Download The Heart

PowerPoint® Lecture Slides
prepared by
Leslie Hendon
University of Alabama,
Birmingham
19
CHAPTER
Part 1
The Heart
Location and Orientation within the Thorax
Capillary beds
of lungs where
gas exchange
occurs
•  Heart—typically weighs 250–350 grams
(healthy heart)
•  Largest organ of the mediastinum
Pulmonary
Circuit
Pulmonary veins
Aorta and branches
Venae cavae
•  Located between the lungs
•  Apex lies to the left of the midline
•  Base is the broad posterior surface
Left atrium
Right atrium
Left ventricle
Heart
Systemic Circuit
Capillary beds of all
body tissues where
gas exchange occurs
Oxygen-rich,
CO2-poor blood
Oxygen-poor,
CO2-rich blood
Figure 19.1
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Location of the Heart in the Thorax
Midsternal line
Rib 2
Structure of the Heart—Coverings
Aorta
Parietal pleura (cut)
Pulmonary trunk
Left lung
Pericardium (cut)
Diaphragm
(c)
(a)
Mediastinum
Mediastinum
Superior
vena cava
Right lung
(b)
Posterior
Right
auricle
of right
atrium
Right
ventricle
(d)
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Superior vena cava
Apex of heart
Diaphragm
Heart
•  Pulmonary circuit—vessels transport blood
to and from the lungs
•  Systemic circuit—vessels transport blood to
and from body tissues
•  (Coronary circuit– supplies blood to the heart
muscle itself)
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The Pulmonary and Systemic Circuits
Right ventricle
•  A muscular double pump
•  Atria—receive blood from the pulmonary and
systemic circuits
•  Ventricles—the pumping chambers of the heart that
eject blood from the heart
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Pulmonary
arteries
The Heart
Aorta
Left lung
Fat in
epicardium
Rib 5
Pericardium
(cut)
Apex of
heart
Figure 19.2
•  Pericardium—two primary layers
•  Fibrous pericardium
•  Strong layer of dense connective tissue
•  Serous pericardium
•  Formed from two layers
•  Parietal layer of the serous
pericardium
•  Visceral layer of the serous
pericardium
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1
Layers of the Pericardium and of the Heart
Wall
Structure of the Heart—Layers of the Heart
Wall
•  Epicardium
Pericardium
•  = Visceral layer of the serous pericardium
Myocardium
•  Myocardium
Pulmonary
trunk
•  Consists of cardiac muscle
•  Muscle arranged in circular and spiral patterns
•  Endocardium
Fibrous pericardium
Parietal layer of serous
pericardium
Pericardial cavity
•  Endothelium resting on a layer of connective tissue
•  Lines the internal walls of the heart
Epicardium (visceral
layer of serous
Heart
pericardium)
wall
Myocardium
Endocardium
Heart chamber
Figure 19.3
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Circular and Spiral Arrangements of Cardiac
Muscle Bundles
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Heart Chambers
•  Right and left atria
•  Superior chambers
•  Right and left ventricles
•  Inferior chambers
•  Internal divisions
•  Interventricular septa
•  Interatrial septa
Cardiac
muscle
bundles
•  External markings
•  Coronary sulcus
•  Anterior interventricular sulcus
•  Posterior interventricular sulcus
PLAY
Figure 19.4
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Gross Anatomy of the Heart
Left common carotid
artery
Left subclavian artery
Superior vena cava
Aortic arch
Ligamentum arteriosum
Right pulmonary artery
Left pulmonary artery
Ascending aorta
Pulmonary trunk
Left pulmonary veins
Right atrium
Right coronary artery
(in coronary sulcus)
Anterior cardiac vein
Circumflex artery
Left coronary artery
(in coronary sulcus)
Left ventricle
Inferior vena cava
(b) Anterior view
Apex
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•  Crista terminalis
•  Landmark used to locate veins entering right
atrium
•  Fossa ovalis
Great cardiac vein
Anterior interventricular
artery (in anterior
interventricular sulcus)
Small cardiac vein
•  Forms right border of heart
•  Receives blood from systemic circuit
•  Pectinate muscles
•  Ridges inside anterior of right atrium
Auricle of
left atrium
Right ventricle
Right marginal artery
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Right Atrium
Brachiocephalic trunk
Right pulmonary
veins
Rotating Heart
Figure 19.5b
•  Depression in interatrial septum
•  Remnant of foramen ovale
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2
Right Ventricle
Left Atrium
•  Receives blood from right atrium through the
tricuspid valve (or right AV valve)
•  Pumps blood into pulmonary circuit via
pulmonary trunk
•  Internal walls of right ventricle
•  Makes up heart’s posterior surface
•  Receives oxygen-rich blood from lungs
through pulmonary veins
•  Opens into the left ventricle through
•  Trabeculae carneae : irregular ridges of muscle
•  Papillary muscles: connect to ...
