Transport in Humans Candidates should be able to: (a) name the main blood vessels to and from the heart, lungs, liver and kidney (b) state the functions of blood red blood cells – haemoglobin and oxygen transport white blood cells – phagocytosis, antibody formation and tissue rejection platelets – fibrinogen to fibrin, causing clotting plasma – transport of blood cells, ions, soluble food substances, hormones, carbon dioxide, urea, vitamins, plasma proteins (c) relate the structure of arteries, veins and capillaries to their functions (d) describe the structure and function of the heart in terms of muscular contraction and the working of valves (histology of the heart muscle, names of nerves and transmitter substances are not required) (e) describe coronary heart disease in terms of the occlusion of coronary arteries and list the possible causes, such as diet, stress, smoking, and the possible preventative measures 1© Nur Huda (2012)

Main blood vessels 2

Heart Vena cava (from the body) Pulmonary artery (to the lungs) Aorta (to the body) Pulmonary vein (from the lungs) Left atrium Left ventricle Thick muscular wall of left ventricle Right atrium Right ventricle Semi-lunar valve Tricuspid valve Bicuspid valve 3 deoxygenatedoxygenated

Heart Right atrium Receives deoxygenated blood from vena cava Right atrium contracts, force blood to enter right ventricle Triscupid valve Prevents backflow of blood to right atrium Right ventricle Right ventricle contracts and pumps deoxygenated blood to the lungs via pulmonary artery Semi-lunar valve Prevents backflow to right ventricle Superior vena cava Inferior vena cava Pulmonary artery Right atrium Triscupid valve Right ventricle Semi-lunar valve 4

Heart Left atrium Receives oxygenated blood from the lungs via pulmonary vein Left atrium contracts, forces blood to enter left ventricle Biscupid valve Prevents backflow of blood to left atrium Left ventricle Left ventricle contracts and pumps oxygenated blood to the rest of the body via the aorta Semi-lunar valve Prevents backflow to left ventricle Semi-lunar valve Left atrium Biscupid valve Pulmonary vein Aorta Left ventricle 5

Common exams questions Why does left ventricle has muscular wall than the right ventricle? –Left ventricle pump blood to the rest of the body, a greater distance compared to right ventricle which pump blood into the lungs. Hence, it has a thicker muscle wall to produce strong force to pump blood over longer distance. Function of septum –Prevent mixing of oxygenated and deoxygenated blood Function of valve –To prevent backflow of blood and ensure blood flow in one direction 6

Blood vessels artery blood flowing from the heart heart arteries arterioles capillaries venules veins blood flowing back to the heart vein a capillary network links arteries and veins Heart  Artery  Arteriole  Capillary  Venule  Vein  Heart 7

Blood vessels ArteryVeinCapillary Structure Thick and muscular wall Thin and less muscular wall Very thin wall (One-cell thick/ one layer of cells) Elastic tissueNot elastic Narrow lumenWide lumenVery small lumen Valves absentValves presentValves absent Function Carries blood away from heart Carries blood towards the heart Allows exchange of materials between blood and body cells Transport oxygenated blood except pulmonary artery Transport deoxygenated blood except pulmonary vein -- Blood Flow Very fast flow Highest pressure Slow and smooth flow Lowest pressure Slow and smooth flow Pressure is between artery and vein

Blood vessels ArteryVeinCapillary - Thick muscular wall to withstand the pressure of blood exerted on the walls because artery receive blood directly from the heart and the blood is under high pressure. - Elastic to enable the artery wall to stretch and recoil to push the blood forward - Small lumen to maintain the high pressure - Artery receive blood directly from the heart and the blood is under high pressure, hence no valve to impede the flow - Thin outer wall and wide lumen as blood pressure is the lowest - Valve ensure blood flows in one direction back to the heart because blood in veins is under low pressure and there is no direct force to push the blood forward. - Thin wall of one layer of cells to allow higher rate of diffusion of substances - Permeable walls to allow diffusion of substances - Branching of capillaries to increase the surface area to volume ratio for diffusion of substances - Slow blood flow gives more time for the diffusion of substances 9

Coronary Heart Disease Coronary artery becomes hardened and narrow due to fatty deposits in the innermost lining of coronary artery. More resistance for blood to flow and the heart will overwork to pump blood. Blood clot of coronary artery will prevent blood flow to the muscle tissues in the heart. Blood and oxygen supply to the cardiac muscles is reduced. Heart muscles becomes deprived of oxygen and die. When too much heart muscles tissues is damaged, it leads to heart attack and even death. (myocardial infarction= heart attack) (Occlusion = blood clot) (atherosclerosis: fatty deposits on the inner arterial walls) Fatty deposit Narrow artery 10

Coronary Heart Disease CausesPreventive measure High saturated fats diet - Increases the cholesterol level in the blood and build up fatty deposits. Reduce intake of high saturated fats Smoking -Nicotine increase risk of blood clotting in arteries -Carbon monoxide increases the risk of fatty deposits on the inner surface or arterial wall Quit smoking Lack of exercise - Result in unfit heart which slows down blood circulation and may allow fatty substances to deposit easily in the arteries Exercise regularly Stress Manage stress 11

Blood PartsFunctionAppearance PlasmaTransport dissolved substances (e.g blood cells, ions, soluble food substances, hormones, carbon dioxide, urea, vitamins, plasma proteins) Pale yellow fluid White blood cells -Destroy harmful bacteria by phagocytosis -Produce antibody -Defend the body against infection -Involve in tissue rejection after organ transplant PlateletsFibrinogen converted into fibrin, causing blood clot Red blood cells -contain a red pigment called haemoglobin which binds to oxygen -transport oxygen from the lungs to other parts of the body 12

Blood clot When blood vessels are damaged, platelets release an enzyme that catalyses the conversion of the soluble protein fibrinogen to insoluble threads of fibrin Fibrin threads entangle blood cells which forms a clot Blood clot prevents entry of foreign particles through open wound or cuts red blood cell fibrin thread Red blood cells entangled in fibrin threads, forming a blood clot red blood cellfibrin thread Fibrin threads entangle red blood cells clot 13