Transcript File
The Heart and Blood Vessels Lesson objectives By the end of this lesson you should be able to explain: • Why there is a requirement for circulatory systems in larger organisms • Distinguish between open and closed circulatory systems • Describe the structure and function of arteries, vain and capillaries The need for a circulatory system • In small organisms diffusion is sufficient to allow molecules to move from one place to another • However in large organisms diffusion is to slow so there is a requirement for some king of circulatory system Open circulatory systems Typical in animals like insects, spiders and crabs Closed circulatory systems Arteries, veins and capillaries Structure of arteries and veins Blood vessels Arteries Veins Carry blood away from the heart Blood is under high pressure Thick, strong walls Carry blood to the heart Small lumen Large lumen No valves Have valves Blood is under low pressure Thin, weaker walls Valves • The blood pressure in veins is lower than that of arteries • There is a danger that the blood in veins might flow backwards • To prevent this veins have valves Capillaries What have you learned? Can you explain: • Why there is a requirement for circulatory systems in larger organisms? • Distinguish between open and closed circulatory systems? • Describe the structure and function of arteries, vain and capillaries? Lesson objectives By the end of this lesson you should know: • How to draw the heart and label its associated structures. • The functions of the parts of the heart • Describe the flow of blood through the heart Cardiac Muscle How to draw and label the heart Structure of the heart and major blood vessels Blood flow through the heart Howstuffworks "The Heart" What do you know? Can you . . . • Draw the heart and label its associated structures? • State the functions of the parts of the heart? • Describe the flow of blood through the heart? Lesson objectives By the end of this lesson you should know: • That the human circulatory system is a system of double circulation. • The muscle of the heart is supplied with blood via the coronary circulation. • Be able to dissect, display and identify the parts of the heart. Double Circulation The circulatory system Coronary circulation Dissect, display and identify an ox’s or a sheep’s heart Dissect, display and identify an ox’s or a sheep’s heart • Squeeze the ventricles – the soft side is the right ventricle. • Squeeze to locate the position of the septum. • Use a blade to cut into the right ventricle just to the side of the septum. • Cut from the base of the layer of fat to the pointed end. • Then cut across just below the layer of fat. • Pull back this angular flap to see inside the right ventricle. • Now repeat on the left side. • Remove the top of each atrium to see into the atrial cavity. • Identify the arteries – pulmonary connected to right ventricle, aorta to left ventricle. • Look into the stumps of the arteries to see the semilunar valves. • Pin down the dissection and flag label. What do you know? Can you . . • Understand how the human circulatory system is a system of double circulation? • Describe the coronary circulation? • Are you able to dissect, display and identify the parts of the heart? Lesson objectives • • • • • By the end of this lesson you should know: What causes the characteristic ‘lub dub’ sound of heartbeat. Factors that can influence heartbeat. Describe a portal system and give an example. Explain what causes a pulse and blood pressure. Explain the effects of smoking, diet and exercise on the circulatory system. The sounds of heartbeat • The ‘lub-dub’ sound is caused by the valves being forced shut. • The low pitched, quieter, long lasting ‘lub’ sound is due to the bicuspid and tricuspid valves being forced shut when the ventricles contract. • The higher pitched, louder much shorter ‘dub’ sound is due to the semilunar valves snapping shut. Changing the rate of heartbeat • Nerves link the pacemaker to the brain – allowing the rate of heartbeat to be altered • Heart rate increases because of factors like exercise, excitement and drugs (such as caffeine) • The rate of heartbeat is decreased by factors such as rest, sleep and drugs (such as alcohol) Portal system • A portal system is one in which the blood starts and ends in the capillaries • Example – the hepatic portal vein Pulse • The pulse that we feel in our wrist or neck is caused by the surge of blood in the arteries triggered by ventricular systole • The pulse rate indicates the rate of heartbeat • Normal adult heartbeat rate is 72 per minute Blood pressure • Contraction –systole • Relaxed-diastole • Blood entering the aorta is under high pressure • Pressure decreases as it flows through the circulatory system • Blood pressure is the force exerted by the blood against the walls of the blood vessels (mainly arteries) • Blood pressure readings are given as 2 values Lifestyle and the heart Smoking cigarettes is bad for the heart and circulatory system because: • Nicotine increases the heart rate and raises blood pressure • Carbon monoxide reduces the ability of the blood to carry oxygen • Chemicals in smoke increase the risk of blood clots Lifestyle and the heart Diet may affect the heart in 3 ways: • A fat rich diet increases the chances of the arteries becoming blocked (leads to heart attacks) • To much salt raises the blood pressure • Being severely overweight increases blood pressure and results in heart attacks Exercise • Enlarges and strengthens heart • Causes loss of weight What do you know? • • • • • Can you . . Explain what causes the characteristic ‘lub dub’ sound of heartbeat. Name the factors that can influence heartbeat. Describe a portal system and give an example. Explain what causes a pulse and blood pressure. Explain the effects of smoking, diet and exercise on the circulatory system. Lesson objectives (HL) By the end of this lesson you should be know: • How heartbeat is controlled. • Describe the stages of heartbeat (cardiac cycle) How heartbeat is controlled Path of nerve impulses in the heart The stages of a heartbeat Diastole refers to when heart muscle is relaxed; systole is when the heart is contracted There are 3 stages in the cardiac cycle: 1. Blood enters the heart 2. Blood is pumped to the ventricles 3. Blood is pumped from the heart What do you know? Can you . . • Understand how heartbeat is controlled. • Describe the stages of heartbeat (cardiac cycle)