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Chapter 22
Heart
Why have a heart?
Move nutrients and oxygen through the
body.
How does the heart do its job?
• First, get oxygen into the blood
• Second, get oxygenated blood to
the rest of the body
Fig. 22.2
Location of heart
Superior border
2nd rib
Right
border
Sternum
• Slightly left of center, posterior to
sternum
• Rotated; right border sits anterior to
left border
• Base of heart is posterior and
Left
superior
border
– formed by left atrium
Diaphragm
• Superior border
Inferior border
(a) Borders of the heart
– formed by ascending aorta, pulmonary
trunk, superior vena cava
• Conical bottom end is apex
• Inferior border
– formed by right ventricle
Fig. 22.2
Location of heart
Trachea
Left lung
Aortic arch
Right lung
• From anterior view,
Superior
right ventricle is most
vena cava
obvious
• Left ventricle sits
behind
Ascending aorta
Pulmonary trunk
Right atrium
Right ventricle
(b) Heart and lungs, anterior view
Left ventricle
Fig. 22.6
Blood flow
• Blood flows into the heart from
the superior vena cava and
the inferior vena cava
Superior
vena cava
– Superior vena cava carries blood
from head, neck, arms, superior
Right
trunk
atrium
– Inferior vena cava carries blood Opening for
from lower limbs, inferior trunk
inferior
vena cava
– This blood is high in CO2 and
Right ventricle
low in O2
Inferior
vena cava
Pulmonary
artery
Fig. 22.6
• Blood first enters the right
atrium, then the right
ventricle
• The right ventricle pumps
blood out the pulmonary
arteries to the lungs
– In the lungs, the blood
exchanges CO2 for O2
Superior
vena cava
Pulmonary
artery
Right
atrium
Opening for
inferior
vena cava
Right
ventricle
Inferior
vena cava
Pulmonary
artery
Pulmonary
trunk
Fig. 22.1
• Flow and gas exchange in
lungs is called pulmonary
circulation
Systemic
circulation
4
Lung
Lung
Basic pattern of blood flow
2
2
Pulmonary
circulation
1 Right side of heart
2 Lungs
3 Left side of heart
Pulmonary
circulation
Right 3
1
side
Left
side
Heart
4 Systemic cells
Systemic
circulation
4
Oxygenated blood
Deoxygenated blood
Gas exchange
• Blood returns to the
heart through the
pulmonary veins
• The pulmonary veins
empty into the left
atrium
Fig. 22.5b Heart,
Posterior View
Left pulmonary artery
Left pulmonary
veins
Left atrium
Right pulmonary artery
Right pulmonary
veins
Right atrium
Left
ventricle
Right ventricle
• The left atrium pumps blood
into the left ventricle
• The left ventricle pumps
blood out the aorta to the
body
Fig. 22.6
Aortic
arch
Ascending
aorta
Descending
aorta
Left atrium
Right
atrium
Right
ventricle
Left
ventricle
Fig. 22.6
Form and Function
• What differences do you notice
between the atria and the
Right
ventricles?
atrium
• What’s different between the
right and left ventricle?
Right
ventricle
Left atrium
Left
ventricle
Fig. 22.6
Form and Function
• Atria do not make powerful
contractions
• Left ventricle makes more
powerful contractions than
right ventricle
• How does the body ensure
blood flows in only one
direction?
