Discover how your heart works, one beat at a time.
Join us on a journey through the heart’s anatomy and function. From the chambers and valves to its electrical system, this clear and accessible guide will help you understand the incredible mechanics behind every heartbeat.
Empowering you with the knowledge to better understand your heart and take charge of your health.
In this section, we take a closer look at the structure and function of the heart — from the four chambers that keep blood moving, to the vessels that carry oxygen throughout the body. Learn how blood flows through the heart in a precise sequence, and how the pericardium helps protect and support each beat. We also explain what your heartbeat tells us, including the normal “lub-dub” sounds and what changes in rhythm or tone might reveal about heart valve function.
The heart muscle, or myocardium, is a specialised type of muscle that forms the walls of the heart. It contracts and relaxes with every heartbeat to pump blood throughout the body.
Unlike other muscles, the heart works continuously, even during rest. It has its own electrical system that sends signals to trigger each beat. These signals begin in the heart’s natural pacemaker, the sinoatrial node.
The muscle is made of cells called cardiomyocytes, connected by structures that allow electrical messages to pass quickly between them. This helps the heart beat in a smooth and coordinated way.
There are two key functions:
Systolic function: when the heart contracts and pushes blood out.
Diastolic function: when the heart relaxes and fills with blood.
Both are vital for healthy circulation. Conditions like high blood pressure or heart muscle damage can affect how the heart works. Doctors often measure these functions to help diagnose and manage heart conditions.
The heart has four valves that make sure blood flows in the right direction with every heartbeat.
Tricuspid valve: Sits between the right atrium and right ventricle. It opens to let blood flow into the right ventricle, then closes to stop it from flowing backward.
Pulmonary valve: Located between the right ventricle and the pulmonary artery. It opens when the right ventricle pumps blood to the lungs and closes to prevent blood from returning to the heart.
Mitral valve: Also called the bicuspid valve, it lies between the left atrium and left ventricle. It opens to let blood fill the left ventricle and closes when the ventricle contracts.
Aortic valve: Found between the left ventricle and the aorta, the main artery of the body. It opens to send blood out to the body and closes to stop it from flowing back into the heart.
Each valve plays a vital role in keeping blood moving in the right direction. If a valve becomes narrowed or leaky, it can affect how well the heart works and may need further assessment or treatment.
The coronary arteries are blood vessels that supply the heart with oxygen and nutrients. These arteries are essential for the proper functioning of the heart, and any blockages or damage can lead to serious health problems.
There are two main coronary arteries: the left coronary artery and the right coronary artery.
The left coronary artery branches into two smaller arteries — the left anterior descending artery and the circumflex artery. These supply blood to the left side of the heart, including the left ventricle, which is responsible for pumping oxygen-rich blood to the rest of the body.
The left anterior descending artery (LAD) is the larger of the two branches and plays a critical role in heart function. It supplies blood to the front and side of the heart, especially the left ventricle.
The right coronary artery supplies blood to the right side of the heart, including the right ventricle, which sends blood to the lungs to receive oxygen.
The coronary arteries lie on the surface of the heart and are surrounded by a layer of fat and connective tissue called the epicardium.
Blockages in these arteries can lead to coronary artery disease (CAD), a common cause of heart attacks. CAD develops when plaque builds up inside the artery walls, causing them to narrow and limiting blood flow to the heart.
The human heart is a remarkable organ that works continuously to pump blood around the body, delivering oxygen and nutrients to every cell. A key part of this process is the heart’s conduction system.
This system is a network of specialised cells that create and coordinate the electrical signals that control the heartbeat. These signals ensure the heart contracts in a regular and efficient rhythm.
The process begins in the sinoatrial (SA) node, located in the upper right chamber of the heart called the right atrium. Known as the heart’s natural pacemaker, the SA node generates the electrical impulses that start each heartbeat.
