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EXPLAINAITION OF HUMAN HEART AND ITS FUNCTIONS
(simplified)
Please note:-

Starred parts are extra information
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Underlined parts are for better understanding
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HEART AND ITS FUNCTIONS

1] What exactly is heart?
→ The human heart is one of the most important organs responsible for
sustaining life
...
The human heart functions throughout a person’s
lifespan and is one of the most robust and hardest working muscles present
in the human body
...
It is derived from the
embryonic mesodermal germ layer
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This replenishes oxygen and circulates nutrients
among the cells and tissues
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Blood delivers oxygen, hormones, glucose and other components to
various parts of the body, including the human heart
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•

TYPES OF CIRCULATIONS

There are Two Main types of Circulation
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Now, the heart itself is a muscle and therefore, it needs a constant supply of
oxygenated blood
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CORONARY CIRCULATION
Coronary circulation is an essential portion of the circulation, where
oxygenated blood is supplied to the heart
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Moreover, organs like
the brain need a steady flow of fresh, oxygenated blood to ensure
functionality
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The valves that separate these chambers are called atrioventricular
valves, composed of the tricuspid valve on the left and the mitral valve on the
right
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Similar to the atria, valves also separate the ventricular

chambers
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The heart also has a wall that is composed of three layers: the outer
layer epicardium (thin layer), the middle layer myocardium (thick layer), and
the innermost layer endocardium (thin layer)
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The heart structure is made more complex because of the mechanisms that
allow blood to be distributed throughout the body and return to the heart
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The vessels that bring oxygen-free blood back into the heart are
called veins; those that bring oxygen-rich blood away from the heart and to
other body parts are called arteries
...
The aorta is considered a main artery in the
body
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EXTERNAL STRUCTURE OF HEART

PERICARDIUM
The human heart is situated to the left of the chest and is enclosed within a
fluid-filled cavity described as the pericardial cavity
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The pericardium is a fibre membrane found as an external covering around
the heart
...
Apart
from the lubrication, the pericardium also helps by holding the heart in its
position and by maintaining a hollow space for the heart to expand itself when
it is full
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Namely Visceral Layer and
Parietal Layer
Visceral Layer: It directly covers the outside of the heart
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STRUCTURE OF HEART WALL
The heart wall is made up of 3 layers, namely:
Epicardium
– Epicardium is the outermost layer of the heart
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Myocardium
– This is a layer of muscle tissue and it constitutes the middle layer wall of the
heart
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Endocardium
– It is the innermost layer that lines the inner heart chambers and covers the
heart valves
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INTERNAL STRUCTRE OF HEART
The internal structure of the heart is rather intricate with several chambers
and valves that control the flow of blood
...
For instance, most fish have two chambers, and reptiles and
amphibians have three chambers
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Humans are mammals; hence, we have four chambers,
namely: Left atrium, Right atrium, Left ventricle, Right ventricle
ATRIA
– are thin and have less muscular walls and are smaller than ventricles
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VENTRICLES
- are larger and more muscular chambers responsible for pumping and
pushing blood out into circulation
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The right ventricle and right atrium are comparatively smaller than the left
chambers
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The blood originating from
the right side flows through the pulmonary circulation, while blood arising
from the left chambers is pumped throughout the body
...
All vertebrates, including humans, possess this type of
circulation
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The blood vessels typically comprise the following:
VEINS
- supply deoxygenated blood to the heart via inferior and superior vena cava,
and it eventually drains into the right atrium
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ARTERIES
- are muscular-walled tubes mainly involved in supplying oxygenated blood
away from the heart to all other parts of the body
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VALVES
Valves are flaps of fibrous tissues located in the cardiac chambers between
the veins
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Flaps also prevent the blood from flowing backwards
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The valve between the right ventricle and
right atrium is the tricuspid valve, and the one which is found between the left
ventricle and left atrium is known as the mitral valve
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It is also found between
the pulmonary artery and the right ventricle
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What is pulmonary circulation? Explain
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The system then brings oxygenated blood back to the heart to be
pumped throughout the body
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Define systemic circulation
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3
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→The heart is a muscle, and it needs a constant supply of oxygenated blood
to survive and work effectively
...
The coronary
arteries supply oxygenated blood to the heart, and the cardiac veins drain the
blood once it has been deoxygenated by the tissues of the heart
...
Briefly explain the structure of the human heart
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The ventricles are the chambers that pump blood and atrium are the
chambers that receive the blood
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”
5
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→
•
•
•
•

Left atrium
Right atrium
Left ventricle
Right ventricle

6
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→The pericardium is a fibrous membrane that envelops the heart
...
Furthermore, the
pericardium also holds the heart in its position and provides a hollow space
for the heart to expand and contract
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Explain the three layers of the heart wall
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It is composed of
a thin layer of membrane that protects and lubricates the outer section
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It is responsible for the heart’s “pumping”
action
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Prevents blood from sticking, thereby
avoiding the formation of fatal blood clots
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Explain the three major blood vessels of the human body
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Capillaries – They are minuscule, tube-like vessels which form a
network between the arteries and veins
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9
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→Valves are flaps of tissues that are present in cardiac chambers between
the veins
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Examples include the
atrioventricular valves, tricuspid valves, mitral valves and the semilunar valves
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What is meant by myocardial infarction?
→Myocardial infarction is a serious medical condition where the blood flow to
the heart is reduced or entirely stopped
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