The heart Cardiovascular system
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Transcript of The heart Cardiovascular system
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The heartCardiovascular system
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Today’s goal
• Describe the gross anatomy of the human heart– Muscle layers– Chambers– membranes
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Heart AnatomyYou know this…
• Approximately the size of a fist• Location, location, location– In the mediastinum between second rib and fifth
intercostal space– On the superior surface of diaphragm– Two-thirds to the left of the midsternal line
• Enclosed in pericardium, a double-walled sac
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Figure 18.1a
Point ofmaximalintensity(PMI)
Diaphragm
(a)
Sternum2nd ribMidsternal line
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Figure 18.1c
(c)
Superiorvena cava
Left lung
AortaParietalpleura (cut)
Pericardium(cut)
Pulmonarytrunk
DiaphragmApex ofheart
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Pericardium
• Superficial fibrous pericardium• Protects, anchors, and prevents overfilling
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Pericardium
• Deep two-layered serous pericardium• See notes, October, 2012
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Figure 18.2
Fibrous pericardiumParietal layer ofserous pericardiumPericardial cavityEpicardium(visceral layerof serouspericardium)MyocardiumEndocardium
Pulmonarytrunk
Heart chamber
Heartwall
PericardiumMyocardium
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Layers of the Heart Wall1. Epicardium—visceral pericardium
-(layer of the serous pericardium)2. Myocardium – Spiral bundles of cardiac muscle cells
3. Endocardium is continuous with endothelial lining of blood vessels
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Figure 18.2
Fibrous pericardiumParietal layer ofserous pericardiumPericardial cavityEpicardium(visceral layerof serouspericardium)MyocardiumEndocardium
Pulmonarytrunk
Heart chamber
Heartwall
PericardiumMyocardium
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Figure 18.3
Cardiacmusclebundles
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Chambers
• Four chambers– Two atria• Separated internally by the septum
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Chambers
• Two ventricles– Separated by the interventricular septum– Anterior and posterior interventricular sulci mark
the position of the septum externally
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Figure 18.4b
(b) Anterior view
Brachiocephalic trunk
Superior vena cava
Right pulmonaryarteryAscending aortaPulmonary trunk
Right pulmonaryveins
Right atriumRight coronary artery(in coronary sulcus)Anterior cardiac veinRight ventricle
Right marginal artery
Small cardiac vein
Inferior vena cava
Left common carotidarteryLeft subclavian artery
Ligamentum arteriosumLeft pulmonary artery
Left pulmonary veins
Circumflex artery
Left coronary artery(in coronary sulcus)
Left ventricle
Great cardiac veinAnterior interventricularartery (in anteriorinterventricular sulcus)Apex
Aortic arch
Auricle ofleft atrium
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Atria: The Receiving Chambers
• Vessels entering right atrium– Superior vena cava – Inferior vena cava– Coronary sinus
• Vessels entering left atrium– Right and left pulmonary veins
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Ventricles: The Discharging Chambers
• Papillary muscles project into the ventricular cavities
• Vessel leaving the right ventricle– Pulmonary trunk
• Vessel leaving the left ventricle– Aorta
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Figure 18.4e
AortaLeft pulmonaryarteryLeft atriumLeft pulmonaryveins
Mitral (bicuspid)valve
Aortic valvePulmonary valveLeft ventricle
Papillary muscleInterventricularseptumEpicardiumMyocardiumEndocardium
(e) Frontal section
Superior vena cavaRight pulmonaryarteryPulmonary trunkRight atriumRight pulmonaryveinsFossa ovalisPectinate musclesTricuspid valveRight ventricle
Chordae tendineaeTrabeculae carneaeInferior vena cava
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Pathway of Blood Through the Heart • The heart is two side-by-side pumps
– Right side is the pump for the pulmonary circuit• Vessels that carry blood to and from the lungs
– Left side is the pump for the systemic circuit• Vessels that carry the blood to and from all body tissues
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Figure 18.5
Oxygen-rich,CO2-poor bloodOxygen-poor,CO2-rich blood
Capillary bedsof lungs wheregas exchangeoccurs
Capillary beds of allbody tissues wheregas exchange occurs
Pulmonary veinsPulmonary arteries
PulmonaryCircuit
SystemicCircuit
Aorta and branches
Left atrium
HeartLeft ventricleRight atrium
Right ventricle
Venae cavae
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Pathway of Blood Through the Heart
• Right atrium tricuspid valve right ventricle• Right ventricle pulmonary semilunar valve
pulmonary trunk pulmonary arteries lungs
PLAY Animation: Rotatable heart (sectioned)
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PLAY Animation: Rotatable heart (sectioned)
Pathway of Blood Through the Heart
• Lungs pulmonary veins left atrium• Left atrium bicuspid valve left ventricle• Left ventricle aortic semilunar valve aorta• Aorta systemic circulation
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1 Start with blood in the right atrium2 Start with blood in the pulmonary vein3. You pick!
