The heart

The heart

The heart is a muscular organ that pumps blood to all parts of the body. It is about the size of a clenched fist and lies between the two lungs, just behind the sternum (Barclay, 1). All parts of the body require oxygen for proper functioning. This oxygen moves to the various parts of the body via the blood. Deoxygenated blood travels through veins to the heart, which then pumps it to the lungs for oxygenation. From the lungs, oxygenated blood moves back to the heart, which pumps the blood to the various body parts through the arteries. The heart, together with the blood vessels, makes up the cardiovascular, which is responsible for supplying the body with oxygen and other nutrients as required.

Order of Blood Flow

Deoxygenated blood returns to the heart from various parts of the body through veins. The veins join one of two major veins: the superior vena cava and the inferior vena cava. The superior vena cava receives blood from the head, neck, and arms. The inferior vena cava receives blood from the rest of the body, also called the lower part of the body. Both veins open into the right atrium, where they deposit the deoxygenated blood. Once the right atrium becomes full of blood, its muscles contract, forcing the tricuspid valve open. The tricuspid valve resides between the right atrium and the right ventricle. Blood passes through the tricuspid valve and enters the right ventricle. After blood fills the right ventricle, its walls start to contract, resulting in pressure build-up. The pressure forces the three leaflets of the tricuspid valve to touch each other, effectively shutting the opening. This process prevents blood from going back into the right atrium as the right ventricle contracts. The contraction forces blood out of the right ventricle through the pulmonary artery. This motion precedes the closing of the pulmonary valves that prevent the back-flow of blood into the right ventricle. The pulmonary valve consists of three flexible cup-like structures capable of holding blood (“How the Heart Works”). Low-pressure levels in the right ventricle may cause blood to move backward from the lungs through the pulmonary artery. When this happens, the blood fills the cusps of the pulmonary valve, making their sides come into contact. Consequently, the pulmonary valve shuts, preventing blood from flowing back into the right ventricle.

The deoxygenated blood flows through the two branches of the pulmonary artery to the right and left lungs. In the lungs, the red blood cells collect oxygen by binding it to hemoglobin. At the same time, carbon (IV) oxide is released. The oxygenated blood leaves the lungs via four pulmonary veins, each emptying a different segment of the lungs. The veins open into the left atrium, which is the chamber that receives the oxygenated blood. When full, the left atrium contracts forcing the opening of the mitral valve. This opening allows blood to move into the left ventricle. The mitral valve, also known as the bicuspid valve, has only two leaflets. The left ventricle is the most muscular of the compartments because it pumps blood for the longest distance, to all parts of the body. When the left ventricle contracts after filling with blood, the pressure build-up results in the closing of the mitral valve when its two cusps come together to prevent blood from returning to the left atrium. Also, the aortic valve opens to allow blood into the aorta. The aortic valve also has three cusps, just like the pulmonary valve. The cusps fill with blood when blood flows backward in the aorta, and the valve shuts, preventing the blood from getting back to the left atrium. The aorta is the main artery in the body as it supplies blood to all parts. Branches of the aorta supply this blood to the various body organs and limbs. As the blood moves through different body parts, the body cells collect oxygen and other nutrients. As oxygen leaves the blood, it is replaced by carbon IV oxide from various tissues. The blood, now devoid of oxygen, flows back to the heart through the superior vena cava and inferior vena cava, and the cycle continues.

As ventricles are filling with blood, the mitral and tricuspid valves while the aortic and pulmonary valves shut. The reverse is true during ventricular contractions. This series of events ensures that the ventricles are entirely full before they begin pumping the blood out. Also, it ensures that blood flows only in one direction. The edges of the tricuspid and mitral valves have thin thread-like attachments called chordae tendineae that connect them to papillary muscles. These muscles allow limited opening and shutting the valves in a given direction, thus preventing the leaflets from flopping back into the atria.

Conclusion

Blood circulation is a continuous process facilitated by the heart throughout the lifetime of an individual. It is vital as it avails nutrients and oxygen to different body organs. Failure in the operation of this system results in death due to insufficient oxygen and nutrient supply to body organs.

 

 

Works Cited

Barclay, Tim, Phd. “Heart.” InnerBody.com, 1999-2019, www.innerbody.com/image/card01.html

“How the Heart Works.” CardioSmart: American College of Cardiology, 11 March 2008, www.cardiosmart.org/Heart-Basics/How-the-Heart-Works

“How the Normal Heart Works.” Children’s Hospital of Philadelphia, 2019, www.chop.edu/pages/how-normal-heart-works