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THE HEART: ITS STRUCTURE, FUNCTION, AND DISEASES
Maxmadaliyeva Aziza Lazizovna
Tashkent Medical Academy 1st-year student
of the Faculty of Medical Treatment
Scientific supervisor:
Tursunmetov Ibodulla
Department of Medical Biology and Histology
Tashkent Medical Academy
Annotation:
This article provides general information about the structure and
function of the heart, as well as the factors affecting its activity. It highlights the main
types of heart diseases, their causes, and prevention methods. The article also includes
useful lifestyle recommendations for maintaining a healthy heart and describes modern
diagnostic techniques.
Keywords:
heart, epicardium, myocardium, endocardium, infarction, stroke,
intercalated discs, bundle of His, pacemaker cells.
Introduction
The human div is a complex and highly organized system, in which each organ
has its own unique function. Within this system, the heart holds a special place. The
heart is one of the most vital organs that sustains life by ensuring blood circulation
throughout the entire div. With its help, cells receive blood rich in oxygen and
nutrients, which directly influences the functioning of all organs.
According to the World Health Organization (WHO), cardiovascular diseases
rank among the leading causes of death globally. Each year, millions of people lose
their lives due to heart-related conditions. In particular, ischemic heart disease, heart
attacks, and hypertension are widespread. These conditions not only affect the elderly
but are increasingly seen among young people and even children, turning into a serious
socio-economic problem.
Heart diseases often develop silently. In the early stages, their symptoms may go
unnoticed. However, over time, signs such as fatigue, shortness of breath, and rapid
heartbeat may appear, significantly reducing a person’s quality of life.
Another important point is that most heart diseases are preventable. A healthy
diet, regular physical activity, stress management, avoiding harmful habits, and routine
medical check-ups play a crucial role in maintaining heart health.
This article provides a detailed overview of the heart’s structure, main functions,
factors negatively affecting its performance, causes and symptoms of heart diseases,
and prevention methods. The article is written for a general audience, with scientific
information presented in a clear and simple language.
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The main goal of the article is to increase awareness about the heart, emphasize
the importance of heart health, and promote a healthy lifestyle.
Methods
For this article, an analysis was conducted based on scientific articles, clinical
studies, laboratory results, and epidemiological data from the period 2015-2023. The
article reviews the types, causes, diagnostic methods, and treatment options for heart
diseases. Additionally, the research examines the latest advancements in heart disease
detection and treatment methods, including modern technologies like ultrasound and
ECG for diagnosis and management.
Data Collection Methods:
ECG (Electrocardiogram):
Analyzing the heart's electrical activity helps to
study its rhythm and impulses, aiding in the detection of various heart diseases and
problems. Studying the heart's electrical activity allows for the early detection of
conditions such as coronary heart disease and arrhythmias.
Echocardiogram (Heart Ultrasound Examination):
Plays a crucial role in
evaluating the structure and function of the heart. This method provides detailed
images of the heart, assessing the strength of the heart muscles, its contractions, and
blood flow. As a result, anatomical changes in the heart, such as valve issues,
myocardial infarction, or ischemic conditions, can be analyzed.
Laboratory Research:
Blood tests help analyze biomarkers related to heart
diseases, allowing for the study of inflammation processes and the div's response.
Levels of creatinine, urea, lipids, and sodium help assess the condition of the heart and
kidney function.
Angiography:
Used to examine coronary arteries, this method helps identify
blockages, clots, and atherosclerotic changes in blood vessels. Angiography is widely
used to detect the risk of heart attacks or ischemic diseases.
Ultrasound Examinations (Doppler Method):
Ultrasound is used to assess
blood flow and the functioning of the heart. The Doppler method, in particular, is
employed to measure blood flow in the left and right chambers of the heart and evaluate
their performance.
Main Body: The Structure of the Heart
The heart (cor) is a muscular organ located in the thoracic cavity. It constantly
contracts (systole) and expands (diastole) throughout an individual's life, except for
brief pauses, and supplies blood to the entire div. Thus, the heart is the central organ
in the circulatory system. In an average adult, the heart contracts approximately 70-75
times per minute, and 100,000 times per day. This is equivalent to lifting 20 tons of
weight to a height of one meter within that time.
