INTRODUCTION

The circulatory system is an organ system that passes nutrients (such as amino acids, electrolytes and lymph), gases, hormones, blood cells, etc. to and from cells in the body

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to help fight diseases and help stabilize body temperature and pH to maintain homeostasis

This system may be seen strictly as a blood distribution network, but some consider the circulatory system as composed of the cardiovascular system, which distributes blood and the lymphatic system, which distributes lymph. While humans, as well as other vertebrates, have a closed cardiovascular system (meaning that the blood never leaves the network of arteries, veins and capillaries), some invertebrate groups have an open cardiovascular system. The most primitive animal phyla lack circulatory systems. The lymphatic system, on the other hand, is an open system.

Two types of fluids move through the circulatory system: blood and lymph. The blood, heart, and blood vessels form the cardiovascular system. The lymph, lymph nodes, and lymph vessels form the lymphatic system. The cardiovascular system and the lymphatic system collectively make up the circulatory system.

Singular circulation - The single circulatory system or single-circuit system is the simpler system that exists in vertebrates that have gills as the site of gas exchange.

The blood from the body is brought by the veins into the heart; then the heart pumps this deoxygenated blood toward the gills. In the gills the blood becomes loaded with oxygen and releases carbon dioxide. The oxygenated blood from the gills is then distributed by arteries to the body. The oxygen is delivered to the tissues through capillaries, these in turn unite to form veins, and the veins go back to the heart. Thus, blood only goes through one circuit.

Double circulation - The double circulatory system of blood flow refers to the separate systems of pulmonary circulation and the systemic circulation in amphibians, birds and mammals. All animals with lungs have a double circulatory system.

Double circulation has two routes or circuits.

Heart—lung—heart (pulmonary circulation) Heart—body—heart (systemic circulation)

The right ventricle pumps the blood throughout pulmonary artery to the lungs for purification. After being purified, the blood returns to the left auricle through the pulmonary vein. From here the blood comes to the left ventricle and then from here it is pumped to the arteries to the rest of the body. The impure blood then returns to the right auricle and then goes to the right ventricle.

This helps to maintain a higher blood pressure and a higher speed of flow of the blood. In turn this helps to maintain steeper diffusion gradients than in fish and so the exchange of metabolites (oxygen etc.) is more efficient. Fish, however, are ectotherms and so have a

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lower metabolic rate than endothermic mammals. This means that they can get away with a less efficient circulatory system as their demands for oxygen etc are much less.

Depending upon the medium of transportation, circulatory system can be divided into:-

1. Water vascular system – water is the medium of transportation. In other words, The water vascular system is a hydraulic system usually used by echinoderms, such as starfish and sea urchins, for locomotion, food and waste transportation, and respiration. The system is composed of canals connecting numerous tube feet. Echinoderms move by alternately contracting muscles that force water into the tube feet, causing them to extend and push against the ground, then relaxing to allow the feet to retract. Water canal system is another example of water vascular system used by primitive sponges. E.g. – in sponges (water canal system), in hydra (gastro-vascular system) and in star fish (ambulacral system).

2. Blood vascular system – blood is the medium of transportation. It is of 2 types:-

Open circulatory system – blood flows through vessels, which open into tissue spaces, membrane lined sinuses. An open circulatory system is a system in which the heart pumps blood into the hemocoel which is positioned in between the ectoderm and endoderm. The fluid described in the definition is called hemolymph, or blood. Hemolymph flows into an interconnected system of sinuses so that the tissues receive nutrients, fluid and oxygen directly. In animals that have an open circulatory system, there is a high percentage of the body that is blood volume. These animals have a tendency to have low blood pressure, with some exceptions. In some animals, the contractions of some species’ hearts or the muscles surrounding the heart can attain higher pressures.e.g. - arthropods, non cephalopods, mollusks and tunicates.

Closed circulatory system – In a closed circulatory system, blood flows from arteries to capillaries and through veins, but the tissues surrounding the vessels are not directly bathed by blood. Some invertebrates and all vertebrates have closed circulatory systems. A closed circulatory system allows more of a complete separation of function than an open circulatory system does. The blood volume in these animals is considerably lower than that of animals with open circulatory systems. In animals with closed circulatory systems, the heart is the chambered organ that pushes the blood into the arterial system. The heart also sustains the high pressure necessary for the blood to reach all of the extremities of the body.

In the closed circulatory system of mammals, there are two subdivisions—the systemic circulation and the pulmonary circulation. The pulmonary circulation involves circulation of deoxygenated blood from the heart to the lungs, so that it may be properly oxygenated. Systemic circulation takes care of sending blood to the rest of the body. It was discovered by William Harvey.

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Advantages and disadvantages of open and closed circulatory system

There are more disadvantages to having an open circulatory system but having an open circulatory system suits those animals well. Because of the limits to diffusion, animals with open circulatory systems usually have relatively low metabolic rates.

There are a variety of advantages to having a closed circulatory system. Every cell of the body is, at maximum, only two or three cells’ distance from a capillary. There is the ability for such animals to have incredible control over oxygen delivery to tissues. A unique characteristic to closed circulatory systems is that capability for a closed circulation to include the process of ultrafiltration in blood circulation. One of the most important advantages of the setup of the closed circulatory system is that the systemic and pulmonary branches of the system can maintain their respective pressures. 

OPEN CIRCULATORY SYSTEM CLOSED CIRCULATORY SYSTEM

TYPES OF HEART

1. On the basis of the types of blood it receives Venous heart – receiving deoxygenated blood only, e.g. fishes as heart

receives deoxygenated blood from all over the body except the gills. Arterio-venous heart – receiving deoxygenated blood from the body and

oxygenated blood from lungs/gills. E.g. amphibians, reptiles, birds, mammals.

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2. On the basis of origin of impulse

Myogenic – In the human heart, contraction is initiated by a special modified heart muscle known as sinoatrial node. It is located in the right atrium. The SA node has the inherent power of generating a wave of contraction and controlling the heart beat. Hence, it is known as the pacemaker. Since the heart beat is initiated by the SA node and the impulse of contraction originates in the heart itself, the human heart is termed myogenic. The hearts of vertebrates and molluscs are also myogenic.

Neurogenic - impulse for heart beat is brought by nerves eg most invertebrates. The autonomic nervous system, comprising the sympathetic and parasympathetic nervous systems, modulates the rhythm and strength of cardiac contraction. These signals from the spinal cord and brain are carried via nerves (the sympathetic and parasympathetic nerves, respectively), and release neurotransmitters onto the heart which speed or slow down the heart, respectively. The sympathetic nervous system also increases the strength of the contraction.

