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Cardiovascular System Notes:
The Heart
The human heart creates enough pressure to squirt blood 30 feet.
Interesting Cardiovascular System Facts
NOTES – THE HEART
• Location: • cavity between the lungs, 2/3 left of midsagittal
• roughly the size of a fist
© 2013 Pearson Education, Inc.
Figure 18.2b Location of the heart in the mediastinum.
Mediastinum
HeartLeft lung
Body of T7 vertebra
Posterior
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Figure 18.2c Location of the heart in the mediastinum.
Superiorvena cava
Pulmonarytrunk
Diaphragm
Aorta
Parietal pleura(cut)
Left lung
Pericardium (cut)
Apex of heart
• Heart Anatomy• PERICARDIUM • outer membrane of the
heart
• 2 layers 1. Parietal pericardium: external (outer) layer
2. Visceral pericardium (epicardium): part of the heart wall
• Functions: • protection – physical barrier• anchors heart to other structures
• provides lubrication to reduce friction – allows the heart to beat easily
1. Epicardium: outer portion (visceral pericardium)
• 3 layers
• THE HEART WALL
EPICARDIUM
2. Myocardium: middle layer consists of twisted cardiac muscle
• THIS IS THE LAYER THAT ACTUALLY CONTRACTS
MYOCARDIUM
3. Endocardium: inner layer made of epithelial tissue
ENDOCARDIUM
© 2013 Pearson Education, Inc.
Figure 18.3 The pericardial layers and layers of the heart wall.
Pericardium
Myocardium
Pulmonarytrunk Fibrous pericardium
Parietal layer of serous pericardium
Pericardial cavity
Epicardium (viscerallayer of serouspericardium)
Myocardium
Endocardium
Heart chamber
Heart wall
© 2013 Pearson Education, Inc.
Homeostatic Imbalance
• Pericarditis– Inflammation of pericardium– Roughens membrane surfaces pericardial
friction rub (creaking sound) heard with stethoscope
– Cardiac tamponade• Excess fluid sometimes compresses heart
limited pumping ability
© 2013 Pearson Education, Inc.
The Pulmonary and Systemic Circuits
• Receiving chambers of heart:– Right atrium
• Receives blood returning from systemic circuit
– Left atrium• Receives blood returning from pulmonary circuit
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The Pulmonary and Systemic Circuits
• Pumping chambers of heart:– Right ventricle
• Pumps blood through pulmonary circuit
– Left ventricle• Pumps blood through systemic circuit
© 2013 Pearson Education, Inc.
Capillary beds oflungs where gasexchange occurs
Pulmonary CircuitPulmonaryarteries Pulmonary veins
Aorta and branchesVenaecavae
Leftatrium
LeftventricleRight
atrium
Rightventricle
Heart
Systemic Circuit
Oxygen-rich,CO2-poor bloodOxygen-poor,CO2-rich blood
Capillary beds of allbody tissues wheregas exchange occurs
Figure 18.1 The systemic and pulmonary circuits.
© 2013 Pearson Education, Inc.
Figure 18.4 The circular and spiral arrangement of cardiac muscle bundles in the myocardium of the heart.
Cardiacmusclebundles
• HEART CHAMBERS• 4 chambers
• Atrium (left/right atria)
• divided by the INTERATRIAL SEPTUM
• Function of Atria: receives blood from veins
(pig heart)
• RIGHT ATRIA
• receives blood from superior & inferior vena cava
• blood that’s been used• oxygen poor – high in CO2
• receives blood from pulmonary veins
• LEFT ATRIA
• coming from lungs• rich in oxygen
• Ventricles (left/right)
• muscular pumps – divided by INTERVENTRICULAR SEPTUM
(pig heart)
• RIGHT VENTRICLE
• receives blood from the right atria (O2 poor)
• pumps blood to the lungs through the PULMONARY ARTERIES
• LEFT VENTRICLE
• receives blood (O2 rich) from the left atrium
• pumps blood to the body through the AORTA
© 2013 Pearson Education, Inc.
Figure 18.10 Anatomical differences between the right and left ventricles.
Rightventricle
Interventricularseptum
Leftventricle
• Systemic Circulation
• heart – lungs – heart – body – heart
• HEART VALVES (4)
• allow for “one way” circulation
• 2 Atrioventricular Valves (AV valves)
1. Tricuspid Valve: between right atria and right ventricle
2. Bicuspid or Mitral Valve: between left atria and left ventricle
• heavier & stronger of the two
© 2013 Pearson Education, Inc.
Figure 18.6a Heart valves.