The heart of an average adult is slightly compressed when viewed from the front
and back, and has a conical shape, roughly the size of the individual's clenched fist.
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The heart consists of four chambers: two atria and two ventricles. The left atrium and
left ventricle form the left or arterial part of the heart, while the right atrium and right
ventricle form the right or venous part.
The average weight of the heart is 300 grams in men and slightly less, between
200-250 grams, in women. In adults, the heart's length ranges from 10-15 cm, its width
(at the base) is 8-11 cm, and the thickness of the front and back walls is 6-8.5 cm. The
sharp (right) and blunt (left) edges of the heart separate its anterior and posterior
surfaces. The heart's weight accounts for about 1:200 or 1:75 of the total div weight.
In newborns, the heart is round in shape, positioned slightly higher, and weighs
between 23-27 grams. In eight-month-old infants, the heart's weight is doubled; at ages
2-3, it triples, and by age 16, it increases 11-fold. The heart is asymmetrically
positioned in the lower part of the anterior chest cavity. The major blood vessels
extending from the heart hold it in place, while the diaphragm's central part touches the
heart's lower surface. The heart is surrounded by the lungs and pleural sacs on the sides,
partially touching the V-VI rib arches and the sternum in the front, excluding the lungs.
The position of the heart varies among individuals, depending on factors such as
age, gender, div posture, and physique. Additionally, it is influenced by the
movement of the diaphragm during breathing and the functioning of the heart. For
example, in newborns, the heart is round in shape, and the diaphragm, being higher and
more domed, is positioned more horizontally and higher. The heart is slightly displaced
to the back due to the prominence of the diaphragm, which pushes it away from the
sternum.
The structure of the front view of the heart. The posterior view of the heart.
The heart consists of four chambers: two atria and two ventricles. The atria receive
blood from the veins, while the ventricles pump blood into the arteries. The right atrium
is irregularly cuboidal in shape. The right atrium is separated from the left atrium by
the interatrial septum, and from the right ventricle by the ostium atrioventricularis
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dextrum. Externally, the right atrium is bounded by the right auricle. The inner surface
of the auricle contains trabeculae muscles. The function of the right auricle is to
increase the volume of the right atrium. The superior vena cava opening, inferior vena
cava opening, right atrioventricular opening, as well as the openings of the sinus
venosus (which collects blood from the heart veins) between the second and third
openings, and the opening of the right ventricle’s anterior vein, and small heart veins
(20-30 Teberiev veins) located in the walls of both the right and left atria, drain into
the right atrium through tiny openings.
The right ventricle is pyramid-shaped and positioned inversely. It has two
openings at the upper wide base: the posterior atrioventricular opening and the anterior
pulmonary trunk opening. Between the atrial and ventricular openings, three-layered
valves are located. The left atrium is an irregular cubic shape. The left auricle is located
in the anterior wall of the left atrium, with trabecular muscles inside. The auricle’s
function is to increase the volume of the left atrium. The left ventricle is cone-shaped,
with the apex pointing downward. The upper wide base of the left ventricle contains
two openings: the aortic opening on the right and the atrioventricular opening on the
left. Between the atrioventricular openings, a two-leaflet valve is present.
The heart is a muscular organ. It is the main component responsible for driving
blood through the circulatory system. The heart wall consists of three layers: the inner
layer is the endocardium, the middle layer is the myocardium, and the outer layer is the
epicardium. The heart is surrounded by a connective tissue membrane, the pericardium,
also known as the heart sac. Between the epicardium and the pericardium is a cavity
filled with fluid, which helps ease the heart’s movements by reducing friction.
The endocardium is the heart's inner and relatively thin layer. It covers the inner
surfaces of all the chambers of the heart, as well as the muscular ridges, tendon fibers,
and valves. The myocardium is the thickest and most developed layer of the heart. It is
made up of striated muscle tissue, with both typical and atypical muscle fibers. Typical
muscle fibers are responsible for contraction, while atypical fibers conduct electrical
impulses.
The epicardium is the outer layer of the heart wall and is made of thin connective
tissue. It contains a certain amount of fat and numerous blood vessels. Its surface is
covered by a single layer of flat cells (mesothelium). The heart wall is nourished by the
coronary arteries, which branch out and direct blood to all three layers of the heart wall
before dividing into capillaries. These capillaries merge to form the coronary veins,
which drain into the right atrium or the vena cava. The heart also contains a special
vascular system called the Thebesian veins, which directly drain into the heart
chambers.
