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THE NORMAL HEART

Anatomy of the heart

What’s new?

Robert H Whitaker
C

Abstract
Despite centuries of writings and research into cardiac anatomy and
function, the topic is still advancing, particularly in relation to clinical
applications and embryological significance
...

We encourage clinicians to use the same terminology
...


C

C

Keywords Atrium; cardiac embryology; chambers; coronary arteries;
heart; pericardium; venous drainage; ventricle

The anatomy of the coronary sinus has taken on new clinical
importance as a result of the expansion of electrophysiological
investigations and interventions
...

The outer layer is the tough fibrous pericardium, which blends
with the adventitia of the aorta, the pulmonary trunk, the superior vena cava and the central tendon of the diaphragm
...

These two layers of serous pericardium are continuous with
each other as they reflect off the major vessels behind and above
the heart
...
The plane between
the superior vena cava and the pulmonary veins posteriorly, and
the aorta and pulmonary trunk anteriorly, made by the folding of
the heart, is termed the ‘transverse sinus’ of the pericardium
...


The heart is a midline, valvular, muscular pump that is coneshaped and the size of a fist
...
The
inferior (diaphragmatic) surface sits on the central tendon of the
diaphragm, whereas the base faces posteriorly and lies immediately anterior to the oesophagus and (posterior to that) the
descending aorta
...
The
left surface (left ventricle) and right surface (right atrium) are
each related laterally to a lung and a phrenic nerve in the fibrous
pericardium
...
The constituent parts of the
anterior and inferior surfaces are dictated largely by the position
of the interventricular septum
...

The interventricular septum bulges to the right because the
wall of the left ventricle is much thicker (10 mm) than that of the
right ventricle (3e5 mm)
...
The thicker,
muscular part of the interventricular septum is formed from the
ventricular walls
...
This skeleton
both divides and separates the atria electrically from the ventricles and is the remnant of the atrioventricular (AV) cushions
...


Features of the chambers
Right atrium
The inferior vena cava passes through the diaphragm at the level
of T8 and immediately enters the right atrium, which lacks a true
valve
...
The superior vena cava enters the superior
aspect of the chamber
...
This smooth area is
separated from the muscular part, with its musculi pectinati, by
the crista terminalis internally and the sulcus terminalis externally
...

Between the opening of the inferior vena cava and the AV
orifice lies the opening of the coronary sinus, which is protected

Robert H Whitaker MA MD MChir FRCS is an Anatomy Teacher at the
University of Cambridge, UK
...
He
qualified from the University of Cambridge and University College
Hospital, London, UK
...


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Ó 2014 Elsevier Ltd
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THE NORMAL HEART

spread of excitation to the ventricular walls so that the inferior
aspects of the ventricles contract first
...
5 All autonomic
nerves pass via the superficial and deep cardiac plexuses on the
lateral and medial aspects of the aortic arch
...

The coronary sinus empties during systole
...

Right ventricle
Blood enters the right ventricle via the tricuspid valve, which has
anterior, septal and posterior (lying inferiorly) cusps attached to
papillary muscles by fibrous chordae tendineae
...
Some of this
muscle joins the anterior papillary muscle, low on the anterior
septal wall, as the septomarginal trabecula (moderator band) and
carries part of the right bundle branch of conducting tissue,
which ensures that the right ventricle contracts simultaneously
with the left
...


Blood supply to the heart
The ostia of the coronary arteries arise in the aortic sinuses superior to the attachment of the base of the relevant cusp e the right
from the anterior sinus (also known as sinus 1 or right coronary
aortic sinus) and the left from the left posterior sinus (also known
as sinus 2 or left coronary aortic sinus)
...
The third
sinus is named the right posterior sinus or non-coronary sinus
...
In 90% of individuals, it provides a
posterior (inferior) interventricular branch as it reaches the posterior interventricular groove on the inferior surface of the heart;
this anastomoses with the termination of the anterior interventricular artery (left coronary) in the groove at the apex of the heart
...
The terminology and development of the smooth and
muscular parts of the left atrium correspond to those of the right
atrium except that the smooth part arises from incorporation of
the pulmonary veins
...
The mitral valve is an active
valve and not simply a flap of tissue
...
The smooth
outflow tract is the aortic vestibule, corresponding to the membranous part of the interventricular septum, leading to the
aortic valve with its two posterior cusps and one anterior cusp
(APAP e AorticePosterioreAnteriorePosterior)
...
The trabeculated pattern of the musculi pectinati in the auricles and the trabeculae carneae in the ventricles is
an efficient means of gaining power without excessively thickening the wall of the chamber
...


Left coronary artery
The left coronary artery arises from the left posterior aortic sinus
and passes anteriorly between the left atrial appendage and

Coronary arteries and branches
Left atrial

Left conus

Right conus

Left atrial

Sinuatrial nodal

Circumflex
Right coronary

Diagonal

Right atrial

Conducting system of the heart

Left
marginal

Atrioventricular
nodal

Specialized cardiac muscle fibres form the:
 sinuatrial node (in the right atrial wall between the opening of the superior vena cava and the auricle)
 AV node (in the left wall of the right atrium, at the superior
limit of the interventricular septum)
 AV bundle (arising from the AV node and descending in
the interventricular septum)
...
The plexus of Purkinje fibres allows

MEDICINE 42:8

Left coronary

Right marginal

Posterior (inferior)
interventricular and
septal branches

Anterior interventricular
(anterior descending) and
septal branches

Figure 1

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THE NORMAL HEART

The circumflex artery continues first in the anterior and then
in the posterior AV groove, and anastomoses with the terminal
branches of the right coronary artery
...

The 10% of individuals in whom most of both ventricles and
the septum are supplied by the left coronary artery are said to
have left cardiac (coronary) dominance
...
Note that the coronary arteries fill and distribute blood to the heart during diastole
when cardiac muscle is relaxed and vascular resistance low
...
8 Drainage of both ventricles starts with the great
cardiac vein in the anterior interventricular groove (Figure 2),
which passes to the left in the anterior AV groove, where it collects
the left marginal vein
...
The confluence of these veins is the 3-cm
long coronary sinus, lying in the posterior AV groove
...
The small cardiac vein sometimes drains directly into the
right atrium
...
In addition, 20
e30% of all drainage is in the venae cordis minimae (Thebesian
veins) e small venous channels seen throughout the myocardium
that drain directly into the chambers of the heart
...
Here it
divides into the:
 circumflex artery and the
 anterior interventricular artery
...
The importance of attitudinally appropriate
description of cardiac anatomy
...

2 Horsthuis T, Christoffels VM, Anderson RH, Moorman AF
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3 Manner J
...
Clin Anat 2009; 22: 21e35
...
The clinical anatomy of the mitral valve
...

5 Hildreth V, Anderson RH, Henderson DJ
...
Clin Anat
2009; 22: 36e46
...
The normal
and abnormal anatomy of the coronary arteries
...

7 Loukas M, Bilinsky S, Bilinsky E, Matusz P, Anderson RH
...
Clin Anat 2009; 22: 146e60
...
Cardiac veins: a review of the
literature
...


Oblique vein
left atrium

Coronary sinus

Anterior cardiac
veins

Small cardiac
vein

Middle cardiac vein
Great cardiac vein
Posterior ventricular vein

Figure 2

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