The heart
Has involuntary muscle, 4 chambers (right atria, left atria, right ventricle and left ventricle).
The ventricles
The ventricle pumps blood at high pressure out to the arteries (to the lungs or other parts of the body).
The pressure generated by the left ventricle is greater than that generated by the right ventricle as the systemic circuit is more extensive than the pulmonary circuit.
The atrium
The atrium receives blood at lower pressure from the veins (coming from the lungs or other parts of the body).
The pressure generated by the atria is lower than that generated by the ventricles since the distance from atria to ventricles is less than that from ventricles to circulatory system.
The valves
1) Ensure that the blood flows in the correct direction.
2) Very important; without them, the flow of blood would be chaotic.
3) Found in the heart and veins.
Tricuspid valve
- Separates the right atrium from the right ventricle.
- It opens to allow the de-oxygenated blood collected in the right atrium to flow into the right ventricle.
- It closes as the right ventricle contracts, preventing the blood from returning to the right atrium; thereby forcing it to exit through the pulmonary valve into the pulmonary artery.
Bicuspid valve / Mitral valve
- Separates the left atrium from the left ventricle.
- It opens to allow the oxygenated blood collected in the left atrium to flow into the left ventricle.
- It closes as the left ventricle contracts, thereby forcing it to exit through the aortic valve into the aorta.
- Separates the right ventricle from the pulmonary artery.
- As the ventricles contracts, it opens to allow the de-oxygenated blood collected in the right ventricle to flow into the lungs.
- It closes as the ventricles relax, preventing blood from returning to the heart.
- Separates the left ventricle from the aorta.
- As the ventricle contracts, it opens to allow the oxgenated blood collected in the left ventricle to flow throughout the body.
- It closes as the ventricles relax, preventing blood from returning to the heart.
Superior Vena Cava is one of the two main veins bringing de-oxygenated blood from the body to the heart. Veins from the head and upper body feed into the Superior Vena Cava, which empties into the righ atrium.
Inferior Vena Cava is the other main vein that brings de-oxygenated blood from the body to the heart. Veins from the legs and the lower torso feed into the Inferior Vena Cava, which empties into the right atrium.
Aorta
Carries oxygenated blood from the left ventricle to the systematic circulation. The aorta is an elastic artery and as such is quite distensible. When the left ventricle contracts to force into the aorta, the aorta expands. This stretching gives the potential energy that will help to maintain blood pressure during diastole, as during this time the aorta contracts passively.
Pulmonary Artery
The pulmonary arteries carry blood from the heart to the lungs. They are the only arteries other than the umbilical arteries in the fetus that carry de-oxygenated blood.
In the human heart, the pulmonary trunk (pulmonary artery or main pulmonary artery) begins at the base of the right ventricle. It is short and wide - about 5cm in length and 3cm in diameter. It then branches into 2 pulmonary arteries (left and right), which deliver de-oxygenated blood to the corresponding lung.
Pulmonary vein
The 4 pulmonary veins carry oxygenated blood from the lungs to the left atrium of the heart. They are the only veins in the post-fetal human body that carry oxygenated blood.
Chordae Tendineae
The chordae tendineae, or heart strings, are cord-like tendons that connect the papillary muscles to the tricuspid valve and bicuspid valve. When the right ventricle of the heart contracts, the blood pressure pushes the tricuspid valve which closes and prevents backflow of the blood into the right atrium. The chordae tendineae prevents the flaps from being averted into the right atrium. Similarly, these cord-like tendons hold in position other flaps like the bicuspid valve.
Papillary muscle
In anatomy, the papillary muscles of the heart serve to limit the movement of the mitral and tricuspid valves. These muscles contract to tighten the chodae tendineae, which in turn prevent inversion.
This occurs in respond to pressure gradients. Instead, they brace the valves against the high pressure, preventing regurgitation of ventricular blood back into the atrial cavities.
Coronary arteries
The heart is composed primarily of cardiac muscle that continuously contract and relaxes, it must have a constant supply of oxygen and nutrients.
The coronary arteries are a network of blood vessels that carry oxygen and nutrient rich blood to the cardiac muscle tissues. The larger vessels travel along the surface of the heart. The smaller branches, the cappilaries, penetrate the heart muscle. They are so small that the Red Blood Cells must travel in a single file.
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