The Structure of the Heart
The first diagram (immediately below) is a cut-away section through
the heart, showing its physical appearance and labelling its major
components and blood vessels. The simpler diagrams below it are
line drawings including essential information in a form that is
easier to reproduce in exams.
Illustration of the Physical Form of the Heart
Diagram (1): Physical Appearance and Major Components of the Heart
The heart is a muscular cone-shaped
organ about the size of a clenched fist of the
It is located in the upper body (chest area) between
the lungs, and with its pointed end (called the
apex) downwards, forwards, and pointing
towards the left.
The main purpose of the heart is to pump blood
around the body.
The basic structure of the heart (illustrated
above) may be described as follows:
The Heart is divided into separate right and
left sections by the interventricular septum,
or "septum" when the context is clearly
that of the heart. Each of these (right and left)
sections is also divided into upper and lower
compartments known as atria and ventricles,
The four main chambres of the heart are:
- Right Atrium (Labelled "RA" in the diagrams on this page)
- Right Ventricle (Labelled "RV" in the diagrams on this page)
- Left Atrium (Labelled "LA" in the diagrams on this page)
- Left Ventricle (Labelled "LV" in the diagrams on this page)
Deoxygenated blood (from
the body) is pumped through the right atrium and
the right ventricle (to the lungs), while oxygenated
blood (from the lungs) is pumped through the
left atrium and the left ventricle (to the body).
- Deoxygenated blood enters the right atrium from the Superior vena cava and the Inferior vena cava.
- Deoxygenated blood leaves the right ventricle by Pulmonary artery, which takes blood to the lungs via the right and left brances of the pulmonary artery.
- Oxygenated blood enters the left atrium from the Pulmonary veins.
These may be labelled as "right pulmonary veins" and "left pulmonary veins".
- Oxygenated blood leaves
the left ventricle by Ascending aorta,
which takes blood to the body via its system
of arteries, arterioles, and capillaries.
Major arteries leading from the heart (via
the ascending aorta) include the brachiocephalic
artery, the left common carotid artery,
and the left subclavian artery (illustrated
above). These are just a few of the main
arteries of the body.
It is essential that blood flows
in the correct direction through the heart so
the structure of the heart includes a series of
- The Tricuspid valve separates the right atrium from the right ventricle.
- The Pulmonic / Pulmonary valve separates the right ventricle from the pulmonary artery.
- The Mitral (also known as the Bicuspid) valve separates the left atrium from the left ventricle.
- The Aortic valve separates the left ventricle from the ascending aorta.
Line Drawings of the Basic Structure of the Heart
(1) above is a clear illustration of the structure
of the heart it may be difficult to reproduce
quickly in examinations. The following diagrams
are less detailed and not as fully labelled (the
same information as above applies so more labels
could be added), but may be more convenient to
sketch rapidly if required to do so.
Diagram (2)a is a simplification of Diagram (1);
Diagram 2(b) includes additional information about
structures concerned with the system of electical
conduction operating in the heart (which is described
on the page about The Functions of the Heart).
More about the functioning of the heart and the vascular system generally are included on other pages of this website.