Left Heart.

As mentioned in chambers of heart, the heart is made up of

• four chambers (two upper and two lower),
• four valves,
• attached veins which carry blood to the heart and
• arteries which carry blood from the heart.

Left Side of Heart.

The left side of the heart or the left heart consists of:

• The upper chamber called the left atrium,
• The lower chamber called the left ventricle,
• The mitral valve has two cusps and is therefore also called the bicuspid valve. It is situated between the left atrium and the left ventricle.
• The aorta which originates from the left ventricle and is the main artery of the circulatory system and is responsible for supplying oxygenated blood to the various parts of the body.

The left atrium and left ventricle collectively form the left heart but occasionally this term is used to include the aorta also.

Picture of left and right heart.

Blood Flow through Left Heart.

• The left atrium receives oxygenated blood from the lungs which is brought by the pulmonary veins (usually four, two from each lung). The left atrium receives this blood by relaxation of its muscles and dilatation.
• Once full, the left atrium contracts and pushes the oxygenated blood into the left ventricle through the bicuspid valve which is situated between the left atrium and the left ventricle. The left ventricle receives this blood by relaxation and once full, it contracts and pushes this blood into the aorta for supply to all parts of the body.
• The mitral valve or the bicuspid valve is a non return valve which opens when the left atrium contracts to enable the blood to flow into the left ventricle, but closes when the left ventricle is full and about to contract in order to prevent back flow of blood back into the left atrium. It has two leaflets or cusps and hence the name – bicuspid.
• The aortic valve, which is situated at the junction of the left ventricle and the aorta opens when the left ventricle contracts to facilitate the blood to be pumped into the aorta and closes when the left ventricle has pumped out the blood.

The left side of the heart, especially the left ventricle is thicker than the right because it has to pump blood with a great force that can deliver blood to all parts of the body while the right ventricle has to pump blood only to the lungs. It also has pump against greater pressure, because diastolic pressure in the aorta is 80 mm of Hg while in the pulmonary artery (which is on the right side of the heart)  it is only 10 mm of Hg.

It is necessary to know that the contraction and relaxation of the left and right atria take place at the same time. Similarly the left and right ventricles relax (diastole) and contract at the same time (systole).

Also read Right Heart.

Related posts:

1. Left Ventricle of the Heart.
2. Left Atrium.
3. Right Ventricle of the Heart.
4. What Does Heart Do|Function of Heart.
5. Right Heart.
6. Heart Chambers.
7. Blood Flow in the Heart.
8. Parts of the Heart.