3. On the basis of structure

Tubular heart – e.g. insects like cockroach having 13 chambered heart

Pulsating vessels – annelids, holothurians, amphioxus

Chambered heart – hearts of vertebrates and mollusc

Ampullar accessory heart – branchial hearts of cephalopods like octopus, insects, heart bulbils of amphioxus, lymph hearts of frog.

HUMAN HEART

The human heart has a mass of between 250 and 350 grams and is about the size of a fist.

It is enclosed in a double-walled protective sac called the pericardium. The superficial part of this sac is called the fibrous pericardium. This sac protects the heart, anchors its surrounding structures, and prevents overfilling of the heart with blood.

The outer wall of the human heart is composed of three layers. The outer layer is called the epicardium, or visceral pericardium since it is also the inner wall of the pericardium. The middle layer is called the myocardium and is composed of muscle which contracts. The inner layer is called the endocardium and is in contact with the blood that the heart

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pumps. Also, it merges with the inner lining (endothelium) of blood vessels and covers heart valves.

Auricle is divided by an interatrial septum into right and left auricles. On this septum, a depression fossa ovalis is present which is remnant of embryonic foramen ovale, an aperture present between right and left auricles. Three large veins pour blood in the right auricle by separate pores. Eustachian valve is present at the opening of the post caval and protects the post caval. A coronary valve or the besian valve is present at the opening of coronary sinus. Two pulmonary veins bring oxygenated blood into left auricle. The opening of pulmonary vein is without any valve as its opening is oblique, which prevents back flow of blood. Ventricle is also divided by an interventricular septum.

Hence, the human heart has four chambers, two superior atria and two inferior ventricles. The atria are the receiving chambers and the ventricles are the discharging chambers.

The pathways of blood through the human heart are part of the pulmonary and systemic circuits. These pathways include the tricuspid valve, the mitral valve, the aortic valve, and the pulmonary valve. The mitral and tricuspid valves are classified as the atrioventricular (AV) valves. This is because they are found between the atria and ventricles. The aortic and pulmonary semi-lunar valves separate the left and right ventricle from the pulmonary artery and the aorta respectively. The inner surface of ventricle has number of irregular muscle ridges called trabeculae carnaeae or columnae carnaeae. Large protrusions called papillary muscles are also present. These are inserted at ventricular wall at one end and continued at the other by chordae tendinae which prevent the pushing of flaps into atrium during ventricular contraction. It is called moderator band which is a component of larger septomarginal trabecula.

The interatrioventricular septum separates the left atrium and ventricle from the right atrium and ventricle, dividing the heart into two functionally separate and anatomically

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distinct units.Left ventricle has thickest muscles as it pumps oxygenated blood to the whole body.

Before birth, the major portion of blood from the right side by-passes the pulmonary circulation(as no air in the lungs) through foramen ovale(in between right and left auricle) and ductus anteriosus(in between pulmonary and systemic aorta). At the time of the birth, with the start of breathing., these bypass cease to act.

Foramen ovale closes to become fossa ovalis and Ductus arteriosus closes to become ligamentum arteriosum.

FUNCTIONING OF HUMAN HEART

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Blood flows through the heart in one direction, from the atria to the ventricles, and out of the great arteries, or the aorta for example. Blood is prevented from flowing backwards by the tricuspid,bicuspid, aortic, and pulmonary valve.

The heart acts as a double pump. The function of the right side of the heart is to collect de-oxygenated blood, in the right atrium, from the body (via superior and inferior vena cavae) and pump it, via the right ventricle, into the lungs (pulmonary circulation) so that carbon dioxide can be dropped off and oxygen picked up (gas exchange). This happens through the passive process of diffusion.

The left side collects oxygenated blood from the lungs into the left atrium. From the left atrium the blood moves to the left ventricle which pumps it out to the body (via the aorta).

On both sides, the lower ventricles are thicker and stronger than the upper atria. The muscle wall surrounding the left ventricle is thicker than the wall surrounding the right ventricle due to the higher force needed to pump the blood through the systemic circulation.

Starting in the right atrium, the blood flows through the tricuspid valve to the right ventricle. Here, it is pumped out of the pulmonary semilunar valve and travels through the pulmonary artery to the lungs. From there, blood flows back through the pulmonary vein to the left atrium. It then travels through the mitral valve to the left ventricle, from where it is pumped through the aortic semilunar valve to the aorta and to the rest of the body. The (relatively) deoxygenated blood finally returns to the heart through the inferior vena cava and superior vena cava, and enters the right atrium where the process began.

CARDIAC CYCLE

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The cardiac cycle is the sequence of events that occurs when the hear beats. There are two phases of the cardiac cycle. In the diastole phase, the heart ventricles are relaxed and the heart fills with blood. In the systole phase, the ventricles contract and pump blood to the arteries. One cardiac cycle is completed when the heart fills with blood and the blood is pumped out of the heart. The events of the cardiac cycle described below trace the path of the blood as it enters the heart, is pumped to the lungs, travels back to the heart and is pumped out to the rest of the body. It is important to note that the events that occur in the first and second diastole phases actually happen at the same time. The same is also true for the events of the first and second systole phases.

Cardiac Cycle: 1st Diastole Phase

During the diastole phase, the atria and ventricles are relaxed and the atrioventricular valves are open. De-oxygenated blood from the superior and inferior vena cavae flows into the right atrium. The open atrioventricular valves allow blood to pass through to the ventricles. The SA node contracts triggering the atria to contract. The right atrium empties its contents into the right ventricle. The tricuspid valve prevents the blood from flowing back into the right atrium.

Cardiac Cycle: 1st Systole Phase

During the systole phase, the right ventricle receives impulses from the Purkinje fibers and contracts. The atrioventricular valves close and the semi lunar valves open. The de-oxygenated blood is pumped into the pulmonary artery. The pulmonary valve prevents the blood from flowing back into the right ventricle.

The pulmonary artery carries the blood to the lungs. There the blood picks up oxygen and is returned to the left atrium of the heart by the pulmonary veins.

Due to the closure of the A-V valves, a sound lubb is produced and is known as the first heart sound. Initially, when the ventricles contract, the pressure of blood within it is lower than that in the aorta and so the semi lunar valves don’t open. Therefore, the ventricles contract as a closed chamber. As the ventricular systole continues, the pressure of blood within the ventricle increases more than that of aorta as a result of which, the semi lunar valves open thus allowing blood to flow into the aorta and its main branches. The period between closure of A-V valves and opening of semi lunar valves is called isovolumetric systole/contraction.