These impulses travel to the atrioventricular (AV) node, located near the centre of the heart. The AV node delays the signal slightly, giving the atria time to contract and empty blood into the ventricles before they contract.
From the AV node, the signal travels down the bundle of His, which splits into the right and left branches for each ventricle. These branches lead into the Purkinje fibres, which spread across the ventricular walls and trigger a strong, coordinated contraction of the heart muscle.
The conduction system keeps the heart beating in a steady and organised way, making sure blood is pumped efficiently to the lungs and the rest of the body.
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The heart is made up of four chambers that work together to circulate blood efficiently through the lungs and the rest of the body. These chambers are divided into two sides: right and left, each with an upper and lower chamber.
The upper chambers are the right atrium and left atrium. They receive blood returning to the heart. The lower chambers are the right ventricle and left ventricle, which pump blood out of the heart.
The right atrium collects oxygen-poor blood from the body and passes it to the right ventricle, which sends it to the lungs for oxygen. The left atrium receives oxygen-rich blood from the lungs and transfers it to the left ventricle, which pumps it through the aorta to supply the entire body.
Each chamber has a specific role in the cycle of blood flow, and their coordinated activity ensures that the heart functions smoothly and effectively.
>Blood flows through the heart in a precise sequence, allowing oxygen-poor blood to be sent to the lungs and oxygen-rich blood to be pumped to the rest of the body.
The process begins when oxygen-poor blood returns from the body and enters the right atrium. It then moves into the right ventricle, which pumps the blood through the pulmonary artery to the lungs. In the lungs, the blood picks up oxygen and releases carbon dioxide.
Oxygen-rich blood then returns to the heart via the pulmonary veins and enters the left atrium. From there, it flows into the left ventricle, which pumps it out through the aorta to supply the rest of the body with oxygen and nutrients.
This cycle of circulation repeats with every heartbeat, ensuring that every cell in the body receives what it needs to function properly. The coordination of valves, chambers, and muscle contraction is essential for maintaining efficient blood flow.
This cycle of circulation repeats with every heartbeat, ensuring that every cell in the body receives what it needs to function properly. The coordination of valves, chambers, and muscle contraction is essential for maintaining efficient blood flow.
The pericardium is a thin, double-layered sac that surrounds and protects the heart. While the heart muscle pumps continuously, the pericardium helps to anchor it in place and reduce friction during each beat.
It has two main layers:
Between these layers is pericardial fluid, which prevents friction as the heart moves. The pericardium also helps limit excessive movement, prevents overexpansion, and acts as a barrier against infection.
Sometimes, the pericardium can be affected by conditions such as:
Doctors may use tests like an echocardiogram, ECG, or chest scan to assess the pericardium and decide on treatment if needed.
When a healthcare professional listens to your heart with a stethoscope, they are assessing the sounds made by your heart valves as they open and close. These sounds can provide important clues about how well your heart is functioning.
A normal heartbeat produces two main sounds, often described as “lub-dub.”
These sounds help healthcare professionals evaluate whether the valves are working properly. A clear, regular “lub-dub” usually indicates healthy valve function. Extra sounds or unusual rhythms can suggest changes in how blood is flowing through the heart.
One common example is a heart murmur, which is an additional whooshing or swishing sound. Murmurs can be harmless or may point to issues like valve narrowing (stenosis) or leaking (regurgitation).
If abnormal sounds are heard, further testing such as an echocardiogram may be recommended to examine the structure and function of the heart in more detail.
When first-line therapies for angina, such as beta blockers, calcium channel blockers, and nitrates, prove inadequate or are not well-tolerated, second-line therapies may be considered.
Perhexiline is a unique medication that enhances the heart's ability to utilize fatty acids for energy, reducing its reliance on oxygen and lowering oxygen demand. This action helps improve blood flow and alleviates chest pain in some patients with refractory angina.
