Download Anatomy of the Heart

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Anatomy of the Heart
L. Maximilian Buja
Embryologic Development . . . . . . . . . . . . . . . . . . . . . . . . . . 3
External Anatomy of the Heart and Great Vessels . . . . . . 7
Pericardium. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Heart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Key Points
recently formed cardiac tube is a single chambered structure
and is composed of the following components, extending
from inferior (caudal) to superior (cephalad): the sinus
venosus, which connects to the major veins; the atrium; the
ventricle; the bulbus cordis or conus; and the truncus arteriosus, which connects through six pairs of aortic arches to two
dorsal aortae1–7 (Fig. 1.1).
Initially, the single chambered heart is a straight tube
residing in the pericardial cavity. The bulboventricular portion grows much more rapidly than the pericardial cavity. As
a result, further extension in a longitudinal direction cannot
occur, and the heart tube is forced to bend. The cephalic
ventricular portion of the tube bends in a ventral and caudal
direction and to the right, whereas the caudal atrial portion
progresses in a dorsal and cranial direction and to the left.
This process, known as d(dextro)-bulboventricular looping,
results in the atrial region establishing a position superior to
the ventricular region and the cardiac apex being pointed to
the left (Fig. 1.1).
The external shape changes are accompanied by a
complex process of internal septation that leads to the formation of a four-chambered heart (Fig. 1.2). In the atrium,
a septum primum forms and then develops two openings:
ostium primum and ostium secundum. A septum secundum then develops on the right of the septum primum.
The foramen ovale is formed in the midportion of the developing interatrial septum as a result of the growth and
positioning of the septum secundum adjacent to the
septum primum. The sinus venosus is incorporated into the
superior portion of the developing atria. Ventricular septation is partially accomplished by the upward growth of
muscular tissue to form the muscular interventricular
septum. Endocardial cushion tissue develops and provides
the essential tissue for formation of the atrioventricular
valves, the closure of the ostium primum in the atrial
septum, and the formation of the membranous interventricular septum.
The primitive bulbus cordis contributes several key
components of the forming heart. The proximal third of the
• External looping and internal septation to form fourchambered heart.
• Relationship of embryologic defects to congenital heart
disease.
• Structure-function relationships of the pericardium.
• Distribution of the coronary arteries and anatomic
variations.
• Definition of anatomic right and left atria and right and
left ventricles.
• Structure of the four cardiac valves and concept of functional valve apparatus.
• Anatomy of the cardiac conduction system and cardiac
innervation.
This chapter presents basic features of the anatomy of the
heart and great vessels, including the embryologic development of these structures and their configuration in the
mature state. Basic knowledge of cardiovascular anatomy is
essential for effective diagnosis and treatment of cardiovascular diseases.
Embryologic Development
Basic Embryology
Development of the cardiovascular system occurs in the
early first trimester fetus. Beginning at about 3 weeks’ gestation, elements of splanchnic mesoderm differentiate into a
primitive cardiac tube and pericardial cavity, and vascular
channels form and fuse to form blood vessels.1–7 The primitive cardiac tube results from the moving together and fusion
of two lateral endothelial heart tubes. Subsequently, the
epimyocardial mantle and cardiac jelly develop. These components differentiate into the endocardium, producing the
internal endothelial lining of the heart, the myocardium
forming the muscular wall, and the epicardium or visceral
pericardium producing the outside covering of the heart. The
3
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s
us
Conoventricular
At.r Tr.
sulcus
Art. At.l.
Ventricle
Atrium
A
B
2.08 mm
C
3.0 mm
III
IV
VI
Con
Vent.r. Vent.l.
5.2 mm
III
IV
VI
At.r
nu
s
Tr.
Art.
At.l.
Co
At.l.
us
At.r
Tr.
Art.
Vent.r.
Vent.l.
D 6.0 mm
E 8.8 mm
FIGURE 1.1. Ventral views of human embryonic hearts that show
bending of cardiac tube and establishment of major anatomic components. At., atrium; l., left; r., right; Tr. Art., truncus arteriosus.
bulbus cordis forms the trabeculated part of the right ventricle; the midportion, or conus cordis, forms the outflow
tracts of both ventricles; and the distal part, the truncus
arteriosus, forms the proximal parts of the aorta and pulmonary artery. The junction between the primitive ventricle
and the bulbus cordis is designated the primary interventricular foramen. While the ventricular septation process
proceeds, the primitive ventricle develops into the major
component of the definitive left ventricle, and the proximal
one third of the bulbus cordis gives rise to the major component of the definitive right ventricle.
