The Cardiovascular System: The Heart The Cardiovascular System: The Heart 12.
The Heart
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Transcript of The Heart
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The Heart
Anatomy and Physiology
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Cardiovascular System (Overview) Heart beats over 100,000 times a
each day Pumps a total of 8000 liters of blood Closed System Pulmonary Circuit/ Systemic Circuit Works with the respiratory system
and blood for the delivery of oxygen and nutrients and removal of waste
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Vessels Arteries (Efferent): Blood Away
Most cases oxygen rich Veins (Afferent): Blood Toward
Most cases oxygen poor Capillaries: vessels in between/
exchange vessels. Gas exchange: Semi-permeable
membrane
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Anatomy of the Heart Four Chambers Upper Chambers
Atrium (Atria) Lower Chambers
Ventricles• Position within the thorax
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Thoracic Location Anterior Chest/ Posterior to the
sternum Lies slightly to the left of the midline Sits at an angle Rotated toward the left side Surrounded by the pericardial cavity
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Pericardium Fist into the center of a balloon Subdivided: Visceral and Parietal Pericardial Sac: 10-20 ml of
pericardial fluid Secreted by the pericardial
membranes Lubricant Pericarditis
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Superficial Anatomy of the Heart Atria, the top chambers: Auricle Grooves
Coronary Sulcus Anterior interventricular sulcus Posterior interventricular sulcus Fat Deposits for cushion Base and Apex
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Internal Anatomy Interatrial Septum Interventricular Septum Atrioventricular Valves
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Right Atrium Blood Received from Superior Vena
Cava (SVC) and Inferior Vena Cava (IVC)
Coronary Sinus also returns blood to the heart
Foramen Ovale: Oval window that connects atria during the time when fetus in the uterus. Closes after birth
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Right Ventricle Cusps (Tricuspid): An AV Valve Connected by the Chordae Tendineae to
the papillary muscles Allows for the doors to swing open, but
only in one direction Pulmonary Trunk, Pulmonary Semi-Lunar
valves. Into Pulmonary Arteries (left and right)
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Left Atrium Blood returning from the lungs Four Pulmonary Veins Pools in the atria Through the Mitral Valve (bicuspid)
AV Valve
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Left Ventricle Pumps at great pressure, systemic
circulation Aortic Semi-Lunar Valve Aortic Arch Descending Aorta Pulmonary Trunk is attached to the Aortic
Arch by the Ligamentum Arteriosum Aortic Rupture/Aortic Stenosis
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Structural Difference Left Ventricle Large, must push
harder Six to seven times
as much force Thicker wall When it pumps it
bulges into the right ventricle
Right Ventricle Smaller, less
pressure Assisted by the left
ventricle as both ventricles pump at the same time
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Closer Look at the Valves AV Valves
Prevents backflow into atria During vent relax, loose, valves open Vents contract, valves close
Semi-Lunar Valves Prevents backflow into vents Support each other like legs of a tripod MVP Rheumatic Fever
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The Heart Wall Three Layers
Epicardium Myocardium Endocardium
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Cardiac Muscle Tissue Muscle cells are intercalated discs Calcium plays a role Automaticity Smaller than typical skeletal muscle
cell
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Blood Supply to Heart Myocardium needs blood Sensitive to low blood supply Coronary Circulation Right Coronary Artery
Rt Atrium Portions of both vent SA and AV nodes Posterior interventricular branch
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Blood supply (cont) Left Coronary Artery
Lt atrium, Lt vent, Intervent septum Gives rise to circumflex branch and
anterior interventricular branch Cardiac Veins
Coronary Sinus Posterior and middle cardiac veins Small cardiac veins, anterior cardiac
veins
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Innervation of the Heart Cardiac centers of the medulla Cardioacceleratory Center Cardioinhibitory Center Vagus Nerve Baroreceptors and Chemoreceptors
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Conduction System Sinoatrial Node (SA) Atrioventricular Node (AV) Internodal pathways (Bundle
Branches: Bundle of His) Purkinje Fibers
