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The Cardiovascular System(The Circulatory System)· A closed system of the heart and blood
vessels· The heart pumps blood· Blood vessels allow blood to circulate to all
parts of the body· The function of the cardiovascular
system is to deliver oxygen and nutrients and to remove carbon dioxide and other waste products
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The Heart· Location
· Thorax between the lungs· Pointed apex directed toward left hip
· About the size of your fist
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The Heart
Figure 11.1
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The Heart: Coverings· Pericardium – a double serous
membrane· Visceral pericardium
· Next to heart· Parietal pericardium
· Outside layer· Serous fluid fills the space
between the layers of pericardium
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The Heart: Heart Wall· Three layers
· Epicardium· Outside layer· This layer is the parietal
pericardium· Connective tissue layer
· Myocardium· Middle layer· Mostly cardiac muscle
· Endocardium· Inner layer· Endothelium
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External Heart Anatomy
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Internal Heart Anatomy
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The Heart: Chambers· Right and left side act as
separate pumps· Four chambers
· Atria· Receiving chambers
· Right atrium· Left atrium
· Ventricles· Discharging chambers
· Right ventricle· Left ventricle
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The Heart: Valves
· Allow blood to flow in only one direction
· Four valves· Atrioventricular valves
– between atria and ventricles· Bicuspid valve
(left)· Tricuspid valve
(right) · Semilunar valves
between ventricle and artery· Pulmonary
semilunar valve· Aortic semilunar
valve
Valves open as blood is pumped throughHeld in place by chordae tendineae (“heart strings”)Close to prevent backflow
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The Heart: Associated Great Vessels
· Aorta· Leaves left ventricle
· Pulmonary arteries· Leave right ventricle
· Vena cava· Enters right atrium
· Pulmonary veins (four)· Enter left atrium
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The Heart: Cardiac Cycle
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Blood Circulation
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Coronary Circulation· Blood in the heart
chambers does not nourish the myocardium
· The heart has its own nourishing circulatory system
· Coronary arteries
· Cardiac veins
· Blood empties into the right atrium via the coronary sinus
Heart Attack: A Block of one of these arteries that cause the muscle cells to die.
One treatment is a bypass surgery
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The Heart: Conduction System· Intrinsic
conduction system (nodal system)· Heart muscle
cells contract, without nerve impulses, in a regular, continuous way
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The Heart: Conduction SystemSpecial tissue sets
the pace
Sinoatrial node
Pacemaker
Atrioventricular node
Atrioventricular bundle
Bundle branches
Purkinje fibers
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Heart Contractions
Figure 11.5
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The Heart: Cardiac Cycle· Atria contract simultaneously
· Atria relax, then ventricles contract
· Systole = contraction
· Diastole = relaxation
· Mid-to-late diastole – blood flows into ventricles
· Ventricular systole – blood pressure builds before ventricle contracts, pushing out blood
· Early diastole – atria finish re-filling, ventricular pressure is low
·Cardiac cycle – events of one complete heart beat
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Blood Pressure
Measurements by health professionals are made on the pressure in large arteries
· Systolic – pressure at the peak of ventricular contraction
· Diastolic – pressure when ventricles relax
· Pressure in blood vessels decreases as the distance away from the heart increases
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Measuring Arterial Blood Pressure
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Variations in Blood Pressure· Human normal range is variable
· Normal· 140–110 mm Hg systolic· 80–75 mm Hg diastolic
· Hypotension· Low systolic (below 110 mm HG)· Often associated with illness
· Hypertension· High systolic (above 140 mm HG)· Can be dangerous if it is chronic
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Blood Vessels: The Vascular System
· Taking blood to the tissues and back· Arteries· Arterioles· Capillaries· Venules· Veins
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Blood Vessels: Anatomy· Three layers (tunics)
· Tunic intima· Tunic media
Smooth muscle
Controlled by sympathetic nervous system
· Tunic externaMostly fibrous connective tissue
Also called Tunica adventitia
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Differences Between Blood Vessel Types
· Walls of arteries are the thickest
· Lumens of veins are larger
· Skeletal muscle “milks” blood in veins toward the heart
· Walls of capillaries are only one cell layer thick to allow for exchanges between blood and tissue
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The Vascular System
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Movement of Blood Through Vessels
· Most arterial blood is pumped by the heart
· Veins use the milking action of muscles to help move blood
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Major Arteries of Systemic Circulation
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Major Veins of Systemic Circulation
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Capillary Beds
· True capillaries – exchange vessels
· Oxygen and nutrients cross to cells
· Carbon dioxide and metabolic waste products cross into blood
·Capillary beds consist of two types of vessels
· Vascular shunt – directly connects an arteriole to a venule
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Diffusion at Capillary Beds
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Hepatic Portal Circulation
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Blood flow to the liverLiver receives blood from 2 sources
◦Hepatic Artery◦Hepatic Portal Vein
Leaves via Hepatic VeinSinusoids
◦Chambers in liver where cells and blood have direct contact
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Breakdown of RBC’sOccurs in LiverPhagocytosisProtein portion broken down firstIron (Fe3+) gets recycled
◦Transported back to bone marrowOther parts are stored till reused or
metabolized