Separate aortic and pulmonary channels are formed by
separation of the truncus arteriosus by a spiral aorticopulmonary septum (Fig. 1.3). As a result of extensive remodeling
of the double aortic arch system, the definitive major vessel
system develops into a single aorta with left-sided aortic
arch, a pulmonary trunk with right and left main pulmonary
arteries, and the ductus arteriosus, which connects the aortic
arch and the left pulmonary artery.
The heart develops in the fetus as myocardial contractile
activity commences, and a functional circulation is established. The foramen ovale in the interatrial septum and the
ductus arteriosus remain open. In the fetus, pulmonary vascular resistance is high in the unexpanded lungs and systemic vascular resistance is low. As a result of these anatomic
and physiologic features, the fetal circulation involves right
to left shunting of blood across the open foramen ovale and
the patent ductus arteriosus to provide oxygenated blood
from the placenta to the general circulation (Fig. 1.4). After
birth, the lungs expand, pulmonary vascular resistance
drops, and systemic vascular resistance increases. This leads
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to functional closure of the foramen ovale and ductus arteriosus and, subsequently, fibrous closure of these structures.
These closures establish complete separation of the rightsided and left-sided circulations in the mature cardiovascular
system.
Co
Ventricle
Co
n
us
Truncus
arteriosus
nu
I
Co
n
I
II
III
IV
I
II
1
Relationship to Congenital Heart Disease
Knowledge of normal and abnormal embryologic development of the heart and blood vessels provides an essential
basis for and understanding of the morphogenesis of congenital heart disease.8,9 The position of the atria is determined
by general body habitus. The anatomic right atrium is defined
as the atrium receiving the systemic venous drainage. The
anatomic left atrium is defined as the atrium receiving the
pulmonary venous drainage. In situs solitus, the right atrium
is on the right and the left atrium on the left side of the body.
In situs inversus, the anatomic right atrium is on the left side
and the anatomic left atrium is on the right side of the body.
The right and left ventricles are normally connected to the
corresponding atria, but the ventricles may be inverted.
Inversion of the ventricles is a major feature of a condition
known as congenitally corrected transposition of the great
vessels. This condition arises when the primitive heart
undergoes levo(l)-bulboventricular looping rather than the
usual dextro(d)-bulboventricular looping; hence, the alternative designation of corrected transposition as l-transposition.
Other positional anomalies of the heart include dextrocardia
and right-sided aortic arch.
Abnormalities in atrial septation give rise to three types
of atrial septal defects; in order of frequency they are the
ostium secundum defect, ostium primum defect, and sinus
venosus defect. Ostium secundum defects are located in
the midportion of the interatrial septum and result from
inadequate formation of septum secundum and/or septum
primum to cover the foramen ovale. Ostium primum defects
are located in the inferior portion of the interatrial septum
and result from a defect in formation of endocardial cushion
tissue. Severe endocardial cushion deficiency can lead to
a common atrioventricular canal anomaly with ostium
primum atrial septal defect, membranous ventricular septal
defect, and abnormal atrioventricular valve. The sinus
venosus atrial septal defect is located in the superior portion
of the interatrial septum and results from defective incorporation of the primitive sinus venosus into the forming
heart; this defect is often associated with partial anomalous
pulmonary venosus drainage into the right atrium. Abnormalities in ventricular septation give rise to ventricular
septal defects, usually in the region of the membranous
septum. Formation of the membranous interventricular
septum involves contributions from the conal ridges of the
bulbus cordis and the endocardial cushions. Deficiencies in
contributions from these embryonic structures leads to the
formation of membranous ventricular septal defects. Abnormalities in septation of the great vessels give rise to congenital complete transposition of the great vessels, or
d-transposition, since the abnormal septation of the great
vessels occurs with normal dextro-bulboventricular looping
and the atria and ventricles are in normal position. Congenital complete transposition is often accompanied by
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Septum spurium
Interatrial
septum primum
Ostium I
Atrio-vent. canal
Intervent. septum
A
B
4–5 mm
6–7 mm
Septum II
S. sp.
Right
atrium
Ostium II
(opening)
Ostium I
(closing)
Septum I
Ostium II
Septum
spurium
Septum I
Ostium I
(closed)
Septum II
(caudal limb)
A_V. canal cushion
Intervent. foramen
(closes at 15–17 mm.)
Left
ventricle
C
D
8–9 mm
Septum II
S. sp.
12–15 mm
Crista
Ostium II
terminalis
in septum I
S II
Foramen
ovale
S II
Functional
outlet F.O.
Septum I
(valvula F.O.)
