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Cardiovascular system
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How does the structure of the heart allow it to function in pumping blood?
Essential Question:
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Function?
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Location of Heart
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Heart coverings
double sac of serous membrane pericardium• visceral pericardium (epicardium)
hugs external heart surfacepart of heart wall
• parietal pericardium anchors heart to surrounding structures• filled with serous fluid why?• pericarditis inflammation of pericardium
decrease in serous fluidlayers stick togetherpainful
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Walls of heart• epicardium
outer most layervisceral pericardiumconnective tissue
• myocardiummiddle layermostly cardiac muscle
• endocardiumlines heart cavitiesepithelial tissue
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Chambers of the heart
atria
• receiving chambers
ventricles• pumping chambers
interventricular septum divides right side from left side
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Heart external structure
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Pulmonary circulation
from right side of heart (rightventricle), to pulmonary arteries, to lungs, to pulmonary veins andthen back to left side of heart (left atrium)
function gas exchangeget rid of carbon dioxidepick up oxygen
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systemic circulation
from left ventricle, to aorta, to arteries,to body tissues (capillaries), to veins, to inferior and superior vena cavas, to right atrium
function: brings oxygen to tissuespicks up wastes
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Heart Valvesfunction one way flow of bloodAtrioventricular valves:tricuspid valve between right atrium and right ventricle
Mitral (bicuspid valve) between left atrium and left ventricle
pulmonary semilunar valve between right ventricle and pulmonary trunk
aortic semilunar valve between left ventricle and aorta
http://www.medicinenet.com/heart_valve_disease/article.htm
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Chordinae tendinae "heart strings that anchor the valves
each set of valves works at different times.
Incompetent valve valve does not close properly, blood back flows
valvular stenosis valve flap becomes stiff can be due to repeated bacterial infectionsforces heart to contract more vigorously
Treatment: Valve replacement
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Cardiac Circulationcoronary arteries feed heart muscle with nutrientscardiac veins drain heart musclecoronary sinus vein that empties into right atrium
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Problems with blood flow to heart muscle
angina pectoris chest pain due to lack of oxygen to cardiac muscle
Myocardial infarction = heart attack or coronary
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Conduction System of Heart
pumps 6 quarts of blood/ 1000 times per day cardiac muscle can contract spontaneously, not needing a nerve
impulsecontraction occur regularlyatrial cells beat 60 times/minuteventricular cells beat 2040 times/minute
So how do they beat at the same time?
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two controlling systems:
1. nerves from autonomic nervous systemaccelerate or slow heart rate
2. Intrinsic conduction system (nodal system)built in heart tissueregulates at ~75 beats/minute
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Intrinsic conduction system
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sinoatrial node (SA) located in right atrium= Pacemaker
atrioventricular node (AV) located at junction of right atrium and right ventricle
atrioventricular bundle (bundle of His)
bundle branches located in interventricular septum
Purkinje fibers muscle of ventricle walls
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Problems with heart conduction:
1. heart block damage to AV node, causes ventricles to beat at own rate (slower)
2. damage to SA node slower heart rateinstall artificial pacemaker inserted
3. ischemia lack of blood supply to heart muscle leads to fibrillation rapid uncoordinated contractions(looks like a bag of worms)heart cannot pumptreatment defibrillator
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4. tachycardia rapid heart rate, over 100 beats/minprolonged could lead to fibrillation
5. bradycardia slower than normal heart rate <60 beats/min
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Cardiac cycle and heart soundsSystole heart contractiondiastole heart relaxation
cardiac cycle = one complete heartbeat when both atria and ventricles contract and relax 0.8 seconds/ cycle based on 75 beats/min
heart sounds:"lub dup" lub = AV valves closing dup = semilunar valves closing
Heart murmur = abnormal sounds, caused by valve problem
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Cardiac events
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Cardiac output
= amount of blood pumped out by each side of the heart in 1 minute
= heart rate X stroke volume
stroke volume = volume of blood pumped out by a ventricle per heartbeat
ex. cardiac output = 75 beats/min X 70 ml/beat = 5250 ml/min
therefore: the entire amount of blood in your body passes through your body per minute
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regulation of stroke volume
normally pump 60% of blood in ventricles
regulated by:1. the stretching ability of the heart muscle before
contractionmore stretched = stronger contraction
2. amount of venous return to heart more blood = more stretching
if volume or speed increased = higher stroke volume
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regulation of heart rate
regulated by autonomic nervous system sympathetic division increases heart rate parasympathetic = decreases heart rate
epinephrine, thyroxine hormones that increase heart rate
also affected by age, gender, exercise, body tempfemales 7280 beats/minmales 6472 beats/min
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regulation of cardiac output
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congestive heart failure heart is "worn out" heart is weakprogressive conditioncause atherosclerosis, high blood pressure, myocardial
infarctstreatment = digitalis slows and steadies the heart rhythm
Pulmonary congestion if left heart fails, right side still pumps blood to lungs
blood vessels in lungs swellfluid leaks into lung air spaces pulmonary edemaif untreatedsuffocation
Peripheral congestion right side failsedema in distal parts of body puts strain on heart heart fails
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Blood Vessels What are the differences?
