Cardiac anatomy and physiology
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Transcript of Cardiac anatomy and physiology
Cardiac Anatomy and Physiology
Iris Ken R. Rico, OTRPLecturer
OUTLINE: Introduction Functions of the Heart Size, Form, and Location of the Heart Anatomy of the Heart
Pericardium External Anatomy Heart Chambers and Internal Anatomy
Right and Left AtriaRight and Left Ventricles
Heart ValvesAtrioventricular valves
• Tricupsid valve• Mitral valve
Semi-lunar valves• Aortic valve• Pulmonic valve
Route of Blood Flow Through the Heart Blood Supply to the Heart
Histology of the Heart Heart Wall Cardiac Muscle
Electrical Activity of the Heart Action Potentials in Cardiac Muscle Conduction System of the Heart Electrocardiogram
Cardiac Cycle Heart sounds Regulation of Heart Function
Intrinsic Regulation of the Heart Extrinsic Regulation of the Heart
Control of the Heart by Sympathetic and Parasympathetic Nerves Excitation of the Heart by Sympathetic Nerves Parasympathetic (Vagal) Stimulation of the Heart
Effect of Potassium and calcium Ions on heart Function Effect of Potassium Ions Effect of Calcium Ions
Effect of Temperature on Heart Function Systems Pathology
Effects of Aging on the Heart
FUNCTIONS OF THE HEART
Generating blood pressure.Routing blood.Ensuring one-way blood flow.Regulating blood supply.
SIZE, FORM, AND LOCATION OF THE
HEART
Blunt cone and size of a closed fist> age 65 LocationMediastinum = heart, trachea, esophagusKnowledge on the shape and location of the heart Lies obliquely in the mediastinum, with its base directed
posteriorly and slightly superiorly and the apex directed anteriorly and slightly inferiorly
Apex = directed to the left, approximately 2/3 pf the heart’s mass, lies left of the midline of the sternum, deep to the left 5th ICS, approximately 7-9 cm to the left of the sternum near the midclavicular line
Base = located deep to the sternum and extends to the level of the 2nd ICS
Size/dimensionsAt rest and during exercise
ANATOMY OF THE HEART
Pericardium
Pericardial cavityPericardium or pericardial sac
Two layers:Fibrous pericardiumSerous pericardium
Parietal pericardium Visceral pericardium or Epicardium Pericardial fluid
External Anatomy
Atria (R/L)Ventricles Coronary sulcusAnterior ventricular sulcusPosterior interventicular sulcus6 veins that carry blood to the heartPulmonary trunk and aorta
Heart Chambers and Internal Anatomy
Right (pulmonic) pump: circulates blood to the lungs
Left (systemic) pump: circulates blood to the body
Right Atrium
Thin muscle wallMost blood flow into the right atrium during
inspiration when RA pressure drops below that in IVC and SVC (higher to lower pressure)
High flow; low pressure systemFunction: Receives unoxygenated blood from
the venous systemInflow: Superior and inferior vena cavaOutflow: Tricuspid valve
Left Atrium
Slightly thicker than the right atriumBreathing does not affect fillingFunction: Receives oxygenated blood from the
lungsInflow: 4 Pulmonic veinsOutflow: Mitral (Bicuspid) valveNormal filling pressure: 4-12mmHg
Right Ventricle
Function: Delivers unoxygenated blood to the lungs
Inflow: Tricuspid valveOutflow: Pulmonic valveFour muscular bands:
Infundibulum septumParietal bandSeptal bandModerator band
Normal systolic pressure: 15– 28mmHgEnd diastolic pressure: 0-8mmHg
Left Ventricle
Function: Delivers oxygenated blood to the body
Inflow: Mitral valveOutflow: Aortic valveNormal systolic pressure: 120mmHg (100-140)End diastolic pressure: 4-12mmHg
Cardiac Skeleton
Anulus fibrosus – firm anchor to which most of the heart’s muscles and valves are attachedGives structure to the heart and acts as an insulator
to ensure that electrical impulses move through the AV node and bundle only
Consists of tough fibrous rings surrounding the AV valves, and the bases of the aortic and the pulmonary trunks connected by the tendon of the conus
Heart Valves
Atrioventricular valveTricuspid valveBicuspid or mitral valve
Semilunar valveAortic valvePulmonary valve
Papillary muscles – contract when ventricle walls contractDo not help the valves to closePull vanes inward toward the ventricles to
prevent bulging too far backward toward the atria
Chordae tendinae – connect valve leaflet to papillary muscles in the ventricles
Route of Blood Flow through the
Heart
Blood Supply to the Heart
Coronary Arteries
Left coronary artery – originates from the left side of the aorta 3 branches:
Anterior interventricular artery – lies in the anterior interventricular sulcus
Circumflex artery – extends around the coronary sulcus on the left to the posterior surface of the heart
Left marginal artery – extends inferiorly along the
lateral wall of the left coronary artery
Right coronary artery – originates on the right side of the aorta and extends around the coronary sulcus on the right to the posterior interventricular sulcus
2 branches:Posterior interventricular artery – lies in the posterior