Atriovent.
valves
Bundle
of his
E
25–30 mm
F
100 mm. to birth
FIGURE 1.2. Longitudinal sections of embryonic heart in frontal
plane that show extent of growth of various cardiac septa at progressive stages of development. These diagrams depict the stages of
partitioning of the human embryo. Stippled areas indicate the distribution of endocardial cushion tissue; muscle is shown in diagonal
hatching, and epicardium in solid black. The lightly stippled areas
in the atrioventricular canal in B and C indicate location of dorsal
and ventral endocardial cushions of the atrioventricular canal before
they have grown sufficiently to fuse with each other in the plane of
the diagram.
atrial or ventricular septal defects or other congenital
lesions. Severe maldevelopment of the heart can give rise to
a hypoplastic left heart or hypoplastic right heart and associated valvular atresia. Other anomalies include vascular
rings, persistent patent ductus arteriosus, and coarctation of
the aorta.
Cardiovascular malformations occur in about 0.8% of
live births.10 However, the incidence of congenital heart
disease is significantly higher because cardiac malforma-
tions occur 10 times more often in stillborn than in liveborn
infants. Children with congenital heart disease are predominantly male. However, specific defects have a defi nite sex
preponderance: females have a higher incidence of patent
ductus; arteriosus and atrial septal defect are more common
in females; and males have a higher incidence of valvular
aortic stenosis, congenital aneurysm of the sinus of Valsalva,
coarctation of the aorta, tetralogy of Fallot, and congenital
complete transposition of the great arteries.10
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Dextrodorsal
truncus ridge
Truncus
arteriosus
communis
Dextrodorsal
conus ridge
Right
atrium
Pulmonary
channel
S.-v. truncus
ridge
Aortic
channel
S.-v.
conus
ridge
Conovent. flange
Arrow
in aortic
channel
Atrioventricular
canal
Left
atrium
Conus
art.
Ventral
atriovent.
canal
cushion
Dorsal atriovent.
canal cushion
Right
ventricle
Left
ventricle
Interventricular
septum
A
B
FIGURE 1.3. Frontal plane dissections of developing heart show
important relations in establishing aortic and pulmonary outlets.
The truncus arteriosus has been drawn with its cut end turned
Superior vena cava
Crista
terminalis
Septum II
Limbus of
foramen
ovale
upward, in order to show the absence of truncus ridges in the early
stages and their relationships in later stages.
Septum I
(remnant)
Margin of interatrial
foramen II
Septum I = valvula
foraminis ovalis
Orifices of
pulmonary veins
Valve of
inferior
vena cava
Valve of
coronary
sinus
Tricuspid valve
Septum
membranaceum
Left atrium
Mitral valve
Tendinous
cords
Papillary
muscle
Interventricular septum
(muscular portion)
Right ventricle
FIGURE 1.4. Schematic drawing to show interrelations of septum
primum and septum secundum during the latter part of fetal life.
Note especially that the lower part of septum primum is positioned
so as to act as a one-way valve at the oval foramen in septum secundum. The split arrow indicates that a considerable part of the blood
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Trabeculae
carneae of
left ventricle
from the inferior vena cava passes through the foramen ovale to the
left atrium while the remainder eddies back into the right atrium
to mix with the blood being returned by way of the superior vena
cava.
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External Anatomy of the Heart and
Great Vessels
Pericardium
The anatomy of the heart and great vessels has been well
documented in previous publications.11–17 The normal location of the heart is in the mediastinum to the left of the
midline with the cardiac apex pointed to the left (Fig. 1.5).
The heart is rotated and tilted in the chest, and as a result
about two thirds of the anterior surface of the heart is composed of the right ventricle, and the left third of the anterior
surface is composed of the left ventricle. The right inferior
border (obtuse border) of the heart is formed by the right
ventricle and the left lateral border is formed by the left
ventricle. Located superior to the right and left ventricles
are the right and left auricles of the right and left atria,
respectively. The anterior superior surface of the heart is
constituted by the outflow portion (conus) of the right
ventricle and the pulmonary trunk, which extends from
right to left as it exits the pericardium. The pulmonary
trunk then gives rise to the left and right main pulmonary
arteries. The aorta is located posterior to the pulmonary
trunk. The aorta takes origin from the left ventricle and is
oriented from left to right as it exits the pericardium. The
aorta then curves to the left and inferiorly, creating a leftsided aortic arch. The aortic arch gives origin to the right
innominate, left common carotid, and left subclavian arteries. The aorta then continues inferiorly as the descending
thoracic aorta.
Innominate
artery
Right innominate vein
R. int. mam. vein
Thymus gland
Reflection of
pericardium
Vena cava
sup.