•  Chordae tendineae: “heart strings”– attach to valve
cusps
•  Mitral valve (left atrioventricular valve or Left
AV valve or Bicuspid valve)
•  Pulmonary semilunar valve
•  Located at opening of right ventricle and pulmonary
trunk
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Left Ventricle
Heart Chambers
Aorta
•  Forms apex of the heart
•  Internal walls of left ventricle
Superior vena cava
Right pulmonary artery
Pulmonary trunk
Right atrium
•  Trabeculae carneae
•  Papillary muscles
•  Chordae tendineae
Right pulmonary
veins
Fossa ovalis
•  Pumps blood through systemic circuit via
Pectinate muscles
Tricuspid valve
•  Aortic semilunar valve (aortic valve)
Left atrium
Left pulmonary veins
Mitral (bicuspid) valve
Aortic valve
Pulmonary valve
Right ventricle
Left ventricle
Chordae tendineae
Papillary muscle
Interventricular septum
Epicardium
Myocardium
Endocardium
Trabeculae carneae
Inferior vena cava
PLAY
Left pulmonary artery
Rotating Heart Section
(e) Frontal section
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Inferior View of the Heart
Aorta
Left pulmonary artery
Heart Valves— Valve Structure
Superior vena cava
Right pulmonary artery
Right pulmonary veins
Left pulmonary veins
Auricle of left atrium
Left atrium
Great cardiac vein
Posterior vein of
left ventricle
Left ventricle
Figure 19.5e
•  Each valve composed of
•  Endocardium with connective tissue core
•  Atrioventricular (AV) valves
Right atrium
•  Between atria and ventricles
Inferior vena cava
Coronary sinus
Right coronary artery
(in coronary sulcus)
Posterior interventricular
artery (in posterior
interventricular sulcus)
Middle cardiac vein
Right ventricle
•  Aortic and pulmonary (semilunar) valves
•  At junction of ventricles and great arteries
Apex
(d) Inferior view; surface shown rests on the diaphragm.
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Figure 19.5d
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3
Fibrous Skeleton
Heart Valves—Valve Structure
Pulmonary valve
Aortic valve
•  Surrounds all four valves
Area of cutaway
Mitral valve
•  Composed of dense connective tissue
Myocardium
Tricuspid valve
•  Functions:
• 
• 
• 
• 
Tricuspid
(right atrioventricular)
valve
Anchors valve cusps
Prevents overdilation of valve openings
Main point of insertion for cardiac muscle
Blocks direct spread of electrical impulses
from atria into ventricles
Mitral
(left atrioventricular)
valve
Aortic
valve
Pulmonary
valve
Fibrous
skeleton
(a)
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Function of the Atrioventricular Valves
1 Blood returning to
the heart fills atria,
putting pressure
against atrioventricular
valves; atrioventricular
valves are forced
open.
2 As ventricles fill,
atrioventricular
valve flaps hang
limply into
ventricles.
3 Atria contract,
forcing additional
blood into ventricles.
Anterior
Figure 19.6a
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Function of the Atrioventricular Valves
Direction of
blood flow
Atrium
Cusp of
atrioventricular
valve (open)
Chordae
tendineae
Ventricle
Papillary
muscle
1 Ventrles cicontract,
forcing blood against
atrioventricular valve
cusps.