Left atrium
Right
atrium
Right
ventricle
Left
ventricle
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Valves
• Both atria fill at the same time, contract at
the same time
• Contraction of atria forces open valves
between atria and ventricles
• Right atrioventricular valve (AKA tricuspid
valve) separates right atrium from right
ventricle
• Left atrioventricular valve (AKA bicuspid
valve) separates left atrium from left ventricle
Valves
Fig. 22.7
• Right atrioventricular
valve (AKA tricuspid valve)
separates right atrium from
Right
right ventricle
atrioventricular
valve
• Left atrioventricular valve
(AKA bicuspid valve)
separates left atrium from Aortic semilunar
valve
left ventricle
Pulmonary
semilunar valve
Posterior
Left
atrioventricular
valve
Fibrous
skeleton
Anterior
Valves
Left atrium
• Atrioventricular valves are attached
to inside of ventricles by chordae
tendineae attached to papillary
muscles inside ventricle
– prevents inversion of valve flaps
when ventricle contracts
– typically 3 papillary muscles in
right ventricle, 2 in left ventricle
Left
A/V valve
Right
A/V valve
Chordae
tendineae
Papillary
muscles
Valves
• Contraction of ventricles forces
atrioventricular valves closed and opens
semilunar valves
Valves
Fig. 22.7
• Pulmonary semilunar
valve separates right
ventricle from pulmonary
Right
trunk
atrioventricular
valve
• Aortic semilunar valve
separates left ventricle from
Aortic semilunar
aorta
valve
• As ventricles relax,
semilunar valves close
Pulmonary
semilunar valve
Posterior
Left
atrioventricular
valve
Fibrous
skeleton
Anterior
Valves
• Semilunar valves don’t
have chordae tendineae
• Cupped structure of valve
fills with blood as ventricles
contract, pushing valve
back into place
Pulmonary
semilunar
valve
Left
A/V valve
Aortic
semilunar
valve
Right
A/V valve
Chordae
tendineae
Papillary
muscles
Copyright © McGraw-Hill Education. Permission required for reproduction or display.
(a) Ventricular Systole (Contraction)
Copyright © McGraw-Hill Education. Permission required for reproduction or display.
(b) Ventricular Diastole (Relaxation)
Sounds of a heartbeat
• Lub-dub, lub-dub, lub-dub
• “lub” is sound of
atrioventricular valves closing
• “dub” is sound of semilunar
valves closing
• Sounds are not heard best in
exact spot of valve
Aortic
semilunar
valve
Pulmonary
semilunar valve
Left
atrioventricular
valve
Right
atrioventricular
valve
Actual location of heart valve
Area where valve sound is best heard
Locations of individual heart valves and the ideal
listening sites for each valve
are shown.
Walls of heart chambers
• Anterior walls of atria lined with
muscular ridges called pectinate
muscles (pecten = comb)
– Increase strength of contraction with
little increase in heart mass
• Wall between atria is interatrial
septum
Pectinate
muscles
Interatrial
septum
Walls of heart chambers
• Walls of ventricles have larger, more
irregular muscular ridges called
trabeculae carneae
– Assist with contraction, pull on papillary
muscles, prevent formation of vacuum
during contraction
Trabeculae
carneae
• Wall between ventricles is
interventricular septum
Interventricular
septum
Fig. 22.3
Heart wall structure
• Epicardium is visceral layer
of pericardium
• Myocardium: cardiac muscle
– thickest layer
– contracts to pump blood
• Endocardium: innermost
layer
– simple squamous epithelium
(AKA endothelium) and areolar
connective tissue
Visceral layer of
serous pericardium
(epicardium)
Myocardium
Endocardium
Heart
wall
Fig. 22.4
Simple squamous
epithelium
Epicardium
Areolar connective
(visceral layer of
tissue and fat
serous pericardium)
Myocardium (cardiac muscle)
Areolar connective tissue
Endothelium
Endocardium
Fibrous skeleton of heart
Fig. 22.7
• Dense regular connective tissue
• Structural support between atria
and ventricles
Right
A/V
• Anchor for heart valves
valve
• Rigid framework for attachment
Aortic
of cardiac muscle tissue
semilunar
valve
• Electric insulator between
ventricles
Pulmonary
semilunar valve
Posterior
Left
atrioventricular
valve
Fibrous
skeleton
Anterior
Fig. 22.2
Pericardium
• Heart sits inside
pericardium
– fibrous sac – very
tough
– serous lining made of
two layers of epithelial
tissue with tiny amount
of water between
