THE STRUCTURE

    Normally, when you look at a diagram of the human heart, you are looking at the heart dissected from its ventral surface. So the right side of the heart will be facing your left and vice versa.

    The whole heart is enveloped by a two-layered sac known as the pericardium. The pericardium is attached to the  breastbone, the diaphragm, and the membranes of the thorax, thus together with the arteries and veins attached to the heart, the pericardium help in holding the heart in a fixed position in the body. Between the two pericardial membranes is the pericardial fluid which reduce friction when the heart is beating. The pericardium also protects the heart muscle, otherwise known as myocardium.

    The right side of the heart is completely separated from the left side by means of a muscular wall — the median septum, which runs down the middle of the heart. The median septum is very important as it prevents the deoxygenated blood in the right side from mixing with the oxygenated blood in the left side.

    The heart is divided into four chambers. The two upper chambers are the atria (singular: atrium) and the two lower chambers are the ventricles. Great blood vessels main arteries and veins branches out from the heart, leading to and from all parts of the body.

    As you may have noticed, the wall of the left ventricle is thicker than the wall of the right ventricle. This is because the left ventricle exerts a greater pressure on the heart muscles than the right ventricle does.

    Valves in the heart are like doors that only open in one direction. They have important roles to play.

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©Copyright TQ Team 25896, 1999. The Circulatory System- Online Learning.