What Is The heart And It’s Functions

n this article, we explore the structure of the heart, how it pumps blood around the body, and the electrical system that controls it.
The human heart is an organ that pumps blood throughout the body via the circulatory system, supplying oxygen and nutrients to the tissues and removing carbon dioxide and other wastes.The human heart is a finely-tuned instrument that serves the whole body. It is a muscular organ around the size of a closed fist, and it sits in the chest, slightly to the left of center.
The heart beats around 100,000 times a day, pumping approximately 8 pints of blood throughout the body 24/7.

The heart consists of four chambers:
The atria: These are the two upper chambers, which receive blood.
The ventricles: These are the two lower chambers, which discharge blood.
A wall of tissue called the septum separates the left and right atria and the left and right ventricle. Valves separate the atria from the ventricles.
The heart’s walls consist of three layers of tissue:
Myocardium: This is the muscular tissue of the heart.
Endocardium: This tissue lines the inside of the heart and protects the valves and chambers.
A double-walled sac called the pericardium encases the heart, which serves to protect the heart and anchor it inside the chest. This is a thin protective coating that surrounds the other parts.Between the outer layer, the parietal pericardium, and the inner layer, the serous pericardium, runs pericardial fluid, which lubricates the heart during contractions and movements of the lungs and diaphragm.
Epicardium: This protective layer consists mostly of connective tissue and forms the innermost layer of the pericardium.
Valves
The heart has four valves to ensure that blood only flows in one direction:
Aortic valve: This is between the left ventricle and the aorta.
Mitral valve: This is between the left atrium and the left ventricle.
Pulmonary valve: This is between the right ventricle and the pulmonary artery.
Tricuspid valve: This is between the right atrium and right ventricle.
Most people are familiar with the sound of the heart. In fact, the heart makes many types of sound, and doctors can distinguish these to monitor the health of the heart.The tricuspid valve and the mitral valve make up the atrioventricular (AV) valves, which connect the atria and the ventricles.

The opening and closing of the valves are key contributors to the sound of the heartbeat. If there is leaking or a blockage of the heart valves, it can create sounds called “murmurs.”
The sinoatrial node produces the electrical pulses that drive heart contractions.The electrical signal begins at the sino-atrial node, sometimes called the sinus, or SA, node. This is the heart’s pacemaker, and it sits at the top of the right atrium. The signal causes the atria to contract, pushing blood down into the ventricles.
The electrical impulse then travels to an area of cells at the bottom of the right atrium, between the atria and ventricles, called the atrioventricular, or AV, node.

Human heart function.
The rate at which the heart contracts depends on many factors, such as:
activity and exercise
emotional factors
some medical conditions
a fever
some medications
dehydration.
The heart circulates blood through two pathways: the pulmonary circuit and the systemic circuit.

In the pulmonary circuit, deoxygenated blood leaves the right ventricle of the heart via the pulmonary artery and travels to the lungs, then returns as oxygenated blood to the left atrium of the heart via the pulmonary vein.

In the systemic circuit, oxygenated blood leaves the body via the left ventricle to the aorta, and from there enters the arteries and capillaries where it supplies the body’s tissues with oxygen. Deoxygenated blood returns via veins to the venae cavae, re-entering the heart’s right atrium.

Of course, the heart is also a muscle, so it needs a fresh supply of oxygen and nutrients, too, Phillips said.


The cardiovascular system circulates blood from the heart to the lungs and around the body via blood vessels. (Image credit: The BioDigital HumanTM developed by NYU School of Medicine and BioDigital Systems LLC)
“After the blood leaves the heart through the aortic valve, two sets of arteries bring oxygenated blood to feed the heart muscle,” he said. The left main coronary artery, on one side of the aorta, branches into the left anterior descending artery and the left circumflex artery. The right coronary artery branches out on the right side of the aorta.

Blockage of any of these arteries can cause a heart attack, or damage to the muscle of the heart, Phillips said. A heart attack is distinct from cardiac arrest, which is a sudden loss of heart function that usually occurs as a result of electrical disturbances of the heart rhythm. A heart attack can lead to cardiac arrest, but the latter can also be caused by other problems, he said.
Systolic pressure: This shows how much pressure the blood creates against the artery walls during systole.
Diastolic pressure: This shows how much pressure is in the arteries during diastole.
A person can feel their pulse at points where arteries pass close to the skin’s surface, such as on the wrist or neck. The pulse is the same as the heart rate. When you feel your pulse, you feel the rush of blood as the heart pumps it through the body.
The heart contains electrical “pacemaker” cells, which cause it to contract — producing a heartbeat.

“Each cell has the ability to be the ‘band leader’ and [to] have everyone follow,” Phillips said. In people with an irregular heartbeat, or atrial fibrillation, every cell tries to be the band leader, he said, which causes them to beat out of sync with one another.

A healthy heart contraction happens in five stages. In the first stage (early diastole), the heart is relaxed. Then the atrium contracts (atrial systole) to push blood into the ventricle. Next, the ventricles start contracting without changing volume. Then the ventricles continue contracting while empty. Finally, the ventricles stop contracting and relax. Then the cycle repeats.

Valves prevent backflow, keeping the blood flowing in one direction through the heart.




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