The pericardium is similar to the epicardium in structure but is covered by a
double layer of mesothelium.
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Physiology and Histology of the Heart
The myocardium is made up of striated muscle tissue, with typical and atypical
muscle fibers distinguished within it. Typical muscle fibers are responsible for
contraction, while atypical fibers are responsible for conduction of electrical impulses.
Typical muscle fibers are formed by some contracting muscle cells, called
cardiomyocytes. Cardiomyocytes differ from atypical muscle cells and skeletal striated
muscle fibers in their structural and cytochemical properties. These cells are arranged
sequentially to form muscle fibers. The muscle fibers are divided into segments or cell
clusters via intercalated discs.
The structure of these cells is examined in the general histology section, muscle
tissue chapter, and in the specific heart muscle tissue section. The contracting muscle
cells of the heart are similar in shape to cylinders, with a length of 50–100 micrometers
and a diameter of 17–20 micrometers. The central part of the cardiomyocytes contains
an oval-shaped nucleus. The heart muscle fibers are surrounded by the sarcolemma.
This explanation touches on the fundamental histological and physiological
characteristics of heart muscle tissue.
The electron microscope has revealed that the sarcolemma consists of an inner
plasma membrane and an outer basal membrane. The sarcolemma participates in the
formation of intercalated discs.
Conduction System of the Heart
This system is composed of conductive (atypical) heart muscle cells that generate
impulses (excitations) and transmit them to the contractile (typical) heart muscle cells.
The conduction system of the heart includes the sinoatrial or sinus (Kis Flak) node, the
atrioventricular or atrioventricular (Ashof Tovar) node, the bundle of His, and its
branches that transmit the excitation to the contractile myocytes. The bundle of His
divides into right and left branches, from which the heart's special atypical fibers,
known as Purkinje fibers, originate.
Three types of cells are distinguished in the conduction system. Impulses are
generated in the sinoatrial node. The center of the node primarily contains self-
contracting cells, also known as pacemaker cells. Surrounding the sinoatrial node are
intermediate cells, which are especially numerous in the atrioventricular node, while
pacemaker cells are relatively sparse in this node.
Intermediate cells are thin and elongated, with cross-sections smaller than those
of typical cardiomyocytes. The cytoplasm of intermediate cells contains more
miofibrils, which are often aligned parallel to each other, and A- and I-disks are clearly
visible. Some intermediate cells contain short T-tubules. These cells transmit the
excitation impulse from the pacemaker cells to the bundle of His cells and the
contractile (typical) cardiomyocytes.
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The function of the heart is based on the rhythmic contraction of the myocardium.
The contraction phase is called systole, and the relaxation phase is called diastole. The
heart contracts automatically. The impulses that ensure myocardial contraction are
generated in the heart's conduction system. These impulses, normally produced 60–80
times per minute in the sinoatrial node, first spread to the atrial myocardium, then pass
through the atrioventricular node, the bundle of His, and the Purkinje fibers to reach
the ventricular myocardium, causing the ventricles to contract. During transmission to
the ventricles, the speed of the impulses slows down. As a result, the atria complete
their contraction before the ventricles.The cycle of contraction and relaxation of the
heart forms the cardiac cycle. This cycle consists of atrial systole (0.1 sec), ventricular
systole (0.33–0.35 sec), diastole (the phase in which both atria and ventricles relax),
and a pause (0.4 sec). During atrial contraction, the blood pressure in the atria increases
(from 1–2 mmHg up to 6–9 mmHg in the right atrium, and up to 8–9 mmHg in the left
atrium), causing blood to flow into the ventricles through the valves. Only about 30%
of the blood is pushed into the ventricles during atrial systole; the remaining 70% flows
in passively during the general pause.Ventricular systole is also divided into phases.