2
Atrioventricular
valves close.
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
Atrium
Cusps of
atrioventricular
valve (closed)
Blood in
ventricle
(a) AV valves open; atrial pressure greater than ventricular pressure
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Figure 19.7a
Function of the Semilunar Valves
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Figure 19.7b
Heart Sounds
Aorta
Pulmonary
trunk
As ventricles contract
and intraventricular
pressure rises, blood
is pushed up against
semilunar valves,
forcing them open.
•  “Lub-dup”—sound of valves closing
•  First sound “lub”
•  The AV valves closing
•  Second sound “dup”
•  The semilunar valves closing
(a) Semilunar valves open
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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Figure 19.8
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4
Heart Sounds
Heart Sounds
Pulmonary valve
Aortic valve
•  Each valve sound is best heard near a
different heart corner
Area of cutaway
Mitral valve
Myocardium
Tricuspid valve
Tricuspid
(right atrioventricular)
valve
Mitral
(left atrioventricular)
valve
Aortic
valve
• 
• 
• 
• 
Pulmonary valve—superior left corner
Aortic valve—superior right corner
Mitral (bicuspid) valve—at the apex
Tricuspid valve—inferior right corner
Pulmonary
valve
Fibrous
skeleton
Anterior
(a)
Figure 19.6a
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Heart Sounds
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Pathway of Blood Through the Heart
Aortic valve sounds
heard in 2nd intercostal
space at right sternal
margin
•  Beginning with oxygen-poor blood in the
superior and inferior venae cavae...
Pulmonary valve
sounds heard in 2nd
intercostal space at left
sternal margin
•  Go through pulmonary and systemic circuits
•  A blood drop passes through all structures
sequentially
•  Atria contract together
•  Ventricles contract together
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
Figure 19.9
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Blood Flow Through the Heart
Superior vena cava (SVC)
Inferior vena cava (IVC)
Coronary sinus
SVC
Right
atrium
Tricuspid
valve
Right
ventricle
Tricuspid
valve
Right
atrium
IVC
Pulmonary
trunk
•  70–80 beats per minute at rest
•  Systole—contraction of a heart chamber
•  Diastole—expansion/relaxation of a heart
chamber
Pulmonary
semilunar
valve
Right
ventricle
To heart
Heartbeat
Pulmonary
semilunar valve
Pulmonary
trunk
Coronary
sinus
Oxygen-poor blood
returns from the body
tissues back to the heart.
Two pulmonary arteries
To lungs
carry the blood to the
lungs (pulmonary circuit)
Pulmonary
to be oxygenated.
arteries
•  Systole and diastole also refer to
Oxygen-rich blood
Oxygen-poor blood
To body
Oxygen-rich blood is
delivered to the body
tissues (systemic circuit).
Aorta
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Aortic
semilunar
valve
Pulmonary
veins
Left
atrium
Mitral
valve
Left
ventricle
Aortic
semilunar
valve
Left
ventricle
•  Stage of heartbeat when ventricles contract
and expand
Oxygen-rich blood returns To heart
to the heart via the four
pulmonary veins.
