The Heart

The heart is a strong, powerful organ, consisting of cardiac muscle. The heart pumps continuously, without resting and without becoming fatigued. Its function is to pump blood to the lungs and around the body. The heart is one of the key organs in the Circulatory System.

Anatomy of the heart

The heart consists of four chambers and is divided into left and right by a wall of muscle called the septum. The right side of the heart consists of an atrium which recieves blood returning from the body, and the right ventricle, which then pumps blood out to the lungs, via the pulmonary artery.

The left side again contains an atrium and a ventricle. The left atrium recieves the oxygenated blood returning from the lungs and the ventricle then pumps this blood around the body.

Due to the distance which the blood being pumped from the left ventricle has to travel, a more forceful contraction is required. For this reason the muscular wall of the left side is thicker than that of the right side.

The atria and ventricles are separated by valves known as Atrioventricular, or AV valves. The purpose of these valves is to prevent blood from flowing in the wrong direction. Following the movement of blood from the atrium, into the ventricle, the AV valve snaps shut which causes the first heart sound of the heart beat (often described “lub dub”, with the closing of the AV valves being the “lub”)

The “dub” sound is caused by the closing of two other valves, known as the Semilunar or SL valves. These are located between each ventricle and the artery leaving the heart, and again prevent the blood flowing backwards.

The way in which the cardiac muscle contracts in order to force blood around the body is highly specialised and is described on the heart beat page.

Box diagram of the heart

A box diagram is a great way to learn and remember the passage of blood through the heart. The chambers are simplified into boxes with arrows indicating the passage of oxygenated and deoxygenated blood.

Facts about the human heart

Here are 7 fascinating facts about the Human Heart that everyone would like to know!

1. It takes 20 seconds for blood to circulate the entire body. Oxygenated blood leaves the aorta about about 1 mile an hour.

2. The power output of the heart ranges from 1-5 watts per minute. Which is the equivalent to the usage of a 60 watt bulb. It has been said that enough energy is produced a day to drive a truck 20 miles.

3. “Ventricle” means “little belly” in Latin where as “Atrium” is Latin for “entrance hall”.

4. Red blood cells live for upto 4 months and make approximately 250,000 round trips around the body before returning to the bone marrow, where they were born, to die. Between 2.5 and 3 million red blood cells (erythrocytes) are lost and replaced every second.

5. Human blood is colourless, it is the hemoglobin that makes it red.

6. Due to the heart having its own electrical impulse, it will continue to beat even when removed from the body as long as it has an adequate supply of oxygen.

7. On average, the human body has about 5 liters (almost 9 pints) of blood continually traveling through it by way of the circulatory system. A kitchen tap would need to be turned on all the way for at least 45 years to equal the amount of blood pumped by the heart in an average lifetime.

Resources

Related Articles

Capillaries

Capillaries are the smallest of all blood vessels and form the connection between veins and arteries. As arteries branch and divide into arterioles and continue to reduce in size as they reach the...

Blood Pressure

The rate and distribution of blood flow through the circulatory system is variable and related to several factors including physical activity, cardiac output (the amount of blood pumped out of the...

Arteries

Arteries are blood vessels which carry blood away from the heart. All of which, with the exception of the pulmonary artery, carry oxygenated blood. The most widely known artery within the human body is...