Circulatory Systems, Heart & Blood Vessels (PDF)

Unit 9 - Circulatory Systems, Heart & Blood Vessels 9.1 Circulatory System Circulatory system The circulatory system is an organ system, the role of which is to transport blood around the body Components of the circulatory system include: blood vessels a pump valves to ensure one-way...

Unit 9 - Circulatory Systems, Heart & Blood Vessels 9.1 Circulatory System Circulatory system The circulatory system is an organ system, the role of which is to transport blood around the body Components of the circulatory system include: blood vessels a pump valves to ensure one-way flow of blood Circulatory Systems of Fish & Mammals (Extended) Circulatory systems in Fish Fish have a two-chambered heart and a single circulation This means that for every one circuit of the body, the blood passes through the heart once Circulatory systems in Mammals Mammals have a four-chambered heart and a double circulation This means that for every one circuit of the body, the blood passes through the heart twice The right side of the heart receives deoxygenated blood from the body and pumps it to the lungs (the pulmonary circulation) The left side of the heart receives oxygenated blood from the lungs and pumps it to the body (the systemic circulation) Advantages of Double Circulation (Extended) Blood travelling through the small capillaries in the lungs loses a lot of pressure that was given to it by the pumping of the heart, meaning it cannot travel as fast By returning the blood to the heart after going through the lungs its pressure can be raised again before sending it to the body, meaning cells can be supplied with the oxygen and glucose they need for respiration faster and more frequently 9.2 The Mammalian Heart The Mammalian Heart The heart is labelled as if it was in the chest so what is your left on a diagram is actually the right hand side and vice versa The right side of the heart receives deoxygenated blood from the body and pumps it to the lungs The left side of the heart receives oxygenated blood from the lungs and pumps it to the body Blood is pumped towards the heart in veins and away from the heart in arteries The two sides of the heart are separated by a muscle wall called the septum The heart is made of muscle tissue which are supplied with blood by the coronary arteries Remember A-A: Arteries carry blood Away from the heart 9.3 Monitoring Activity of the Heart Monitoring Activity of the Heart Heart activity can be monitored by using an ECG, measuring pulse rate or listening to the sounds of valves closing using a stethoscope Heart rate (and pulse rate) is measured in beats per minute (bpm) To investigate the effects of exercise on heart rate, record the pulse rate at rest for a minute Immediately after they do some exercise, record the pulse rate every minute until it returns to the resting rate  This experiment will show that during exercise the heart rate increases and may take several minutes to return to normal 9.4 Investigating Effect of Physical Activity on Heart Rate Investigating Effect of Physical Activity on Heart Rate It is relatively simple to investigate the effects of exercise on the body in the classroom Breathing rate can be measured by counting the number of breaths per minute, while heart rate can be measured by taking a pulse Either can be measured before and after an activity is performed and the results plotted on a bar chart It is important that the time over which breathing rate and pulse rate are measured is consistent, and that individuals fully recover (rest) before starting a new activity Increased physical activity results in an increased heart rate and breathing rate Heart rate remains high for a period of time after physical has stopped, there is a gradual return to resting heart rate Explaining the Effect of Physical Activity on Heart Rate (Extended) So that sufficient blood is taken to the working muscles to provide them with enough nutrients and oxygen for increased respiration An increase in heart rate also allows for waste products to be removed at a faster rate Following exercise, the heart continues to beat faster for a while to ensure that all excess waste products are removed from muscle cells It is also likely that muscle cells have been respiring anaerobically during exercise and so have built up an oxygen debt This needs to be ‘repaid’ following exercise and so the heart continues to beat faster to ensure that extra oxygen is still being delivered to muscle cells The extra oxygen is used to break down the lactic acid that has been built up in cells as a result of anaerobic respiration 9.5 Coronary Heart Disease Coronary Heart Disease The heart is made of muscle cells that need their own supply of blood to deliver oxygen, glucose and other nutrients and remove carbon dioxide and other waste products The blood is supplied by the coronary arteries  If a coronary artery becomes partially or completely blocked by fatty deposits called ‘Plaques’ (mainly formed from cholesterol), the arteries are not as elastic as they should be and therefore cannot stretch to accommodate the blood which is being forced through them - leading to coronary heart disease Partial blockage of the coronary arteries creates a restricted blood flow to the cardiac muscle cells and results in severe chest pains called angina Complete blockage means cells in that area of the heart will not be able to respire and can no longer contract, leading to a heart attack Diet, Exercise & Coronary Heart Disease Reducing the risks of developing coronary heart disease Quit smoking Diet - reduce animal fats and eat more fruits and vegetables - this will reduce cholesterol levels in the blood and help with weight loss if overweight Exercise regularly - again, this will help with weight loss, decrease blood pressure and cholesterol levels and help reduce stress 9.6 Identifying Structures in the Heart Identifying Structures in the Heart (Extended) The ventricles have thicker muscle walls than the atria as they are pumping blood out of the heart and so need to generate a higher pressure  The left ventricle has a thicker muscle wall than the right ventricle as it has to pump blood at high pressure around the entire body, whereas the right ventricle is pumping blood at lower pressure to the lungs The septum separates the two sides of the heart and so prevents mixing of oxygenated and deoxygenated blood The function of valves The basic function of all valves is to prevent blood from flowing backwards There are two sets of valves in the heart: The atrioventricular valves separate the atria from the ventricles The valve on the right side of the heart is called the TRICUSPID and the valve on the left side is called the BICUSPID These valves are pushed open when the atria contract but when the ventricles contract they are pushed shut to prevent blood from flowing back into the atria The semilunar valves are found in the two blood arteries that come out of the top of the heart They are unusual in that they are the only two arteries in the body that contain