hi everyone welcome to IGCSE study buddy where you can revise biology topics from the Cambridge IGCSE syllabus if you are enjoying this video so far please don't forget to hit the like button and subscribe to my channel this video summarizes part 1 of chapter 9 transport in animals in most animals the circulatory system is the primary method used to transport nutrients and gases through the body in the blood the circulatory system is a system of blood vessels with a pump and valves to ensure one-way flow of blood fish have a single circulatory system the heart of a fish has two Chambers an Atrium and a ventricle in a single circulatory system blood passes through the heart only once to complete a full circuit through the body of the fish this diagram illustrates the single circulation of a fish the pink arrows represent the oxygenated blood flow or blood rich in oxygen the blue arrows represent deoxygenated blood flow as you may notice fish do not have lungs since oxygen is absorbed when the blood passes the gills so deoxygenated blood from the body capillaries move through the two chambers of a fisher's Heart The Atrium and The ventricle and then reaches the Gill capillaries where oxygen is absorbed into the blood thereafter the blood becomes oxygenated and moves from the Gill capillaries to the body capillaries completing one circuit so when the heart pumps the blood to the gills to be oxygenated it's called Gill circulation the blood then continues through the rest of the body before arriving back at the atrium and this is called systemic circulation moving on to the double circulation of a mammal so mammals have a double circulatory system the mammalian heart has four chambers this means that blood passes through the heart twice for every one circuit of the body so here's a diagram to explain the double circulation of a mammal the Red Arrows represent the oxygenated blood flow and the blue arrows represent deoxygenated blood flow the heart is labeled as if it was in the chest so what is on your left on a diagram is actually the right hand side and vice versa so deoxygenated blood enters the right atrium labeled as r a on the diagram via the vena cava then it moves into the right ventricle next the deoxygenated blood is pumped by the right ventricle to the lungs to become oxygenated the pulmonary artery carries this blood away from the heart gas exchange happens at the lungs and the deoxygenated blood becomes oxygenated blood then oxygenated blood enters the left atrium via the pulmonary vein then it moves to the left ventricle oxygenated blood is pumped by the left ventricle to the wrist of the body the aorta carries this oxygenated blood away from the heart body cells use the oxygen and cause the blood to become deoxygenated the deoxygenated blood returns to the heart and the cycle repeats the right side of the heart receives deoxygenated blood from the body and pumps it to the lungs that is called pulmonary circulation the left side of the heart receives oxygenated blood from the lungs and pumps it to the body this is called systemic circulation what is the advantage of a double circulation mammals are larger than fish so they have a greater requirement for oxygen and glucose for respiration double circulation allows this oxygen and glucose to be delivered faster and more efficiently through the blood since a double circulation maintains a higher blood pressure than a single circulation system let's learn the structures of the mammalian heart now this is the right atrium one of the heart's four chambers this is the vena cava deoxygenated blood coming from the body flows into the right atrium through this vein this is the tricuspid valve it is an atrioventricular valve which separates the Atria from the ventricles on each side of the heart and prevents the blood from flowing back into the Atria once the right atrium is filled with blood the heart muscles of the right atrium contracts and the blood is pushed through the tricuspid valve into the right ventricle this is the right ventricle the next chamber of the heart this is the semilunar valve it prevents blood flowing backwards into the heart the walls of The ventricle contract and the blood is pushed through the semilunar valve into the pulmonary artery this is the pulmonary artery it is a blood vessel that carries deoxygenated blood away from the heart to the lungs to be oxygenated this is the septum it is a muscle wall that separates the two sides of the heart therefore it prevents the mixing of oxygenated and deoxygenated blood this is the left atrium another one of the heart's four chambers this is the pulmonary vein oxygenated or oxygen rich blood returning from the lungs enters the left atrium through this vein this is the bicuspid valve it is an atrioventricular valve which separates the left atrium from the left ventricle and prevents the blood from flowing back into the lift atrium once the left atrium is filled with blood the heart muscles of the left atrium contracts and the blood is pushed through the bicuspid valve into the left ventricle this is the left ventricle a chamber