A+P - cardiovascular system.

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  The cardiovascular system is sometimes referred to as the circulatory system and consists of:​

  • Heart​
  • Blood vessels​
  • Blood​

  The cardiovascular system is the major transport system in your body, carrying food, oxygen and all other essential products to cells, and taking away waste products of respiration and other cellular processes, such as carbon dioxide ​
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  Oxygen is transported from the lungs to the body’s tissues, while carbon dioxide is carried from the body’s tissues to the lungs for excretion
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  Heart.

  • The heart is a unique hollow muscle and is the pump of the cardiovascular system​.
  • It is located under the sternum (which provides protection) and is about the size of a closed fist​.
  • The function of the heart is to drive blood into and through the arteries in order to deliver it to the tissues and working muscles.
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  Heart.

  • The heart is surrounded by a twin- layered sac known as the pericardium​.
  • The cavity between the layers is filled with pericardial fluid, whose purpose is to prevent friction as the heart beats​.
  • The heart wall itself is made up of three layers; the epicardium (the outer layer), the myocardium (the strong middle layer that forms most of the heart wall) and the endocardium (the inner layer)​.
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  Heart.

  • The right side of the heart is separated from the left by a solid wall known as the septum​.
  • This prevents the blood on the right side coming into contact with the blood on the left side​.
  • The heart can be thought of as two pumps; the two chambers on the right and the two chambers on the left​.
  • The top chambers are called atrium and the bottom chambers are called ventricles​.
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  Heart.

  • The chambers on the right side of the heart supply blood at a low pressure to the lungs via the pulmonary arteries, arterioles and capillaries, where gaseous exchange takes place​.
  • The blood is then returned to the left side of the heart via capillaries, venules and pulmonary veins​.
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  Heart.

  • When the chambers of the left side of the heart are full, it contracts simultaneously with the right side, acting as a high pressure pump​.
  • Its supplies oxygenated blood via the arteries, arterioles and capillaries to the tissues of the body such as the muscle cells​.
  • Oxygen passes from the blood to the cells and carbon dioxide is taken on board​.
  • The blood then returns to the heart, into the right atrium, via the capillaries, venuoles and pulmonary veins​.
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  Heart.

  • Circuit 1- Heart to the lungs and back to the heart= pulmonary circulation​.
  • Circuit 2- Heart to the rest of the body and back to the heart= systemic circulation​.
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  The Main Parts of the Heart.

  • Coronary Arteries​.
  • Atria​.
  • Ventricles​.
  • Bicuspid Valve​.
  • Tricuspid Valve​.
  • Semi-Lunar Valves (Aortic and Pulmonary Valve).
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  Coronary Arteries.

  • These are the blood vessels that supply oxygenated blood to the heart muscle.​
  • There are two coronary arteries; one on the left and one on the right​.
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  Atria.

  • These are the upper chambers of the heart​.
  • They receive blood returning to your heart from either the body or the lungs​.
  • The right atrium receives deoxygenated blood from the body via the superior and inferior vena cava​.
  • The left atrium receives oxygenated blood from the lungs via the left and right pulmonary veins​.
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  Ventricles.

  • The pumping chambers of the heart​.
  • They have thicker walls than the atria​.
  • The right ventricle pumps blood to the pulmonary circulation to the lungs and the left ventricle pumps blood to the systemic circulation to the rest of the body​.
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  Bicuspid (Mitral) Valve​.

  • One of the four valves in the heart, situated between the left atrium and the left ventricle​.
  • It allows blood to flow in one direction only, from the left atrium to the left ventricle​.
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  Tricuspid Valve.

  • Situated between the right atrium and the right ventricle, it allows blood to flow through to the ventricle and prevents it from flowing back out of the heart .
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  Semi-Lunar valves (Aortic/Pulmonary Valve)​.

  • The aortic valve is situated between the left ventricle and the aorta and prevents the flow from the aorta back into the left ventricle.
  • The pulmonary valve is situated between the right ventricle and the pulmonary artery​.
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  The Major Blood Vessels of the Heart.

  • Aorta​
  • Superior Vena Cava​
  • Inferior Vena Cava​
  • Pulmonary Vein​
  • Pulmonary Artery​
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  Valve. Blood. From. To.

  Aorta. Oxygenated. Left ventricle. Body.

  Superior vena cava. Deoxygenated. Upper body. Right atrium.

  Inferior vena cava. Deoxygenated. Lower body. Right atrium.

  Pulmonary vein. Oxygenated. Lungs. Left atrium.

  Pulmonary artery. Deoxygenated. Right ventricle. Lungs.
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  Structure of Blood Vessels.

  • As the heart contracts, blood flows around the body in a complex network of vessels​.
  • 96000km of blood vessels​.
  • Two and a half times around the world.
  • In our body we have arteries, arterioles, capillaries, venules and veins​.
  • The structure of these is determined by their different functions and the pressure of the blood within them​.
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  Structure of Blood Vessels.

  • Blood flowing through the arteries appears bright red due to its oxygenation​.
  • As it moves through the arterioles and capillaries it drops off oxygen and picks up carbon dioxide​.
  • By the time it reaches the veins it is darker shade of red than oxygenated blood​.
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  Arteries.

  • Arteries carry blood away from the heart, and with the exception of the pulmonary artery they carry oxygenated blood​.
  • They have thick muscular walls that carry blood at high speeds under high pressure​.
  • When the heart ejects blood into the large arteries, the arteries expand to accommodate the blood​.
  • Arteries do not contain valves as the pressure within them remains high at all times, except at the point where the pulmonary artery leaves the heart.
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  Arteries.