When ventricular pressure rises, the atrioventricular valves close, but the semilunar
valves (aortic and pulmonary) remain shut. During this isometric contraction phase, all
muscle fibers contract, increasing tension. When the ventricular pressure exceeds the
pressure in the aorta and pulmonary trunk, the semilunar valves open and blood is
ejected into the arteries—this marks the beginning of the ejection phase. In humans,
blood is ejected into the vascular system when the pressure in the left ventricle reaches
65–75 mmHg and in the right ventricle 5–12 mmHg. Within 0.10–0.12 seconds,
ventricular pressure sharply rises (110–130 mmHg in the left ventricle, 25–35 mmHg
in the right ventricle) in the rapid ejection phase, followed by the slow ejection phase
(lasting 0.10–0.15 sec).Next, the ventricles begin to relax; their pressure drops rapidly,
the pressure in the large vessels rises, and the semilunar valves close. When ventricular
pressure drops to 0 mmHg, the atrioventricular valves open, and blood starts flowing
from the atria into the ventricles. This is divided into a rapid filling phase (0.08 sec)
and a slow filling phase (0.07 sec). Ventricular diastole ends with the complete filling
of the chambers.The duration of the phases in the cardiac cycle is variable and depends
on heart rate. Thus, studying the phases of the cardiac cycle is an important method for
assessing the function of the heart muscle. The cardiac output is the amount of blood
ejected from the heart per minute. The volumes from the left and right ventricles are
equal. In a resting adult, the average cardiac output is 4.5–5 liters per minute. The
amount of blood pumped with each heartbeat is known as stroke volume, averaging
65–70 ml. The strength and rate of heart contractions adjust according to the div’s
need for oxygen and nutrients. Although the impulses that stimulate the heartbeat
originate within the heart, its activity is regulated by the nervous system. The vagus
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nerve decreases the strength and rate of heart contractions, while the sympathetic
nerves increase them. The heart muscle also possesses auto-regulation: the more blood
that enters the heart, the more forcefully it contracts. The force of contraction depends
on how stretched the muscle fibers are before contraction—this is their initial length.
The more the muscle fiber is stretched, the stronger the contraction. This is known as
the Frank-Starling law of the heart.
Heart Diseases
Arterial Hypertension
Arterial hypertension, or high blood pressure, is a serious condition that increases
the risk of heart attacks and strokes. During heart contraction (systole), the pressure in
the arteries of an adult typically ranges from 120–140 mmHg, while during relaxation
(diastole), it falls to 80–90 mmHg. If these values are elevated, it indicates high blood
pressure, which can lead to severe consequences.
In developed countries, the number of people suffering from hypertension is
significantly high. In 90% of cases, this condition does not result from a single easily
treatable cause, which is why a comprehensive treatment approach is necessary.
Ischemic Lesions
Myocardial Infarction
This acute condition is a clinical form of ischemic heart disease, caused by
necrosis (tissue death) of the heart muscle (myocardium) due to complete or partial
lack of blood supply. It disrupts the function of the entire cardiovascular system and
poses a serious threat to the patient’s life.
The main and most common cause of myocardial infarction is impaired blood
flow in the coronary arteries, which supply the heart muscle with blood and oxygen.
This is often associated with atherosclerosis — the buildup of atherosclerotic plaques
on the arterial walls.
Ischemic Heart Disease
This disease is characterized by a reduction in blood flow to the heart muscle. The
heart works intensively, and any lack of blood supply immediately affects its function.
The coronary arteries, which surround and nourish the heart muscle, are responsible
for delivering this blood.
Symptoms of this condition may include shortness of breath and chest pain
(angina). In nearly 90% of cases, coronary artery disease is caused by atherosclerosis,
a condition that damages the walls of the arteries. While it was once considered a part
of the natural aging process, it is now known that even children can suffer from
atherosclerosis.
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Valve Defects
Acquired Heart Defects
Among the most common heart defects are valve dysfunctions. Valve dysfunction
in the heart involves the backflow of blood or insufficient opening. This condition is
often a result of infectious damage or autoimmune reactions.
Congenital Heart Defects
Congenital heart defects usually arise due to hereditary diseases or disruptions
during embryonic development.
Tetralogy of Fallot
The most severe form of congenital heart defects is Tetralogy of Fallot. This
condition involves hemodynamic disturbances, reduced blood flow to the lungs, and
venous blood flowing from the right ventricle to the aorta. The development of
Tetralogy of Fallot involves four main factors:
Ventricular Septal Defect (VSD) — This defect, also known as an inter-
ventricular septal defect (IVSD), connects the left and right sections of the heart. In
Tetralogy of Fallot, the VSD is always large and non-restrictive. Typically, this is a
perimembranous VSD, muscular VSD, or subarterial VSD.