Aorta
Mitral
valve
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Left
atrium
Four
pulmonary
veins
Figure 19.10
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5
Structure of Heart Wall
Structure of Heart Wall
•  Walls differ in thickness
•  Left ventricle—
three times
thicker than right
•  Atria—thin walls
•  Ventricles—thick walls
•  Systemic circuit
•  Longer than pulmonary circuit
•  Offers greater resistance to blood flow
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Cardiac Muscle Tissue
•  Exerts more
pumping force
•  Flattens right
ventricle into a
crescent shape
Left
ventricle
Right
ventricle
Interventricular
septum
Figure 19.11
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Cardiac Muscle Tissue
•  Cardiac muscle cells
•  Forms a thick layer called myocardium
•  Striated like skeletal muscle
•  Contractions pump blood through the heart
and into blood vessels
•  Contracts by sliding filament mechanism
• 
• 
• 
• 
Short
Branching
Have one or two nuclei
Not fused colonies like skeletal muscle
•  Cells join at intercalated discs
•  Complex junctions
•  Form cellular networks
•  Cells are separated by delicate endomysium
•  Binds adjacent cardiac fibers
•  Contains blood vessels and nerves
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Cardiac Muscle Tissue
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Microscopic Anatomy of Cardiac Muscle
Nucleus
Intercalated discs
Cardiac muscle cell
Gap junctions
Fasciae adherens
•  Intercalated discs—complex junctions
•  Adjacent sarcolemmas interlock
•  Possess three types of cell junctions
•  Desmosomes
•  Fasciae adherans—long desmosome-like
junctions
•  Gap junctions
(a)
Cardiac
muscle cell
Mitochondrion
Nucleus
Intercalated
disc
Mitochondrion
T tubule
Sarcoplasmic
reticulum
(b)
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Nucleus
Sarcolemma
I band
A band
Z disc
I band
Figure 19.12
6
Cardiac Muscle Tissue
Cardiac Muscle Tissue
•  Muscle triggered to contract by Ca2+ entering
the sarcoplasm
•  Not all cardiac cells are innervated
•  Action potential signals along sarcolemma
and t-tubules cause sarcoplasmic reticulum to
release Ca2+ ions
•  Ions diffuse to sarcomeres
•  Trigger sliding filament mechanism
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•  These cells will contract in rhythmic manner
without innervation
•  They possess an inherent rhythmicity
•  This is the basis for rhythmic heartbeat
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Conducting System
Conducting System
Superior vena cava
•  Cardiac muscle tissue has intrinsic ability to:
Right atrium
1 The sinoatrial (SA)
node (pacemaker)
generates impulses.
•  Generate and conduct impulses
•  Signal these cells to contract rhythmically
Internodal pathway
2 The impulses
•  Conducting system
•  A series of specialized cardiac muscle cells
that organize the beat of the contractile cells
•  Sinoatrial (SA) node sets the inherent rate of
contraction: it beats the fastest, so the rest of the
myocardium follows
pause (0.1 sec) 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.
Left atrium
Purkinje
fibers
Interventricular
septum
5 The Purkinje fibers
stimulate the contractile
cells of both ventricles.
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Innervation
•  Heart rate is altered
by external controls
•  Nerves to the heart
include
•  Visceral sensory
fibers
•  Parasympathetic
branches of the
vagus nerve
•  Sympathetic
fibers—from
cervical and
upper thoracic
chain ganglia
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Figure 19.14
Blood Supply to the Heart
Dorsal motor nucleus
of vagus
The vagus nerve
(parasympathetic)
decreases heart rate.
Cardioacceleratory
center
Sympathetic
trunk
ganglion
Cardioinhibitory
center
Medulla oblongata
Thoracic spinal cord
Sympathetic trunk
Sympathetic cardiac
nerves increase heart rate
and force of contraction.
AV node
SA node
Parasympathetic fibers
•  Functional blood supply
•  Coronary arteries
•  Arise from the aorta
•  Located in the coronary sulcus
•  Main branches
•  Left and right coronary arteries (these are the first
branches off of the ascending aorta)
•  --> left coronary artery branches into anterior interventricular*
art.
