The Heart
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The heart=a muscular double pump with 2 functions
Overview
 The right side receives
oxygen-poor blood from the
body and tissues and then
pumps it to the lungs to
pick up oxygen and dispel
carbon dioxide
 Its left side receives
oxygenated blood returning
from the lungs and pumps
this blood throughout the
body to supply oxygen and
nutrients to the body
tissues
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Simplified…
 Four chambers
 Two atria, two ventricles
 Double pump – the ventricles
 Two circulations
 Systemic circuit: blood vessels that transport
blood to and from all the body tissues
 Pulmonary circuit: blood vessels that carry
blood to and from the lungs
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Chest x rays
Normal female
Lateral (male)
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Starting from the outside…
Pericardium
(see next slide)
Without most of pericardial layers
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Chambers of the heart
divided by septae:
 Two atria-divided
by interatrial septum
 Right atrium
 Left atrium
 Two ventriclesdivided by
interventricular
septum
 Right ventricle
 Left ventricle
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Valves
three tricuspid
one bicuspid
(cusp means flap)
 “Tricuspid” valve
 RA to RV
 Pulmonary or pulmonic valve
 RV to pulmonary trunk (branches R and L)
 Mitral valve (the bicuspid one)
 LA to LV
 Aortic valve
 LV to aorta
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Function of AV valves
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Function of semilunar valves
(Aortic and pulmonic valves)
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more on valves
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Simplified flow: print and fill in details
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Heartbeat
Definition: a single sequence of atrial contraction followed by ventricular contraction
See http://www.geocities.com/Athens/Forum/6100/1heart.html
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Systole: contraction
Diastole: filling
Normal rate: 60-100
Slow: bradycardia
Fast: tachycardia
***Note: blood goes to RA, then RV, then lungs, then LA, then LV, then
body; but the fact that a given drop of blood passes through the heart
chambers sequentially does not mean that the four chambers contract in
that order; the 2 atria always contract together, followed by the
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simultaneous contraction of the 2 ventricles
Conducting System of Heart
Conduction System of the Heart
 SA node: sinoatrial node. The pacemaker.
 Specialized cardiac muscle cells.
 Generate spontaneous action potentials (autorhythmic tissue).
 Action potentials pass to atrial muscle cells and to the AV node
 AV node: atrioventricular node.
 Action potentials conducted more slowly here than in any other part of
system.
 Ensures ventricles receive signal to contract after atria have contracted
 AV bundle: passes through hole in cardiac skeleton to reach
interventricular septum
 Right and left bundle branches: extend beneath endocardium to
apices of right and left ventricles
 Purkinje fibers:
 Large diameter cardiac muscle cells with few myofibrils.
 Many gap junctions.
 Conduct action potential to ventricular muscle cells (myocardium)
Impulse Conduction through
the Heart
Artificial
Pacemaker
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Another flow chart
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Use to study
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