Mediastinum
Left lung
Ascending aorta
Pleura (cut)
Pericardium (cut)
Apex of heart
Diaphragm (cut)
(c) Serous membranes of the heart and lungs
Fig. 22.2
Pericardium
Posterior
• Restricts heart
movement, prevents
Thoracic vertebra
bouncing
Aortic arch (cut)
• Prevents heart overfilling
with blood
Heart
Left lung
Right lung
Sternum
Anterior
(d) Cross-sectional view
Fig. 22.3
Pericardium
• Outer layer is fibrous
pericardium
– dense connective tissue
– attached to diaphragm and
base of aorta, pulmonary
trunk, vena cava
Fibrous pericardium
Parietal layer of
serous pericardium
Pericardial cavity
Visceral layer of
serous pericardium
(epicardium)
Fibrous pericardium
Parietal layer of serous pericardium
Pericardial cavity
Fig. 22.3
Pericardium
• Inner layer is serous
pericardium
– double layer formed from
single “balloon” stretched
around heart
– parietal layer connected to
fibrous pericardium
– pericardial cavity contains
serous fluid secreted by
serous membranes
– visceral layer covers
outside of heart (AKA
epicardium)
Fibrous pericardium
Parietal layer of
serous pericardium
Pericardial cavity
Visceral layer of
serous pericardium
(epicardium)
Fibrous pericardium
Parietal layer of serous pericardium
Pericardial cavity
Fig. 22.3
Pericarditis
• Inflammation of pericardium
makes blood vessels leaky
• Fluid accumulates in
pericardial cavity
– prevents heart from pumping
fully
Fig. 22.5a
External anatomy of heart
• Coronary sulcus extends
around heart between atria
and ventricles
• Blood vessels in adipose
tissue run through sulci
• Right and left coronary
arteries supply blood to heart
wall
– only branches off ascending
aorta
Ascending aorta
Right atrium
Right coronary artery
(in coronary sulcus)
Left coronary artery
(in coronary sulcus)
Circumflex artery
(in coronary sulcus)
Right ventricle
Left ventricle
Apex of heart
Descending aorta
Fig. 22.5a
External anatomy of heart
Ascending aorta
• Circumflex artery supplies
left atrium and ventricle
Right atrium
Right coronary artery
(in coronary sulcus)
Left coronary artery
(in coronary sulcus)
Circumflex artery
(in coronary sulcus)
Right ventricle
Left ventricle
Apex of heart
Descending aorta
Fig. 22.9 (a) Coronary arteries
Aortic arch
Superior vena cava
Aortic semilunar valve
Branches of right
coronary artery
Right atrium
Right coronary artery
Posterior
interventricular artery
Right marginal artery
Pulmonary trunk
Left coronary artery
Left atrium
Circumflex artery
Anterior interventricular
artery
Branches of left
coronary artery
Left ventricle
Right ventricle
• Right coronary artery branches into
– right marginal artery: supplies right border of heart
– posterior interventricular artery: supplies posterior left and right ventricles
Fig. 22.9 (a) Coronary arteries
Aortic arch
Superior vena cava
Aortic semilunar valve
Branches of right
coronary artery
Right atrium
Right coronary artery
Posterior
interventricular artery
Right marginal artery
Pulmonary trunk
Left coronary artery
Left atrium
Circumflex artery
Anterior interventricular
artery
Branches of left
coronary artery
Left ventricle
Right ventricle
• Left coronary artery branches into
– circumflex artery: supplies left atrium and left ventricle
– anterior interventricular artery: supplies anterior left and right ventricles and interventricular
septum
• pattern of arterial branching varies among individuals
Fig. 22.9 (b) Coronary veins
Polymer cast of coronary vessels
Aortic arch
Superior vena cava
Right atrium
Pulmonary trunk
Left atrium
Coronary sinus
Middle cardiac vein
Small cardiac vein
Right ventricle
•
•
•
•
•
Great cardiac vein
Left ventricle
Blood returns from cardiac muscle through cardiac veins
Great cardiac vein runs beside anterior interventricular artery
Middle cardiac vein runs by posterior interventricular artery
Small cardiac vein runs by right marginal artery
All drain into coronary sinus on posterior heart
– drains into right atrium
Page 664
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Enlarged heart
• Abnormal growth of heart can cause swelling in
limbs, dizziness, irregular heartbeat, shortness of
breath, sudden death
Cardiomegaly in an adult female. Note how
the heart shadow encompasses most of the
width of the thorax.
