Your heart is roughly the size of a fist and sits in the middle of your chest, slightly to the left. It’s the muscle at the centre of your circulation system, pumping blood around your body as your heart beats. This blood sends oxygen and nutrients to all parts of your body, and carries away unwanted carbon dioxide and waste products. Show Structure of your heartYour heart is made up of three layers of tissue:
These layers are surrounded by the pericardium, a thin outer lining protecting your heart. There are four chambers that make up the heart – two on the left side and two on the right. The two small upper chambers are the atria. The two larger lower chambers are the ventricles. These left and right sides of the heart are separated by a wall of muscle called the septum. Circulatory systemYour heart pumps blood around the body all the time - about five litres (eight pints) of it - and this is called circulation. Your heart, blood and blood vessels together make up your cardiovascular system (or heart and circulatory system). The right side of the heart receives blood that is low in oxygen because most has been used up by the brain and body. It pumps this to your lungs, where it picks up a fresh supply of oxygen. The blood then returns to the left side of the heart, ready to be pumped back out to the brain and the rest of your body. Blood vesselsYour blood is pumped around your body through a network of blood vessels:
Blood vessels are able to widen or narrow depending on how much blood each part of your body requires. This action is partly controlled by hormones. ValvesYour heart has four valves. They act like gates, keeping the blood moving in the right direction:
For your heart to keep pumping regularly, it needs electrical signals which are sent to the heart muscle telling it when to contract and relax. The electrical signal starts in the right atrium where your heart’s natural pacemaker - the sino–atrial node - is situated. This signal crosses the atria, making them contract. Blood is pumped through the valves into the ventricles. Where the atria meet the ventricles, there is an area of special cells - called the atrio-ventricular node - which pass the electrical signals throughout your heart muscle by a system of electrical pathways, known as the conducting system. The muscles of the ventricles then contract, and blood is pumped through the pulmonary and aortic valves into the main arteries. The heart’s natural ‘pacemaker’ - the sino-atrial node - produces another electrical signal, and the cycle starts again. Blood pressureThis is the measurement of the pressure within the arteries. It plays a vital role in the way your heart delivers fresh blood to all your blood vessels. For blood to travel throughout your body quickly enough, it has to be under pressure. This is created by the relationship between three things:
One heartbeat is a single cycle in which your heart contracts and relaxes to pump blood. At rest, the normal heart beats approximately 60 to 100 times every minute, and it increases when you exercise. To ensure an adequate blood supply around your body, the four chambers of your heart have to pump regularly and in the right sequence. There are two phases to your heart’s pumping cycle:
Read more from Chest Heart & Stroke Scotland on how the heart works. What can go wrong?StructureSome people are born with a heart that has not developed properly in the womb before birth - this is called congenital heart disease. Sometimes you can inherit a heart condition from your family. Cardiovascular systemProblems with your heart and circulation system include:
Heart disease can happen when your coronary arteries become narrowed by a gradual build-up of fatty material - called atheroma. If your coronary arteries are narrowed or blocked, the blood supply to your heart will be impaired. This is the most common form of heart disease, known as coronary heart disease (sometimes called coronary artery disease or ischaemic heart disease). Eventually, your arteries may become so narrow they can’t deliver enough blood to your heart. This can cause angina - a pain or discomfort in your chest, arm, neck, stomach or jaw. If the fatty material breaks off or ruptures, a blood clot will form, which can cause heart attack (or stroke, if the artery affected is carrying blood to your brain). Electrical systemNormally your heart will beat between 60 to 100 times per minute. This regular rhythmic beating is dependent upon electrical signals being conducted throughout your heart. If the electrical signals within your heart are interrupted, your heart can beat too quickly (tachycardia), too slowly (bradycardia) and/or in an irregular way. This is called an arrhythmia - see Chest Heart & Stroke Scotland. Conditions affecting the pumping of your heart There are some conditions which can damage your heart muscle, making it weak and unable to pump as efficiently as before:
There are also conditions - like high blood pressure (hypertension) - which mean your heart has to work harder. When your heart muscle can’t meet your body’s demands for blood and oxygen, you can develop various symptoms, like breathlessness, extreme tiredness and ankle swelling. This is called heart failure because of the failure of your heart to pump blood around the body and work efficiently. ValvesYour heart can’t function normally if the heart valves aren't working properly, as it can affect the flow of blood through the heart. There are two main ways that the valves can be affected:
Further informationTry the British Heart Foundation's Know your heart, an interactive tool narrated and presented by Dr Hilary Jones.
The heart is a pump, usually beating about 60 to 100 times per minute. With each heartbeat, the heart sends blood throughout our bodies, carrying oxygen to every cell. After delivering the oxygen, the blood returns to the heart. The heart then sends the blood to the lungs to pick up more oxygen. This cycle repeats over and over again. What Does the Circulatory System Do?The circulatory system is made up of blood vessels that carry blood away from and towards the heart. Arteries carry blood away from the heart and veins carry blood back to the heart. The circulatory system carries oxygen, nutrients, and hormones to cells, and removes waste products, like carbon dioxide. These roadways travel in one direction only, to keep things going where they should.
The heart has four chambers — two on top and two on bottom:
The atria are separated from the ventricles by the atrioventricular valves:
Two valves also separate the ventricles from the large blood vessels that carry blood leaving the heart:
What Are the Parts of the Circulatory System?Two pathways come from the heart:
In pulmonary circulation:
In systemic circulation:
How Does the Heart Beat?The heart gets messages from the body that tell it when to pump more or less blood depending on a person's needs. For example, when we're sleeping, it pumps just enough to provide for the lower amounts of oxygen needed by our bodies at rest. But when we're exercising, the heart pumps faster so that our muscles get more oxygen and can work harder. How the heart beats is controlled by a system of electrical signals in the heart. The sinus (or sinoatrial) node is a small area of tissue in the wall of the right atrium. It sends out an electrical signal to start the contracting (pumping) of the heart muscle. This node is called the pacemaker of the heart because it sets the rate of the heartbeat and causes the rest of the heart to contract in its rhythm. These electrical impulses make the atria contract first. Then the impulses travel down to the atrioventricular (or AV) node, which acts as a kind of relay station. From here, the electrical signal travels through the right and left ventricles, making them contract. One complete heartbeat is made up of two phases:
How Can I Help Keep My Child's Heart Healthy?To help keep your child's heart healthy:
Let the doctor know if your child has any chest pain, trouble breathing, or dizzy or fainting spells; or if your child feels like the heart sometimes goes really fast or skips a beat. |