Chapter 42 medium circulatory system Concept 42 1 Circulatory systems link exchange surfaces with cells through out the body Diffusion time is proportional to the square of the distance Small or thin animals can exchange material directly with its surround Most animals cells exchange materials with environment via fluid filled Central functions of Circulatory system 1 Transport Nutrients gases CO2 and O2 and waste products 2 Communication transport of hormones 3 Fight infections through transport of white blood cells and antibody proteins 4 control body temp transpiration of heat 5 control of body pH through transport of buffers General properties of circulatory systems A circulatory system has Circulatory fluid Blood or hemolymph Set of interconnecting vessels blood vessels Muscular pump the heart Can be open or closed Open circulatory system insects other arthropods and most mollusks blood bathe the organs directly No distinction between blood and interstitial fluid this body fluid is called hemolymph from the interstitial fluid and cells Closed Circulatory System confined to vessels and is distinct More efficient at transporting circulatory fluids to tissues Annelids cephalopods and vertebrates Organization of vertebrate circulatory system Cardiovascular system humans and other vertebrates closed circulatory 3 types of blood vessels Arteries Veins and Capillaries Arteries branch into arterioles and carry blood away from the heart to Capillary beds networks of capillaries are the sites of chemical exchange between the blood and interstitial fluid Venules converge into veins and return blood from capillaries to the system capillaries heart Arteries and veins are distinguish by direction of blood flow In the heart blood enters an atrium and is pumped out though a ventricle Double circulation Double circulation oxygen poor and oxygen rich blood are pumped separately from the right and left sides of the heart Amphibians reptiles and mammals have this Oxygen poor blood flows through the pulmonary circuit to pick up oxygen from the lungs Oxygen rich blood delivers oxygen though the systematic circuit Mammals and birds 4 chamber hearts 2 Atria 2 ventricles Left side Oxygen rich Right Side oxygen poor are endotherms generate own heat and require more oxygen than ectotherms Concept 42 2 coordinated cycles of heart contraction drive double circulation in mammals Mammalian circulation Blood begins its flow with the Right Ventricle pumping blood to lungs Through pulmonary trunk divides into arteries Oxygen rich blood from lungs enters left atrium and is pumped through aorta largest artery to the body tissues by the left ventricle Coronary arteries Aorta provides blood to heart Blood returns to heart through superior vena cava head neck forelimbs and inferior vena cava blood from lower half flow into right atrium Heart Valves prevent backflow of blood and then against the semilunar dup valves Valves are located between atria and ventricles Atrioventricular valve Tricuspid valve separates the right atrium from the right ventricle Bicuspid Valve separates the left atrium form left ventricles Valve located between the pulmonary trunk and right ventricle Pulmonary Semilunar Valve Aortic semilunar valve valve located between aorta and left ventricle Lup dup sound of heart beat is recoil of blood against the AV valves lub Heart Murmur When backflow occurs Cardiac cycle rhythmic cycle of heart contracting and relaxing Systole contraction or pumping phase Diastole relaxing or filling phase Heart Rate Pulse or BPM Stroke Volume amount of blood pumped in a single contraction cardiac output volume of blood pumped into systematic circulation per minute depends on both BPM and SV BPM SV Maintaining the Heart s Rhythmic Beat Sinaerial SA node pace maker Atrioventricular AV node receives signals from SA node delayed and travel to the purkinje fibers that make the ventricles contact Electrocardiogram EKG or ECG record impulse that travel through Pace maker is controlled by sympathetic and parasympathetic nervous cardiac cycle systems SN speeds it up PSN slows it down Hormones and temp regulate pace maker Epinephrine and higher temps increase heart rate Concept 42 3 patterns of blood pressure and flow reflect the structure and arrangement of blood vessels Blood vessel structure and function Vessels cavity Central lumen Endothelium Epithelial layer that lines blood vessels smooth and minimizes resistance Arteries are composed of endothelium Inner layer lines central lumen Smooth Muscle middle layer allows for vasoconstriction or vasodilation Connective Tissue outer layer protects the blood vessel Arteries have thicker walls to accommodate the high blood pressure 20 year old at rest 120 70mmHg systolic diastolic Changes in blood pressure during the cardiac cycle Systolic pressure pressure in arteries during ventricular systole it is the highest pressure in the arteries systolic pressure diastolic pressure pressure in the arteries during diastole lower than Pulse rhythmic bulging of artery wall with each heart beat Arteries Arterioles Capillaries Capillaries have thin walls the endothelium plus its basal lamina to facilitate the exchange of materials Smallest of blood vessels site of gas exchange and nutrient waste exchange O2 and nutrients diffuse from blood into interstitial fluid CO2 and organic waste diffuse from interstitial fluid to blood blood goes Capillaries Venules small veins Veins Veins have thinner walls compared to arteries muscle contraction drives blood flow One way valves prevent backflow Movement of blood 1 Smooth Muscle contraction of venules 2 Skeletal muscle contraction 3 Expansion of vena cava during inhalation Blood Flow velocity Velocity of blood flow is slowest in capillary beds as a result of the high resistance and large total cross sectional area Blood flow in capillaries is necessarily slow for exchange of materials Velocity is fastest in arteries Anatomy of Capillaries facilitate Exchange Exchange happens in capillaries because 1 Small diameter slows blood flow 2 Thin porous walls one cell wall thick 3 Numerous exchange is by diffusion and bulk transport across cells of the capillary wall and through parts between cells 4 Excess fluid not retaken by capillaries is called Lymph a Carried away by lympcapillaries Hydrostatic Pressure Blood Pressure pressure that blood exacts Rigid vessels BP is sustained less rigid vessels deform and blood Blood Pressure against the wall of a
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