Cardiac Cycle: 2nd Diastole Phase

In the next diastole period, the semi lunar valves close due to the fall of pressure of blood in the ventricles which is now less than that in the aorta, they close so as to prevent back ________________________________________________________________________________________________

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flow of blood from the aorta to the ventricles and the atrioventricular valves open. Blood from the pulmonary veins fills the left atrium. (Blood from the vena cava is also filling the right atrium.) The SA node contracts again triggering the atria to contract. The left atrium empties its contents into the left ventricle and the right atrium to the right ventricle. The mitral valve prevents the oxygenated blood from flowing back into the left atrium. At the end of the atrial systole, the atria get empty.

The closure of semi lunar valves at the beginning of ventricular diastole produces a sound dup and is known as the second heart sound. After the closure of the semilunar valves, the ventricles become closed chambers again.

The period between closure of semilunar valves and opening of A-V valves is called isovolumetric diastole/relaxation.

Cardiac Cycle: 2nd Systole Phase

During the following systole phase, the atrioventricular valves close and the semilunar valves open. The left ventricle receives impulses from the Purkinje fibers and contracts. Oxygenated blood is pumped into the aorta. The aortic valve prevents the oxygenated blood from flowing back into the left ventricle.

The aorta branches out to provide oxygenated blood to all parts of the body. The oxygen depleted blood is returned to the heart via the vena cavae.

The ventricular filling of blood can be divided into 3 phases:-

First Rapid Filling – With the beginning of ventricular diastole, intraventricular pressure declines and the AV valve open. Due to it, blood, already stored in atria, rushes into the ventricle rapidly. This also creates a sound – the 3rd heart sound.

Diastasis/Slow Filling – After the first rapid rushing of blood, blood keeps on entering the ventricles, though at a slow rate.

Second Rapid Filling – this occurs with the atrial systole which again cause rapid squeezing of blood into the ventricle. This creates the 4th heart sound.

HEART BEAT

The physiological properties of cardiac muscles

Responsivness (excitability) and rhythmicity Conductivity

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Contractility

Extensibility

Elasticity

It has longer refractory period, therefore, it never develops fatigue.

It doesn’t show summation or tetanus.

It obeys all or none principle (The all-or-none law is the principle that the strength by which a nerve or muscle fiber responds to a stimulus is not dependent on the strength of the stimulus. If the stimulus is any strength above threshold, the nerve or muscle fiber will give a complete response or otherwise no response at all.)

Origin and conduction of heart beat

The heart is formed of cardiac muscles which have the property of excitability and conductivity. So, when the cardiac muscles are stimulated by a specific stimulus, these got excited and initiate the waves of electric potential called cardiac impulses which are conducted along the special cardiac muscle fibers on the wall of the heart chambers.

Initiation of heartbeat is under three special bundles of cardiac muscles called nodal tissues:

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1. Sinu-auricular or sino-atrial node (S.A. node). It lies in the right wall of right auricle, below the opening of superior vena cava. It is also called right sided structure as it represents sinus venosus which has completely merged .into the wall of right atrium. It is also called pacemaker as it is first to originate the cardiac impulses and determines the rate of heart beat. So the atrial contraction precedes the ventricular contraction. It has the highest degree of autorhythmicity (70-80 times/ minute) but least conductivity. It maintains the basic rhythm of heart beat. These cardiac impulses are conducted along the tracts of special cardiac muscle fibers (called internal pathways) over both the auricles at the rate of 1 meter/second. These impulses reach the A.V. node about 0.03 second after their origin from S.A. node. These impulses cannot be passed to the wall of ventricles as the cardiac muscle fibers of auricles and ventricles are separated by a thin layer of fats, annular pad.

2. Atrio-ventricular node (A.V. node). It lies in the right atrium near the junction of interauricular and interventricular septum close to opening of coronary sinus. It is stimulated by the waves of contraction initiated by S.A. node. It generates the cardiac impulses, which are conducted to the muscles of the ventricles through bundle of His and Purkinje fibers at the rate of 1.5 to 4 meters/second.

3. Bundle of His. It is also called A.V. bundle. It arises from A.V. node, descends in the interventricular septum and divides into two branches which descend along two sides of interventricular septum and supply the wall of ventricle of their own side by a network of fine fibers called Purkinje fibers in the myocardium of the ventricles. These bring about synchronous contraction of the ventricles from the apex of heart which forces the blood into the pulmonary arch and aortic arch.

S.A. node, A.V. node, Bundle of His (A.V. bundle) and Purkinje fibers collectively form the conducting system of the heart and is responsible for autorhythmicity of heart. When S.A. node is damaged, then it is not able to generate the cardiac impulses, then the heart beat becomes irregular called arrhythmia. It is corrected by an artificial pacemaker. It is set in the chest of the patient, by surgical grafting, to pump the required amount of blood. It stimulates the heart electrically at regular intervals to beat at normal rate. So human heart is called myogenic or autorhythmic heart.

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Regulation of heart beat

Apart from the myogenic control exercised on the heart beat by the nodal tissues, the heart beat is also regulated by two controls so that the rate of heart beat can be adjusted according to the body needs e.g. it increases during exercise, fear, anger etc. while decreases during the rest.

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1. Nervous control. The rate of heart beat as well as the strength of the beat are under two cardiovascular centers of the autonomic nervous system, these centers are located in the upper part of the ventral wall of the medulla oblongata.

(a) Cardiac acceleratory center. It is associated with the sympathetic nerve fibers which, in turn, are associated with the S.A. node. Otto Loewi reported that these nerve fibers stimulate and increase the rate and depth of the contraction of S.A. node through a neurotransmitter chemical called adrenalin (epinephrine). It increases the rate of heart beat (about 200 to 250 times/minutes) as well as strength of heart beat (two-fold).

(b) Cardiac inhibitory center. It is associated with the vagal or parasympathetic nerve fibers which, in turn, are associated with the S.A. node. Otto Loewi reported that these nerve fibers inhibit and decrease the rate and depth of contraction of S.A. node through a neurotransmitter chemical called acetylcholine. It decreases the rate of heart beat (about 20 to 30 times/ minute) as well as strength of heart beat (by 20 to 30 per cent).

Cardiac acceleratory center dominates during exercise while cardiac inhibitory center dominates during the rest.

2. Hormonal control. It consists of two amine hormones–epinephrine (adrenalin) and norepinephrine (noradrenalin) which are secreted by adrenal medulla of adrenal gland. Both hormones accelerate the rate of heart beat but operate in different conditions. Epinephrine increases the heart beat during emergency conditions, while norepinephrine increases heart beat during normal conditions.