Nicorandil is another second-line option with a dual mechanism of action. It opens potassium channels in smooth muscle cells, causing vasodilation and enhancing coronary blood flow. Additionally, nicorandil also stimulates nitric oxide release, further dilating blood vessels and reducing heart workload.
Trimetazidine is an anti-ischemic agent that improves cardiac efficiency by enhancing glucose metabolism and shifting the heart's energy production to a more oxygen-efficient process. As second-line therapies, these medications offer alternative approaches for managing angina in individuals who do not respond adequately to first-line treatments or those experiencing side effects from other medications.
Lipid-lowering therapies are essential in managing coronary artery disease (CAD), a condition where the arteries supplying blood to the heart become narrowed. Among the most commonly prescribed treatments are statins, which reduce cholesterol production in the liver and significantly lower the risk of heart attacks and strokes.
Other medications may be used to target different aspects of lipid metabolism:
In recent years, a newer class of medications known as PCSK9 inhibitors—such as Repatha (evolocumab)—has become available. These drugs block a specific enzyme involved in cholesterol regulation and can dramatically lower LDL cholesterol, particularly in patients who do not achieve target levels with statins alone.
Together, these therapies provide a range of options to personalise treatment and improve cardiovascular outcomes.
Nitrates are widely used to treat angina and provide quick relief from chest pain. These medications are commonly available as sublingual sprays or tablets, skin patches, and long-acting tablets.
Nitrates work by dilating blood vessels, allowing for increased blood flow and reduced vascular resistance. This reduces the heart’s workload and lowers its oxygen demand, offering prompt relief from angina symptoms.
Sublingual nitrates act quickly and are typically used at the onset of angina symptoms, while patches and long-acting tablets are used for ongoing prevention.
Common side effects include headaches, dizziness, and flushing. These often improve with continued use but should be discussed with a healthcare provider if persistent or bothersome.
Calcium channel blockers, including amlodipine, felodipine, Cardizem (diltiazem), and verapamil, are commonly prescribed for the treatment of angina.
These medications work by inhibiting the influx of calcium into the muscle cells of the heart and blood vessels, causing them to relax. This relaxation leads to the widening of blood vessels, which improves blood flow and reduces blood pressure.
For individuals with angina, calcium channel blockers reduce the heart’s workload and oxygen demand, helping to relieve chest pain and prevent angina episodes.
While effective, they may cause side effects such as headaches, dizziness, facial flushing, and ankle swelling. These effects should be monitored and discussed with your healthcare provider if they persist.
Beta blockers, such as metoprolol, propranolol, atenolol, carvedilol, and bisoprolol, play a crucial role in managing angina.
These medications work by blocking specific receptors in the heart, which slows the heart rate and reduces the strength of each contraction. This results in a lower oxygen demand by the heart and helps relieve chest pain associated with angina.
Beta blockers are highly effective in both relieving symptoms and preventing angina episodes. However, they may cause side effects in some individuals, including tiredness, worsened asthma symptoms, more vivid dreams, and erectile dysfunction in some males.
It is important to consult your healthcare provider to determine whether beta blockers are a suitable option for your angina and overall heart health.
Anti-platelet medications play a crucial role in preventing blood clot formation and reducing the risk of serious cardiovascular events such as heart attacks and strokes. Commonly used agents include aspirin, clopidogrel, and ticagrelor.
Aspirin: This well-known medication inhibits platelet activation, reducing the likelihood that platelets will clump together and form clots. It is widely used for both primary and secondary prevention of heart attacks and strokes.
Clopidogrel: A potent anti-platelet agent, clopidogrel works by blocking specific receptors on platelets to prevent aggregation. It is commonly prescribed for patients with acute coronary syndrome, those undergoing stent placement, and some individuals with peripheral arterial disease.
Ticagrelor: Ticagrelor also inhibits platelet activation and is typically used in the treatment of acute coronary syndrome. It is often prescribed alongside aspirin to provide dual anti-platelet therapy and further reduce the risk of heart-related events.
