Chambers & Valves

Here we are looking at Learning Objective 5.

Recognise and describe the 4 chambers of the heart.

We are also looking at Learning objective 6.

Recognise and describe the 4 main valves of the heart and appreciate when, and by what means they open and close.

Chambers of the heart

The human heart has 2 upper and 2 lower chambers. The upper chambers receive blood and are the left and right atria. The lower chambers are responsible for pumping blood out of the heart to other parts of the body and are the left and right ventricles. The ventricles are more muscular than the atria.

The specific functions of each chamber are outlined below:

Left atrium: Receives oxygenated blood from the lungs through the pulmonary vein and pumps it into the left ventricle beneath it. The left atrium forms the base of the heart.
Left ventricle: Pumps oxygenated blood out of the heart to the rest of the body, through the aorta. It is the thickest chamber of the heart (3x thicker than the right ventricle) and its contractions create blood pressure. The left ventricle constitutes the apex of the heart.
Right atrium: Receives de-oxygenated blood from the body through the superior and inferior vena cava and pumps it into the right ventricle.
Right ventricle: Pumps deoxygenated blood through the pulmonary artery to the lungs where it is oxygenated then returned to the heart.

Figure showing the chambers of the heart

Valves of the heart

The heart valves consist of tissue-paper thin membranes which are attached to the heart wall called leaflets or cusps. The leaflets allow the movement of blood through the heart by opening and prevent the back-flow of blood by closing.

An interesting fact is that the heart valves withstand about 80 million beats per year and 5-6 billion beats in an average lifetime, highlighting the strength of these structures.

The heart has 4 valves namely; the bicuspid (mitral) valve, tricuspid valve, aortic valve and pulmonary valve.

The bicuspid valve has 2 leaflets while the tricuspid, pulmonary and aortic valves have 3 leaflets. The leaflets are supported by a fibrous tissue which also maintains the shape of the valve called the annulus.

Figure showing the valves of the heart

Bicuspid valve

The bicuspid valve is also known as the mitral valve and is located between the left atrium and ventricle.

Tricuspid valve

The tricuspid valve is located between the right atrium and ventricle.

Pneumonic

L-Left atrium

A-And Left ventricle

B- Bicuspid/Mitral valve

R-Right atrium

A-and Right ventricle

T-Tricuspid valve.

LABRAT!

Between the Left atrium And left ventricle is the Bicuspid valve (mitral valve) and between the Right atrium And Right ventricle is the Tricuspid valve. Easy peezy.

LABRAT

Pulmonary valve

The pulmonary valve is located between the right ventricle and pulmonary artery.

Aortic valve

The aortic valve is located between the left ventricle and the aorta.

Function of each valve in the heart through the cardiac cycle

1. Initially, the bicuspid and tricuspid valves are open and blood flows from the left atrium to the left ventricle and the right atrium to the right ventricle, respectively.

2. Overtime the ventricles become filled with blood, after this they contract to pump this blood to different parts of the body and lungs. The bicuspid and tricuspid valves close to prevent the back flow of blood into the left atrium and right atrium respectively during this contraction.

3. The contraction of the left ventricle forces the aortic valve open. Blood is then pumped out of the left ventricle into the aorta, then distributed around the body. Likewise, the contraction of the right ventricle forces the pulmonary valve open. Blood is pumped out of the right ventricle into the pulmonary artery then to the lungs.

4. After the contraction of both ventricles, they relax. This leads to the closing of the aortic and pulmonary valves, preventing the back-flow of blood from the aorta to the left ventricle and pulmonary artery to the right ventricle respectively. This cycle is repeated, providing a continuous supply of blood to the entire body.

Figure showing step 1 of the cardiac cycle

Figure showing step 3 of the cardiac cycle

Figure showing step 2 of the cardiac cycle

Figure showing step 4 of the cardiac cycle

Clinic corner

Heart valve diseases exist in 2 forms; regurgitation and stenosis.

Regurgitation refers to when a valve becomes incompetent and begins to allow the back-flow of blood. Stenosis refers to the narrowing of a valve which leads to the obstruction of blood flow between chambers of the heart.

Regurgitation negatively impacts the heart by making it work more than it should to pump the normal volume of blood. Stenosis makes the heart pump blood more forcefully to allow passage through the narrowing valve.

Both diseases could be congenital, caused by ageing, infection or damage to heart muscle from a previous heart attack.

Symptoms include;

Lethargy
Loss of breath
Oedema of the ankles and feet.

Diagnosis is usually by an echocardiogram.

Treatment is by administering medication such as

ACE inhibitors
Anticoagulants

Treatment can also be by surgery.

The video below shows the procedure of valve replacement surgery. Do watch to gain better understanding.

Figure comparing a normal pulmonary valve with one that has stenosis

Figure comparing a normal mitral valve with a regurgitating mitral valve

Image credits: National Institutes of Health (USA) 2017, Wikimedia 2010, Openstax College 2013, Jason Synder 2011, Cleveland Clinic 2018, Mariana Ruiz 2006, Bruce Blaus 2017 - All Image Usage Complies with CC BY-SA 3.0

Youtube video: British Heart Foundation 2014.

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