interventricular sulcusRight marginal artery – extends inferiorly along the
lateral wall of the right ventricleResting person – heart gives approximately 70%
of its oxygen
Cardiac Veins
Drain blood form the cardiac musclePathways nearly parallel to the coronary
arteries and most drain blood into the coronary sinus (large vein located within the coronary sulcus on the posterior aspect of the heart)
Some drain directly into the right atrium
HISTOLOGY OF THE HEART
Heart Wall
Epicardium or visceral pericardiumMyocardium Endocardium Trabeculae carnea
Cardiac Muscle
Cardiac muscle cell3 major types of cardiac muscle
Atrial muscleVentricular muscleExcitatory and conducive muscle fibers
Specialized fibers that contract only feebly because of few contractile fibrils
Physiologic Anatomy
ELECTRICAL ACTIVITY OF THE
HEART
Action Potentials in Cardiac Muscle
105 millivoltsAfter the initial spike, the membrane remains
depolarized for about ___ second in atrial muscle and ____ second in ventricular muscle exhibiting a plateau followed by repolarization
Depolarization phaseEarly repolarization phasePlateau phaseFinal repolarization phase
What causes the long action potential and plateau?
2 types of channelsFast sodium channelsSlow calcium channels
Immediately after the onset of action potential, permeability of cardiac muscle for potassium ions decreases about fivefold
Conduction System of the Heart
Sinoatrial nodeAtrioventricular nodeAtrioventricular bundleRight and left bundle branchesPurkinje fibers
Sinoatrial node
Pacemaker of the Heart Is a small flattened, ellipsoidal strip of specialized
muscle about ___ millimeters wide, ___millimeters long, and ___ millimeter thick
Located in the superior posterolateral wall of the right atrium immediately below and slightly lateral to the opening of the SVC
Generates the normal rhythmical impulseSinus nodal fibers connect directly with the atrial
muscle fibersEctopic pacemaker Stokes-Adam syndrome
Atrioventricular node
Located in the posterior wall of the right atrium immediately behind the tricuspid valve and adjacent opening of the coronary sinus
Delay transmission of impulse from atria to ventricles to allow time for atria to empty their blood into the ventricles before ventricular contraction begins
Discharge at an intrinsic rhythmical rate
Atrioventricular bundle
Composed of multiple small fascicles passing through the fibrous tissue separating the atria from the ventricles
Delay from A-V node to bundle is about 0.13 second
Right and left bundle branches
Purkinje fibers
Very large fibersTransmit velocity about 6 times that in usual
ventricular muscle and 150 times that in some A-V nodal fibers
Rapid transmission of action potentialDischarge at an intrinsic rhythmical rate
Electrocardiogram
Recording device that detect the small electrical changes resulting form the action potentials in all of the cardiac muscle cells
Normal ECG consists of:
P waveAtrial depolarization
QRS complexVentricular depolarization
T waveVentricular repolarization
PQ/PR interval – beginning of the P wave and beginning of QRS complexAtria contract and begin to relaxEnd – ventricle begin to depolarizeNormal PQ interval is 0.16 second sometimes called
the PR interval cause the Q wave is frequently absentQT interval – beginning of the QRS complex to the
end of the T waveRepresents the length of time required for ventricular
depolarization and repolarization0.35 second
CARDIAC CYCLE
Beginning of one heartbeat to the beginning of the next beat
Includes systole, diastole, and a short pause called diastasis cordis
Duration depends on heart rateEntire heart rests for 0.4 seconds
Components of cardiac event:
Ventricular systoleIsometric contraction phaseRapid ejection phaseSlow ejection phase
Ventricular diastoleIsometric interval phaseAtrial systole phaseSlow ventricular filling phaseRapid ventricular filling phase
Isometric contraction phase
• Isovolumetric contraction phase = all valves closed and no ejection of blood
• Beginning of ventricular contraction• Increase in pressure = AV close• Atria fills with blood• Tension is increasing in the muscle but no shortening of
the muscle fibers is occuring
Rapid ejection phase
• Left ventricular pressure exceeds 80mmHg and right ventricular pressure exceeds 8mmHg = aortic and pulmonic valves open
• Pouring of blood from atria to ventricles• 70% emptied during first third of ejection period
Slow ejection phase
• Remaining 30% of blood in the ventricle is emptied during 2/3 of ejection phase
Isometric interval phase
• A.K.A. - Isovolumetric interval phase• Relaxation phase and is the beginning of diastole• Ventricular pressure lower than in the aorta and
pulmonary artery = momentary backflow of blood and closure of semilunar valves (2nd heart sound)
• Ventricular pressure drops to 00mmHg
Rapid ventricular filling phase
