The heart and circulation
Adrian Whyte and Joanna Johnson, Contributor

Always remember that the left side of the heart deals with oxygenated blood only!
And the right side of the heart deals with deoxygenated blood only!

FACTS ABOUT YOUR HEART

* Your heart is a muscular organ that functions to pump blood.

* Your heart pumps oxygen-poor blood to the lungs to become oxygen rich.

* Your heart pumps oxygen-rich blood to all parts of the body.

* Like most mammals, your heart has a left side and a right side.

* The left side is completely separated by a thick muscular wall called the septum.

* The heart is also separated into upper and lower chambers.

* The upper chambers are called atria.

* The lower chambers are called ventricles.

* Between the upper and lower chambers, there are one-way valves.

* These valves allow for blood to flow from upper chamber to lower chamber, and never the other way around.

* The valves that separate the atria from ventricles are called atria-ventricular valves.

* You can only find deoxygenated blood on the right side of the heart.

* You can only find oxygenated blood on the left side of the heart.

MISCONCEPTION ALERT!

When you look at a diagram of the heart, remember that the right side of the heart appears on the left and the left side of the heart appears towards the right! So don't be confused!

FUNCTION OF THE PARTS OF THE HEART

SUPERIOR VENA CAVA AND INFERIOR VENA CAVA

The superior vena cava and inferior vena cava are the main veins bringing de-oxygenated blood from the body to the heart. They empty into the right atrium of the heart.

RIGHT ATRIUM

The right atrium receives deoxygenated blood from the body through the superior vena cava (head and upper body) and inferior vena cava (legs and lower torso).

The sinoatrial node sends an impulse that causes the cardiac muscle tissue of the atrium to contract in a coordinated, wave-like manner.

The tricuspid valve, which separates the right atrium from the right ventricle, opens to allow the de-oxygenated blood collected in the right atrium to flow into the right ventricle.

TRICUSPID VALVE

The tricuspid valve separates the right atrium from the right ventricle.

It opens to allow the deoxygenated blood collected in the right atrium to flow into the right ventricle.

It closes as the right ventricle contracts, preventing blood from returning to the right atrium, thereby, forcing it to exit through the pulmonary valve into the pulmonary artery.

RIGHT VENTRICLE

The right ventricle receives de-oxygenated blood as the right atrium contracts. The pulmonary valve leading into the pulmonary artery is closed, allowing the ventricle to fill with blood.

Once the ventricles are full, they contract. As the right ventricle contracts, the tricuspid valve closes and the semi lunar (pulmonary) valve opens. The closure of the tricuspid valve

SEMI LUNAR/PULMONARY VALVE

The pulmonary valve separates the right ventricle from the pulmonary artery. As the ventricles contract, it opens to allow the de-oxygenated blood collected in the right ventricle to flow to the lungs. It closes as the ventricles relax, preventing blood from returning to the heart.

PULMONARY ARTERY

The pulmonary artery is the vessel transporting deoxygenated blood from the right ventricle to the lungs. This happens so that the blood can become oxygen rich.

A common misconception is that all arteries carry oxygen-rich blood. It is more appropriate to classify arteries as vessels carrying blood away from the heart.

PULMONARY VEIN

The pulmonary vein is the vessel transporting oxygen-rich blood from the lungs to the left atrium. A common misconception is that all veins carry deoxygenated blood. It is more appropriate to classify veins as vessels carrying blood to the heart.

LEFT ATRIUM

The left atrium receives oxygenated blood from the lungs through the pulmonary vein. As the contraction triggered by the sinoatrial node progresses through the atria, the blood passes through the mitral valve into the left ventricle

MITRAL VALUE

The 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, preventing blood from returning to the left atrium; thereby, forcing it to exit through the aortic valve into the aorta.

LEFT VENTRICLE

The left ventricle receives oxygenated blood as the left atrium contracts. The blood passes through the mitral valve into the right ventricle. The aortic valve leading into the aorta is closed, allowing the ventricle to fill with blood.

Once the ventricles are full, they contract. As the left ventricle contracts, the mitral valve closes and the aortic valve opens. The closure of the mitral valve prevents blood from backing into the left atrium and the opening of the aortic valve allows the blood to flow into the aorta and flow throughout the body. Please note that the left ventricle is the most muscular part of the heart. Can you guess why?

AORTIC VALVE

The aortic valve separates the left ventricle from the aorta. As the ventricles contract, it opens to allow the oxygenated blood collected in the left ventricle to flow throughout the body. It closes as the ventricles relax, preventing blood from returning to the heart.

AORTA

The aorta is the largest single blood vessel in the body. It is approximately the diameter of your thumb. This vessel carries oxygen-rich blood from the left ventricle to the various parts of the body.

ROUTE OF BLOOD VESSEL

Finally, the route of blood through the heart is:

vena cava > right atrium > tricuspid>> right ventricle > semi-lunar valve > pulmonary artery > lungs > pulmonary vein > left atrium > bicuspid valve > left ventricle > semi-lunar valve > aorta > body, then return to the heart via the vena cava.

NOTE: Always remember that the left side of the heart deals with oxygenated blood only! And the right side of the heart deals with deoxygenated blood only!

* Adrian Whyte and Joanna Johnson teach Biology at Ardenne High School
masterbio@gmail.com.