valves These valves open when the ventricles contract so blood squeezes past them out of the heart, but then shut to avoid blood flowing back into the heart 9.7 Functioning of the Heart Functioning of the Heart (Extended) Deoxygenated blood coming from the body flows into the right atrium via the vena cava Once the right atrium has filled with blood the heart gives a little beat and the blood is pushed through the tricuspid (atrioventricular) valve into the right ventricle The walls of the ventricle contract and the blood is pushed into the pulmonary artery through the semilunar valve which prevents blood flowing backwards into the heart The blood travels to the lungs and moves through the capillaries past the alveoli where gas exchange takes place (this is why there has to be low pressure on this side of the heart – blood is going directly to capillaries which would burst under higher pressure) Oxygen-rich blood returns to the left atrium via the pulmonary vein It passes through the bicuspid (atrioventricular) valve into the left ventricle  The thicker muscle walls of the ventricle contract strongly to push the blood forcefully into the aorta and all the way around the body The semilunar valve in the aorta prevents the blood flowing back down into the heart 9.8 Blood Vessels Blood vessels The blood vessels are a system of closed tubes within which blood flows Different types of blood vessels transport blood in different directions, and to different parts of the body Arteries These blood vessels carry blood away from the heart at high pressure Arteries transport oxygenated The single exception to this is the pulmonary artery The walls of arteries are thick and muscular and contain elastic fibres Arteries have a narrow lumen Veins These blood vessels carry blood towards the heart at low pressure Veins transport deoxygenated blood away from the body The single exception to this is the pulmonary vein The walls of veins are thin in comparison to arteries Veins have a wide lumen Valves in veins prevent blood from flowing backwards Capillaries These blood vessels carry blood to the cells of the tissues Capillaries transport oxygenated blood from the arteries to the cells, and deoxygenated blood from the cells to the veins The walls of capillaries are one cell thick and contain gaps to allow fluid to leak out Capillaries have a very narrow lumen How Structure of Blood Vessels is Adapted to their Function (Extended) Arteries Have thick muscular walls containing elastic fibres to withstand the high pressure of blood and maintain the blood pressure as it recoils after the blood has passed through Have a narrow lumen to maintain high pressure Veins Have a large lumen as blood pressure is low Contain valves to prevent the backflow of blood as it is under low pressure Capillaries Have walls that are one cell thick so that substances can easily diffuse in and out of them Have ‘leaky’ walls so that blood plasma can leak out and form tissue fluid surrounding cells Arterioles and venules As arteries divide more as they get further away from the heart, they get narrower The narrow vessels that connect arteries to capillaries are called arterioles Veins also get narrower the further away they are from the heart The narrow vessels that connect capillaries to veins are called venules 9.9 Circulation Around the Body Main Blood Vessels in the Body Blood is carried away from the heart and towards organs in arteries These narrow to arterioles and then capillaries as they pass through the organ The capillaries widen to venules and finally veins as they move away from the organs Veins carry blood back toward the heart Blood Vessels & the Liver (Extended) You must be able to identify the main blood vessels to and from the liver The hepatic artery brings oxygenated blood from the heart to the liver The hepatic vein brings deoxygenated blood from the liver back to the heart  The hepatic portal vein transports deoxygenated blood from the gut to the liver 9.10 Components of Blood Components of Blood Blood consists of red blood cells, white blood cells, platelets and plasma Identifying Red & White Blood Cells You need to be able to identify red and white blood cells in photomicrographs and diagrams Red blood cells have a concave disc shape with no nucleus White blood cells are usually round in shape with a nucleus Components of Blood: Function Plasma is important for the transport of carbon dioxide, digested food (nutrients), urea, mineral ions, hormones and heat energy Red blood cells transport oxygen around the body from the lungs to cells which require it for aerobic respiration They carry the oxygen in the form of oxyhaemoglobin White blood cells defend the body against infection by pathogens by carrying out phagocytosis and antibody production Platelets are involved in helping the blood to clot 9.11 Blood Clotting Blood Clotting Platelets are fragments of cells which are involved in blood clotting and forming scabs where the skin has been cut or punctured Blood clotting prevents continued / significant blood loss from wounds Scab formation seals the wound with an insoluble patch that prevents entry of microorganisms that could cause infection It remains in place until new skin has grown underneath it, sealing the skin again 9.12 White Blood Cells Lymphocytes & Phagocytes (Extended) White blood cells are part of the body’s immune system, defending against infection by pathogenic microorganisms There are two main types, phagocytes and lymphocytes Phagocytes Carry out phagocytosis by engulfing and digesting pathogens Phagocytes have a sensitive cell surface membrane that can detect chemicals produced by pathogenic cells Once they encounter the pathogenic cell, they will engulf it and release digestive enzymes to digest it  They can be easily recognised under the microscope by their multi-lobed nucleus and their granular cytoplasm Lymphocytes Produce antibodies to destroy pathogenic cells and antitoxins to neutralise toxins released by pathogens They can easily be recognised under the microscope by their large round nucleus which takes up nearly the whole cell and their clear, non-granular cytoplasm 9.13 Conversion of Fibrinogen Conversion of Fibrinogen: Extended Platelets are fragments of cells which are involved in blood clotting and forming scabs where the skin has been cut or punctured Blood clotting prevents continued / significant blood loss from wounds Scab formation seals the wound with an insoluble patch that prevents entry of microorganisms that could cause infection It remains in place until new skin has grown underneath it, sealing the skin again How the blood clots When the skin is broken (i.e. there is a wound) platelets arrive to stop the bleeding A series of reactions occur within the blood plasma Platelets release chemicals that cause soluble fibrinogen proteins to convert into insoluble fibrin and form an insoluble mesh across the wound, trapping red blood cells and therefore forming a clot The clot eventually dries and develops into a scab to protect the wound from bacteria entering