The heart has structures and mechanisms, which ensure it is
designed for acting as a pump to allow blood to circulate around the body via
the circulatory system. The heart needs to be able to pump oxygenated blood around
the whole body to ensure all cells have sufficient oxygen for respiration. This
is fundamental for organisms, to produce substances, such as ATP, for survival.
In this essay, we will discuss the different structures and mechanisms of the
heart, and how they are adapted to ensure sufficient blood is pumped around the
body. We will also explore what would happen if a mutation occurred in any of
these structures or mechanisms.
The heart and the circulatory system varies between each
organism, this is usually based on the organisms’ surface area to volume ratio.
For example, fish have a large surface area to volume ratio, therefore only
require a single circulatory system. Whereas elephants have a small surface
area to volume ratio requiring a double circulatory system. Humans specifically
have a double circulatory system, a separated systemic and pulmonary circuit. These
two separate systems allow for a major advantage ‘it allows pressure to be
different in both circuits.’ (Moyes and Schulte, 2008, p. 362). The lungs contain thin
capillaries to allow for efficient gas exchange, if blood entered these thin capillaries
at high pressure they would rupture, therefore low pressure if required for the
pulmonary circuit. However a higher pressure if required for the systemic circuit
as when blood exits the aorta it needs to be able to pump oxygenated blood all
around the body. These two systems a vital to ensure the different conditions
needed in each part of the body are met.
The heart is made of four chambers, the most vital being
the left ventricle as this is where blood is at its highest pressure, as it
needs to be able to reach all body extremities. The ventricular muscle is
usually made of two different myocardia. ‘The outer layer of compact myocardium
which is tightly packed cells arranged in a regular pattern, and an inner layer
of spongy myocardium, a meshwork of loosely connected cells’ (Moyes and Schulte, 2008, p. 369). In humans there is
usually more compact myocardium, perhaps due to the high pressure at which blood
is flowing. The left ventricle is specifically thicker to withstand the pressure,
however if the pressure increases too high (hypertension) this could lead to
serious health complications and a possible permanent damage to the heart.
Not only, are the heart chambers adapted to withstand different
pressures. The blood vessels are also,
The heart is surrounded by the pericardium which is a fibrous
covering, the outer layer usually made of connective tissue, which surrounds
the heart, it also ‘contains fluid with lubricates the heart in the pericardial
space to prevent friction’ whilst the heart beats. (Know
the Structures and Functions about Your Heart, 2015)