Asc. aorta
Probe in
transv.
sinus
Right
auricle
Right
atrium
The pericardial cavity is a fluid-filled space that surrounds
the heart and proximal great vessels. The pericardial space
is enclosed by a thin layer of connective tissue that is lined
by a single layer of mesothelial cells. There are two components: the visceral and parietal pericardium. The visceral
pericardium covers the epicardium of the heart, and the
parietal pericardium forms the outer layer. The superior
extent of the pericardial cavity representing the transition
of visceral to parietal pericardium occurs approximately 2 to
3 cm superior to the heart at the level of the great vessels,
thereby enclosing the proximal aorta and pulmonary trunk
in the pericardial cavity (Fig. 1.5). The pericardial cavity
normally contains about 20 cc of serous fluid, which serves
to lubricate the heart and facilitate cardiac motion.
The pericardium can be affected by a variety of inflammatory and neoplastic conditions. Hemorrhage into the pericardium may occur as a result of cardiac rupture, usually
secondary to acute myocardial infarction, or rupture of the
proximal aorta following aortic dissection. The severity of
cardiac dysfunction secondary to pericardial disease is influenced acutely by the amount and rapidity of fluid accumulation in the pericardial cavity and chronically by the severity
of inflammation and fibrosis. Rapid accumulation of 100 to
200 mL of fluid or blood in the pericardial cavity can induce
cardiac tamponade, whereas the slow accumulation of
several hundred milliliters can be accommodated in the
Left subclavian artery
Left innominate vein
Pleura
Pulmonary
artery
Pleura
Fibrous
pericardium
Serous
pericardium
Conus
arteriosus
Left
auricle
Coronary
sulcus
Right
ventricle
FIGURE 1.5. Ventral view of heart in situ
with the pericardial sac opened.
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Margo
acutus
Incisura
apicis
cordis
Pleura
Margo
obtusus
Left
ventricle
Anterior
longitudinal
sulcus
Apex
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cavity with stretching of the pericardial lining before
impaired cardiac function develops.
Heart
Basic Structure
The anatomy of the heart has been documented in detail.11–17
The heart is composed of three layers: the epicardium, the
myocardium, and the endocardium. The epicardium consists
of fatty connective tissue and is lined by the visceral pericardium. The major coronary arteries and veins traverse the
epicardium. The myocardium constitutes most of the mass
of the heart and is composed of cardiac myocytes, vessels,
and connective tissue. The cardiac myocytes represent
approximately 80% of the mass but only 20% of the number
of cells in the myocardium. The endocardium is divided into
the nonvalvular (visceral) and valvular endocardium. The
endocardium consists of thin fibrocellular connective tissue,
which is lined by a single layer of endothelial cells.
Cardiac Dimensions
Several sources have provided information regarding dimensions and measurements of the heart.11–17 The weight of the
heart varies in relationship to body dimensions, including
length and weight. Hudson11 has published a useful guide
regarding fresh heart weight in males and females. The adult
male heart weight has the following parameters: 0.45% of
body weight, average 300 g, range 250 to 350 g. The adult
female heart weight has the following parameters: 0.40% of
body weight, average 250 g, range 200 to 300 g. Selective measurements of right ventricular and left ventricular weights
can be made, and ranges have been established for determination of selective enlargement of right and left ventricles as
Right pulmonary veins
1
well as biventricular enlargement.15 The thickness of the
walls of the cardiac chambers is as follows: right and left
atria, 0.1 to 0.2 cm; right ventricle, 0.4 to 0.5 cm; left ventricle, 1.2 to 1.5 cm (free wall, excluding papillary muscles and
large trabeculae). The average circumferences of the cardiac
valves are as follows: aortic, 7.5 cm; pulmonic, 8.5 cm; mitral,
10.0 cm; and tricuspid, 12.0 cm.
Coronary Vasculature
The anatomy and physiology of the coronary circulation have
been described in detail.18–25 In the normal heart, oxygenated
blood is supplied by two coronary arteries that are the first
branches of the aorta. The origin of the left and right coronary arteries from the aorta is through their ostia positioned
in the left and right aortic sinuses of Valsalva, which are
located just distal to the left and right cusps, respectively, of
the aortic valve (Figs. 1.5, 1.6, and 1.7). The left main coronary artery is a short vessel with a length of 0.5 to 1.5 cm.
The left main coronary artery divides into left anterior
descending and left circumflex branches and, occasionally, a
left marginal branch. The left anterior descending coronary
artery and its left diagonal and septal branches supply the
anterior portion of the left ventricles and interventricular
septum. The left circumflex coronary artery and its circumflex marginal branches supply the lateral left ventricle. The
right coronary artery supplies the right ventricle and, in
about 90% of hearts, it extends posteriorly to give rise to the
posterior descending coronary artery.
