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DANIEL
YEO
HEART ANATOMY
Health Maintenance A | Daniel Yong Tze Yeo
1. Surrounding features
a) Gross location
The heart lies within the middle mediastinum a.k.a. the pericardium.
The middle mediastinum is surrounded by the other mediastinal portions, and hence the lungs. It is
externally invested by the parietal pleura of the lungs.
Hence, consider the pericardium in relation to the lungs.
The middle mediastinum is fused to the diaphragm on the bottom.
b) Associated layers
i) Major layers
Fibrous pericardium is mostly inflexible and is the outermost
Serous pericardium functions similar to other kinds of pleura; hence visceral and parietal layers.
Layer
Fibrous pericardium
Serous pericardium
Parietal
Visceral
Innervation Phrenic nerve
Phrenic nerve
Insensitive
Gross
Forms all of pericardium outside
Like the pleura, invests all of heart and vessels,
anatomy
Fuses with all great vessels except
with reflections in certain places.
the IVC (fused to diaphragm at T8)
(Reflections discussed later)
Function
Inflexible but slippery
Stuck to parietal pleura so lungs
glide over it
Clinical
Cardiac effusions can lead to
The only source of
compression (cardiac tamponade)
localized pain of
No pain
pericardium
The pain of angina comes from sympathetic innervations of muscles in heart.
The pain of pericarditis comes from the parietal serous pericardium. This passes through the
phrenic nerve, and hence refers to the shoulder.
ii) Clinically significant reflections
The two main defects coming fom reflections of the serous pericardium are the:

Transverse sinus

Oblique sinus
Defect
Transverse sinus
Oblique sinus
Embryological
Breakdown of dorsal mesocardium
Buckling of heart tube
origin
Leaving patency between arterial and
Creates cul-de-sac
venous ends of heart tube
Description
Located posterior to heart
Located posterior to heart
Horizontal sinus superiorly
J-shaped cul-de-sac
Relation to SVC, aortic arch, pulmonary
trunk and left auricle
Access
Pass finger superiorly through
Under apex and behind the heart
Surgical
Divides arteries from veins
Functional significance:
significance
When a finger is put through it
Allows left atrium to pulsate


Arteries (aorta and pulmonary
trunk) are pushed anteriorly
In fact, the majority of the oblique sinus
Veins (SVC) and left auricle are
overlies the left atrium posteriorly.
pushed posteriorly
A ligature is passed through this sinus to
occlude the aorta and pulmonary trunk
in certain operations.
2. Heart
a) Fibrous skeleton
In reality, the right atrium and ventricle are more anterior rather than “right” of the left atrium and
ventricle. One can consider these right and left chambers as being functionally separate.
Atria and ventricles are divided by an “8” shaped fibrous skeleton in the sagittal plane.

Atria on the right

Ventricles on the left
There is no muscular continuity across the fibrous skeleton.
The only physiological link is the atrioventricular bundle.
b) Major chambers and compartments
Chamber
Receives vessels
Right atrium
IVC
Right ventricle
Left atrium
Left ventricle
Pulmonary trunk
Pulmonary veins
Aorta
Most of anterior
All of posterior
Seen posteriorly,
surface of heart
surface of heart
but not of
SVC
Relation in heart
All of right border
posterior surface
Small portion (the
left auricle) peeks
Peeks out on the
onto left border
left anteriorly,
forming the left
border
Anterior surface
*Note that, as in most anatomical
diagrams, the left auricle is drawn
exaggerated.
It is nowhere near this big in reality.
But it can be visualized
radiologically as a slight concavity
in that area.
Posterior surface
Note the oblique and transverse sinuses
from the defects between the visceral
pericardium and parietal pericardium are
shown here.
Diaphragmatic (inferior) surface
This is the clearest representation of how the
chambers are divided up.
Important features are:


Arterioventricular groove (red)
o
Coronary sinus
o
Right coronary artery
Interventricular groove (blue)
o
Middle cardiac vein
o
Posterior interventricular
artery
Note that the coronary sinus is venous, and the right coronary artery is arterial.
Hence:

Middle cardiac vein arises from coronary sinus

Posterior interventricular artery arises from right coronary artery
3. Surface markings of the heart

Right border (red)

Inferior border (blue)

Left border (yellow)

Intersection at the right and inferior borders (purple)

Intersection of the left and inferior borders (green)
Diagram of surface markings of heart
Lower border of right 2nd costal
Lower border of left 2nd costal
cartilage
cartilage
2cm from sternal margin
Lower border of right 6th costal
Left 5th intercostal space
cartilage
9cm from midline
APEX