve impulses, in
a regular, continuous way
- Sinoatrial node – Pacemaker initiates contraction
- Sequential stimulation occurs at other autorhythmic
cells
- Atrioventricular node
- Atrioventricular bundle
- Bundle branches
- Purkinje fibers
• Heart rate controlled by its own internal
control center. The SA Node (known as the
pacemaker, 75/min) is located in the wall of
the right atrium and sends out signals that
cause the atria to contract.
• These signals also travel to the AV Node
(50/min) located in the septum between the
atria, which relays the signals to the
ventricles via the bundle of His (30/min)
and Purkinje fibers causing them to
contract.
Animation
Figure 18.14 Cardiac intrinsic conduction system and action potential succession during one heartbeat.
Superior vena cava
Right atrium
1 The sinoatrial
Pacemaker potential
(SA) node
(pacemaker)
generates impulses.
Internodal pathway
2 The impulses
SA node
Left atrium
pause (0.1 s) at the
atrioventricular
(AV) node.
3 The
atrioventricular
(AV) bundle
connects the atria
to the ventricles.
4 The bundle branches
conduct the impulses
through the
interventricular septum.
5 The Purkinje fibers
depolarize the contractile
cells of both ventricles.
(a) Anatomy of the intrinsic conduction system showing the
sequence of electrical excitation
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Atrial muscle
Purkinje
fibers
AV node
Interventricular
septum
Ventricular
muscle
Pacemaker
potential
Plateau
Milliseconds
(b) Comparison of action potential shape at
various locations
Extrinsic Innervation of the Heart
• Heartbeat is modified by the ANS
• Cardiac centers are located in the medulla
oblongata
• Cardioacceleratory center innervates SA and AV
nodes, heart muscle, and coronary arteries through
sympathetic neurons
• Cardioinhibitory center inhibits SA and AV nodes
through parasympathetic fibers in the vagus nerves
Figure 18.15 Autonomic innervation of the heart.
The vagus nerve
(parasympathetic)
decreases heart rate.
Dorsal motor nucleus of vagus
Cardioinhibitory center
Medulla oblongata
Cardioacceleratory
center
Sympathetic trunk ganglion
Thoracic spinal cord
Sympathetic trunk
Sympathetic cardiac
nerves increase heart rate
and force of contraction.
SA node
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AV node
Parasympathetic fibers
Sympathetic fibers
Interneurons
Homeostatic Imbalances
•
Defects in the intrinsic conduction system may
result in
1. Arrhythmias: irregular heart rhythms
2. Fibrillation: rapid, irregular contractions; useless for
pumping blood
Homeostatic Imbalances
• Defective SA node may result in
• Ectopic focus: abnormal pacemaker takes over
• If AV node takes over, there will be a junctional
rhythm (40–60 bpm)
• Defective AV node may result in
• Partial or total heart block
• Few or no impulses from SA node reach the ventricles
• Electrocardiogram
• A graphic record of the hearts electrical
activity.
• 3 characteristic waves called the P wave,
QRS complex, and the T wave.
Figure 18.16 An electrocardiogram tracing (lead I).
QRS complex
Sinoatrial
node
Atrial
depolarization
Ventricular
depolarization
Ventricular
repolarization
Atrioventricular
node
P-Q
Interval
S-T
Segment
Q-T
Interval
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Figure 18.17 The sequence of depolarization and repolarization of the heart related to the deflection waves of an ECG tracing.
SA node
Depolarization
R
Repolarization
R
T
P
Q
S
1 Atrial depolarization, initiated
by the SA node, causes the
P wave.
R
AV node
T
P
Q
S
4 Ventricular depolarization
is complete.
R
T
P
T
P
Q
S
2 With atrial depolarization
complete, the impulse is
delayed at the AV node.
R
Q
S
5 Ventricular repolarization
begins at apex, causing the
T wave.
R
T
P
T
P
Q
S
3 Ventricular depolarization
begins at apex, causing the
QRS complex. Atrial
repolarization occurs.
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Q
S
6 Ventricular repolarization
is complete.
Figure 18.18 Normal and abnormal ECG tracings.
(a) Normal sinus rhythm.
(c)
(b) Junctional rhythm. The SA
node is nonfunctional, P waves
are absent, and heart is paced by
the AV node at 40 - 60 beats/min.
Second-degree heart block. (d) Ventricular fibrillation. These
chaotic, grossly irregular ECG
Some P waves are not conducted
deflections are seen in acute
through the AV node; hence more
heart attack and electrical shock.
P than QRS waves are seen. In
this tracing, the ratio of P waves
to QRS waves is mostly 2:1.
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Animation
• Depolarization describes the electrical activity just
before contraction.
• Repolarization begins just before the relaxation phase.
• P wave is depolarization of the atria.
• QRS complex is depolarization of the ventricles.
• T wave is repolarization of the vetricles.
• Repolarization of atria is hidden by the QRS
complex.
The Heart: Cardiac Output
Cardiac output (CO)
 Amount of blood pumped by
each side of the heart in one
minute
 CO = (heart rate [HR]) x
(stroke volume [SV])
Stroke volume [SV]
 Volume of blood pumped by
each ventricle in one
contraction
The Heart: Regulation of Heart Rate
 Stroke volume usually remains relatively
constant
- Starling’s law of the heart: the more that
the cardiac muscle is stretched, the
stronger the contraction
 Changing heart rate is the most
common way to change cardiac output
Regulation of Heart Rate
Increased Heart Rate Decreased Heart Rate
1. Sympathetic nervous
system
 Crisis
 Low blood pressure
2. Hormones
 Epinephrine
 Thyroxine
3. Exercise
4. Decreased blood
volume
1. Parasympathetic
nervous system
2. High blood pressure or
blood volume
3. Decreased venous
return