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Understanding EKGs
A Practical Approach
For the Dental Hygienist
CHAPTER
1
The Anatomy of the
Heart: Structure
Understanding EKGs: A Practical Approach, Third Edition
Brenda M. Beasley
Copyright ©2010 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Anatomy of the Heart
• Objectives
– Describe the chambers of the heart
 Atria
 Ventricles
– Identify the location, shape, and size of the
heart
– Name the layers of the heart
– Name the valves of the heart
Understanding EKGs: A Practical Approach, Third Edition
Brenda M. Beasley
Copyright ©2010 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Anatomy of the Heart
• Objectives (continued)
– Describe the structure and function of the
blood vessels
 Arteries
 Veins
 Capillaries
– Discuss concept of pulmonary circulation
– Explain the concept of systemic circulation
Understanding EKGs: A Practical Approach, Third Edition
Brenda M. Beasley
Copyright ©2010 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Anatomy of the Heart
• The heart is muscle
• Myocardium
– Heart muscle
– “Two-sided pump”
• Atrium (atria)
– Upper chambers
– Separated by interatrial septum
– Coronary sulcus-surrounds outside of heart
and divides the atria from the ventricles
Understanding EKGs: A Practical Approach, Third Edition
Brenda M. Beasley
Copyright ©2010 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Anatomy of the Heart
• Ventricles
– Lower chambers
– Separated by interventricular septum
Understanding EKGs: A Practical Approach, Third Edition
Brenda M. Beasley
Copyright ©2010 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Location,
Size, and
and Shape
Shape
Location, Size,
of the
the Heart
Heart
of
Understanding EKGs: A Practical Approach, Third Edition
Brenda M. Beasley
Copyright ©2010 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Location, Size, and Shape
of the Heart
• Located in mediastinum
– Lying in front of spinal column, behind
sternum, and between lungs
– 2/3 lies to left of midline
– Apex lies just above diaphragm
– Base lies at level of the third rib
– Size of owner’s closed fist
Understanding EKGs: A Practical Approach, Third Edition
Brenda M. Beasley
Copyright ©2010 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Location,
Size, and
and Shape
Shape
Location, Size,
of the
the Heart
Heart
of
Understanding EKGs: A Practical Approach, Third Edition
Brenda M. Beasley
Copyright ©2010 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Location,
Size, and
and Shape
Shape
Location, Size,
of the
the Heart
Heart
of
Understanding EKGs: A Practical Approach, Third Edition
Brenda M. Beasley
Copyright ©2010 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Layers of the Heart
• Pericardium
– Closed, two-layered sac
• Parietal pericardium
– Tough, non-elastic, fibrous
connective tissue
• Visceral pericardium
– Thin, serous inner layer of
pericardium
– Pericarditis-inflammation of
the serous pericardium
 Excess of fluid in pericardial
sac is called cardiac
tamponade
 Condition is an EXTREME
EMERGENCY!!!
Understanding EKGs: A Practical Approach, Third Edition
Brenda M. Beasley
Copyright ©2010 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
The Heart Wall
• Epicardium
– Smooth outer surface
 Coronary arteries located on
the surface of Epicardium
• Myocardium
– Thick, middle layer of the
heart, composed of cardiac
muscle cells, responsible for
ability to contract
• Endocardium
– Innermost layer, composed of
connective tissue
 Requires constant and
uninterrupted oxygen supply
Understanding EKGs: A Practical Approach, Third Edition
Brenda M. Beasley
Copyright ©2010 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Valves of the Heart
• Four valves allow blood to flow in one
direction
• Two sets
– Atrioventricular valves
– Semilunar valves
Understanding EKGs: A Practical Approach, Third Edition
Brenda M. Beasley
Copyright ©2010 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Atrioventricular Valves
•
•
•
•
Located between atria and the ventricles
Allow flow from atria into ventricles
Prevent flow backward from ventricles
Tricuspid valve
– Three cusps
– Located between right atrium and right
ventricle
Understanding EKGs: A Practical Approach, Third Edition
Brenda M. Beasley
Copyright ©2010 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Atrioventricular Valves
• Mitral (bicuspid) valve
– Two cusps
– Located between left atrium and left ventricle
Understanding EKGs: A Practical Approach, Third Edition
Brenda M. Beasley
Copyright ©2010 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Semilunar Valves
• Prevent backflow of blood into the ventricles
• Each valve contains three semilunar, or
moon-shaped cusps
• Pulmonic valve
– Located between right ventricle and pulmonary
artery
• Aortic valve
– Located between left ventricle and trunk of aorta
Understanding EKGs: A Practical Approach, Third Edition
Brenda M. Beasley
Copyright ©2010 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Heart Valves Function