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Chapter 10Blood
·The only fluid tissue in the human body
·Classified as a connective tissue
· Living cells = formed elements
· Non-living matrix = plasma
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Blood Plasma· Composed of approximately 90 percent
water· Includes many dissolved substances
· Nutrients· Salts (metal ions)· Respiratory gases· Hormones· Proteins· Waste products
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Formed Elements· Erythrocytes = red blood cells
· Leukocytes = white blood cells
· Platelets = cell fragments
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Erythrocytes (Red Blood Cells)· The main function is to carry oxygen· Anatomy of circulating erythrocytes
· Biconcave disks· Essentially bags of hemoglobin· Anucleate (no nucleus)· Contain very few organelles
· Outnumber white blood cells 1000:1
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Hemoglobin· Iron-containing protein
· Binds strongly, but reversibly, to oxygen
· Each hemoglobin molecule has four oxygen binding sites
· Each erythrocyte has 250 million hemoglobin molecules
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Erythrocytes (Red Blood Cells)
· The main function is to carry oxygen· Anatomy of circulating erythrocytes
· Biconcave disks· Essentially bags of hemoglobin· Anucleate (no nucleus)· Contain very few organelles
· Outnumber white blood cells 1000:1
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Control of Erythrocyte Production
Slide 10.16Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
· Rate is controlled by a hormone (erythropoietin)
· Kidneys produce most erythropoietin as a response to reduced oxygen levels in the blood
· Homeostasis is maintained by negative feedback from blood oxygen levels
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Control of Erythrocyte Production
Slide 10.17Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 10.5
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Fate of Erythrocytes
Slide 10.15Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
· Unable to divide, grow, or synthesize proteins
· Wear out in 100 to 120 days
· When worn out, are eliminated by phagocytes in the spleen or liver
· Lost cells are replaced by division of hemocytoblasts
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Leukocytes (White Blood Cells)· Crucial in the body’s defense against
disease· These are complete cells, with a nucleus
and organelles· Able to move into and out of blood
vessels (diapedesis)· Can move by ameboid motion· Can respond to chemicals released by
damaged tissues
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Leukocyte Levels in the Blood
Slide 10.9Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
· Normal levels are between 4,000 and 11,000 cells per millimeter
· Abnormal leukocyte levels· Leukocytosis
· Above 11,000 leukocytes/ml· Generally indicates an infection
· Leukopenia· Abnormally low leukocyte level· Commonly caused by certain drugs
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Types of Leukocytes
Slide 10.10aCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
· Granulocytes· Granules in their
cytoplasm can be stained
· Include neutrophils, eosinophils, and basophils
Figure 10.4
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Types of Leukocytes
Slide 10.10bCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
· Agranulocytes· Lack visible
cytoplasmic granules
· Include lymphocytes and monocytes
Figure 10.4
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Platelets· Derived from ruptured multinucleate cells (megakaryocytes)
· Needed for the clotting process
· Normal platelet count = 300,000/mm3
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Hemostasis
Slide 10.18Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
· Stoppage of blood flow
· Result of a break in a blood vessel
· Hemostasis involves three phases· Platelet plug formation
· Vascular spasms
· Coagulation
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Platelet Plug Formation
Slide 10.19Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
· Collagen fibers are exposed by a break in a blood vessel
· Platelets become “sticky” and cling to fibers
· Anchored platelets release chemicals to attract more platelets
· Platelets pile up to form a platelet plug
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Vascular Spasms
Slide 10.20Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
· Anchored platelets release serotonin
· Serotonin causes blood vessel muscles to spasm
· Spasms narrow the blood vessel, decreasing blood loss
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Coagulation
Slide 10.21aCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
· Injured tissues release thromboplastin
· PF3 (a phospholipid) interacts with thromboplastin, blood protein clotting factors, and calcium ions to trigger a clotting cascade
· Prothrombin activator converts prothrombin to thrombin (an enzyme)
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Coagulation
Slide 10.21bCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
· Thrombin joins fibrinogen proteins into hair-like fibrin
· Fibrin forms a meshwork (the basis for a clot)
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Blood Clotting
Slide 10.22Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
· Blood usually clots within 3 to 6 minutes
· The clot remains as endothelium regenerates
· The clot is broken down after tissue repair
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Undesirable Clotting
Slide 10.23Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
· Thrombus· A clot in an unbroken blood vessel
· Can be deadly in areas like the heart
· Embolus· A thrombus that breaks away and floats
freely in the bloodstream
· Can later clog vessels in critical areas such as the brain
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Bleeding Disorders
Slide 10.24Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
· Thrombocytopenia· Platelet deficiency
· Even normal movements can cause bleeding from small blood vessels that require platelets for clotting
· Hemophilia· Hereditary bleeding disorder
· Normal clotting factors are missing
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Heart DiseaseAtherosclerosis
◦Formed from fatty acid deposits that build-upPlatelets collect on outer surface
◦Release clotting factor, causes blood clot Thrombus If breaks free, embolus
◦Stroke, mycardial infarction, cononary thrombus
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Causes of Heart DiseaseAgeGenetic FactorsHypertensionSmokingDiet