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HLTAP301A Consists of heart and blood vessels The heart is the pump that pushes blood through the blood vessels ◦ Blood vessels are the “pipes” of our plumbing system Transport system for the supply of O2 to cells of the body and removal of waste to excretory organs Every cell in body is in contact with a blood vessel Cells rely on O2 and nutrients to function, grow and reproduce This is the delivery and waste removal system of the body Cardiovascular system Cone shaped muscular organ Approximately the size of a closed fist Located in thoracic cavity between lungs and sternum Two thirds located to left of mid-line, one third to right Position of heart in body Centre of cardiovascular system Four chambered muscular pump Pumps oxygenated blood to all body cells Pumps deoxygenated blood to lungs to dispose of CO2 and pick up more O2 Per day, the heart ◦ Beats approx 100,000 times ◦ Pumps 8,000 litres of blood The heart has three layers 1. The pericardium Outer serous layer Surrounds and protects the heart Has two layers Visceral and parietal Contains serous fluid that prevents friction The heart has three layers 2. The myocardium Middle muscle layer Provides pumping action of the heart 3. The endocardium Inner epithelium layer Thin and smooth to allow blood easily through heart Forms valves and is continuous with lining of blood vessels Four chambered muscular pump Divided into right and left by strong muscular wall called septum ◦ Right side contains blood low in O2 ◦ Left side contains blood high in O2 Heart further divided transversely by valves Upper chambers are atria (one is called atrium) ◦ Thin walled ◦ Receives blood Lower chambers are ventricles ◦ Delivery chambers Right atrium ◦ Receives de-oxygenated blood via superior vena cava and inferior vena cava Right ventricle ◦ Receives blood from RA and pumps to lungs via pulmonary artery Left atrium ◦ Receives oxygenated blood from lungs via four pulmonary veins Left ventricle ◦ Receives blood from LA and pumps to aorta Heart chambers Largest artery in the body Carries oxygenated blood to all parts of body except lungs Separate atria and ventricles Atrioventricular valves (AV) ◦ Right AV valve called tricuspid valve ◦ Left AV valve called bicuspid or mitral valve ◦ Both AV valves attached to walls of ventricles by thin threads of tissue called chordae tendinae (heart strings) ◦ Heart strings keep valves from flipping back into atria Valves that exit ventricles are called semi-lunar valves Heart valves Heart has its own blood supply Supply is from right and left coronary artery that branch off aorta Partial blockage of any of these arteries causes insufficient blood supply to heart = myocardial ischaemia Complete obstruction = myocardial infarction Coronary arteries One complete contraction and relaxation of heart Contracting phase called systole Relaxing phase called diastole Fluid that transports O2 and nutrients to all cells of the body and returns CO2 and waste Is a type of connective tissue as nearly half is made up of cells that move freely in the plasma Three to five times more viscous than H2O Colour varies from bright orange to dark red depending on amount of O2 carried Amount of circulating blood depends on size of person Average adult has approx 5 litres 8% of body weight Transportation ◦ O2 from lungs to all body cells ◦ CO2 from cells to lungs ◦ Nutrients and electrolytes, salts and vitamins from digestive system or body stores ◦ Waste from cells to where they were released Liver Lungs ◦ Hormones from sites of origin to organs they affect Regulation ◦ Buffers in blood keep pH at about 7.4 ◦ Regulates amount of fluid to tissues ◦ Transports heat generated by muscles to other parts of body maintaining body temperature Protection ◦ Defence against disease ◦ Carries cells and anti-bodies of immune system ◦ Contains factors that protect against blood loss from site of injury Plasma ◦ Liquid portion ◦ Over half total blood volume ◦ 90% H2O ◦ 10% dissolved or suspended substances Protein essential for growth and rebuilding of body tissues ◦ Contains nutrients Glucose Lipids Vitamins Drugs Hormones Formed elements ◦ Erythrocytes (RBC) Mature cell does not contain nucleus Carry O2 bound to RBC by haemoglobin HB gives blood red colour Most numerous of blood cells Life span 120 days Formed elements ◦ Leucocytes (WBC) Contain nucleus Out numbered by RBC 700:1 Colourless Life span 6 – 8 hours Types Neutrophils Esinophils Basophils Lymphocytes Monocytes Formed elements ◦ Platelets (thrombocytes) Smallest elements Fragments of cells Essential to blood clotting Life span 10 days Origin of formed elements ◦ Produced in bone marrow ◦ Called stem cells Bodies natural ability to control unexpected blood loss Contraction of smooth muscle in blood vessel causing vasoconstriction Platelet plug forms by platelets becoming sticky Blood clot is formed Arteries ◦ Carry blood away from heart ◦ Thick walls – blood under pressure ◦ Pressure creates pulse ◦ Bright cherry red in colour ◦ Smallest branches called arterioles ◦ Largest artery – aorta Veins ◦ Return blood to heart ◦ Carry blood low in O2 ◦ Exception – pulmonary vein ◦ Darker, more bluish red in colour ◦ Walls thinner due to less pressure ◦ Flow as a result of skeletal muscle movement ◦ Have valves to prevent back flow of blood ◦ Smallest veins called venules ◦ Largest vein in body – great saphenous (in leg) Capillaries ◦ Microscopic one cell thick ◦ Connect arteriole and venules ◦ Contain mixture of venous and arterial blood ◦ Thin walls allow exchange of O2 and CO2 and also nutrients and waste Structure ◦ Composed of three layers ◦ Thickness depends on size and type of blood vessels ◦ First layer is tunica adventitia Outer layer Connective tissue Thicker in artery than veins Structure ◦ Second layer tunica media Middle layer Smooth muscle Thicker in artery than veins ◦ Third layer tunica intima Inner layer Single layer of endothelial cells Blood vessel layers Structure ◦ Lumen Internal space through which blood flows ◦ Valves Major structural difference between veins and arteries Venous blood flows against gravity Valves prevent back flow Heart rate is the number of heart beats per minute Normal adult heart rate is around 72 BPM Volume of blood pumped in one minute = cardiac output (average 5 litres per minute) Irregularity = arrhythmia Slow rate = bradycardia Fast rate = tachycardia Rapid uncoordinated contractions = fibrillations Caused by a wave of increased pressure as blood is forced out of the heart Pulse rate = heart rate Can be felt as artery passes over bone Measure of pressure exerted by blood on walls of blood vessels Measured in large artery by a sphygmomanometer Results are expressed in millimetres of mercury Systolic = pressure during contraction of ventricles Diastolic = pressure during relaxation of ventricles Blood pressure