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SA Node Pacemaker Cells 50 msec from SA to AV Stimulates rt and lt atria Action spreads through cell to cell
contact
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AV Node Less efficient pathways 100 msec Junction as a pausing location Important so that the atria
depolarize before the ventricles
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AV Bundle and Bundle Branches Only electrical connection between
atria and ventricles Left bundle branch serves left
ventricle Conduct the impulse to the purkinje
fibers Purkinje rapidly fire
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ECG or EKG P wave QRS Complex T wave P-R Interval (no more than .2 sec) Q-T Interval Rate/Rhythm ST Segment
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Heart Attacks Myocardial Infarction (MI) Coronary Thrombosis Cardiac Enzymes
Lactate Dehydrogenase (LDH) Serum Glutamic Transaminase (SGOT) Creatine Phosphokinase (CPK) CPK-MB: Special CPK in cardiac muscle
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Cardiac Cycle The period between start of one heart
beat and the next is a single cardiac cycle Contractions/Relaxations Systole (Contraction) Pump Diastole (Relaxation) Fill Fluid moves from high to low pressure Atrial and ventricular systole not at same
time
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Phases Atrial Systole (Beginning) 100 msec Blood pushed through AV valves Ventricles already 70% full, Atria tops off
(70% is passive from previous cardiac cycle)
At end of Atrial Systole, vents have max blood: End Diastolic Volume (130ml)
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Phases (Cont) Ventricular Systole 270 msec Vent contract at first it is isovolumetric
contraction all heart valves closed, no blood flow yet
As pressure increases, semilunar valves open (ventricular ejection)
Pressures slowly decline, before the valves close, blood returns to vents
Stroke volume 80 ml (60%) of EDV End-Systolic pressure 50 ml 40% of EDV
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Phases (Cont) Ventricular Diastole 430 msec All valves close Vent myocardium resting Vent pressure is higher than atrial blood
cannot flow to vents This is isovolumetric relaxation Vent pressures drop, event atrial pressure
is higher, the AV valves open
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Heart Sounds Ausculation Four Sounds (S1-S4) S1 Lubb: Start of Vent contraction,
AV valves close S2: Dupp: vent filling, semi-lunar
valves close S3-S4 harder to hear: Blood flowing
into vents and atrial contraction
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Cardiodynamics Movements and forces generated
during cardiac contractions EDV, ESV, SV, and Ejection Fraction
(which is percentage of the EDV represented by SV)
SV most important CO (Cardiac Ouput) CO= SV x HR (80 ml x 75= 6 l/m)
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Factors controlling SV EDV (filling time and venous return) ESV three factors
Preload degree of stretching during vent diastole: stretching of muscle: At rest not a lot, during exercise it increases• More in More Out: Frank-Starling Principle
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Factors controlling SV (cont) ESV Factor two
Contractility: amount of force at contraction. Some cause increase contractility (CA entry for example) Some cause decrease (CA blocking)
Generally three things control it Autonomic Activity (epi and norepi, or Ach decreasing SA and AV nodes) Hormones: Epi/Norepi/ Glucagon (+), Thyroid (+) Ions: Calcium (hyper +/hypo -), Potassium (hyper weak contractions/hypo rate decreases)
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Factors controlling SV (Cont) ESV Factor Three
Afterload: amount of tension the contracting ventricle must produce to force open semilunar valves
As afterload increases, stroke volume decreases
Heart failure and increase in PVR
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Factors Affecting HR What can affect this? Brady and Tachy Autonomic Innervation: Ach and NE Ach for example opens K channels slows
rate of depolarization, decline in HR NE release increase rate by open CA
channels All happening at the SA
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Factors Affecting HR (Cont) Hormones Epi, Norepi, Thyroid increase
contractility thus increase HR Changes in Ions (earlier discussed) Changes in Body Temp: decrease
temp, decrease HR, Increase temp, increase HR
Open Heart Surgery, chilly room
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HR and B/P Palpated where arteries are close to
bones: Radial, Brachial, Carotid, Femoral
B/P Systolic/Diastolic 120/80 Measured in mm of Hg B/P Cuff/ Placement Lab