Chapter 9 Transport in Animals Syllabus Learning Objectives • Find out about the human circulatory system • Learn about the structure and function of the heart • Think about factors that increase the risk of developing heart disease • Investigate how exercise affects heart rate • Compare the structure and function of arteries, veins and capillaries • Find out about the components of blood, and what they do • Explain how the structures of arteries, veins and capillaries are related to their functions Activity Questions Answers • Draw a very simple diagram of a human (animal) cell, showing its nucleus, cell membrane and cytoplasm. • Draw arrows pointing into the cell, and label them to show what the cell needs to take in to stay alive. • Draw arrows pointing out of the cell, and label them to show what the cell has to get rid of. • Think about how these substances are brought to the cell and taken away from it. • Share your ideas with the rest of the class. 9.1 Circulatory system 1. Delivery System: • The circulatory system transports oxygen, nutrients, and waste throughout the body. 2. Network of Tubes: • Blood vessels carry blood everywhere, like a network of tubes. 3. Pumping Heart: • The heart acts like a pump, keeping blood flowing through the vessels. 4. One-Way Traffic (Valves): • Blood flows in a specific direction inside vessels, controlled by valves. 5. Oxygen Cycle: • Oxygen enters lungs. • Blood picks up oxygen and becomes "oxygenated blood". • The heart pumps it out. • Cells use oxygen. • Blood becomes "deoxygenated". • Deoxygenated blood goes back to lungs and picks up fresh oxygen, repeating the cycle. 6. Continuous Loop: • This cycle keeps our body functioning! Oxygenating the blood: Oxygen Pick-up: • Oxygen enters lungs. • Blood in the LEFT heart chamber becomes oxygenated (picks up oxygen). Delivery to Cells: • Heart pumps oxygenated blood throughout the body. • Cells use oxygen for respiration. Waste Removal: • Blood loses oxygen and becomes deoxygenated. Back to the Lungs: • Deoxygenated blood returns to the RIGHT heart chamber. • Blood travels to the lungs to pick up fresh oxygen, repeating the cycle. Double and single circulatory systems: Double Circulation (Mammals, Birds, Reptiles): • Blood goes through the heart twice per body circuit. Two loops: • Pulmonary system - blood to lungs and back. • Systemic system - blood to body and back. Advantages: • Delivers oxygen more efficiently and faster, especially to active tissues. • Blood pressure maintained throughout the body due to separate loops. Single Circulation (Fish): • Blood goes through the heart once per body circuit. • Slower oxygen delivery to body organs. Advantages: • Simple but efficient: It's less efficient for oxygen delivery compared to the double circulatory system.. • Lower Activity: Works well for fish with lower oxygen needs. • Diffusion: Oxygen reaches nearby tissues directly from gills. • Limited: Less efficient oxygen delivery for larger or active fish. 9.2 The heart • Function: Pumps blood throughout the body. • Muscle Type: Special muscle that contracts and relaxes rhythmically. • Chambers: Four chambers - 2 upper atria, 2 lower ventricles. • Left Side: Receives oxygenated blood from lungs (pulmonary veins). Pumps it to the body (aorta). • Right Side: Receives deoxygenated blood from body (venae cavae). Pumps it to the lungs (pulmonary artery). • Muscle Power: Strong contractions in ventricles push blood out. Valves: Atrioventricular Valves: • Permit blood flow from atria to ventricles, prevent reverse flow. Semilunar Valves: • Allow blood flow from ventricles to arteries, block reverse flow. Function: • Ensure one-way blood flow, maintaining circulation efficiency. Structure: • Atrioventricular valves prevent backflow into atria, semilunar valves prevent return to ventricles. Importance: • Proper valve function crucial for efficient circulation, preventing blood mixing and ensuring tissue perfusion. Differences in muscle wall thickness: 1. Different Functions: • Atria: Receive blood from the body and lungs, then supply it to the ventricles (acting as collection chambers). • Ventricles: Pump blood out of the heart (the real workhorses). 2. Muscle Power: • Ventricle walls are much thicker and more muscular than atria for powerful pumping. 