• 
and the circumflex artery
•  --> right coronary artery branches into marginal art. and
• 
posterior interventricular* artery
•  (*or descending)
Sympathetic fibers
Interneurons
Figure 19.15
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Blood Supply to the Heart
Aorta
Pulmonary
trunk
Left atrium
Superior
vena cava
Anastomosis
(junction of
vessels)
Left
coronary
artery
Right
atrium
Right
coronary
artery
Right
ventricle
Disorders of the Heart
Circumflex
artery
Left
ventricle
Right
marginal
artery
•  Coronary artery disease
Superior
vena cava
Anterior
interventricular
artery
Posterior
interventricular
artery
(a) The major coronary arteries
Great
cardiac
vein
Anterior
cardiac
veins
Coronary
sinus
Small
cardiac vein
Middle cardiac vein
•  Atherosclerosis—fatty deposits
•  Angina pectoris—chest pain
•  Myocardial infarction—blocked coronary
artery
•  Heart attack
•  Silent ischemia—no pain or warning
(b) The major cardiac veins
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Figure 19.16
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Disorders of the Heart
Disorders of the Conduction System
•  Heart failure
•  Arrythmias—variation from normal heart
rhythm
•  Progressive weakening of the heart
•  Cannot meet the body’s demands for
oxygenated blood
•  Congestive heart failure (CHF)
•  Heart enlarges
•  Pumping efficiency declines
•  Pulmonary arterial hypertension
•  Ventricular fibrillation
•  Rapid, random firing of electrical impulses
in the ventricles
•  Results from crippled conducting system
•  Common cause of cardiac arrest
•  Enlargement and potential failure of right
ventricle
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Disorders of the Conductory System
Development of the Heart
•  Arrythmias (continued)
•  Heart folds into thorax region about Day 20–
21
•  Heart starts pumping about Day 22
•  Earliest heart chambers are unpaired
•  From “tail to head,” the chambers are
•  Atrial fibrillation
•  Impulses circle within atrial myocardium,
stimulating AV node
•  Promotes formation of clots
•  Leads to strokes
•  Occur in episodes characterized by
•  Anxiety, fatigue, shortness of breath,
palpitations
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• 
• 
• 
• 
Sinus venosus
Atrium
Ventricle
Bulbus cordis
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Development of the Heart
Development of the Heart
•  Sinus venosus—will become
•  Ventricle—is the strongest pumping
chamber
•  Smooth-walled part of right atrium, coronary
sinus, and SA node
•  Also contributes to back wall of left atrium
•  Atrium—will become
•  Gives rise to the left ventricle
•  Bulbus cordis
•  Bulbus cordis and truncus arteriosus give rise
to the pulmonary trunk and first part of aorta
•  Bulbus cordis gives rise to the left ventricle
•  Ridged parts of right and left atria
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Heart Development
Congenital Heart Defects
•  Can be traced to month 2 of development
Arterial end
4a
4
Tubular
heart
Arterial end
Ductus
arteriosus
Inferior
vena cava
Ventricle
Ventricle
Atrium
3
2
Pulmonary
trunk
Foramen
ovale
Ventricle
1
(a)Day 20:
Endothelial
tubes begin
to fuse.
Aorta
Superior
vena cava
(b) Day 22:
Heart starts
pumping.
Venous end
(c) Day 24: Heart
continues to
elongate and
starts to bend.
Venous end
(d) Day 28: Bending
continues as ventricle
moves caudally and
atrium moves cranially.
(e) Day 35: Bending
is complete.
Figure 19.17
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Congenital Heart Defects
Occurs in
about 1 in every
1500 births
(a) Ventricular septal defect.
(b) Coarctation of the aorta.
The superior part of the interA part of the aorta is narrowed,
ventricular septum fails to form;
increasing the workload of
thus, blood mixes between the
the left ventricle.
two ventricles. More blood is
shunted from left to right because
the left ventricle is stronger.
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•  Two basic categories of defect
•  Inadequately oxygenated blood reaches body
tissues
•  Ventricles labor under increased workload
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The Heart in Old Age
Narrowed
aorta
Occurs in
about 1 in every
500 births
•  Most common defect is ventricular septal
defect
Occurs in
about 1 in
every
2000 births
•  Heart usually functions well throughout life
•  Regular exercise increases the strength of
the heart
•  Aerobic exercise can help clear fatty deposits
in coronary arteries
(c) Tetralogy of Fallot.
Multiple defects (tetra = four):
(1) Pulmonary trunk too narrow
and pulmonary valve stenosed,
resulting in (2) hypertrophied
right ventricle; (3) ventricular
septal defect; (4) aorta opens
from both ventricles.
Figure 19.18
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9
The Heart in Old Age
• 
Age-related changes
1.  Hardening and thickening of heart valve
cusps
2.  Decline in cardiac reserve
3.  Fibrosis of cardiac muscle
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