Normal heart on x-ray
© ISM/Phototake
Fig. 22.7
Cardiac muscle
Contraction of bundles:
Narrows heart
Shortens heart
Cardiac muscle bundles
• Fibers arranged in spiral bundles
around and between heart chambers
• Contractions start at top of atria, move
around atria, then start from bottom of
ventricle and travel up
Spiral arrangement of
cardiac muscle
Fig. 22.10
Openings of
transverse (T) tubules
Intercalated disc
Cardiac muscle
Folded
sarcolemma
• fibers are striated
• intercalated discs have
desmosomes and gap
junctions
– link cells electrically and
mechanically
– impulses sent immediately
form one cell to next
Desmosomes
Gap junctions
Endomysium
Intercalated
discs
Sarcolemma
(a) Cross section of
cardiac muscle cells
Nucleus
Mitochondrion
(b) Intercellular junctions
Fig. 22.11
Sinoatrial node (pacemaker)
Internodal pathway
Atrioventricular node
Atrioventricular bundle
(bundle of His)
Purkinje fibers
Left bundles
Purkinje fibers
• Heart is autorhythmic
Right bundle
– starts its own beating
• Specialized cells that initiate and
conduct muscle impulses are
collectively the conducting system
1. Muscle impulse is
generated at the
sinoatrial node. It
spreads throughout the
atria and to the
atrioventricular node
by the internodal
pathway.
Fig. 22.11
Sinoatrial node (pacemaker)
Atrioventricular node
Internodal
pathway
Atrioventricular
node
Atrioventricular
bundle
2. Atrioventricular node cells delay the
muscle impulse as it passes to the
atrioventricular bundle.
Fig. 22.11
Sinoatrial node (pacemaker)
Atrioventricular node
Internodal
pathway
Atrioventricular
node
Atrioventricular
bundle
3. The atrioventricular bundle (bundle of His) conducts
the muscle impulse into the interventricular septum.
Atrioventricular
bundle
Interventricular
septum
Fig. 22.11
4. Within the interventricular septum, the left and right
bundles split from the atrioventricular bundle.
Atrioventricular
bundle
Interventricular
septum
Left and right
bundles
Fig. 22.11
5. The muscle impulse is delivered to Purkinje fibers in each
ventricle and distributed throughout the ventricular myocardium.
Atrioventricular
bundle
Interventricular
septum
Left and right
bundles
Purkinje fibers
Fig. 22.11
Superior vena cava
Right atrium
Left atrium
Sinoatrial node (pacemaker)
Internodal
pathway
Internodal pathway
Atrioventricular node
Atrioventricular bundle
(bundle of His)
Interventricular
septum
Right bundle
Purkinje fibers
Atrioventricular
bundle
Left bundles
Purkinje fibers
1
Atrioventricular
node
Muscle impulse is generated at the sinoatrial node. It spreads throughout the atria and
to the atrioventricular node by the internodal pathway.
2
Atrioventricular node cells delay the
muscle impulse as it passes to the
atrioventricular bundle.
Atrioventricular
bundle
Interventricular
septum
Left and right
bundles
3
The atrioventricular bundle (bundle
of His) conducts the muscle impulse
into the interventricular septum.
4
Within the interventricular septum, the
left and right bundles split from the
atrioventricular bundle.
Purkinje fibers
5
The muscle impulse is delivered to Purkinje
fibers in each ventricle and distributed
throughout the ventricular myocardium.
