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42.1 Circulatory systems link exchange surfaces with cells throughout the body By: Ethan Wright Overview • Gases are needed by organism ▫ Excreted as waste • Dilema: ▫ Multicellular organisms cannot happen directly Specialized systems required Solution one • Body Shape ▫ Facilitates direct diffusion ▫ Hydras, jellies, and other cnidarians Diploblastic Allows for diffusion for all cells Circulatory System (Solution 2) • 3 Components: ▫ Fluid ▫ Interconnecting vessels ▫ Pump Open Circulatory System • Fluid bathes organs directly ▫ Circulatory fluid = hemolymph Closed System • Circulatory fluid = blood • Confined to vessels • Advantages: ▫ High blood pressure ▫ Delivery of O2 ▫ Regulation of blood flow to organs Cardiovascular System • Arteries ▫ Carry blood away from heart Arterioles Branches of arteries • Capillaries ▫ Microscopic vessels Converge into – venules veins heart Circulation • Atria – receive blood • Ventricles – pump blood • Single Circulation – blood passes through heart once in each complete circuit • Double Circulation – one circuit, oxygen-poor blood goes to capillary beds (gas exchange tissues) ▫ 2nd circuit delivers oxygen-rich blood to body Single vs. Double Circulation 42.2 Coordinated cycles of heart contraction drive double circulation in mammals • Cardiac cycle ▫ Systole – contraction phase ▫ Diastole – relaxation phase • 2 determining factors of cardiac output: ▫ Heart rate ▫ Stroke volume Maintaining Heart Rhythm • Heart beats independently (no nerve signals) • Sinoatrial (SA) node ▫ Pacemaker of heart ▫ cluster of autorhythmic cells Generate electrical impulses (gap junctions) • Atrioventricular (AV) node Concept 42.3: Patterns of blood pressure and flow reflect the structure and arrangement of blood vessels Grace Castro Blood Vessels • Capillaries • Arteries • Veins • Central lumen and endothelium Vein LM Artery Red blood cells 100 m Valve Basal lamina Endothelium Smooth muscle Connective tissue Endothelium Capillary Smooth muscle Connective tissue Artery Vein Capillary 15 m Red blood cell Venule LM Arteriole Blood Flow Velocity • Capillary beds: slowest velocity ▫ High resistance and large cross-sectional area ▫ Essential for blood transfer with interstitial fluid Area (cm2) Velocity (cm/sec) 50 40 30 20 10 0 Pressure (mm Hg) 5,000 4,000 3,000 2,000 1,000 0 120 100 80 60 40 20 0 Systolic pressure Diastolic pressure Blood Pressure • Blood flows from high pressure to low pressure • Pressure on exerted on wall of vessels • Becomes smaller in capillaries- reduced space resists the flow • Systolic pressure: arteries during ventricular systole • Diastolic pressure : arteries during diastole © 2011 Pearson Education, Inc. Regulation of Blood Pressure • Signals cause contraction or relaxation • Vasoconstriction contraction of smooth muscle in arteriole walls • Vasodilation is the relaxation of smooth muscles in the arterioles Blood Pressure and Gravity • Animals with longer necks require greater systolic pressure • Blood is pumped through veins: ▫ Rhythmic contraction of smooth muscles ▫ Contraction of skeletal muscles during exercise ▫ Change in pressure within thoracic cavity during inhalation • Valves prevent backflow of blood Direction of blood flow in vein (toward heart) Valve (open) Skeletal muscle Valve (closed) Mechanisms to Regulate Blood Flow in Capillaries • • • • Blood amount varies in capillary sites Contraction of smooth muscle layer Precapillary sphincters Regulated by nerve impulses, hormones, and other chemicals Precapillary sphincters Thoroughfare channel Arteriole (a) Sphincters relaxed Arteriole (b) Sphincters contracted Capillaries Venule Venule Figure 42.15 INTERSTITIAL FLUID Net fluid movement out Body cell Blood pressure Osmotic pressure Arterial end of capillary Direction of blood flow Venous end of capillary Fluid Return • Lymphatic system • Lymph reenters circulation at the venous end of the capillary bed and indirectly through the lymphatic system • Valves prevent backflow of fluid • Lymph nodes: filled with white blood cells Concept 42.4: Blood components contribute to exchange, transport, and defense • open circulation, the fluid that is pumped comes into direct contact with all cells • The closed circulatory systems of vertebrates contain blood • Blood consists of several kinds of cells suspended in a liquid matrix called plasma • The cellular elements occupy about 45% of the volume of blood • Blood plasma is about 90% water • inorganic salts in the form of dissolved ions, sometimes called electrolytes • plasma proteins, which influence blood pH, osmotic pressure, and viscosity • plasma proteins function in lipid transport, immunity, and blood clotting • Suspended in blood plasma are two types of cells ▫ Red blood cells (erythrocytes) transport oxygen O2 ▫ White blood cells (leukocytes) function in defense • Platelets, a third cellular element, are fragments of cells that are involved in clotting ▫ Have no nuclei erythrocytes • They contain hemoglobin, the iron-containing protein that transports O2 ▫ Sickle-cell is caused by abnormal hemoglobin that forms aggregates: rupture blood vessels • Each molecule of hemoglobin binds up to four molecules of O2 • In mammals, mature erythrocytes lack nuclei and mitochondria ▫ Anaerobic respiration Leukocytes • There are five major types of white blood cells, or leukocytes: monocytes, neutrophils, basophils, eosinophils, and lymphocytes • They function in defense by phagocytizing bacteria and debris or by producing antibodies • They are found both in and outside of the circulatory system Blood Clotting • Coagulation is the formation of a solid clot from liquid blood • A cascade of complex reactions converts inactive fibrinogen to fibrin, forming a clot • A blood clot formed within a blood vessel is called a thrombus and can block blood flow • The cellular of blood wear Stem Cells andelements the Replacement of out and are being replaced constantly Cellular Elements • Erythrocytes, leukocytes, and platelets develop from a common source of stem cells in the marrow of bones • The hormone erythropoietin (EPO) stimulates erythrocyte production when O2 delivery is low Cardiovascular diseases • Cholesterol, a steroid, helps maintain membrane fluidity • Low-density lipoprotein (LDL) delivers cholesterol to cells for membrane production • High-density lipoprotein (HDL) scavenges cholesterol for return to the liver • Risk for heart disease increases with a high LDL to HDL ratio • Inflammation • heart attack is the death of cardiac muscle tissue resulting from blockage of one or more coronary arteries • stroke is the death of nervous tissue in the brain, usually resulting from rupture or blockage of arteries in the head • Hypertension, or high blood pressure, promotes atherosclerosis and increases the risk of heart attack and stroke • atherosclerosis, is caused by the buildup of plaque deposits within arteries 42.5 An Overview by Griffin Schroeter Main Idea Gas Exchange Occurs Across Specialized Respiratory Surfaces Gas Exchange • The uptake of molecular O2 from the environment and the discharge of CO2 to the environment • Partial Pressure ▫ The pressure exerted by a particular gas in a mixture of gases. ▫ Calculated by multiplying the pressure that the gas mixture exerts and the fraction of the mixture represented by a particular gas. Predicting Gas Flow • A gas always diffuses from a region of higher partial pressure to a region of lower partial pressure • Air is more conductive to gas exchange than water because air has a higher O2 content, lower density, and lower viscosity What is a specialized respiratory • For adequate diffusion of O2 and CO2 between surface? air/water and an animal’s cells requires large, moist respiratory surfaces • Gills, Tracheal system, Lungs Gills • Outfoldings of the body surface specialized for gas exchange in water. The effectiveness by some gills, including those of fishes, is increased by ventilation and countercurrent exchange between blood and water • Ventilation- movement of the respiratory medium over the respiratory surface • Countercurrent Exchange- the exchange of a substance or heat between two fluids flowing in opposite directions Tracheal Systems • Found in insects • A system consisting of tiny, branching tubes that penetrate the body, bringing O2 directly to the cells Lungs • Spiders, land snails, and most terrestrial vertebrates have internal lungs ▫ Lungs are localized respiratory organs ▫ The size and complexity of the lungs correlate with the organism’s metabolic rate Mammalian Respiratory Systems Branch of pulmonary vein (oxygen-rich blood) Terminal bronchiole Nasal cavity Pharynx Left lung Larynx (Esophagus) Trachea Right lung Branch of pulmonary artery (oxygen-poor blood) Alveoli 50 m Capillaries Bronchus Bronchiole Diaphragm (Heart) Dense capillary bed enveloping alveoli (SEM Mammalian Respiratory System • Trachea- the windpipe • Bronchi- the leading to each lung(singular: Bronchus) • Bronchioles- fine tubes branching off of the bronchi • Alveoli- air sacs clustered at the tips of the tiniest bronchioles. Gas exchange occurs here