• Chamber pressure governs opening and
closing of heart valves
• Ventricular systole
– Contraction of ventricles
 Atrioventricular valves close and semilunar valves
open
Understanding EKGs: A Practical Approach, Third Edition
Brenda M. Beasley
Copyright ©2010 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Heart Valves Function
• Ventricular diastole
– Relaxation of ventricles
 Atrioventricular valves are open and semilunar
valves are closed
Understanding EKGs: A Practical Approach, Third Edition
Brenda M. Beasley
Copyright ©2010 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Blood Vessels
• Blood vessels are the “container” for fluid
or blood
– Arteries
– Veins
– Capillaries
Understanding EKGs: A Practical Approach, Third Edition
Brenda M. Beasley
Copyright ©2010 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Arteries
• Thick wall and muscular
• Function under high
pressure
• Carry blood AWAY FROM
heart
• Regulates blood pressure
by changes in peripheral
vascular resistance
• Arteries
– Larger vessels
• Arterioles
– Small vessels
Understanding EKGs: A Practical Approach, Third Edition
Brenda M. Beasley
Copyright ©2010 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Arteries
Understanding EKGs: A Practical Approach, Third Edition
Brenda M. Beasley
Copyright ©2010 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Arterial Wall Layers
Understanding EKGs: A Practical Approach, Third Edition
Brenda M. Beasley
Copyright ©2010 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Coronary Arteries and Coronary Sinus
• Coronary Arteries
– Two main coronary arteries
– The right and the left
– Arise from the trunk of the aorta
– Provide oxygenated blood throughout the
heart muscle
Understanding EKGs: A Practical Approach, Third Edition
Brenda M. Beasley
Copyright ©2010 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Coronary Arteries and Coronary Sinus
• Left Coronary Artery
– Divides into the left anterior descending
artery and circumflex artery
– Anterior descending supplies most of
anterior portion of the heart
– Circumflex extends around to posterior
side of heart
– Major branch supplies lateral wall of left
ventricle
Understanding EKGs: A Practical Approach, Third Edition
Brenda M. Beasley
Copyright ©2010 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Coronary Arteries and Coronary Sinus
• Right Coronary Artery
– Extends around to posterior portion of
heart
– Branches supply blood to lateral wall
– Posterior interventricular artery supplies
posterior and inferior part of left ventricle
– Also supplies a portion of the electrical
conduction system
Understanding EKGs: A Practical Approach, Third Edition
Brenda M. Beasley
Copyright ©2010 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Coronary Arteries and Coronary Sinus
• Coronary Sinus {also called the Great Cardiac
Vein}
– Serves to receive deoxygenated blood
from the veins of the myocardium
– Empties into the right atrium
Understanding EKGs: A Practical Approach, Third Edition
Brenda M. Beasley
Copyright ©2010 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Veins
• Vessels that carry
blood back to the
heart
• Venules
– Smaller vessels
• Operate under low
pressure
Understanding EKGs: A Practical Approach, Third Edition
Brenda M. Beasley
Copyright ©2010 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Capillaries
• Tiny blood vessels
whose walls are
thinnest of all
• Vast majority of gas
exchange occurs
• Circulation
– Movement through a
course (body) that
leads back to initial
point (heart)
Understanding EKGs: A Practical Approach, Third Edition
Brenda M. Beasley
Copyright ©2010 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Circulation
Understanding EKGs: A Practical Approach, Third Edition
Brenda M. Beasley
Copyright ©2010 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Capillaries
Understanding EKGs: A Practical Approach, Third Edition
Brenda M. Beasley
Copyright ©2010 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Pulmonary Circulation
• Blood flow between the heart and lungs
– Blood leaves heart through right ventricle,
travels into PULMONARY artery to lungs and
back through PULMONARY veins to left
atrium
Understanding EKGs: A Practical Approach, Third Edition
Brenda M. Beasley
Copyright ©2010 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Systemic Circulation
• Blood flow between the heart and body
– Blood leaves the left ventricle, travels through
the arteries, capillaries, and veins of the
BODY SYSTEM and back to the right atrium
Understanding EKGs: A Practical Approach, Third Edition
Brenda M. Beasley
Copyright ©2010 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Summary
• Understanding anatomy of heart and blood
vessels will assist you in the
understanding of dysrhythmias and their
causes
• ANY QUESTIONS?
Understanding EKGs: A Practical Approach, Third Edition
Brenda M. Beasley
Copyright ©2010 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.