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S. MORRIS 2006 What is the circulatory system? Ø The circulatory system carries blood and dissolved substances to and from different places in the body. Ø The Heart has the job of pumping these things around the body. Ø The Heart pumps blood and substances around the body in tubes called blood vessels. Ø The Heart and blood vessels together make up the Circulatory System. The Heart • Very muscular, about the size of your fist • Major portion of the heart known as MYOCARDIUM and composed of cardiac muscle • A PERICARDIAL SAC covers the heart, made from epithelial and fibrous tissue, that contains lubricating liquid Our circulatory system is a double circulatory system. This means it has two parts parts. Lungs the right side of the left side of the system the system deals with deals with deoxygenated oxygenated blood. blood. Body cells The SEPTUM separates / divides the 2 sides How does this system work? pulmonary vein lungs pulmonary artery head & arms aorta main vein Right Left liver digestive system kidneys legs Circulatory System The Heart This is a vein. It brings These are arteries. blood from the body, They carry blood except the lungs. away from the heart. 2 atria Coronary arteries, the hearts own 2 ventricles blood supply The heart has four chambers now lets look inside the heart The Heart Artery to Lungs Artery to Head and Body Vein from Head and Body Vein from Lungs Right Atrium Left Atrium valve valve Right Ventricle Left Ventricle The Valves • There are 4 valves in the heart: – 2 Atrioventricular Valves (AV Valves) – 2 Semi-Lunar valves (SL Valves) AV Valves • Between the artia and ventricles • Control the flow of blood between the chambers, and prevent backflow – TRICUSPID VALVE: between the right atrium and right ventricle. It has 3 flaps. – BICUSPID VALVE: between the left atrium and left ventricle. It has 2 flaps. Chordae Tendinae • support the valves and prevent them from inverting. They are attached to muscles in the ventricular walls The SL Valves • Between the ventricles and the attached blood vessels • Blood flows through these valves as it leaves the heart • Pulmonary SL Valve: right side, right ventricle pumps blood to lungs through the pulmonary artery • Aortic SL Valve: left side, left ventricle pumps blood to body through the aorta IMPORTANT • Deoxygenated blood NEVER mixes with oxygenated blood. • Remember too that both atria contract at the same time (simultaneously), and the ventricles both contract at the same time (simultaneously). How does the Heart work? STEP ONE blood from the blood from body the lungs The heart beat begins when the heart muscles relax and blood flows into the atria. How does the Heart work? STEP TWO The atria then contract and the valves open to allow blood into the ventricles. How does the Heart work? STEP THREE The valves close to stop blood flowing backwards. The ventricles contract forcing the blood to leave the heart. At the same time, the atria are relaxing and once again filling with blood. The cycle then repeats itself. Heartbeat: the sound you hear • LUB – first heart sound – Occurs when the A-V valves close due to ventricle contraction and is known as Systole (pressure in ventricle is higher than pressure in the atrium) – Louder and longer than the second heart sound • DUB – Sharp and short sound – Occurs when the S-L valves snap shut – Known as Diastole (when the ventricles relax) NOTE • Systole: refers to CONTRACTION of the heart muscle • Diastole: refers to RELAXATION of the heart • Cardiac Cycle is another name for the heartbeat, it occurs on average 70 times per minute in an adult. What controls the heartbeat? • 2 ways: Intrinsic (without the brain telling it) and Extrinsic (brain involved) • Intrinsic: has special tissue called Nodal Tissue (has both nerve and muscle tissue) 1. SA (sinoatrial) Node: located in the upper back wall of the right atrium (also called the Pacemaker of the heart) • Initiates the heartbeat by sending a signal every 0.85 seconds to make the atria contract 2. AV (atrioventricular) Node: found at the base of the right atrium near the septum • When pulse from the SA node reaches the AV node, the AV node sends out a signal to special fibers called Purkinjie Fibers to message the ventricles to contract Text page 245 • Intrinsic controls the steady beating of your heart, Extrinsic factors can control how fast your heat beats • This involves Nervous Control, by a part of your brain called the Medulla Oblongata • This part of your brain can sped up or slow down your heart rate depending on stimuli it receives from the Autonomic Nervous System (ie. Stress, oxygen levels, blood pressure) Blood Pressure • Measured using a SPHYGMANOMETER • 2 numbers: – First number (bigger number ALWAYS) is the highest arterial pressure reached during ejection of blood from ventricles of the heart (SYSTOLIC) – Second number (lower number ALWAYS) is the lowest arterial pressure while the ventricles are relaxing (DIASTOLIC) • Blood pressure decreases with distance from the heart and as a result the velocity of blood also decreases gradually, which is very important because the slow movement going into capillaries allows for exchange of substances between blood in capillaries and surrounding tissues. blood from the heart gets around the body through blood vessels There are 3 types of blood vessels a. ARTERY b. VEIN c. CAPILLARY The ARTERY Arteries carry blood away from the heart. the elastic fibres allow the artery to stretch under pressure thick muscle and the thick muscle can elastic fibres contract to push the blood along. The VEIN Veins carry blood towards from the heart. veins have valves which act to stop the blood from going in the wrong direction. thin muscle and elastic fibres body muscles surround the veins so that when they contract to move the body, they also squeeze the veins and push the blood along the vessel. The CAPILLARY Capillaries link Arteries with Veins they exchange materials between the blood and other body cells. the wall of a capillary is only one cell thick The exchange of materials between the blood and the body can only occur through capillaries. The CAPILLARY A collection of capillaries is known as a capillary bed. bed artery vein capillaries body cell what’s in digested food red blood cells white blood cells oxygen waste (urea) carbon dioxide platelets plasma hormones The Blood red blood cell white blood cell platelets plasma Red Blood Cells contain haemoglobin, a a biconcave disc that is molecule specially designed round and flat without a to hold oxygen and carry it nucleus to cells that need it. can change shape to an amazing extent, without breaking, as it squeezes single file through the capillaries. White Blood Cells there are many different types and all contain a big nucleus. the two main ones are the lymphocytes and the macrophages. macrophages ‘eat’ and digest micro- organisms . some lymphocytes fight disease by making antibodies to destroy invaders by dissolving them. other lymphocytes make antitoxins to break down poisons. Platelets Platelets are bits of cell broken off larger cells. Platelets produce tiny fibrinogen fibres to form a net. This net traps other blood cells to form a blood clot. Plasma It also contains useful things like; • carbon dioxide A straw- • glucose coloured • amino acids liquid that carries the • proteins cells and the • minerals platelets which help • vitamins blood clot. • hormones • waste materials like urea. SUMMARY copy and complete the following; away Arteries take blood ______ from the heart. The walls of an artery muscular are made up of thick _________ walls and elastic fibres. Veins carry towards blood ________ the heart and also have valves. The _________ link capillaries arteries and veins, and have a one cell thick wall. Blood is made up of plasma four main things ______, the liquid part of the blood; Red Blood oxygen Cells to carry ______; White Blood cells to protect the body from platelets disease and _________ to help blood clot.
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