Page 669
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0.8 second
R
Millivolts
+1
3 T wave
1 P wave
0
Q
S
2 QRS complex
–1
The events of a single cardiac cycle as recorded on an electrocardiogram.
Fig. 22.13a
Copyright © McGraw-Hill Education. Permission required for reproduction or display.
(a) Ventricular Systole (Contraction)
Ventricular systole
•
•
•
•
Contraction of ventricles
Semilunar valves open
Blood flows into arteries
Larger of blood pressure measurements
Aortic arch
Blood flow into
ascending aorta
Ascending
aorta
Pulmonary
trunk
Blood flow into
right atrium
Blood flow into
pulmonary trunk
Right
atrium
Left
atrium
Ventricular contraction pushes
blood against the open AV
valves, causing them to close.
Contracting papillary muscles
and the chordae tendineae
prevent valve flaps from
everting into atria.
Ventricles contract, forcing
semilunar valves to open and
blood to enter the pulmonary
trunk and the ascending aorta.
Atrioventricular valves closed
Semilunar valves open
Right ventricle
Left ventricle
Cusp of
semilunar
valve
Cusp of
atrioventricular
valve
Blood in
ventricle
Posterior
Left AV
valve (closed)
Right AV
valve (closed)
Left ventricle
Right
ventricle
Aortic semilunar
valve (open)
Pulmonary
semilunar
valve (open)
Anterior
Transverse section
(b) Ventricular Diastole (Relaxation)
Fig. 22.13b
Aortic arch
Ventricular diastole
•
•
•
•
Relaxation of ventricles
AV valves open
Blood flows into ventricles from atria
Smaller of blood pressure
measurements
Blood flow into
right atrium
Blood flow into
left ventricle
Right
atrium
Left
atrium
During ventricular relaxation,
some blood in the ascending
aorta and pulmonary trunk
flows back toward the
ventricles, filling the semilunar
valve cusps and forcing them
to close.
Blood flow into
right ventricle
Ventricles relax and fill with
blood both passively and
then by atrial contraction as
AV valves remain open.
Atrioventricular valves open
Semilunar valves closed
Atrium
Right ventricle
Cusp of
atrioventricular
valve
Left ventricle
Blood
Cusps of
semilunar
valve
Chordae
tendineae
Papillary
muscle
Posterior
Left AV
valve (open)
Right AV
valve (open)
Left ventricle
Right ventricle
Aortic semilunar
valve (closed)
Pulmonary
semilunar
valve (closed)
Anterior
Transverse section
Fig. 23.27
Fetal circulation
• Inferior vena cava flows into right atrium
• Much of the blood bypasses lungs through foramen ovale, opening
between right and left atria
• Ductus arteriosus takes blood directly from pulmonary trunk to
aorta
Fig. 23.27
Superior vena cava
Fetal Cardiovascular
Structure
Postnatal
Structure
Ductus arteriosus
Ligamentum arteriosum
Ductus venosus
Ligamentum venosum
Foramen ovale
Fossa ovalis
Umbilical arteries
Medial umbilical ligaments
Umbilical vein
Round ligament of liver
(ligamentum teres)
Aortic arch
Ductus arteriosus
Pulmonary artery
Pulmonary trunk
Pulmonary veins
Foramen ovale
Lung
Right atrium
Right ventricle
Heart
6
5
4
3
Liver
2
Ductus venosus
Inferior vena cava
Descending abdominal aorta
Umbilical vein
Umbilicus (not visible)
1
Common iliac artery
Urinary bladder
Umbilical arteries
7
Internal iliac artery
Umbilical cord
8
Placenta
Fig. 22.6
Other heart structures
Ligamentum arteriosum
• Fossa ovalis is location of former
fetal foramen ovale
– hole that moved blood between atria,
bypassing lungs
• Ligamentum arteriosum connects
pulmonary trunk to aorta
– fibrous structure that forms from fetal
ductus arteriosus
• Coronary sinus drains
blood from coronary veins
Fossa ovalis
Opening for
coronary sinus