MGEM2019 Flashcards
Which heart valve has only 2 cusps?
How many cusps semilunar valves have?
Mitral/bicuspid valve
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semilunar valves 3 cusps
mitral valve is potentially at a greater risk of pathology due to the fact there is a better seal/closure between three cusps than there is between two cusps.
Which part of the heart lies directly behind the sternum?
Right ventricle
As the heart forms it twists round so that the right ventricle comes to lie directly behind the sternum. The left ventricle is pushed further to the left, while the two atria are located more posteriorly and are not directly facing the sternum.
Which of these vessels is not an arterial branch arising directly from the abdominal aorta?
Inferior mesenteric artery
Coeliac trunk
Superior mesenteric artery
Common iliac artery
Internal iliac artery
Internal iliac artery
internal iliac artery: this arterial branch arises directly from the common iliac artery rather than from the abdominal aorta. All of the others start directly from the abdominal aorta.
Diagonal branch arise from which branch of left coronary artery?
anterior interventricular artery
Diagonal branch arises from the anterior interventricular branch/artery (itself a branch of the left coronary artery) and provides oxygenated blood to part of the left ventricular wall.
The coronary sinus drains into which structure?
Right atrium
coronary sinus opens into the right atrium, not far from the opening for the inferior vena cava. This allows all of the blood that had been distributed to the myocardium by the coronary arteries to then return back to the right atrium along with venous blood from the rest of the body. The coronary sinus is formed from a number of cardiac veins.
Name the main branches of left & right coronary artery?
Left coronary artery: bifurcate into circumflex branch (from which left marginal branch arise) & anterior interventricular branch (from which diagonal branch arise)
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Right coronary artery: sinoatrial nodal branch, posterior interventricular branch & right marginal branch
relate surface anatomy of heart to the correct placement of a stethoscope for auscultation of heart
Describe normal heart sounds, how they are generated, and where one should listen for them
Describe common causes of heart murmurs, such as valvular heart disease & septal defects
Describe the point(s) in the cardiac cycle where murmurs associated with different forms of cardiac disease would be heard
aortic valve: right edge of sternum at 2nd intercostal space
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pulmonary valve: left edge of sternum at 2nd intercostal space
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bicuspid/mitral valve: 5th intercostal space at left mid-clavicular line
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tricuspid valve: 4th/5th intercostal space at left edge of sternum
inflamm heart disease
Recap fundamental immunology & virology concepts to allow complete comprehension of pathophysiology involved in inflammatory heart disease
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To describe the differences between the 3 types of inflammatory heart disease; endocarditis, myocarditis & pericarditis. & explain the aetiology of each condition
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To understand the infective molecular & immunological mechanisms responsible for acute & chronic presentations of inflammatory heart disease, particularly myocarditis
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To link pathophysiology to testing, diagnosis, treatment and/or management of endocarditis, myocarditis & pericarditis
Describe the gross structure of the heart (atria, ventricles, valves, major afferent and efferent blood vessels)
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& relate these to the function of the organ
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Describe the relationship between the closure of the heart valves and normal heart sounds
Atria: Upper chambers -pump blood to ventricle
Ventricles: Lower chambers -pump blood to lungs/rest of body
Veins: return blood from tissues to atria
Arteries: carry blood away from ventricles to tissues
Septum: Muscular partition that separates left & right sides of heart
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AV valves:
left =bicuspid/mitral =2 cusps
right=tricuspid =3 cusps
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semilunar:
pulmonary & aortic valves =3 cusps
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AV valves close at start of ventricular systole/contraction (semilunar valve open), turbulent blood flow & the wobble/vibration of fibrous tissue around the valves cause 1st heart sound (S1 or “lub”)
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semilunar valves close at start of diastole (AV valve just opened), same factors cause 2nd heart sound (S2 or “dub”)
Describe the coronary circulation & the role of major coronary arteries and their branches in supplying various parts of the heart with oxygenated blood
coronary arteries originate at base of 2 cusps of aortic valve, meaning that when aortic valve is open (i.e. when left ventricle pumping blood into aorta), blood flow into coronary arteries is not good. Coronary blood flow (especially to left coronary artery) is highest in diastole - during diastole, the increased aortic pressure above the valves forces blood into coronary arteries & thence into the musculature of heart
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Left coronary artery: bifurcate into circumflex branch (from which left marginal branch arise) & anterior interventricular branch (from which diagonal branch arise)
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Right coronary artery: sinoatrial nodal branch, posterior interventricular branch & right marginal branch