Pulmonary valveAortic valve
Area of cutaway
Mitral valveTricuspid valve
Myocardium
Mitral(left atrioventricular)valveTricuspid(right atrioventricular) valveAortic valve
Pulmonary valve
Anterior
Cardiacskeleton
© 2013 Pearson Education, Inc.
Figure 18.6b Heart valves.
Pulmonary valveAortic valve
Area of cutaway
Mitral valveTricuspid valve
Myocardium
Mitral(left atrioventricular)valveTricuspid(right atrioventricular) valveAortic valve
Pulmonary valve
© 2013 Pearson Education, Inc.
Figure 18.6c Heart valves.Pulmonary valve
Aortic valve
Area of cutaway
Mitral valve
Tricuspid valve
Chordae tendineae attached to tricuspid valve flap
Papillary muscle
© 2013 Pearson Education, Inc.
Figure 18.6d Heart valves.
Pulmonary valve
Aortic valve
Area of cutaway
Mitral valve
Tricuspid valve
Opening of inferiorvena cava
Tricuspid valve
Myocardium of right ventricle
Papillary muscles
Mitral valveChordae tendineae
Interventricular septum
Myocardium of left ventricle
• CHORDAE TENDINAE and papillary muscles stop valves from being folded backwards
CHORDAE TENDINAE
3. Pulmonary Semilunar Valve: between the pulmonary artery and right ventricle
4. Aortic Semilunar Valve: between aorta and left ventricle
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Animation
© 2013 Pearson Education, Inc.
Homeostatic Imbalance
• Two conditions severely weaken heart:– Incompetent valve
• Blood backflows so heart repumps same blood over and over
– Valvular stenosis• Stiff flaps – constrict opening heart must exert
more force to pump blood
• Valve replaced with mechanical, animal, or cadaver valve
© 2013 Pearson Education, Inc.
Pathway of Blood Through the Heart
• Pulmonary circuit– Right atrium tricuspid valve right
ventricle– Right ventricle pulmonary semilunar valve
pulmonary trunk pulmonary arteries lungs
– Lungs pulmonary veins left atrium
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PLAYPLAY Animation: Rotatable heart (sectioned)
Pathway of Blood Through the Heart
• Systemic circuit– Left atrium mitral valve left ventricle– Left ventricle aortic semilunar valve
aorta– Aorta systemic circulation
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Coronary Circulation
• Functional blood supply to heart muscle itself– Delivered when heart relaxed– Left ventricle receives most blood supply
• Arterial supply varies among individuals
• Contains many anastomoses (junctions)– Provide additional routes for blood delivery– Cannot compensate for coronary artery
occlusion
© 2013 Pearson Education, Inc.
Coronary Circulation: Arteries
• Arteries arise from base of aorta• Left coronary artery branches anterior
interventricular artery and circumflex artery– Supplies interventricular septum, anterior ventricular
walls, left atrium, and posterior wall of left ventricle
• Right coronary artery branches right marginal artery and posterior interventricular artery– Supplies right atrium and most of right ventricle
© 2013 Pearson Education, Inc.
Aorta
Superiorvena cava
Anastomosis(junction ofvessels)
Rightatrium
Rightcoronaryartery
Rightventricle
Rightmarginalartery
Posteriorinterventricularartery
Anterior interventricularartery
Leftventricle
Circumflexartery
Leftcoronaryartery
Left atrium
Pulmonarytrunk
The major coronary arteries
Figure 18.11a Coronary circulation.
© 2013 Pearson Education, Inc.
Homeostatic Imbalances
• Angina pectoris– Thoracic pain caused by fleeting deficiency in
blood delivery to myocardium– Cells weakened
• Myocardial infarction (heart attack)– Prolonged coronary blockage– Areas of cell death repaired with
noncontractile scar tissue
© 2013 Pearson Education, Inc.
Microscopic Anatomy of Cardiac Muscle
• Cardiac muscle cells striated, short, branched, fat, interconnected, 1 (perhaps 2) central nuclei
• Connective tissue matrix (endomysium) connects to cardiac skeleton– Contains numerous capillaries
• T tubules wide, less numerous; SR simpler than in skeletal muscle
• Numerous large mitochondria (25–35% of cell volume)
© 2013 Pearson Education, Inc.
Figure 18.12a Microscopic anatomy of cardiac muscle.
NucleusIntercalated
discsCardiac
muscle cell Gap junctions Desmosomes
© 2013 Pearson Education, Inc.
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 from cell to
cell; electrically couple adjacent cells• Allows heart to be functional syncytium
– Behaves as single coordinated unit