3. Other factors.

High levels of potassium and sodium ions decrease heart rate and strength of contraction

An excess of calcium ions increase heart rate.

Increased body temperature during fever increases heart rate

Strong emotions like fear, anger and anxiety increase heart rate, resulting in increased blood pressure.

Mental states such as depression and grief decrease heart rate.

The heart beat is somewhat faster in females.

The heart beat is fastest at birth, moderately fast in youth, average in adulthood and above average in old age.

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EFFECTS OF DRUGS ON THE HEART

Sometimes, medications may be needed to help prevent or control coronary heart disease (CHD) and so reduce the risk of a first or repeat heart attack. But, if medications are needed, lifestyle changes still must be undertaken.

If prescribed, take medications as directed by your health care provider.

Drugs used to treat CHD include:

Aspirin – Aspirin helps to lower the risk of a heart attack for those who have already had one. It also helps to keep arteries open in those who have had a previous heart bypass or other artery-opening procedure such as coronary angioplasty.

Because of its risks, aspirin is not approved by the Food and Drug Administration for preventing heart attacks in healthy individuals. It may be harmful for some persons, especially those with no risk of heart disease. Patients must be assessed carefully to make sure the benefits of taking aspirin outweigh the risks. Talk to your doctor about whether taking aspirin is right for you.

Digitalis – Acts directly on the heart muscles and peripheral circulation. The drug has been in use for long since it increases tonicity of heart muscles, contractility and irritability, thus making the heart contract faster and harder and is used when the heart's pumping function has been weakened.

ACE (angiotensin converting enzyme) inhibitor – stops the production of a chemical that makes blood vessels narrow and is used to help control high blood pressure and for damaged heart muscle. It may be prescribed after a heart attack to help the heart pump blood better. It is also used for persons with heart failure, a condition in which the heart is unable to pump enough blood to supply the body's needs.

Nitrates (including nitroglycerine) – relaxes blood vessels and stops chest pain

Calcium channel blocker – relaxes blood vessels and is used for high blood pressure and chest pain.

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Thrombolytic agents–also called "clot busting drugs," they are given during a heart attack to break up a blood clot in a coronary artery in order to restore blood flow.

Pilocarpine, Muscarine – when administered, cause slowing of the heart muscles or vagal terminations. The effect of these drugs can be removed by atropine.

Atropine causes acceleration of the heart beat.

Serotonin (5-hydroxytryptaine) influences the blood pressure.

HEART SOUNDS

The heart sounds are the noises generated by the beating heart and the resultant flow of blood through it. This is also called a heartbeat. In cardiac auscultation, an examiner uses a stethoscope to listen for these sounds, which provide important information about the condition of the heart.

In healthy adults, there are two normal heart sounds often described as a lubb and a dub (or dup), that occur in sequence with each heart beat. These are the first heart sound (S1) and second heart sound (S2), produced by the closing of the AV valves and semilunar valves respectively. In addition to these normal sounds, a variety of other sounds may be present including heart murmurs, adventitious sounds, and gallop rhythms S3 and S4.

PRIMARY HEART SOUNDS

Normal heart sounds are associated with heart valves closing, causing changes in blood flow.

S1

The first heart tone, or S1, forms the "lub" of "lub-dub" and is composed of components M1 and T1. Normally M1 precedes T1 slightly. It is caused by the sudden block of reverse blood flow due to closure of the atrioventricular valves, i.e. tricuspid and mitral (bicuspid), at the beginning of ventricular contraction, or systole. When the ventricles begin to contract, so do the papillary muscles in each ventricle. The papillary muscles are attached to the tricuspid and mitral valves via chordae tendineae, which bring the cusps or leaflets of the valve closed (chordae tendineae also prevent the valves from blowing into the atria as ventricular pressure rises due to contraction). The closing of the inlet

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valves prevents regurgitation of blood from the ventricles back into the atria. The S1 sound results from reverberation within the blood associated with the sudden block of flow reversal by the valves. If T1 occurs more than slightly after M1, then the patient likely has a dysfunction of conduction of the right side of the heart such as a Right bundle branch block.

S2

The second heart tone, or S2, forms the "dub" of "lub-dub" and is composed of components A2 and P2. Normally A2 precedes P2 especially during inspiration when a split of S2 can be heard. It is caused by the sudden block of reversing blood flow due to closure of the aortic valve and pulmonary valve at the end of ventricular systole, i.e. beginning of ventricular diastole. As the left ventricle empties, its pressure falls below the pressure in the aorta, aortic blood flow quickly reverses back toward the left ventricle, catching the aortic valve pocketlike cusps and is stopped by aortic (outlet) valve closure. Similarly, as the pressure in the right ventricle falls below the pressure in the pulmonary artery, the pulmonary (outlet) valve closes. The S2 sound results from reverberation within the blood associated with the sudden block of flow reversal.

MURMURS

Heart murmurs are produced as a result of turbulent flow of blood, turbulence sufficient to produce audible noise. They are usually heard as a whooshing sound. The term murmur only refers to a sound believed to originate within blood flow through or near the heart; rapid blood velocity is necessary to produce a murmur. Yet most heart problems do not produce any murmur and most valve problems also do not produce an audible murmur. Effects of inhalation/expiration

Inhalation pressure causes an increase in the venous blood return to the right side of the heart. Therefore, right-sided murmurs generally increase in intensity with inspiration. The increased volume of blood entering the right sided chambers of the heart restricts the amount of blood entering the left sided chambers of the heart. This causes left-sided murmurs to generally decrease in intensity during inspiration.

With expiration, the opposite haemodynamic changes occur. This means that left-sided murmurs generally increase in intensity with expiration. Having the patient lie supine and raising their legs up to a 45 degree angle facilitates an increase in venous return to the right side of the heart producing effects similar to inhalation-increased blood flow.

Other abnormal sounds

Clicks: With the advent of newer, non-invasive imaging techniques, the origin of other, so-called adventitial sounds or "clicks" has been appreciated. These are short, high-pitched sounds.

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Rubs: Patients with pericarditis, an inflammation of the sac surrounding the heart (pericardium), may have an audible pericardial friction rub. This is a characteristic scratching, creaking, high-pitched sound emanating from the rubbing of both layers of inflamed pericardium. It is the loudest in systole, but can often be heard at the beginning and at the end of diastole. It is very dependent on body position and breathing, and changes from hour to hour.

