Need for transport system Chapter 19

Exchange of materials Efficient exchange of materials requires a large surface area Small objects have large surface area:volume ratio Increased volume = decreased surface area Larger organisms have less of inner tissues close to outside surface - therefore less surface area Nomogram – estimates human surface area Small organisms – absorb directly through cell membrane - diffusion is adequate Large organisms – need transport systems & absorbing surfaces - e.g alveoli, villi

Blood Vessels - known as exchange vessels Arteries – pulsate due to pumping of heart - thick walls, narrow lumen Veins – wide lumen = low resistance - have valves Arteries branch into arterioles Veins branch into venules Capillaries - between venules and arterioles - known as exchange vessels

Tissue Fluid Blood: cells, platelets, & dissolved substances – bathed in plasma Blood from arteriole to capillary undergoes pressure filtration Plasma squeezed out through capillary walls = tissue fluid All living cells located close to a capillary bed Dissolved substances diffuse along conc gradient Tissue fluid returns to capillaries at venule side by osmosis Some tissue fluid enters lymphatic system - fluid known as lymph

Heart & Circulation Allows exchange between blood & external/internal environment Heart structure Valves: Between atria & ventricles - atrio-venticular (AV) valves Right AV valve (3 flaps) – tricuspid Left AV valve (2 flaps) – bicuspid (mitral) Semi-Lunar valves – separate ventricles from arteries

Heart & Circulation (2) Pulmonary System – circulates blood between heart & lungs Systemic system – circulates blood between heart & rest of the body Hepatic Portal vein – carries blood from intestinal capillary bed to liver capillary bed Liver has 3 blood vessels associated with it - artery, vein & portal vein

Coronary Blood supply Coronary arteries – branched off from the aorta Divide to form many capillaries Cardiac muscle cells within 10um of a capillary (avg. is 60-80) Coronary veins return blood to vena cava Restricted or blocked supply = coronary heart disease Deprived oxygen supply = muscle cell death - myocardial infarction

Coronary Heart Disease Atherosclerosis: Plaques of fatty material on inner coat of artery – atheromas Enlarged by lipids & cholesterol, hardened by calcium Restrict blood flow to an organ Angina: pain from insufficient blood supply to heart - due to atherosclerosis

Coronary Heart Disease (2) Coronary Thrombosis: Blockage of coronary artery by a blood clot Caused by blood flowing over uneven atheromas Blood clots (thrombus) occur Complete blockage = ‘heart attack’ Clots can break loose and cause blockages elsewhere

Diagnosis, Treatment & Risk Partial blockage detected by an arteriography - produce angiograms If too advanced, coronary bypass is required Aorta & coronary artery joined by veins from patients leg Risk factors: Smoking Stress Poor diet – excess cholesterol/fat Obesity Lack of exercise