There is considerable variation in the anatomic distribution of the coronary arterial branches. However, in most
hearts, branches from both the left circumflex and right
coronary arteries contribute to the blood supply of the posterior left ventricle, resulting in a so-called balanced circulation. In about 10% of hearts, the right coronary artery is
small, and the left circumflex coronary artery gives origin
Left pulmonary veins
Left auricle
Vena cava superior
Left atrium
Aorta
Posterior and
left aortic semilunar valves
Right aortic
semilunar valve
Right coronary
artery
Small cardiac
vein
Anterior cardiac
veins
Preventricular.
arteries
Right marginal
artery
Right ventricle
Circumflex branch
Left coronary
artery
Left aortic sinus
Great cardiac vein
Left pulmonary
semilunar valve
Right and anterior
pulmonary semilunar
valves
Pulmonary artery
Conus arteriosus
Anterior descending
branch of left
coronary artery
Left ventricle
Anterior longitudinal
sulcus
Incisura apicis cordis
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FIGURE 1.6. Cephalic view of the heart with
the epicardium removed to expose the injected
coronary vessels.
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Vena cava superior
Superior right
pulmonary vein
Superior
left pulmonary
vein
Inferior right
pulmonary vein
Inferior left
pulmonary vein
Left atrium
Oblique vein of
left atrium
Interatrial sulcus
Terminal
sulcus
Right atrium
Vena cava
inferior
Valvula venae
cavae
Small
cardiac vein
Right
coronary
artery
Right
ventricle
Middle cardiac
vein
Posterior descending branch of right
coronary artery
Great cardiac vein
Coronary sinus
Posterior vein of
left ventricle
Diaphragmatic
surface of left
ventricle
Posterior longitudinal sulcus
FIGURE 1.7. Dorsocaudal view of the heart
with the epicardium removed to expose the
injected coronary vessels.
to the posterior descending coronary artery and provides the
sole blood supply for the posterior left ventricle, creating a
left dominant circulation. Rarely, the converse right dominant circulation exists when the left circumflex is small and
the posterior left ventricle is supplied primarily by left ventricular branches of the right coronary artery.
The major blood supply to the sinoatrial node via the
sinus node artery is derived from the proximal right coronary artery in about 60% of hearts and from the left circumflex coronary artery in about 40% of hearts.18 The major
atrioventricular nodal artery is derived from the coronary
artery that gives rise to the posterior descending branch,
which is the right coronary artery in about 90% and the left
circumflex coronary artery in about 10% of hearts.
The epicardial coronary arteries deliver oxygenated blood
to the intramyocardial arteries, arterioles, and capillaries
leading to oxygen and substrate extraction in the myocardium (Fig. 1.8). A small amount of unoxygenated blood flows
directly into the ventricular cavities via the thebesian veins.
However, most desaturated blood traverses the myocardial
venules and veins into the epicardial veins, which drain into
the coronary sinus located in the inferoposterior region of
the right atrium.
Collateral blood vessels form during embryologic development of the heart, and they connect different components
of the coronary arterial circulation.18–25 The coronary collateral system is composed of four types of vessels: intramural
branches of the same coronary artery (homocoronary collaterals); intramural branches of two or more coronary arteries
(intercoronary collaterals); atrial branches, which connect
with the vasa vasorum of the aorta and other vessels (extra-
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cardiac collaterals); and intramural branches, which communicate with the cardiac cavities (arterioluminal vessels).
In the normal adult heart, the collateral vessels are thin
walled, small channels, usually less than 50 µm in diameter,
and they contribute little to total coronary blood flow. In
response to coronary arterial narrowing and myocardial
ischemia, the capacity of the coronary collateral system can
greatly increase. The myocardial collateral vessels can
increase in diameter into the range of 200 to 600 µm or
Endocardium
Myocardium
Epicardium
Arterioluminal
vessel
Myocardial sinusoid
Intertrabecular space
Coronary artery
Anastomosis between
myocardial sinusoids
Arteriosinusoidal
vessel
Trabeculae carneae
Anastomoses
between
coronary arteries
Arteriovenous
anastomosis
Capillary bed
Myocardial sinusoid
Venovenous
anastomosis
Capillaries emptying into
myocardial sinusoids
Coronary vein
Thebesian vein
Anastomosis between
thebesian veins
FIGURE 1.8. Diagram of the ventricular wall, showing the relationship between the various intramural vascular channels.
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1
greater, develop muscular media, and transport significant
amounts of blood flow (Fig. 1.9). In addition to the types of
collateral vessels described above, collateral channels also
can develop proximal and distal to a stenosis in a given coronary artery.
Right and Left Atria and Ventricles
FIGURE 1.9. Radiograph of postmortem coronary arteriogram demonstrating an extensive coronary collateral system in a case of coronary heart disease. The proximal part of the left anterior descending
artery is obliterated by old disease (O). The more distal part of the
anterior descending artery (A) has fi lled through a rich anastomotic
network (X) that has formed in the substance of the interventricular
septum between branches of the anterior (A) and posterior (P)
descending arteries.