PULSE RATE

The blood is pumped from the ventricles of the heart to the aorta to be distributed to all the parts of the body. This happens during the ventricular systole and is repeated after 0.8 seconds. The blood from aorta then goes to other arteries of the body. This causes a rhythmic contraction in the aorta and its main arteries and is felt as regular jerks or pulse in them. It can be in the regions where arteries are present superficially like wrists, neck, temples, etc. the pulse rate is, therefore, same as that of heart beat rate.

BLOOD VESSELS AND COURSE OF CIRCULATION OF BLOOD

A blood vessel (artery or vein) is formed of three coats :

1. Tunica interna. It is innermost and is formed of two parts :

(a)  Endothelium. It is inner lining of flattened endothelial cells joined edge to edge. The endothelial cells are more elongated in the artery than in the vein.

(b) Elastic membrane. It is outer layer and is formed of yellow fibrous tissue. It is more developed in an artery.

2.  Tunica media. It is the middle coat formed of smooth circular muscle fibers and a network of elastic fibers. It is better developed in an artery. So artery is more elastic and more contractile.

3.  Tunica externa (Tunica adventitia). It is the outermost coat and is formed of collagen-rich connective tissue which blends with the general tissues of the body. The

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collagen fibers give strength to the blood vessels and prevent over-dilation of the blood vessels. It is less developed in an artery.

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Arteries

Arteries are blood vessels that carry blood away from the heart. This blood is normally oxygenated, exceptions made for the pulmonary and umbilical arteries.

The circulatory system is extremely important for sustaining life. Its proper functioning is responsible for the delivery of oxygen and nutrients to all cells, as well as the removal of carbon dioxide and waste products, maintenance of optimum pH, and the mobility of the elements, proteins and cells of the immune system. In developed countries, the two leading causes of death, myocardial infarction and stroke, each may directly result from an arterial system that has been slowly and progressively compromised by years of deterioration.

Types of arteries

Pulmonary arteries

The pulmonary arteries carry deoxygenated blood that has just returned from the body to the heart towards the lungs, where carbon dioxide is exchanged for oxygen.

Systemic arteries

Systemic arteries can be subdivided into two types - muscular and elastic - according to the relative compositions of elastic and muscle tissue in their tunica media as well as their size and the makeup of the internal and external elastic lamina. The larger arteries (>10mm diameter) are generally elastic and the smaller ones (0.1-10mm) tend to be muscular. Systemic arteries deliver blood to the arterioles, and then to the capillaries, where nutrients and gasses are exchanged.

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The Aorta

The aorta is the root systemic artery. It receives blood directly from the left ventricle of the heart via the aortic valve. As the aorta branches, and these arteries branch in turn, they become successively smaller in diameter, down to the arteriole. The arterioles supply capillaries which in turn empty into venules. The very first branches off of the aorta are the coronary arteries, which supply blood to the heart muscle itself. These are followed by the branches off the aortic arch, namely the brachiocephalic artery, the left common carotid and the left subclavian arteries.

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Arterioles

Arterioles, the smallest of the true arteries, help regulate blood pressure by the variable contraction of the smooth muscle of their walls, and deliver blood to the capillaries.

Arterioles have the greatest collective influence on both local blood flow and on overall blood pressure. They are the primary "adjustable nozzles" in the blood system, across which the greatest pressure drop occurs. The combination of heart output (cardiac output) and systemic vascular resistance, which refers to the collective resistance of all of the body's arterioles, are the principal determinants of arterial blood pressure at any given moment.

CAPILLARIES

The capillaries are where all of the important exchanges happen in the circulatory system. The capillaries are a single cell in diameter to aid fast and easy diffusion of gases, sugars and other nutrients to surrounding tissues.

Functions of capillaries

Capillaries have no smooth muscle surrounding them and have a diameter less than that of red blood cells; a red blood cell is typically 7 micrometers outside diameter, capillaries typically 5 micrometers inside diameter. The red blood cells must distort in order to pass through the capillaries. Only about 5-7% of the total blood volume is contained in the capillaries.

These small diameters of the capillaries provide a relatively large surface area for the exchange of gases and nutrients.

In the lungs, carbon dioxide is exchanged for oxygen In the tissues, oxygen and carbon dioxide and nutrients and wastes are exchanged In the kidneys, wastes are released to be eliminated from the body In the intestine, nutrients are picked up, and wastes released

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VENULES

A venule is a small blood vessel in the microcirculation that allows deoxygenated blood to return from the capillary beds to the larger blood vessels called veins. Venules range from 8 to 100μm in diameter and are formed when capillaries unite.

Venules are blood vessels that drain blood directly from the capillary beds. Many venules unite to form a vein.

Venule walls have three layers: An inner endothelium composed of squamous endothelial cells that act as a membrane, a middle layer of muscle and elastic tissue and an outer layer of fibrous connective tissue. The middle layer is poorly developed so that venules have thinner walls than arterioles. They are extremely porous so that fluid and blood cells can move easily from the bloodstream through their walls.

VEINS

In the circulatory system, veins are blood vessels that carry blood towards the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are the pulmonary and umbilical veins, both of which carry oxygenated blood to the heart. Veins differ from arteries in structure and function; for example, arteries are more muscular than veins, veins contain valves, and arteries carry blood away from the heart.

Veins serve to return blood from organs to the heart. Veins are also called "capacitance vessels" because most of the blood volume (60%) is contained within veins. In systemic circulation oxygenated blood is pumped by the left ventricle through the arteries to the muscles and organs of the body, where its nutrients and gases are exchanged at capillaries, the blood then enter veinules, then veins filled with cellular waste and carbon ________________________________________________________________________________________________

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dioxide. The de-oxygenated blood is taken by veins to the right atrium of the heart, which transfers the blood to the right ventricle, where it is then pumped through the pulmonary arteries to the lungs. In pulmonary circulation the pulmonary veins return oxygenated blood from the lungs to the left atrium, which empties into the left ventricle, completing the cycle of blood circulation.

Although most veins take blood back to the heart, there is an exception. Portal veins carry blood between capillary beds. For example, the hepatic portal vein takes blood from the capillary beds in the digestive tract and transports it to the capillary beds in the liver. The blood is then drained in the gastrointestinal tract and spleen, where it is taken up by the hepatic veins, and blood is taken back into the heart. Since this is an important function in mammals, damage to the hepatic portal vein can be dangerous. Blood clotting in the hepatic portal vein can cause portal hypertension, which results in a decrease of blood fluid to the liver.

CLASSIFICATION

Superficial veins

Superficial veins are those whose course is close to the surface of the body, and have no corresponding arteries.