of the heart this is the semilunar valve in the aorta it prevents blood flowing backwards into the heart the thicker muscle walls of The ventricle contracts strongly to push the blood forcefully through the semilunar valve into the aorta this is the aorta it is a blood vessel that carries oxygenated blood away from the heart all the way around the body here's a simpler diagram that will guide you through double circulation deoxygenated blood enters the right atrium through the vena cava then it moves into the right ventricle through the atrioventricular valve the special name for the one on this side is called the tricuspid valve the right ventricle pumps the deoxygenated blood out to the pulmonary artery via the semilunar valve the blood travels to the lungs and moves through the capillaries past the alveoli where gas exchange takes place the deoxygenated blood becomes oxygenated blood and returns to the heart via the pulmonary vein into the left atrium it then moves into the left ventricle through the atrioventricular valve the special name for the one on this side is called the bicuspid valve the left ventricle pumps oxygenated blood out to the aorta via the semilunar valve the aorta takes the oxygenated blood away from the heart to the wrist of the body here's a small tip to remember which vessels take blood away from the heart remember a pulmonary artery and aorta are arteries and they carry blood away from the heart so artery begins with a and so does away blood this pump towards the heart in veins and away from the heart in arteries next what are coronary arteries the heart is made of muscle tissues like all other tissues in the body the heart muscle needs oxygen rich blood to function coronary arteries Supply blood to the heart muscle the coronary arteries wrap around the outside of the heart moving on to muscular walls the ventricles have thicker muscle walls than the Atria since they pump blood out of the heart so they need to do so at a higher pressure so you will notice that the lower two Chambers the ventricles have thicker muscle walls than the upper two Chambers the Atria also comparing both ventricles the left ventricles muscle wall is thicker than the right ventricles muscle wall this is because it has to pump blood at a higher pressure to the whole body whereas the right ventricle has to pump blood just to the lungs the activity of the heart may be monitored by using an ECG measuring pulse rate or listening to the sounds of valves closing using a stethoscope let's investigate the effect of physical activity on the heart rate first record the pulse rate at rest for a minute next exercise for a while then 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 so why does the physical activity have this effect on the heart rate this is because during exercise the muscle cells of the body need more energy therefore they need more oxygen and glucose for respiration the waste products of respiration also needs to be removed faster from the cells moreover some of the muscle cells may have respired anaerobically without oxygen so the oxygen debt needs to be repaid the heart rate therefore increases to meet these demands finally let's learn about coronary heart disease so far we know that the heart functions as a pump which delivers blood to the rest of the body however the heart muscles themselves also need a blood supply because they too are respiring muscles coronary arteries Supply blood to the heart muscles in order for them to respire and perform their function coronary heart disease is when the coronary artery becomes blocked leading to blood and therefore oxygen starvation in the heart muscles this leads to a heart attack coronary heart disease is caused by the buildup of cholesterol and other fatty substances within the coronary arteries so in this diagram you can see a coronary artery with normal blood flow and a coronary artery with a cholesterol buildup which is restricting the blood flow the possible risk factors for coronary heart disease include diet eating unhealthy amounts of saturated fats increases cholesterol levels in the body lack of exercise physical activity can help control blood cholesterol diabetes and obesity so an inactive person is at a higher risk of getting this disease stress increases the blood pressure increasing the chance of coronary arteries getting blocked smoking increases blood pressure and increases the likelihood of clots forming in the arteries genetic predisposition children of parents with coronary heart disease are more likely to develop coronary heart disease age with increasing age the risk of getting coronary heart disease increases and gender males have a higher chance of developing coronary heart disease than females the risk of coronary heart disease may be reduced in the following ways quit smoking maintain a healthy diet with reduced animal fats and exercise regularly so that concludes part 1 of chapter 9 transport in animals hope you found this video useful thank you for watching and please don't forget to subscribe to IGCSE study buddy for mobile larger revision videos bye bye