Obstruction of the right ventricular outflow tract — This occurs due to one or a
combination of the following anatomical components: infundibular (subvalvular)
stenosis of the right ventricular outflow tract, pulmonary artery stenosis, obstruction
due to hypertrophy of the right ventricular myocardium, and/or hypoplasia of the
pulmonary artery trunk and/or its branches.
Dextroposition of the aorta — The aorta partially shifts to the right ventricle, or
blood flow in the aorta remains dominant due to the activity of the left ventricle.
Causes of death worldwide
Cardiovascular diseases
Cancer
Chronic respiratory diseases
Lower respiratory tract
infections
Road traffic accidents and other
injuries
Alzheimer's disease and
dementia
Diabetes mellitus
Kidney diseases
Other causes (liver disease,
suicide, etc.)
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Right ventricular hypertrophy — Hypertrophy of the right ventricle muscle
component develops over time as the individual ages.
Other Congenital Heart Defects
These include inter-ventricular and inter-atrial septal defects, valve stenosis,
patent ductus arteriosus (blood bypasses the lungs), etc. Most of these conditions can
be treated with surgical methods. The timing of surgery depends on the nature of the
defect, its symptoms, and the severity of the condition.
Discussion:
The heart is a vital organ that sustains human life. Every beat ensures the delivery
of oxygen and nutrients throughout the div. The heart works rhythmically and
automatically through the cardiac cycle.
Today, heart diseases have become the number one cause of death worldwide.
Among them, arterial hypertension and ischemic heart disease are the most common.
In hypertension, blood pressure is elevated, placing excess strain on the heart. Ischemic
heart disease involves reduced blood flow to the heart muscle. The most dangerous
condition is myocardial infarction, which is the death of heart tissue due to lack of
blood supply.
According to global statistics, cardiovascular diseases are the leading cause of
mortality. Additionally, cancer, diabetes, kidney diseases, and respiratory disorders
also significantly increase the risk of death.
To maintain heart health, a healthy lifestyle, regular physical activity, and proper
nutrition are essential. Everyone should take care of their heart — to protect it is to
protect life itself.
Conclusion
The heart is one of the most vital organs in the human div, and its constant,
rhythmic, and healthy functioning determines the quality of life. This muscular organ
ensures blood circulation throughout the div, supplying every cell with oxygen and
nutrients. Any disruption in heart function negatively affects the entire div.
Heart health must always be a priority. Today, heart diseases are widespread
globally and are a major cause of early death. Their main causes include unhealthy
lifestyles, stress, harmful habits, poor diet, and lack of physical activity. However, early
detection can prevent complications and even save lives.
Regular medical check-ups, monitoring blood pressure and heart rhythm, giving
up harmful habits, eating healthy, and staying physically active are essential steps. A
healthy heart is one of life’s greatest treasures — it is the key to a healthy life. Taking
care of the heart is not just a personal duty, but also a responsibility towards family and
society.
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This article provided simple and clear information about the heart’s structure,
functions, diseases, and causes. Its main goal is to raise public awareness and
encourage people to take action in protecting heart health.
References:
1. Q.R. Tukhtaev, F.Kh. Azizova, M. Abdurakhmanov, E.A. Tursunov, Q.I. Rasulov,
M.Kh. Rakhmatova // Histology, Cytology, and Embryology // Textbook – 2021,
pp. 475–482.
2. N.K. Akhmedov // Human Anatomy // Textbook – 2005, p. 5.
3. M.A. Ibodov, Z.Y. Bozorov, Sh.Sh. Rakhmatullaeva // Medoptimal Anatomy,
Volume II // Textbook – 2023, pp. 267–273.
4. A. Gadayev, U. Mirsharapov // Human Anatomy // Textbook – 2021, pp. 393–394.
5. U.M. Mirsharapov, Z.Sh. Sodiqova, S.M. Akhmedova, Kh.Kh. Pulatov // Human
Anatomy // Textbook – 2024, p. 332.
7.
https://mymedic.uz/kasalliklar/yurak-tomir/yurak-kasalliklari/
