Transport in Animals KS4 PDF

**Topic 9 Transport in animals: KS4** **The main transport system of human is the circulatory system, a system of tubes (blood vessels) with a pump (the heart) and valves to ensure one-way flow of blood.** **Its functions:** **1. To transport nutrients and oxygen to the cells.** **2. To remove w...

**Topic 9 Transport in animals: KS4** **The main transport system of human is the circulatory system, a system of tubes (blood vessels) with a pump (the heart) and valves to ensure one-way flow of blood.** **Its functions:** **1. To transport nutrients and oxygen to the cells.** **2. To remove waste and carbon dioxide from the cells.** **3. To provide for efficient gas exchange.** **Single circulation of fish** **Fish have the simplest circulatory system of all the vertebrates.** **A heart, made of one blood-collecting chamber (the atrium)** **and one blood-ejection chamber (the ventricle), sends blood** **to the gills where it is oxygenated. The blood then flows to all** **the parts of the body before returning to the heart.** **This is called a single circulation because the blood goes** **through the heart once for each complete circulation of the** **body. However, as the blood passes through capillaries in the** **gills, blood pressure is lost, but the blood still needs to circulate** **through other organs of the body before returning to the heart** **to increase the blood pressure. This makes the fish circulatory** **system inefficient.** **Double circulation of mammal.** **The blood passes twice through the heart during one** **complete circuit: once on its way to the body and again on its** **way to the lungs.** **A double circulation has the advantage of maintaining a high blood pressure to all the major organs of the body. The right** **side of the heart collects blood from the body, builds up the** **blood pressure and sends it to the lungs to be oxygenated. The** **pressure drops during this process. The left side of the heart** **receives oxygenated blood from the lungs, builds up the blood** **pressure again and pumps the oxygenated blood to the body.**  **The importance of a double circulation** **1. Oxygenated blood is kept separate from deoxygenated blood. The** **septum in the heart ensures this complete separation. Oxygenated** **blood flows through the left side of the heart while deoxygenated** **blood flows through the right.** **2. The blood pressure in the systemic circulation is kept higher than** **that in the pulmonary circulation. The left ventricle, with a thicker wall,** **pumps blood under higher pressure to the body and delivers** **oxygenated blood effectively to all parts of the body.** **The right ventricle has a thinner wall and pumps blood to the lungs under lower pressure, thereby avoiding any lung damage.** **Video Circulatory system** **https://www.youtube.com/watch?v=oE8tGkP5\_tc** **9.2 Heart.** **The heart pumps blood through the circulatory system to all the** **main organs of the body.**  **Blood is pumped away from the heart in arteries and returns** **to the heart in veins.** **The pulmonary vein brings oxygenated blood from the lungs** **into the left atrium. The vena cava brings deoxygenated blood** **from the body tissues into the right atrium. The blood passes** **from each atrium to the ventricle below it, and the ventricle** **pumps it out into the arteries. The left chambers are separated** **from the right chambers by a wall of muscle called a septum.** **In pumping the blood, the muscle in the walls of the atria and** **ventricles contracts and relaxes. The walls of the** **atria contract first and force blood into the two ventricles. Then** **the ventricles contract and send blood into the arteries. Valves** **prevent blood flowing backwards during or after heart** **contractions.** **The heart muscle is supplied with food and oxygen by the** **coronary arteries.** **Monitoring the activity of the heart** **There are several ways by which the activity of the heart can be** **monitored. These include measuring pulse rate, listening to** **heart sounds and the use of electrocardiograms (ECGs).** **Pulse rate** **You feel the ripple of pressure that passes down an artery as a** **result of the heart beat as a 'pulse' when the artery is near the** **surface of the body.** **Heart sounds** **These can be heard using a stethoscope. This instrument** **amplifies the sounds of the heart valves opening and closing.** **ECGs** **An ECG is an electrocardiogram. To obtain an ECG, electrodes,** **attached to an ECG recording machine, are stuck onto the skin on the arms, legs and chest. Electrical activity to do with heartbeat is then monitored and viewed on a computer screen or printed out. Any unusual patterns on the trace can be used to identify heart problems.** **The effect of physical activity on the heart rate:** **A heartbeat is a contraction. Each contraction squeezes blood to** **the lungs and body. At rest, the heart beats about 70 times a minute, but this varies according to a person's age, sex and fitness. It is higher if you are younger and/or female, and lower if you are fit. An increase in physical activity increases the pulse rate, which can rise to 200 beats per minute.** **Why physical activity affects the heart rate** **This is because during exercise the muscles need more energy, so the heart has to deliver more oxygen and glucose for respiration. After exercise has stopped, the pulse rate gradually drops to its resting state. If the individual is fit, this happens quickly, but an unfit person's pulse rate will take longer to return to normal.**