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Pathway of Blood Through the HeartFun facts
• Equal V of blood are pumped through both circuits
• Pulmonary circuit is a short, low-pressure
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Pathway of Blood Through the Heart
• Systemic circuit blood encounters much more resistance in the long pathways
• Anatomy of the ventricles reflects these differences
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Figure 18.6
Rightventricle
Leftventricle
Interventricularseptum
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Coronary Circulation
• The functional blood supply to the heart muscle itself
• Arterial supply varies person to person!• Collateral routes provide additional routes for
blood delivery
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Coronary Circulation
• Arteries – Right – marginal– left coronary (in atrioventricular groove),
circumflex, and anterior interventricular arteries• Veins – Small cardiac, anterior cardiac, and great cardiac
veins
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Figure 18.7a
Rightventricle
Rightcoronaryartery
Rightatrium
Rightmarginalartery Posterior
interventricularartery
Anteriorinterventricularartery
Circumflexartery
Leftcoronaryartery
Aorta
Anastomosis(junction ofvessels)
Leftventricle
Superiorvena cava
(a) The major coronary arteries
Left atrium
Pulmonarytrunk
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Figure 18.7b
Superiorvena cava
Anteriorcardiacveins
Small cardiac veinMiddle cardiac vein
GreatcardiacveinCoronarysinus
(b) The major cardiac veins
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Figure 18.4d
(d) Posterior surface view
AortaLeft pulmonaryarteryLeft pulmonaryveinsAuricle of leftatriumLeft atriumGreat cardiacveinPosterior veinof left ventricleLeft ventricle
Apex
Superior vena cavaRight pulmonary arteryRight pulmonary veins
Right atrium
Inferior vena cava
Right coronary artery(in coronary sulcus)
Coronary sinus
Posteriorinterventricularartery (in posteriorinterventricular sulcus)Middle cardiac veinRight ventricle
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Homeostatic Imbalances
• Angina pectoris– Thoracic pain caused by a fleeting deficiency in
blood delivery to the myocardium– Cells are weakened
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Homeostatic Imbalances
• Myocardial infarction (heart attack)– Prolonged coronary blockage– Areas of cell death are repaired with noncontractile scar tissue
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Heart Valves
• Ensure unidirectional blood flow through the heart• Atrioventricular (AV) valves– Prevent backflow into the atria when ventricles contract– Tricuspid valve (right)– Mitral valve (left)
• Chordae tendineae anchor AV valve cusps to papillary muscles
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Heart Valves
• Semilunar (SL) valves– Prevent backflow into the ventricles when
ventricles relax– Aortic semilunar valve– Pulmonary semilunar valve
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Figure 18.8a
Pulmonary valveAortic valveArea of cutaway
Mitral valveTricuspid valve
Myocardium
Tricuspid(right atrioventricular)valveMitral(left atrioventricular)valveAorticvalve
Pulmonaryvalve
(b)
Pulmonary valveAortic valveArea of cutawayMitral valveTricuspid valve
Myocardium
Tricuspid(right atrioventricular)valve
(a)
Mitral(left atrioventricular)valveAortic valvePulmonaryvalveFibrous
skeletonAnterior
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Figure 18.8b
Pulmonary valveAortic valveArea of cutaway
Mitral valveTricuspid valve
Myocardium
Tricuspid(right atrioventricular)valveMitral(left atrioventricular)valveAorticvalve
Pulmonaryvalve
(b)
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Figure 18.8c
Pulmonaryvalve
AorticvalveArea ofcutawayMitralvalve
Tricuspidvalve
Chordae tendineaeattached to tricuspid valve flap
Papillarymuscle
(c)
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Figure 18.8d
PulmonaryvalveAortic valveArea of cutawayMitral valveTricuspidvalve
Mitral valveChordaetendineae
Interventricularseptum
Myocardiumof left ventricle
Opening of inferiorvena cavaTricuspid valve
Papillarymuscles
Myocardiumof rightventricle
(d)
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Figure 18.9
1 Blood returning to theheart fills atria, puttingpressure againstatrioventricular valves;atrioventricular valves areforced open.
1 Ventricles contract, forcingblood against atrioventricularvalve cusps.
2 As ventricles fill,atrioventricular valve flapshang limply into ventricles.
2 Atrioventricular valvesclose.
3 Atria contract, forcingadditional blood into ventricles.
3 Papillary musclescontract and chordaetendineae tighten,preventing valve flapsfrom everting into atria.
(a) AV valves open; atrial pressure greater than ventricular pressure
(b) AV valves closed; atrial pressure less than ventricular pressure
Direction ofblood flowAtrium
Ventricle
Cusp ofatrioventricularvalve (open)
Chordaetendineae
Papillarymuscle
Atrium
Blood inventricle
Cusps ofatrioventricularvalve (closed)
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Figure 18.10
As ventriclescontract andintraventricularpressure rises,blood is pushed upagainst semilunarvalves, forcing themopen.
As ventricles relaxand intraventricularpressure falls, bloodflows back fromarteries, filling thecusps of semilunarvalves and forcingthem to close.
(a) Semilunar valves open
(b) Semilunar valves closed
AortaPulmonarytrunk
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Done with this lecture!
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Microscopic Anatomy of Cardiac Muscle
• Cardiac muscle cells are striated, short, fat, branched, and interconnected
• Connective tissue matrix (endomysium) connects to the fibrous skeleton
• T tubules are wide but less numerous; SR is simpler than in skeletal muscle
• Numerous large mitochondria (25–35% of cell volume)
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Figure 18.11a
Nucleus
DesmosomesGap junctions
Intercalated discs Cardiac muscle cell
(a)
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Microscopic Anatomy of Cardiac Muscle
• Intercalated discs: junctions between cells anchor cardiac cells – Desmosomes prevent cells from separating during
contraction– Gap junctions allow ions to pass; electrically
couple adjacent cells• Heart muscle behaves as a functional
syncytium
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Figure 18.11b
Nucleus
Nucleus
I bandA band
Cardiacmuscle cell
Sarcolemma
Z disc
Mitochondrion
Mitochondrion
T tubule
Sarcoplasmicreticulum
I band
Intercalateddisc
(b)