Deep veins

Deep veins are deeper in the body and have corresponding arteries.

Pulmonary veins

The pulmonary veins are a set of veins that deliver oxygenated blood from the lungs to the heart.

Systemic veins

Systemic veins drain the tissues of the body and deliver deoxygenated blood to the heart.

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Vasa vasorum

The vasa vasorum (Latin, "vessels of the vessels") is a network of small blood vessels that supply large blood vessels.

The vasa vasorum are found in large arteries and veins such as the aorta and its branches. There are three different types of vasa vasorum:

vasa vasorum internae, that originate directly from the main lumen of the artery and then branch into the vessel wall.

vasa vasorum externae, that originate from branches of the main artery and then dive back into the vessel wall of the main artery.

venous vasa vasorae, that originate within the vessel wall of the artery but then drain into the main lumen or branches of concomitant vein.

COURSE OF BLOOD CIRCULATION

PULMONARY CIRCULATION

Pulmonary circulation is the portion of the cardiovascular system which carries oxygen-depleted blood away from the heart, to the lungs, and returns oxygenated blood back to the heart. The term is contrasted with systemic circulation. A separate system known as the bronchial circulation supplies blood to the tissue of the larger airways of the lung.

Pulmonary circulation is the movement of blood from the heart, to the lungs, and back to the heart again. De-oxygenated blood leaves the heart, goes to the lungs, and then re-enters the heart; oxygen poor blood leaves through the right ventricle through the pulmonary artery, the only artery in the body that carries oxygen-poor blood, to the capillaries where carbon dioxiode diffuses out of the blood cell into the alveoli, and oxygen diffuses out of the alveoli into the blood. Blood leaves the capillaries to the pulmonary vein, the only vein in the body that carries oxygen-rich blood in the body, to the heart, where it re-enters at the left ventricle.

SYSTEMIC CIRCULATION

Systemic circulation is the part of the cardiovascular system which carries oxygenated blood away from the heart to the body, and returns deoxygenated blood back to the heart. This physiologic theory of circulation was first described by William Harvey. Systemic circulation is when blood leaves the heart, goes to every cell in the body and then re-enters the heart, blood leaves through the left ventricle to the aorta the bodies largest artery, the aorta leads to smaller arteries, arteroiles, and finally capularies, waste and carbon dixiode diffuse out of the cell into the blood and oxygen in the blood diffueses out

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of the blood and into the cell, blood then moves to venious capularies, and then the superior vena cava, lower and then to the inferior vena cava, upper at the inferior vena cava the blood re-enters the heart at the right atrium.

PORTAL CIRCULATION

In the circulatory system of animals, a portal venous system occurs when a capillary bed drains into another capillary bed through veins, without first going through the heart. Both capillary beds and the blood vessels that connect them are considered part of the portal venous system.

They are relatively uncommon as the majority of capillary beds drain into veins which then drain into the heart, not into another capillary bed. Portal venous systems are considered venous because the blood vessels that join the two capillary beds are either veins or venules.

There are 3 types of venous portal systems:-

HEPATIC PORTAL SYSTEM

The portal venous system is responsible for directing blood from parts of the gastrointestinal tract to the liver. Substances absorbed in the small intestine travel first to

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the liver for processing before continuing to the heart. Not all of the gastrointestinal tract is part of this system. The system extends from about the lower portion of the esophagus to the upper part of the anal canal. It also includes venous drainage from the spleen and pancreas.

RENAL PORTAL SYSTEM

The renal portal system is a second route by which blood moves from the back half of the body through the kidneys before returning to the heart. This system is found in birds, amphibians, reptiles and fish.

HYPOPHYSIAL PORTAL SYSTEM

The hypophyseal portal system is the system of blood vessels that link the hypothalamus and the anterior pituitary in the brain.

It allows endocrine communication between the two structures. It is part of the hypothalamic-pituitary-adrenal axis. The anterior pituitary receives releasing and inhibitory hormones in the blood. Using these, the anterior pituitary is able to fulfill its function of regulating the other endocrine glands.

It is one of three portal systems of circulation in the human body; that is, it involves two capillary beds connected in series by venules. The others are the hepatic portal system and that in the kidneys.

CORONARY CIRCULATION

Coronary circulation is the circulation of blood in the blood vessels of the heart muscle (the myocardium). The vessels that deliver oxygen-rich blood to the myocardium are

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known as coronary arteries. The vessels that remove the deoxygenated blood from the heart muscle are known as cardiac veins.

The coronary arteries that run on the surface of the heart are called epicardial coronary arteries. These arteries, when healthy, are capable of autoregulation to maintain coronary blood flow at levels appropriate to the needs of the heart muscle. These relatively narrow vessels are commonly affected by atherosclerosis and can become blocked, causing angina or a heart attack. The coronary arteries that run deep within the myocardium are referred to as subendocardial.

The coronary arteries are classified as "end circulation", since they represent the only source of blood supply to the myocardium: there is very little redundant blood supply, which is why blockage of these vessels can be so critical.

Both of these arteries (left and right) originate from the beginning (root) of the aorta, immediately above the aortic valve.

During contraction of the ventricular myocardium (systole), the subendocardial coronary vessels (the vessels that enter the myocardium) are compressed due to the high intraventricular pressures. However, the epicardial coronary vessels (the vessels that run along the outer surface of the heart) remain patent. Because of this, blood flow in the subendocardium stops. As a result most myocardial perfusion occurs during heart relaxation (diastole) when the subendocardial coronary vessels are patent and under low pressure. This contributes to the filling difficulties of the coronary arteries. Compression remains the same.

ANASTOSOMES

When two arteries of the coronary circulation join, dual blood flow to a certain area of the myocardium occurs. These junctions are called anastomoses. If one coronary artery is obstructed by an atheroma, the second artery is still able to supply oxygenated blood to the myocardium. However this can only occur if the atheroma progresses slowly, giving the anastomoses a chance to proliferate. Under the most common configuration of coronary arteries, there exist two anastomoses on the posterior side of the heart. More superiorly, there is an anastomosis between the circumflex artery (a branch of the left coronary artery) and the right coronary artery. More inferiorly, there is an anastomosis between the anterior interventricular artery (a branch of the left coronary artery) and the posterior interventricular artery (a branch of the right coronary artery).

CORONARY VEINS

As blood passes through the coronary circulation, it delivers oxygen and nutrients and collects carbon dioxide and wastes. It then drains into large vascular sinus on the posterior surface of the heart, called the coronary sinus, which empties into the right atrium. A vascular sinus is a venous space with a thin wall that has no smooth muscle to alter its diameter. The principle tributaries carrying blood into the coronary sinus are the

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great cardiac vein, which drains the anterior aspect of the heart, and the middle cardiac vein, which drains the posterior aspect of the heart.