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Artery vs. Vein
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Tunics
1. tunica interna lines the lumen (interior of vessel)endothelium on connective tissuehelps decrease friction
2. tunica media middle coatsmooth muscle, elastic tissueif constrict blood pressure increasesif dilate blood pressure decreases
3. tunica externaoutermost tunicfibrous connective tissuesupports and protects vessels
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Structural Differences between Arteries, Veins, and Capillaries
Arteries Veinsthick tunica media thin tunic media
smaller lumen larger lumen
no valves has valves
close to heart in terms of far from heart in terms of circulation circulation
high pressure low pressure
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Ways blood gets back to heart against gravity
1. valves in veins
2. "milking" by skeletal muscles
3. larger lumen for more blood carrying capacity
4. pressure when we inhale fills veins near heart
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Capillaries
one cell thick tunica interna only
form networks called capillary beds
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Problems with blood vessels
varicose veins cause standing for long periods, obese, pregnancyinefficient venous returnblood poolsvalves do not workveins get twisted and dilated
thrombophlebitis inflammation of a vein that results in clot
pulmonary embolism clot that breaks and goes to lung
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Arteries
moves blood away from heart
"most" carry oxygenated bloodexceptions:
pulmonary arteriesumbilical arteries
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Veins
bring blood to the heart
"most" carry deoxygenated bloodexceptions:
pulmonary veinsumbilical vein
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Special Circulations
1. The brain
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Brain fed by carotids and vertebral arteriesinternal carotid arteries enter skull through temporal bonevertebral arteries enter back of brain and then becomes basilar artery
Circle of Willisbasilar and internal carotids connected by communicating arteriespurpose protects brain
provides alternate route for blood flow if clot or imparied blood flow
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2. Hepatic Portal circulation circulation of digestive organs
drains digestive organs, spleen, and pancreas and deliver to liver viahepatic portal vein
liver processes nutrients from dig. system then goes to inf. vena cava
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3. fetal circulation
all nutrients, excretory and gas exchange through placenta
umbilical vein blood rich with oxygen
2 umbilical arteries oxygen poor
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ductus venosus vessel that bypasses liver
foramen ovule hole between left and right atrium
ductus arteriosus connects aorta and pulmonary trunk (bypasses lungs)
ligmentum arteriosum collapsed ductus arteriosus after birth
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Physiology of circulation
pulse = alternating expansion and recoil of an artery
pulse rate = heart rate
pulse points are also pressure points points where put pressure to stop bleeding
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Blood pressure= the pressure the blood exerts against the inner walls of the blood vessels
keeps blood circulating
= mean pressure within the large systemic arteries
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Blood pressure in various areas of the cardiovascular system
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measuring blood pressure
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Effects of various factors on Blood pressure
1. peripheral resistance amount of friction by blood when it flows
if vessel is narrow increase in resistance if blood is viscous increase if blood volume increases increase
a. neural factors autonomic nervous systemparasympathetic NS no effectsympathetic NS vasoconstricts blood vessels increases
blood pressureex. when getting up suddenly from lying down b.p. initially drops, get vasoconstriction to bring b.p. backup
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b. renal factors: kidneyalters blood volume to regulate arterial pressureIf b.p. too high kidneys release more urine (water from the
bloodstream) excretedif b.p. too low kidneys retain water if b.p. too low kidney releases renin that helps form
angiotensin II vasoconstrictor
c. temperaturecold = vasoconstriction heat vasodilating
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d. chemicals epinephrine increases heart rate and b.p.nicotine increases b.p. by vasoconstriction alcohol/ histamine vasodilation, decrease b.p.
e. diet low salt, low saturated fats, low cholesterol prevents
hypertension (high b.p.)
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Problems with blood pressurenormal blood pressure: systolic 110140 mm Hg diastolic 7580 mm Hg
1. Hypotension = low blood pressuresystolic below 100 mm Hg athletes may have this, not a real problem
orthostatic hypotension elderly condition dizziness when getting up from reclining or lying down
chronic hypotension can indicate poor nutrition, low levels of blood proteins
circulatory shock blood vessels are not filled with enough blood and cannot circulate normally, cause is blood loss
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2. Hypertension high blood pressure"The Silent Killer"140/90 or higher makes heart overwork can cause small tears in blood vessels (accelerate
artherosclerosis) factors that affect blood pressure: diet, obesity, heredity, race,
stress
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Capillary exchange
diffusion through interstitial fluid
4 methods of transport
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bulk fluid exchange depends on hydrostatic pressure
pressure high on arterial end pressure low on venous endhigh low
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Artherosclerosis
damaging process of blood vessel wallsSteps: 1. damage to tunica interna2. platelets initiate clotting3. immune system and inflammatory process repair damage4. repeated damage5. increase in permeability to fatsand cholesterol that sits under tunica interna6. causes narrowing7. arteriosclerosis end stage, lose elasticity, get scar tissue
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What can be done?
1. balloon angioplasty
2. stent implantation
3. clot busting medicines
4. cholesterol lowering medicationsLipitor, Crestor, etc.
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Developmental Aspects fourth week heart is pumping 4th 7th week heart develops 4 chambers after birth bypass structures become blocked becomes more powerful and efficient if exercise as age get:
varicose veinsartherosclerosishypertension
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