3. Pressure and Thickness: • Right Ventricle: Pumps blood to lungs (low pressure) - Thinner wall. • Left Ventricle: Pumps blood to entire body (high pressure) - Thickest wall. Coronary arteries: Heart Needs Its Own Blood Supply: • The heart muscle is so thick that blood inside the chambers can't reach all parts quickly enough for proper function. • Coronary arteries on the heart's exterior supply oxygen and nutrients directly to the heart muscle. • This constant supply is crucial for the heart muscle's aerobic respiration and energy production for contraction. Coronary Artery Blockage: • Cholesterol buildup and narrowing of the coronary arteries can occur. • This restricts blood flow and oxygen delivery to the heart muscle. • If a coronary artery is completely blocked, the heart muscle cannot function (lack of oxygen for energy production). • This blockage is called coronary heart disease (CHD), a major cause of illness and death. Preventing CHD: CHD: A Major Health Threat • Coronary heart disease (CHD) is a leading cause of death in many countries. • While completely eliminating risk isn't possible, there are ways to significantly reduce it. Lifestyle Choices Matter: • Quit Smoking • Healthy Diet • Regular Exercise Benefits of Exercise: • Promotes fitness • Prevents weight gain • Lowers blood pressure • Improves mental well-being (reduces stress and releases feel-good chemicals) Heartbeat: Feeling Your Heartbeat: The Basics • Resting Heart Rate: Most people's hearts beat 60-75 times per minute at rest. • Heartbeat Sounds: You can hear the valves closing as a "lub-dub" with each beat using a stethoscope. • Measuring Heart Rate: This can be done by taking your pulse (feeling the artery expansion/relaxation) at your wrist or neck. Phone apps and smartwatches can also track it. Monitoring Heart Activity • ECG (Electrocardiogram): Used in hospitals, it records the heart's electrical activity using electrodes placed on the body. The recording appears as a graph. How the heart beats: The Heartbeat: A Squeezing Action • The heart's muscular walls contract and relax to pump blood. • Contraction: Squeezes blood out (heart becomes smaller). • Relaxation: Allows blood to flow back into the chambers (heart becomes larger). One-Way Valves: • Atrioventricular valves (tricuspid on right, bicuspid/mitral on left) control blood flow direction. • Atrial contraction pushes blood into ventricles, opening the valves. • Ventricular contraction pushes blood out, closing the valves with the help of attached tendons. 9.3 Blood vessels: Blood Vessel Types: • Arteries, Capillaries, Veins Arteries: • Carry blood away from the heart • Branch out into smaller vessels Capillaries: • Tiniest blood vessels • Deliver oxygen and nutrients to cells Veins: • Carry blood towards the heart • Have valves to control blood flow direction Arteries: Arteries - Delivering Blood Under Pressure • Carry blood away from the heart (high pressure) • Strong walls to handle pumping force • Pulsating flow due to heart contractions • Elastic walls for smoother blood flow (feel pulse at wrist/neck) Capillaries: Capillaries - Tiny Delivery Network • Branch out from arteries, becoming very narrow. • Reach nearly every cell in the body. • Thin walls allow easy exchange of nutrients, oxygen, and waste. • Walls can be just one cell thick! Veins: Veins - Returning Blood to the Heart • Formed by joining capillaries, carrying low-pressure blood. • Wider lumen for smooth, slower blood flow. • Contain valves to prevent backward flow (unlike arteries). • Muscle contractions (e.g., walking) aid blood movement in veins. Table 9.1 summarizes the structure and function of arteries, capillaries and veins Feature Arteries Carry blood away from the heart Function (high pressure) Thick and elastic to withstand Structure of wall pressure Width of lumen Narrow Strong walls handle pumping How structure fits force, narrow lumen maintains pressure function Capillaries Exchange nutrients, oxygen, and waste with cells Veins Carry blood towards the heart (low pressure) Very thin for easy exchange Narrowest Thin walls allow diffusion, narrow lumen maximizes surface area for exchange Thinner and less elastic Wider Wider lumen for increased flow, valves prevent backflow Naming blood vessels: Blood Supply to Organs • Arteries deliver oxygenated blood (except lungs). • Veins carry away deoxygenated blood. • Named based on the organ they connect to (e.g., renal artery/vein for kidneys). Liver: • Hepatic artery supplies oxygenated blood. • Hepatic portal vein brings blood from digestion for processing. • Hepatic veins carry all blood out of the liver. 