BLOOD PRESSURE

Blood pressure (BP) is the pressure exerted by circulating blood upon the walls of blood vessels, and is one of the principal vital signs. During each heartbeat, BP varies between a maximum (systolic) and a minimum (diastolic) pressure. The mean BP, due to pumping by the heart and resistance to flow in blood vessels, decreases as the circulating blood moves away from the heart through arteries. Blood pressure drops most rapidly along the small arteries and arterioles, and continues to decrease as the blood moves through the capillaries and back to the heart through veins. Gravity, valves in veins, and pumping from contraction of skeletal muscles, are some other influences on BP at various places in the body.

The term blood pressure usually refers to the pressure measured at a person's upper arm. It is measured on the inside of an elbow at the brachial artery, which is the upper arm's major blood vessel that carries blood away from the heart. A person's BP is usually expressed in terms of the systolic pressure over diastolic pressure (mmHg), for example 120/80.

In the UK, hypertension is considered when a patient's reading is above 140/90 mmHg.

In a study of 100 subjects with no known history of hypertension, an average blood pressure of 112/64 mmHg was found.

Various factors influence a person's average BP and variations. Factors such as age and gender influence average values. In children, the normal ranges are lower than for adults and depend on height. As adults age, systolic pressure tends to rise and diastolic tends to fall. In the elderly, BP tends to be above the normal adult range, largely because of reduced flexibility of the arteries. Also, an individual's BP varies with exercise, emotional reactions, sleep, digestion and time of day.

Differences between left and right arm BP measurements tend to be random and average to nearly zero if enough measurements are taken. However, in a small percentage of cases there is a consistently present difference greater than 10 mmHg which may need further investigation, e.g. for obstructive arterial disease.

The risk of cardiovascular disease increases progressively above 115/75 mmHg.

   1 year       6 - 9 years       adults   95/65 100/65 110/65 - 140/90

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LYMPHATIC SYSTEM

The lymphatic system can be broadly divided into the conducting system and the lymphoid tissue.

The conducting system carries the lymph and consists of tubular vessels that include the lymph capillaries, the lymph vessels, and the right and left thoracic ducts.

The lymphoid tissue is primarily involved in immune responses and consists of lymphocytes and other white blood cells enmeshed in connective tissue through which the lymph passes. Regions of the lymphoid tissue that are densely packed with lymphocytes are known as lymphoid follicles. Lymphoid tissue can either be structurally well organized as lymph nodes or may consist of loosely organized lymphoid follicles known as the mucosa-associated lymphoid tissue (MALT)

Lymphoid tissue

Lymphoid tissue associated with the lymphatic system is concerned with immune functions in defending the body against the infections and spread of tumors. It consists of connective tissue with various types of white blood cells enmeshed in it, most numerous being the lymphocytes.

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The lymphoid tissue may be primary, secondary, or tertiary depending upon the stage of lymphocyte development and maturation it is involved in. (The tertiary lymphoid tissue typically contains far fewer lymphocytes, and assumes an immune role only when challenged with antigens that result in inflammation. It achieves this by importing the lymphocytes from blood and lymph.

Primary lymphoid organs

The central or primary lymphoid organs generate lymphocytes from immature progenitor cells.

The thymus and the bone marrow constitute the primary lymphoid tissues involved in the production and early selection of lymphocytes.

Secondary lymphoid organs

Secondary or peripheral lymphoid organs maintain mature naive lymphocytes and initiate an adaptive immune response. The peripheral lymphoid organs are the sites of lymphocyte activation by antigen. Activation leads to clonal expansion and affinity maturation. Mature lymphocytes recirculate between the blood and the peripheral lymphoid organs until they encounter their specific antigen.

Secondary lymphoid tissue provides the environment for the foreign or altered native molecules (antigens) to interact with the lymphocytes. It is exemplified by the lymph nodes, and the lymphoid follicles in tonsils, Peyer's patches, spleen, adenoids, skin, etc. that are associated with the mucosa-associated lymphoid tissue (MALT).

Lymph nodes

A lymph node is an organized collection of lymphoid tissue, through which the lymph passes on its way to returning to the blood. Lymph nodes are located at intervals along the lymphatic system. Several afferent lymph vessels bring in lymph, which percolates through the substance of the lymph node, and is drained out by an efferent lymph vessel.

The substance of a lymph node consists of lymphoid follicles in the outer portion called the "cortex", which contains the lymphoid follicles, and an inner portion called "medulla", which is surrounded by the cortex on all sides except for a portion known as the "hilum". The hilum presents as a depression on the surface of the lymph node, which makes the otherwise spherical or ovoid lymph node bean-shaped. The efferent lymph vessel directly emerges from the lymph node here. The arteries and veins supplying the lymph node with blood enter and exit through the hilum.

Lymph follicles are a dense collection of lymphocytes, the number, size and configuration of which change in accordance with the functional state of the lymph node. For example, the follicles expand significantly upon encountering a foreign antigen. The selection of B cells occurs in the germinal center of the lymph nodes.

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Lymph nodes are particularly numerous in the mediastinum in the chest, neck, pelvis, axilla (armpit), inguinal (groin) region, and in association with the blood vessels of the intestines.

LymphaticsTubular vessels transport back lymph to the blood ultimately replacing the volume lost from the blood during the formation of the interstitial fluid. These channels are the lymphatic channels or simply called lymphatics.

ECG

The ECG works mostly by detecting and amplifying the tiny electrical changes on the skin that are caused when the heart muscle "depolarizes" during each heart beat. At rest, each heart muscle cell has a charge across its outer wall, or cell membrane. Reducing this charge towards zero is called de-polarization, which activates the mechanisms in the cell that cause it to contract. During each heartbeat a healthy heart will have an orderly progression of a wave of depolarisation that is triggered by the cells in the sinoatrial node, spreads out through the atrium, passes through "intrinsic conduction pathways" and then spreads all over the ventricles. This is detected as tiny rises and falls in the voltage between two electrodes placed either side of the heart which is displayed as a wavy line either on a screen or on paper. This display indicates the overall rhythm of the heart and weaknesses in different parts of the heart muscle.

A typical ECG tracing of the cardiac cycle (heartbeat) consists of a P wave, a QRS complex, a T wave, and a U wave which is normally visible in 50 to 75% of ECGs. The baseline voltage of the electrocardiogram is known as the isoelectric line. Typically the isoelectric line is measured as the portion of the tracing following the T wave and preceding the next P wave.