The right and left atria and right and left ventricles have
distinctive anatomic features (Figs. 1.10 to 1.17). The anatomic right ventricle is characterized as follows: distinct
muscular infundibulum (conus) arteriosus, which separates
the right semilunar (pulmonary) valve and the right atrioventricular (tricuspid valve); single large anterior papillary
muscle; and coarse trabecular muscles (trabeculae carneae
cordis) at the apical and inflow portion of the chamber.11–17
Key landmarks of the right ventricular infundibular (conus)
region from inferior to superior are the membranous interventricular septum; the crista supraventricularis, an inverted
V-shaped structure with parietal and septal limbs; and the
pulmonic valve. The anatomic left ventricle has the following features: fibrous continuity of annulus of left semilunar
(aortic) valve and anterior leaflet of left atrioventricular
(mitral) valve, two well-developed papillary muscles (anterolateral and posteromedial), and fine trabecular muscles at the
apical and inflow portion of the chamber.11–17 These features
allow determination of the anatomic right ventricle and anatomic left ventricle in complex congenital anomalies involving displacement of the various components of the heart.
Cardiac Valves
The four-chambered heart has four valves: the right semiluminar or pulmonic valve; the right atrioventricular or tricuspid valve; the left semilunar or aortic valve; and the left
Ligamentum arteriosum
Left pulmonary artery
Aorta
Probe in transverse sinus
Right pulmonary
artery
Right auricle
Left pulmonary
veins
Left atrium
Foramina
venarum
minimarum
Right pulmonary
veins
Interatrial
sulcus
Limbus fossae
ovalis
Fossa ovalis
Orifice of coronary sinus
Valvula sinus coronarii
Valvula venae cavae
Vena cava inferior
Vena cava superior
Right ventricle
Crista terminalis
Left ventricle
Right atrium
Tricuspid
valve:
Anterior cusp
Medial cusp
Posterior cusp
Musculus pectinatus
Right coronary artery
Small cardiac vein
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FIGURE 1.10. Right anterior oblique
view of the excised heart, with the right
atrium opened to show its internal
configuration.
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Right coronary artery
Ascending aorta
Superior
vena cava
Pulmonary cone
Right auricular
appendage
Crista supraventricularis
Crista
terminalis
Papillary muscle
of conus
Pulmonary
vein
Interventricular septum
membranaceum
Limbus
fossae ovalis
FIGURE 1.11. Right side of the heart
opened in a plane approximately parallel
to the septa, to show the interior of the
right atrium and the right ventricle. A
segment of the septal leaflet of the tricuspid valve has been removed to expose
more fully the region of the membranous portion of the interventricular
septum.
Septal cusp of
tricuspid valve
(cut)
Valve of inferior
vena cava
(eustachian v.)
Anterior
papillary
muscle (cut)
Inferior vena cava
Posterior
papillary
muscle (cut)
Valve of coronary
sinus (thebesian v.)
Aorta
Crista supraventricularis
Vena cava superior
Papillary muscle of conus
Conus arteriosus
Pulmonary artery
Anterior pulmonary semilunar valve
Crista terminalis
Limbus fossae
ovalis
Fossa
ovalis
FIGURE 1.12. Ventral view of the heart
with the walls of the right atrium and
ventricle opened to show their internal
configuration. This heart has an unusually well-developed moderator band, and
the position of the foramen ovale is
somewhat more cephalic than usual.
CAR001.indd 11
Right
atrium
Right
coronary artery
Vena cava inferior
Tricuspid valve: Anterior cusp
Anterior
papillary
muscle
of left
ventricle
Posterior cusp
Medial cusp
Left ventricle
Trabecula carnea
Moderator band
Posterior papillary muscle
Muscular interventricular septum
Chorda tendineae Anterior papillary muscle
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12
chapter
FIGURE 1.13. Photograph of opened right heart demonstrating
actual structures depicted in the illustrations. Note the muscular
infundibulum separating the tricuspid and pulmonic valves. CA,
1
conus arteriosus, i.e., infundibulum; CS, coronary sinus; PV, pulmonic valve; RA, right atrium; RV, right ventricle.
Aorta
Pulmonary trunk
Great cardiac vein
Left coronary artery
Right semilunar
valve of aorta
Interventricular
septum
membranaceum
Interventricular
septum
musculare
Superior
vena cava
Orifice of right
coronary artery
Right superior
pulmonary vein
Adherent
margin of
valv. foram ov.