  • Arteries have two major properties; elasticity and contractibility.
  • The smooth muscle surrounding the arteries enables their diameter to be decreased and increased as required​.
  • This helps to maintain blood pressure​.
  • Arteries are located deep inside the body, except where you can feel your pulse​.
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  Arterioles.

  • These have thinner walls than arteries​.
  • They control blood distribution by changing their diameter​.
  • This mechanism adjusts blood flow to the capillaries in response to differing demands for oxygen​.
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  Arterioles.

  • During exercise, muscles require an increased blood flow in order to get extra oxygen to the working muscles- so the arterioles dilate, or get wider​.
  • To compensate for this increase in demand, other areas like the gut, have their blood flow temporarily reduced and the diameter of the arterioles here get smaller or constrict​.
  • Arterioles are responsible for the control of blood flow to the capillaries.
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  Capillaries.

  • Capillaries connect arteries and veins by uniting arterioles and venules​.
  • They are the smallest of the blood vessels and are narrow and thin​.
  • The number of capillaries in muscle may be increased through frequent and appropriate exercise.
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  Capillaries.

  • They form an essential part of the cardiovascular system as they allow the diffusion of oxygen and nutrients required by the body’s cells​.
  • Capillaries that surround muscles ensure they get the oxygen and nutrients they need to produce energy​.
  • The walls are only cell thick​.
  • The pressure of blood of capillaries is higher than that in veins but less than that found in arteries​.
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  Veins.

  • Veins facilitate venous return- the return of deoxygenated blood to the heart​.
  • They have thinner walls than arteries and a relatively large diameter​.
  • By the time the blood reaches the veins, it is flowing slowly and at low pressure​.
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  Veins.

  • Contracting muscles push the thin walls of the veins inwards to help squeeze the blood back towards the heart​.
  • As these muscle contractions are intermittent, there are a number of pocket valves in the veins that help to prevent the backflow of blood when the muscles relax​.
  • Veins are mainly close to the surface and can be seen under the skin​.
  • They branch into smaller vessels called venules which extend into the capillary network.
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  Venules.

  • Venules are small vessels that connect the capillaries to the veins​.
  • The venules will take the blood from the capillaries and transport this deoxygenated blood under low pressure to the veins which, in turn, will lead back to the heart.
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  Composition of Red Blood Cells.

  • Carry oxygen to all living cells. Haemoglobin combines with oxygen to form oxyhaemoglobin​.
  • Round, flattened discs with an indented shape, giving them a large surface area and allows them to flow easily in the plasma.
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  Composition of Plasma.

  • The straw coloured liquid in which all blood cells are suspended. 90% water and electrolytes such as sodium and potassium​.
  • The plasma also carries carbon dioxide, as dissolved carbonic acid​.
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  Composition of White Blood Cells.

  • Component of blood that protects the body from infections. They identify, destroy and remove pathogens, such as viruses.
  • White blood cells originate from the bone marrow and are stored in your blood​.
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  Composition of Platelets.

  • Disc shaped cell fragments produced in the bone marrow​.
  • The primary function of platelets is clotting to prevent blood loss​.
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  There are a number of important functions that the cardiovascular system plays during exercise and sports performance:​

  ​

  1. Delivering Oxygen and Nutrients​
  2. Removing Waste Products- carbon dioxide and lactate​
  3. Thermoregulation​
  4. Fighting infection​
  5. Blood clotting​
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  Delivering Oxygen and Nutrients.

  • During exercise your body will need more of these so the cardiovascular system responds to ensure there is a suitable supply to meet the increased demands​.
  • When the cardiovascular system can no longer meet these demands, fatigue will occur in the muscles and performance will deteriorate.
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  Removing Waste Products - CO2 and Lactate.

  • As well as providing oxygen and nutrients to all tissues in the body, the circulatory system carries waste products from the tissues to the kidneys and the liver, and returns carbon dioxide to the lungs​.
  • During exercise your muscles will produce more carbon dioxide and lactate and it is essential that these are removed to prevent fatigue​.
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  Thermoregulation.

  • The cardiovascular system is responsible for the distribution and redistribution of heat within your body to maintain thermal balance during exercise​.
  • This ensures you do not overheat during exercise​.
  • Your cardiovascular system uses either vasodilation or vasoconstriction​.
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  Thermoregulation.

  Vasodilation.

  • During exercise, vasodilation of blood vessels occurs in the parts of the active muscles where gaseous exchange takes place​.
  • Vasodilation is caused by the relaxation of the involuntary muscle fibres in the walls of the blood vessels and causes an increase in diameter of the blood vessels​.
  • This decreases resistance to the flow of the blood to the area supplied by the vessels​.
  • This will result in a decrease in body temperature as heat within the blood can be carried to the surface of the skin​.
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  Thermoregulation.

  Vasoconstriction.

  • Blood vessels can also temporarily shut down or limit blood flow to tissues​.
  • This causes a decrease in diameter of the blood vessels​.
  • This will result in an increase in body temperature, as heat loss is reduced as blood is moved away from the surface.
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  Fighting Infection.

  • Leucocytes (white blood cells) are constantly produced inside the bone marrow​.
  • They are stored in and transported around the body by the blood​.
  • They can consume and ingest pathogens (substances that cause illness) and destroy them, produce antibodies that will also destroy pathogens, and produce antitoxins which will neutralise the toxins that may be released by pathogens​.
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  Blood Clotting.

  • Clotting is a complex process during which platelets form solid clots​.
  • A damaged blood vessel wall is covered by a fibrin clot to help repair the damaged vessel​.
  • Platelets form a plug at the site of the damage ​.
  • Plasma components known as coagulation factors respond to form fibrin strands which strengthen the platelet plug​.
  • This is made possible by the constant supply of blood through the cardiovascular system​.