The Heart

The Heart Muscular pump, about the size of a clenched fist Approximately 12cm long 9cm wide 6cm thick Weighs approx 11 ounces The average adult heart beats – 72 times a minute; 100,000 times a day; 3,600,000 times a year; 2.5 billion times during a lifetime.

Because the heart has its own electrical impulse, it can continue to beat even when separated from the body, as long as it has an adequate supply of oxygen When the body is at rest, it takes only 6 seconds for the blood to go from the heart to the lungs and back, only 8 seconds for it to go the brain and back, and only 16 seconds for it to reach the toes and travel all the way back to the heart 5% of blood supplies the heart, 15-20% goes to the brain and central nervous system, and 22% goes to the kidneys.

The Heart continued Made up of a special muscle called Myocardium This can contract continuously without getting tired Main purpose is to drive blood through the arteries This delivers blood to the working muscles and other tissues. The heart is located in the chest cavity - posterior to the breastbone, between the lungs and superior to the diaphragm The Heart sits in a twin layered sac known as the Pericardium Filled with pericardial fluid Prevents friction as your heart beats.

The heart is split into 4 sections- Right & Left side – separated by the septum Upper & Lower chambers – the atria & ventricles

Atria Latin for “entrance hall,” The upper chambers of the heart They receive blood. Right Atrium – receives deoxygenated blood from the body (Via the Vena Cava) Left Atrium – receives oxygenated blood from the lungs (Via the pulmonary Vein)

Latin for “little belly.” Ventricles Latin for “little belly.” The lower chambers of the heart They have thicker walls and are stronger Job is to pump the blood Right Ventricle pumps blood to the lungs (pulmonary circulation) Left ventricle pumps blood to the body (systemic circulation)

Valves The “thump-thump” of a heartbeat is the sound made by the four valves of the heart closing All valves make sure that the blood flows in one direction, and there is no back flow Chordae Tendineae Cord like tendons that connect to the tricuspid and bicuspid valves Ensure the valves stay the right way round and keep the blood flowing in the same direction. Pulmonary Valve Aortic Valve Bicuspid Valve (mitral valve) Tricuspid Valve

Aorta and Vena Cava The largest Artery is the Aorta The largest vein is the Vena Cava Carries blood directly into the right atrium from the body - Superior vena cava brings blood from the upper body Inferior Vena Cava Brings blood from the lower body. The largest Artery is the Aorta Carries oxygenated blood directly out of the left ventricle to the body tissues

Pulmonary Circulation Pulmonary Vein Carries oxygenated blood from the lungs to the left atrium It is the only vein that carries oxygenated blood. Pulmonary Artery Carries deoxygenated blood from the right ventricle to the lungs. It is the only artery that carries deoxygenated blood

The Heart = Double pump To describe the flow of blood around the heart and the body, you will need to mention that the heart is made up of two pumps Pulmonary circulation Pumps blood to and from the lungs Systemic circulation Pumps blood around the body

The right side of the heart Blood enters the heart from the body via the vena cavae, It goes into the right atrium The right atrium contracts and the blood goes through the tricuspid valve and into the right ventricle The right ventricle contracts and the blood is pushed out of the heart through the semi lunar or pulmonary valve and into the pulmonary artery The pulmonary artery carries the blood to the lungs The heart relaxes and the valves close to stop back flow of the blood In the lungs, the blood becomes oxygenated, and begins it’s journey back to the heart through the pulmonary vein

The Left side of the heart The heart is relaxed, and this allows blood to enter the left atrium from the pulmonary vein The left atrium contracts and pushes blood through the bicuspid valve and into the left ventricle The left ventricle has a very strong muscular wall and contracts very strongly. This closes the bicuspid valve to prevent backflow, and pushes the blood through the aortic valve and into the aorta. This is the largest artery and splits taking the blood to different areas of the body The heart contracts and the aortic valve closes, preventing back flow of the blood.

Cardiac Conduction Cardiac conduction is the rate at which the heart conducts electrical impulses. Cardiac muscle cells contract spontaneously and are coordinated by the sinoatrial node (the pacemaker) located in the right atrium Other factors that influence heart rate include endocrine hormones, body temperature and exercise.

Cardiac Cycle The cardiac cycle is the sequence of events that occur when the heart beats. There are two phases of this cycle which are the diastole and systole phases. During the diastole phase, the atria and ventricles are relaxed and blood flows into the atria and ventricles. In the systole phase, the ventricles contract sending blood to the rest of the body.

Terminology Heart rate (H.R.) Stroke Volume (S.V.) Cardiac Output The amount of times the heart beats in a minute. Usually measured in beats per minute (b.p.m.) Stroke Volume (S.V.) The amount of blood leaving the left ventricle in one beat. Normally measure in mililitres Cardiac Output The amount of blood leaving the heart in one minute Normally measured in litres/minute Cardiac Output = Stroke Volume x Heart Rate

Aorta Superior Vena cava Pulmonary Artery Pulmonary Valve Pulmonary Vein Right Atrium Left Atrium Tricuspid Valve Left Ventricle Bicuspid Valve Right Ventricle Inferior Vena cava Septum