Mitral valve (cut)
Coronary sinus
Papillary
muscle
(cut)
FIGURE 1.14. Left side of the heart opened in a plane approximately
parallel to the septa, to show the interior of the left atrium and left
ventricle. A portion of the anterior leaflet of the mitral valve has
CAR001.indd 12
Inferior
vena cava
been removed to expose more fully the region of the membranous
portion of the interventricular septum and the aortic orifice.
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13
a natom y of t h e h e a rt
Left atrium
Valve of inferior
vena cava
Septum membranaceum
(atriovent. part.)
Septum membranaceum (interventricular part.)
Atrioventricular
bundle
Tricuspid
valve
Papillary
muscle
Mitral
valve
Papillary
muscles
Interventricular
septum
FIGURE 1.15. Frontal section through a heart fi xed in
diastole, showing a ventral view of the dorsal portion.
The plane of section passes through the septum membranaceum and both atrioventricular ostia.
FIGURE 1.16. Photograph showing the relationship of the membranous interventricular septum (lighted) to the tricuspid annulus and
septal leaflet of the tricuspid valve. While the membranous interventricular septum is entirely contained in the left ventricle, the superior portion of the interventricular septum extends superior to the
tricuspid annulus. This anatomic relationship allows for left ventricular to right atrial shunts in certain pathologic states, such as
infective endocarditis of the aortic valve. MIS, membranous interventricular septum; SLTV, septal leaflet of the tricuspid valve.
CAR001.indd 13
FIGURE 1.17. Photograph of opened left ventricle showing continuity of the anterior mitral leaflet and the annulus of the aortic valve.
AML, anterior mitral leaflet; LC, left cusp of aortic valve; NCC,
noncoronary cusp of aortic valve; PPM, posterior papillary muscle;
RC, right coronary cusp of aortic valve.
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14
chapter
Pulmonary annulus fibrosus
1
Conus ligament
Ant. descending br.
Right coronary art.
Left coronary art.
Circumflex br.
Left fibrous
triangle
Aortic
annulus fibrosus
Atrioventricular
bundle
Right fibrous
friangle
Annulus fibrosus
of mitral orifice
Annulus fibrosus
of tricuspid valve
Anastomosing branch
FIGURE 1.18. Ventricular portion of the heart viewed from above
with the atria removed, to show the four cardiac valves and the
fibrous triangles, the annuli fibrosi, and the attachment of the ven-
Post. descending br. of right coronary a.
tricular musculature to them. Epicardial fat has been removed from
the atrioventricular sulcus in order to show the coronary arteries.
atrioventricular or mitral valve (Figs. 1.18 to 1.21). The pulmonic and aortic semilunar valves each have three cusps
separated by three commissures, and the cusps insert into a
fibrous connective tissue annulus. The aortic valve cusps are
designated as the left and right cusps in relationship to the
coronary ostia and a third, noncoronary cusp. With valve
closure during diastole, the cusps of the aortic and pulmonic
valves make contact along a line about 1 to 2 mm below the
free margin. The central points of maximal contact are espe-
cially prominent and are known as the noduli of Arantius.
The most common congenital valve lesion is a malformed
aortic valve, either a unicuspid or bicuspid valve.
The tricuspid or right atrioventricular valve has three
leaflets (cusps) that are separated by three commissures and
insert into a fibrous annulus. The leaflets are designated as
the lateral, medial, and anterior leaflets. The leaflets are
attached to the ventricular muscle by multiple chordae tendineae, which extend from the ventricular surfaces of the
Pulmonary
semilunar valve
Pulmonary
conus
Septal cusp of
tricuspid valve
Ant. desc. branch of
left coronary art.
Noncoronary cusp of
aortic semilunar v.
Septum
membranaceum
Bundle of his
Muscular part of
interventricular
septum
FIGURE 1.19. Interior of the ventricular base of the heart, exposed
by removal of the apical half of the ventricles. The interventricular
septum has been partially removed to show the relations of the
CAR001.indd 14
Mitral valve
interventricular septum membranaceum, and the mitral, the tricuspid and the aortic valves.
11/24/2006 10:09:24 AM
a natom y of t h e h e a rt
leaflets to the mural ventricular wall as well as a welldeveloped anterior papillary muscle and a diminutive structure, the papillary muscle of the conus.
The mitral or left atrioventricular valve has a highly
developed and coordinated group of structures that are
referred to as the mitral valve apparatus (Figs. 1.18 to 1.21).
The mitral valve apparatus consists of fibrous annulus, anterior and posterior leaflets, anterior and posterior commissures, multiple chordae tendineae, and anterolateral and
posteromedial papillary muscles. Chordae tendineae extend
from the ventricular surfaces of both leaflets and attach to
both papillary muscles. Chordae tendineae exhibit a branching pattern with primary chordae arising from the papillary
muscles and branching into secondary and then tertiary
chordae, which insert into the valvular leaflets. Mitral valve
dysfunction can result from a wide variety of pathologic
processes affecting any component of the mitral apparatus,
including the myocardium.