Feature Description Duration

RR interval

The interval between an R wave and the next R wave is the inverse of the heart rate. Normal resting heart rate is between 50 and 100 bpm

0.6 to 1.2s

P wave During normal atrial depolarization, the main electrical vector is directed from the SA node towards the AV node, and spreads from

80ms

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the right atrium to the left atrium. This turns into the P wave on the ECG.

PR interval

The PR interval is measured from the beginning of the P wave to the beginning of the QRS complex. The PR interval reflects the time the electrical impulse takes to travel from the sinus node through the AV node and entering the ventricles. The PR interval is therefore a good estimate of AV node function.

120 to 200ms

PR segment

The PR segment connects the P wave and the QRS complex. This coincides with the electrical conduction from the AV node to the bundle of His to the bundle branches and then to the Purkinje Fibers. This electrical activity does not produce a contraction directly and is merely traveling down towards the ventricles and this shows up flat on the ECG. The PR interval is more clinically relevant.

50 to 120ms

QRS complex

The QRS complex reflects the rapid depolarization of the right and left ventricles. They have a large muscle mass compared to the atria and so the QRS complex usually has a much larger amplitude than the P-wave.

80 to 120ms

ST segment

The ST segment connects the QRS complex and the T wave. The ST segment represents the period when the ventricles are depolarized. It is isoelectric.

80 to 120ms

T wave

The T wave represents the repolarization (or recovery) of the ventricles. The interval from the beginning of the QRS complex to the apex of the T wave is referred to as the absolute refractory period. The last half of the T wave is referred to as the relative refractory period (or vulnerable period).

160ms

ST interval

The ST interval is measured from the J point to the end of the T wave. 320ms

QT interval

The QT interval is measured from the beginning of the QRS complex to the end of the T wave. A prolonged QT interval is a risk factor for ventricular tachyarrhythmias and sudden death. It varies with heart rate and for clinical relevance requires a correction for this, giving the QTc.

300 to 430ms

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PACEMAKER

Natural pacemaker: The natural pacemaker of the heart is the sinus node, one of the major elements in the cardiac conduction system, the system that controls the heart rate. This stunningly designed system generates electrical impulses and conducts them throughout the muscle of the heart, stimulating the heart to contract and pump blood.

The sinus node consists of a cluster of cells that are situated in the upper part of the wall of the right atrium (the right upper chamber of the heart). The electrical impulses are generated there. The sinus node is also called the sinoatrial node or, for short, the SA node.

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The electrical signal generated by the sinus node moves from cell to cell down through the heart until it reaches the atrioventricular node (AV node), a cluster of cells situated in the center of the heart between the atria and ventricles. The AV node serves as a gate that slows the electrical current before the signal is permitted to pass down through to the ventricles. This delay ensures that the atria have a chance to fully contract before the ventricles are stimulated. After passing the AV node, the electrical current travels to the ventricles along special fibers embedded in the walls of the lower part of the heart.

An artificial pacemaker is a medical device which uses electrical impulses, delivered by electrodes contacting the heart muscles, to regulate the beating of the heart. The primary purpose of a pacemaker is to maintain an adequate heart rate, either because the heart's native pacemaker is not fast enough, or there is a block in the heart's electrical conduction system. Modern pacemakers are externally programmable and allow the cardiologist to select the optimum pacing modes for individual patients. Some combine a pacemaker and defibrillator in a single implantable device. Others have multiple electrodes stimulating differing positions within the heart to improve synchronisation of the lower chambers of the heart.

DISEASES OF HEART

Coronary heart disease

Coronary heart disease refers to the failure of the coronary circulation to supply adequate circulation to cardiac muscle and surrounding tissue. Coronary heart disease is most commonly equated with Coronary artery disease.

Coronary artery disease is a disease of the artery caused by the accumulation of atheromatous plaques within the walls of the arteries that supply the myocardium. Angina pectoris (chest pain) and myocardial infarction (heart attack) are symptoms of and conditions caused by coronary heart disease.

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Atherosclerosis

Is a condition in which an artery wall thickens as the result of a build-up of fatty materials such as cholesterol. It is a syndrome affecting arterial blood vessels, a chronic inflammatory response in the walls of arteries, in large part due to the accumulation of macrophage white blood cells and promoted by low-density lipoproteins (plasma proteins that carry cholesterol and triglycerides) without adequate removal of fats and cholesterol from the macrophages by functional high density lipoproteins. It is commonly referred to as a hardening or furring of the arteries. It is caused by the formation of multiple plaques within the arteries.

Ischaemic or ischemic heart disease

Is a disease characterized by ischaemia (reduced blood supply) to the heart muscle, usually due to coronary artery disease (atherosclerosis of the coronary arteries). Its risk increases with age, smoking, hypercholesterolaemia (high cholesterol levels), diabetes, and hypertension (high blood pressure), and is more common in men and those who have close relatives with ischaemic heart disease.

Symptoms of stable ischaemic heart disease include angina (characteristic chest pain on exertion) and decreased exercise tolerance.

Heart failure

Heart failure, also called congestive heart failure (or CHF), and congestive cardiac failure (CCF), is a condition that can result from any structural or functional cardiac disorder that impairs the ability of the heart to fill with or pump a sufficient amount of blood throughout the body. Therefore leading to the heart and body's failure.

Hypertensive heart disease

Hypertensive heart disease is heart disease caused by high blood pressure, especially localised high blood pressure. Conditions that can be caused by hypertensive heart disease include:

Left ventricular hypertrophy Coronary heart disease (Congestive) heart failure Hypertensive cardiomyopathy Cardiac arrhythmias

Inflammatory heart disease

Inflammatory heart disease involves inflammation of the heart muscle and/or the tissue surrounding it.

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Endocarditis – inflammation of the inner layer of the heart, the endocardium. The most common structures involved are the heart valves.

Inflammatory cardiomegaly Myocarditis – inflammation of the myocardium, the muscular part of the heart.

Valvular heart disease

Valvular heart disease is disease process that affects one or more valves of the heart. There are four major heart valve which may be affected by valvular heart disease, including the tricuspid and aortic valves in the right side of the heart, as well as the mitral and aortic valves in the left side of the heart.

Arteriosclerosis

It refers to a stiffening of arteries. Arteriosclerosis is a general term describing any hardening (and loss of elasticity) of medium or large arteries (from the Greek Arterio, meaning artery, and sclerosis, meaning hardening).

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