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Exercise 27
Gross Anatomy of the HeartBI 232
Mediastinum The heart and
pericardial cavity are located within the mediastinum, a centrally located area within the thoracic cavity.
The Pericardium Membranous sac 2 parts: outer fibrous
pericardium that is fused to adjacent structures and an inner serous pericardium which is a delicate serous membrane that forms a double-layered sac around the heart.
The serous pericardium consists of parietal and visceral layers.
The heart Two-sided, double-
pumping organ. The left side controls
the flow of blood to all tissues and cells in the body, where oxygen and nutrients are delivered and wastes are taken away.
The right side sends blood to the lungs, where oxygen stored in RBCs is replenished and CO2 is released
External Anatomy of the Heart
External Anatomy of the Heart
Internal Anatomy of the Heart
Coronary Circulation
Coronary Circulation On the posterior
surface of the heart, the coronary artery branches to become the posterior interventricular artery
Near the apex of the heart the anterior and posterior interventricular arteries form an anastomosis (connection)
Coronary Circulation On the posterior
surface of the heart, the coronary sinus runs along the coronary sulcus and empties into the right atrium.
Great cardiac vein found in the anterior interventricular sulcus
Middle cardiac vein ascends along the posterior interventricular groove
Blood flow Through the Heart Pulmonary
Circulation- Blood from the right side of the heart flows to and from the lungs
Systemic Circulation- Blood from the left side of the heart flows from and to all body tissues.
Position of Heart Base of the heart
extends from the inferior border of the second costal cartilage on the left side to the superior border of the third costal cartilage on the right.
Apex of the heart is located in the left fifth intercostal space, left of the median plane
Heart: muscular pump Actually 2 pumps
acting in unison Systole is
contraction of heart muscle Atrial systole Ventricular systole
Diastole is relaxation of heart muscle Atrial diastole Ventricular diastole
Conduction system of the Heart (Exercise 32) Electrical activity of the
heart stimulates the heart muscle to contract.
Sinoatrial (SA) node = pacemaker of the heart
Atrioventricular (AV) node: there is a slight delay (0.10 second)
Atrioventricular bundle (bundle of His)
Right and left bundle branches
Purkinje fibers: stimulate cardiac muscle of the ventricles to contract
http://youtu.be/te_SY3MeWys
Electrical activity of the Heart Heart produces low-voltage
electrochemical impulses The average potential
difference is -90 millivolts These impulses can travel
through the saline medium of the body and be picked up by sensors attached to the skin
The collective action potentials generated by the atria and ventricles depolarizing and repolarizing can be recorded using an electrocardiograph machine
EKG Waveform
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P wave
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The P wave indicates the depolarization of the atria just prior to the beginning of atrial contraction or systole
QRS complex (QRS interval) Represents the depolarization of the
ventricles which precedes ventricular systole.
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T wave Results from ventricular repolarization, which
occurs before ventricular relaxation or diastole.
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Analysis of the ECG Irregularities in Heart
rate: Tachycardia: Above
100 in adults (in small children this may be normal)
Bradycardia: in young adults below 60 beats per minute (unless person is highly trained aerobic athlete)
Heart Blocks PR intervals are normally
about 0.16 second. Time between the beginning
of atrial depolarization and the beginning of ventricular depolarization.
Long PR might indicate a heart block (reduced conduction between atria and ventricles)
Longer than 0.2 second Complete heart block the
atria do not stimulate ventricular depolarization at all, so atria fire independently of ventricles
Heart Blocks Normal QRS is 0.08 to
0.10 second on average.
Longer than 0.12 may indicate a right or left bundle branch block
QT interval is normally about 0.3 second
This is shorter as the heart rate increases and longer as heart rate slows.
Cardiac Arrhythmias A major diagnostic use is to
detect arrhythmias, abnormal rhythms of the heart
Atrial fibrillation: electrical activity of the heart is uncoordinated causing the upper chambers to quiver.
Ventricular fibrillation: where electrical signals in the ventricles fire in a very fast
uncontrolled manner. Premature ventricular
contraction (PVC): electrical signal causes an early heartbeat that usually goes unnoticed
Today’s lab Dissect sheep heart ID structures on the heart models We will also be doing EKGs (We will be using
the Vernier EKGs rather than the BIOPAC machines mentioned in the lab manual)
After performing your EKG follow the instructions in your lab manual and calculate the mean electrical axis of your heart
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The End
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