Explain the structures of the key tissues and components of the heart and relate this to their functions.

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The key tissue in the heart is cardiac muscle tissue, which is unique to the heart and contracts and relaxes involuntarily. Some examples of other components of the heart include the septum, whose location between the left and right sides of the heart allows it to keep oxygenated and deoxygenated blood separate, and heart valves, which prevent blood from flowing backward. 

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The heart is a complex organ made up of several layers of tissue and other key components that are vital to its operation. First, the heart wall is comprised of three layers of tissue, each with a unique function:

- Epicardium: fibrous tissue making up the outermost section of the heart and serving as a layer of protection.

- Myocardium: middle layer comprising the majority of the heart, made up of interlacing bundles of tissue that facilitate the heart's contraction.

- Endocardium: thin innermost layer of tissue made up of smooth muscle and small blood vessels creating the surface of the heart's valves.

This is all encased inside a pericardium, a fluid-filled, fibroserous sac with an inner and outer layer that holds a lubricating fluid between them. This fluid serves to reduce the friction caused by the heart as it beats.

To keep the myocardium working properly, a continued supply of nutrients and oxygen must be carried through a complex network of blood vessels called coronary arteries and waste supplies must be removed.

Inside the heart is an internal cavity made up of four chambers, each with its own unique purpose: the right and left atria and the right and left ventricles.

The two atria receive the deoxygenated blood—the right from systemic veins and the left from pulmonary veins—while the ventricles pump oxygenated blood out from the heart.

The left ventricle is the thicker of the two and pumps oxygenated blood to all tissues throughout the body, while the right pumps blood to the lungs only.

There are also four valves in the heart that facilitate the movement of blood between the chambers of the heart. The tricuspid valve connects the right atrium and right ventricle, while the mitral valve connects the left atrium and left ventricle.

The pulmonary valve connects the right ventricle and the pulmonary artery, which carries the blood to the lungs. And the aortic valve connects the left ventricle to the aorta, which carries blood to all other parts of the body.

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Explain the structures of the key tissues and components of the heart and relate this to their functions.  

The key heart tissue is cardiac muscle tissue. Cardiac muscle tissue is a specialized type of muscle that only forms in the heart. It is muscle tissue that contracts and relaxes involuntarily. The tissue itself is composed of cells called myoctyes. The contraction of the heart is controlled by two pacemakers called the sinoatrial node and the atrioventricular node. The first node is located above the right atrium of the heart, and the second pacemaker node is located between the right atrium and right ventricle. Each node will generate an electrical impulse that causes the heart chambers to contract and move the blood through.

The blood moves from the right atrium to the right ventricle, and that ventricle sends the blood to the lungs to swap out carbon dioxide for oxygen. This is called pulmonary circulation. The newly oxygenated blood will return to the left atrium and is then pumped into the left ventricle. That ventricle sends blood out to the rest of the body to deliver the oxygen to individual cells for cellular respiration. The left and right side of the heart is divided by a wall called the septum. The septum is crucial to the efficiency of the human heart because it prevents oxygenated blood from mixing with deoxygenated blood. Another key component of the heart is the presence of heart valves that make sure blood cannot flow backward when the individual chambers contract.

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