• Ventricular pressure falls below atrial pressure = AV valves open, blood rushes rapidly from atria to ventricles
Slow ventricular filling phase
• Diastasis or the last part of diastole• Small amount drain from the lungs and peripheral
circulation into the atria and added to ventricles• Towards ends= depolarization of atria begins
Atrial systole phase
• Atrial contraction or atrial kick• 25% more blood to the ventricle during last phase of
ventricular systole
HEART SOUNDS
Stethoscope First heart sound – “Lubb”
Lower pitchOccurs at the beginning of ventricular systole
and results form closure of the AV valvesSecond heart sound - “Dub”
Occurs at the beginning of ventricular systole and results from closure of semilunar valves
Murmurs
REGULATION OF HEART FUNCTION
Cardiac output (CO) – volume of blood puped by either ventricle of the heart each minuteCO = SV x HR
Stroke volume (SV) – volume of blood pumped per ventricle each time the heart contracts
Heart rate – number of times the heart contracts each minute
Resting conditions – 72 beats/min , SV = 70 mL/beat, CO – 5040 mL/min
Athletes - higher SV and lower HR
4 Interrelated factors that govern cardiac output:
PreloadAfterloadContractilityHeart rate
Preload
Ventricular fillingInfluenced by the total volume of circulating blood> venous return > stretch of myocardial fibersFRANK-STARLING’S LAW = the greater the
myocardial stretch, the greater the force of contraction
Afterload
Resistance to ejection of bloodAmount of tension the ventricles must develop to
eject the blood through the semilunar valvesResistance against which the heart must pump the
blood to all parts of the bodyFactors causing higher that normal resistance:
• Systemic and pulmonary arterioles• Increased blood viscosity• Pulmonary valve stenosis
Contractility
Refers to changes in the force of myocardial contraction and is a function of the interaction between the contractile elements
Depends on:• Amount of contractile proteins• Presence of ATP and calcium• Sympathetic stimulation• Pharmacologic agents
Heart Rate
Influenced by many factors:• Exercise• Person’s physical size• Age• Gender differences• Hypotension and hypertension• ANS via sympathetic and parasympathetic branches
Extrinsic Regulation of the Heart
Refers to mechanisms external to the heart, such as either hormonal or nervous regulation
Baroreceptors Plays an important role in regulating the function of the heart Are stretch receptors that monitor pressure in the aorta and in the wall
of the internal carotid arteries, which carry blood to the brain Changes in blood pressure result in changes in the stretch of the walls
of the blood vessels leading to changes in the frequency of action potentials produced by baroreceptors
Chemoreceptors Emotions influence heart function by increasing sympathetic
stimulation of the heart in response to exercise, excitement, anxiety, or anger and by increasing parasympathetic stimulation in response to depression
Alterations in body fluid levels of cardon dioxide, pH, and ion concentrations, as well as changes in body temperature, influence heart function
Control of the Heart by Sympathetic and Parasympathetic Nerves
Excitation of the Heart by Sympathetic NervesStrong = increase heart rate from the normal 70
beats for minute to 180 to 200 and rarely 250 beats per minute
Increase force of contraction, increasing the volume of blood pumped and increasing the ejection pressure
Increases cardiac output tp twofold to threefold
Parasympathetic (Vagal) Stimulation of the HeartStrong = stop heartbeat for a few seconds, but
then the heart usually escapes and beats at a rate of 20 to 40 beats per minute, 40 % normal
Decrease the strength of heart contraction by 20 to 30%
Decrease heart rate rather than to decrease greatly the strength of heart contraction
Effect of Potassium and Calcium Ions on heart Function
Effect of Potassium IonsExcess potassiumLarge quantities = block conduction from atria
to ventricles through the A-V bundleElevation to only 8 to 12 mEq/L
Effect of Calcium IonsOpposite the effect of potassium ions
Effect of Temperature on Heart Function
Increased temperature = increased heart rateDecreased temperature = decreased heart rateNear death due to hypothermiaHeat Contractile strength = enhanced temporarily by
a moderate increase in temperature, but prolonged elevation exhausts metabolic system of the heart and causes weakness
EFFECTS OF AGING ON THE HEART
Gradual changes in functionAge 70 = decreases approximately 1/3 Hypertrophy of the left ventricle = increase pressure in
the aorta against which the left ventricle must pumpGreater amount time to contract and relax, decrease in
maximum heart rateChanges in connective tissue of the heart valves = less
flexible and calcium deposits develop Increased in cardiac arrhythmiasDevelopment of CAD and heart failureAerobic exercise
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