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circumflex branch supply Left atrium & most of Left ventricle, SA node (40%), AV node (20%), Posterior. InterVentricular artery (34%)
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Anterior interventricular artery (=Left anterior descending artery/LAD) supply Anterior 2/3rd of IV septum including AV node, bundle of His & bundle branches. Papillary muscle of tricuspid & mitral valves. Anterior wall of Left ventricle & apex
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Right coronary artery supply R atrium & R ventricle, Papillary muscles of tricuspid valve, AV node (80%)
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Sinoatrial node artery supplies SA node & pulmonary trunk
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Right marginal artery supply R vent., inferior border of heart
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Posterior interventricular artery supply Posterior 1/3rd of IV septum & ventricles either side, Papillary muscle of mitral valve, Apex
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Deoxygenated blood is returned to the chambers of the heart via coronary veins; most of these converge to form coronary sinus (in inferior portion of Left AV groove), which drains into right atrium
Describe the histological structure of cardiac muscle cells & relate this to function of the cells as contractile tissue
Like skeletal muscle, cardiac muscle is STRIATED, as is composed of repeating sarcomeres
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thick filaments=myosin pulling thin filaments=actin towards centre of sarcomere, shorten H zone & I bands, thereby muscle contract
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cardiac myocytes are Branched cells linked together by intercalated disks (=high density of gap junctions) - they’re individual cells & communicate with each other via intercalated disks to contract simultaneously =behave like a functional syncytium. Disks also contain button-like * desmosomes =help hold cardiac myocyte together against mechanical stress
* gap junctions allow cells to communicate rapidly through transmembrane protein channels called connexons. Small ions can move freely from one cell to another through these pores forming an electrical connection that let action potentials spread.
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30-40% of cell volume =mitochondria - provide energy for contraction
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Transverse-tubule & sarcoplasmic reticulum ???
Why are cardiac muscle cells referred to as functional syncytium rather than true syncytium?
cardiac myocytes are Branched cells linked together by intercalated disks - although they can be polynucleate (up to 4 nuclei in 1 cell), they’re still individual cells which communicate with each other via intercalated disks to contract simultaneously, so behave like a syncytium. thus they’re functional syncytium not true syncytium (=multiple cells fuse together, polynucleate & form a mass)
Describe the normal pattern of excitation of the heart & the action potentials of cells
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Describe the cardiac cycle, relating contractile events to heart sounds
Autorhythmic cells of heart initiate & conduct AP
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SAN spontaneously fire AP at ~100 beats per minute (parasympathetic innervation reduce it to resting HR)
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From SAN in right atrium wall, electrical impulse (=depolarisation) spreads across to left atrium, and down to Atrioventricular node
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After a slight AVN nodal delay (~100 msec) to allow time for complete ventricular filling, depolarisation spreads down the conducting system of heart to apex/ventricles.
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contractile myocyte: (25-40 bpm, Na+ FAST channel, then Ca2+ SLOW channel)
* Summit phase: Stimulated by AP initiated by SAN, voltage-gated Na channel open, Sodium into cell cause depolarisation, Na channel become inactivate at positive memb potential ~40mV
* Plummet phase: Voltage-gated K channel open, exit cell, inside cell more negative, MP plummet phase stop quickly as Ca channel open, Ca enter cell, trigger contraction
* Continue phase: K efflux hasn’t stopped & Ca enter cell, both positive ion, so MP doesn’t change=plateau
* Plummet phase: as Ca channel close at end of continue phase but K channel still open so repolarisation
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SAN/AVN autorhythmic cell: (60-100 bpm, Na+ & Ca2+ SLOW channels)
* Climb phase: Ca enter cell =depolarisation reach threshold/MP peak
* Plummet phase: K channel open
* Back to pacemaker potential (gradual MP increase), never go down to resting potential (=AP curve never goes flat)
Describe the cardiac cycle, relating contractile events to heart sounds
Ventricular AP:
Fast ventricle depolarization =QRS complex due to inward Na+ current.
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Plateau (continue phase) =ST segment
Except for a small early repolarization (a brief transient outward current), during most of the plateau phase only SLOW voltage changes occur, due to balancing of small inward (Na & Ca) & outward K+ currents
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fast repolarization= T wave, primarily from outward K+ currents, both K+ fast & slow channel
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R wave =start of ventricular systole - S1 sound
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end of T wave =start of diastole - S2 sound
Explain the relationship between the excitation pattern of the heart & the electrocardiogram, as recorded by Lead II.
P wave = Atrial depolarisation
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QRS Complex = Ventricular depolarisation & atrial repolarisation
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T wave = Ventricular repolarisation
