Lab

1
Lab 3
Structure of the heart and Electrical
conductivity of the heart
2
The Heart

• Located deep in the thorax in the mediastinum
• Contains the heart, pericardium, esophagus and
  descending aorta

3
Pericardium

• Parietal pericardium
• Two layers
• Fibrous layer tough connective tissue
• Serous layer
• Pericardial cavity
• Contains serous fluid reduces the friction
  between outer surface of the heart and the
  parietal pericardium
• Visceral pericardium (epicardium)
• The outer surface of the heart

4
(No Transcript)
5
Heart Wall

• Visceral pericardium (epicardium)
• Epithelial and connective tissue
• Myocardium
• Thickest layer cardiac muscle
• Endocardium
• Endothelium (simple squamous epithelium) and
  connective tissue

6
(No Transcript)
7
Blood Flow Through the Heart
Out to lungs
6
3
4
In from lungs
1
5
2
1
8
Exterior of the Heart
Base
Apex
Anterior View
9
Exterior of the Heart
Aorta
Pulmonary Trunk
Left Ventricle
Anterior View
10
Exterior of the Heart
Aorta
Pulmonary Trunk
Right Ventricle
Anterior View
11
Exterior of the Heart
Aorta
Pulmonary Trunk
Interventricular Groove
Anterior View
12
Exterior of the Heart
Left Auricle
Right Auricle
Anterior View
13
Exterior of the Heart
Left Atrium
Right Atrium
Posterior View
14
Exterior of the Heart
Atrioventricular Sulcus
Posterior Interventricular Sulcus
Posterior View
15
Exterior of the Heart
Superior Vena Cava
Pulmonary Veins
Pulmonary Veins
Coronary Sinus
Inferior Vena Cava
Posterior View
16
Exterior of the Heart
Ligamentum Arteriosum
Right Pulmonary Artery
Left Pulmonary Artery
Pulmonary Trunk
Anterior View
17
Interior of the Heart
Right Atrium
Left Atrium
Fossa Ovalis
Interatrial Septum
Left Ventricle
Interventricular Septum
Right Ventricle
Anterior View
18
Interior of the Heart
Pulmonary Semilunar Valve
Aortic Semilunar Valve
Left AV (bicuspid) (mitral) Valve
Right AV (tricuspid) Valve
Papillary muscles
Chordae tendinae
Trabeculae carneae
Anterior View
19
(No Transcript)
20
(No Transcript)
21
Electrical Conductivity of the Heart

• Important concepts
• The heart produces electrochemical impulses
  similar to the nervous system
• These impulses can travel through the medium of
  the body and be measured electrically in areas
  distant to the heart

22
The Heart as a Pump

• The heart is two pumps acting in unison
• The contraction mode is called systole
• The relaxation mode is called diastole
• There is a systole and diastole for both the
  atria and ventricles
• Contractions are preceded by electrical impulses
  that stimulate the cardiac muscle to contract

23
Electrical Functioning of the Heart

• The initiation of the electrical impulse that
  begins contractions is at the sinoatrial (SA)
  node or pacemaker in the superior portion of the
  right atrium
• The SA node uses the sodium-potassium pump to
  generate voltage differentials across its cell
  membranes
• The cells become polarized
• Spontaneous depolarization sends out an
  electrical impulse initiating contraction

24
Contraction Pathway

• Conduction from the SA node travels across the
  atria causing them to depolarize and creating
  action potentials that cause cardiac muscle in
  the atria to contract
• The impulse reaches the atrioventricular (AV)
  node where it has a slight delay before
  continuing to the ventricals
• This allows atrial contraction to complete before
  ventricular depolarization

25
Contraction Pathway

• The electrical impulse travels from the AV node
  to the atrioventricular bundle (bundle of His)
  and splits into the right and left bundle
  branches and finally to the Purkinje (conduction)
  fibers near the apex of the ventricles
• The Purkinje fibers stimulate the ventricles to
  contract from the apex to the base

26
SA node
Purkinje fibers
AV node
left and right bundle branches
AV bundle (Bundle of His)
Perkinje fibers
27
Electrocardiograph (ECG)

• A machine that measures the electrical activity
  of the heart
• Produces a chart called an electrocardiogram (ECG
  or EKG) where time is measured on the X-axis and
  voltage is measured on the Y-axis
• Measures the length of individual electrical
  events (P, Q, R, S, and T) that equal a full
  contraction of the heart

28
Electrocardiograph (ECG)

• P atrial depolarization
• Q, R, and S ventricular
• depolarization and atrial
• repolarization
• Because ventricles are larger the electrical
  events produced by them are larger
• T ventricle repolarization

29
(No Transcript)
30

• Average resting heart rate 72 beats per minute
• Excessively high resting heart rate (over 100 bpm
  in young adults) is termed tachycardia
• Excessively low resting heart rate (under 60 bpm
  in young adults) is termed bradycardia

31

• A normal P-R interval (time between beginning of
  atrial depolarization and ventricular
  depolarization) is about .16 seconds
• Times greater that .2 seconds may indicate heart
  block and be caused by damage or decreased
  transmission of the AV node