The anterior mitral leaflet is usually a single structure,
whereas the posterior leaflet may be divided into two or three
scallops (Fig. 1.21). The anterior mitral leaflet normally has
a significantly larger area and longer length from annulus to
free margin that the posterior mitral leaflet. As a result, the
anterior leaflet contributes about two thirds of the area of
leaflet tissue involved in closure of the mitral orifice during
systole. Expansion of the posterior leaflet to equal the length
15
FIGURE 1.21. Photograph of mitral valve showing a portion of the
anterior mitral leaflet and the posterior leaflet consisting of multiple
scallops. AML, anterior mitral leaflet; PML, posterior mitral leaflet.
of the anterior leaflet from annulus to free margin is an
important anatomic feature of myxomatous degeneration of
the mitral valve. Other features include general redundancy,
thickening, and a glistening white appearance of leaflet
tissue and chordae tendineae.
Cardiac Conduction System and
Cardiac Innervation
FIGURE 1.20. Photograph of left ventricle showing aortic valve and
a portion of the mitral apparatus, including the anterior mitral
leaflet, chordae tendineae, and papillary muscles. AML, anterior
mitral leaflet; APM, anterior papillary muscle; CT, chordae tendineae; LC, left cusp of aortic valve; PPM posterior papillary muscle.
CAR001.indd 15
The anatomy of the cardiac conduction system has been
defined by meticulous study (Fig. 1.22).26,27 The sinoatrial
node is located in the superficial subepicardium of the
superior right atrium at the junction of the superior
vena cava and the right auricular appendage. The sinoatrial
node contains myocytes that are specialized for the generation of electrical impulses and constitute the cardiac
pacemaker. The electrical impulse propagates selectively
along certain paths in the atria; however, the existence of
anatomically distinct conduction pathways in the atria is
difficult to demonstrate. Atrioventricular conduction is
accomplished by specialized structures, the more proximal
atrioventricular node (node of Tawara) and the more
distal atrioventricular bundle (bundle of His). The atrioventricular node is positioned in the inferior interatricular
septum just anterior and medial to the ostium of the coronary sinus. The specialized conduction tissue then extends
through the fibrous skeleton separating the atria and ventricles to connect to the bundle of His, which is located at
the apex of the muscular interventricular septum. The His
bundle gives origin to the right and left bundle branches,
which extend through the subendocardium of the interventricular septum into the right and left ventricular free
walls.
The heart has a dual innervation from the sympathetic
(thoracolumbar) and parasympathetic (craniosacral) divisions
of the autonomic nervous system (Fig. 1.23). These nerves
interact with the conduction tissue to provide neural modulation of cardiac function.
11/24/2006 10:09:24 AM
16
chapter
Superior
vena cava
Right pulmonary
vein
Sino-atrial
node
1
Left pulmonary
vein
Left
atrial wall
Fossa
ovalis
Mitral
valve
Coronary
orifice
Inferior
vena cava
Septum
membranaceum
Atrio-ventricular
node
Bifurcation
of bundle
Main atrioventricular bundle
(bundle of his)
Left
branch of
bundle
Right branch
of bundle
Branch of bundle in
moderator band
Purkinje
fibers under
endocardium
of papillary musc.
Branch under septal endocard.
Superior cervical
ganglion
Superior cardiac
nerve
Inferior cervical
ganglion
Vagus nerve
Inferior
cardiac
branch
Deep cardiac
plexus
FIGURE 1.22. Schematic diagram of heart
opened frontally, demonstrating the location
and relations of the several parts of the sinoatrial and atrioventricular conduction system.
Superior cardiac
nerve
Middle cardiac nerve
Superior cardiac branch
Inferior cervical ganglion
First thoracic ganglion
Ansa of vieussens
Superficial
cardiac
plexus
Ganglion of
wrisberg
Pulmonary
plexus
Right
coronary
plexus
Left
coronary
plexus
FIGURE 1.23. Ventral view of thorax to show
the nerve supply to the heart.
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Summary
This chapter presented a description and illustration of the
embryologic and anatomic features of the heart and great
vessels. The embryologic development of the cardiac structures was presented, and the relationship of cardiac development to congenital heart diseases was discussed. Key
components of the mature heart were described and illustrated, including the pericardium, the coronary arteries, the
four cardiac valves, the right and left atria and ventricles, and
the cardiac conduction system and cardiac innervation. The
relationship of structure to function was considered. Understanding cardiovascular anatomy is important for the diagnosis and treatment of cardiovascular diseases.
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