9.4 Blood Blood Composition • Blood: Liquid (plasma) containing cells. • Red blood cells (most numerous) carry oxygen. • White blood cells (fewer) fight infection. • Platelets (cell fragments) aid clotting. Red blood cells: Red Blood Cells - Oxygen Carriers • Contain iron-rich protein hemoglobin for oxygen transport. • Hemoglobin picks up oxygen in lungs (oxyhemoglobin). • Releases oxygen in tissues needing it (low oxygen). • Lack nucleus and mitochondria for more space for hemoglobin. • Biconcave disc shape maximizes surface area for gas exchange. • Small size allows passage through tiny capillaries for oxygen delivery to all cells. Extra Information White blood cells: White Blood Cells - Body Defenders • Have nuclei for various functions (unlike red blood cells). • Move around and squeeze through capillaries to reach tissues. Fight pathogens (disease-causing germs) in two ways: • Phagocytes (lobed nucleus) engulf and digest pathogens through a process called phagocytosis. • Lymphocytes (round nucleus) produce antibodies to destroy pathogens. Platelets: Platelets - Plugging the Leaks • Tiny cell fragments (no nucleus) made in bone marrow. • Involved in blood clotting to prevent excessive bleeding and pathogen entry. Platelets clump together and release substances that: • Convert fibrinogen (plasma protein) into fibrin (insoluble mesh). • Trap red blood cells to form a clot, sealing the wound. Plasma: Blood Plasma - The Delivery System • Mostly water, but transports various dissolved substances: • Nutrients (glucose, amino acids, minerals) for cells. • Hormones (e.g., adrenaline) for chemical messaging. • Waste products (carbon dioxide, urea) for removal. Table 9.2 summarizes some of the substances that are transported in blood plasma. Component Source Destination Notes Water Absorbed in small intestine and colon. All cells Excess is removed by the kidneys. Various proteins (including fibrinogen and antibodies) Fibrinogen is made in the liver. Antibodies are made by lymphocytes. Remain in the blood. Fibrinogen helps in blood clotting. Antibodies kill invading pathogens. Lipids including cholesterol and fatty acids Absorbed in the ileum. Also derived from fat reserves in the body. To the liver, for breakdown. To adipose tissue, for storage. To respiring cells, as an energy source. Breakdown of fats yields energy – heart muscle depends largely on fatty acids for its energy supply. High cholesterol levels in the blood increase the risk of developing heart disease. Component Source Destination Notes Carbohydrates, especially glucose Absorbed in the ileum. Also produced by the breakdown of glycogen in the liver. To all cells, for energy release by respiration. Excess glucose is converted to glycogen and stored in the liver. Excretory substances, e.g. urea Produced by amino acid deamination in the liver. To kidneys for excretion. Most of the urea is removed by the kidneys, dissolved in water to form urine. Mineral ions, e.g. Na+, Cl− Absorbed in the ileum and colon. To all cells. Excess ions are excreted by the kidneys. Component Source Destination Notes Hormones Secreted into the blood by endocrine glands. To all parts of the body. Hormones only affect their target cells. Hormones are broken down by the liver, and their remains are excreted by the kidneys. Dissolved gases, e.g. carbon dioxide Carbon dioxide is released by all cells as a waste product of respiration. To the lungs for excretion. Most carbon dioxide is carried as hydrogencarbonate ions (HCO3 −) in the blood plasma. SUMMARY Mammalian Circulatory System: Key Points • Double Circulation: Blood travels through the heart twice per circuit (unlike fish). • Heart Structure: Muscular walls, chambers (atria, ventricles), valves (direct blood flow). • Blood Vessels: Arteries (high pressure, carry blood away) vs. Veins (low pressure, return blood). • Blood Composition: Plasma (liquid), red blood cells (O2 transport), white blood cells (fight infection), platelets (clotting). • Blood Functions: Transports O2, nutrients, waste, hormones; fights disease; clots wounds. • Coronary Heart Disease: Blocked coronary arteries (risk factors: diet, lifestyle, etc.).
