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CARDIOVASCULAR SYSTEM
- Heart, blood vessels, blood
- Consists of 2 circuits:
- Pulmonary Circuit
- Systemic Circuit
ANATOMY OF THE HEART
Pumps 7,000 liters of blood per day
It takes about 1 minute for blood to circulate around the body
Contracts 2.5 billion times in a lefetime
Size of the heart: 14cm long and 9 cm. wide
2 muscular pumps in one:
- left heart pumps blood to the body tissues
- right heart pumps blood to the lungs
The heart circulates the blood through the circulatory system. Blood carries oxygen and
nutrients to the cells
Tisssues Covering the Heart
Pericardium – serous membrane that surrounds the heart
- Fibrous Pericardium – outer layer
- Parietal Pericardium – inner lining of fibrous pericardium
- Visceral Pericardium – inner layer
- Pericardial Cavity – space between the parietal and visceral layers. Contains serous fluid
Walls of the Heart
Epicardium – visceral pericardium
Myocardium – middle layer, thick and consists mostly of cardiac muscle tissue
Endocardium – inner layer consisting of epithelium and connective tissue
Anatomy of the Heart
1. Consists of 4 chambers
- 2 atria – superior chambers, thin muscular walls
- 2 ventricles – inferior chambers, thicker muscular walls
2. Valves:
- Atrioventricular valves:
- Tricuspid: separates right atrium and right ventricle
- Bicuspid (mitral): separates left atrium and left ventricle
- Semilunar valves;
- Pulmonary Semilunar: found between right ventricle and pulmonary artery
- Aortic Semilunar: found between left ventricle and aorta
Valves direct the flow of blood and prevent backflow of blood
Heart Murmur: if a valve is damaged or does not close properly, blood leaks backwards
causing a “noise”
Blood Supply to the Heart
Coronary Arteries – supply blood to tissues of the heart
- the first 2 branches of the aorta
Cardiac Veins – empty into the right atrium (coronary sinus)
Path of Blood through the heart:
Vena Cava  R atrium  tricuspid valve  R ventricle  Pulmonary semilunar valve 
Pulmonary artery  lungs  Pulmonary vein  L atrium  bicuspid valve  L ventricle 
Aortic semilunar valve  aorta  body  vena cava
Heart Attack
- A block or narrowing of a coronary artery or one of its branches deproves the myocardial cells of
oxygen
- Angina Pectoris – may occur during activty or stress
- A complete blockage kills heart tissue – Myocardial Infarction (MI), a heart attack
THE CARDIAC CYCLE
The heart beats in a coordinated fashion
- Systole – contraction of the atria
- Diastole – relaxation
- Cardiac Cycle – contraction and relaxation of the heart
Sounds of the Heart
“lubb – dupp”
- Lubb = ventricular systole, AV valves closing
- Dupp = ventricular diastole, pulmonary and aortic valves closing
The Heart Conduction System
- Sinoatrial (SA) node – maintains rhythym
- pacemaker
- found in the wall of the right atrium where the superior vena cava enters
- Atrioventricular (AV) node – found in the wall between the right atrium and right ventricle in the
interatrial septum
Functional Syncytium – a mass of merging cells that act as a unit.
- atrial syncytium
- ventricular syncytium
SA Node  Junctional Fibers  Atrtial Synctium  AV node  AV Bundle (Bundle of His) 
Bundle Branches  Purkinje Fibers 
Blood Pressure
Systolic blood pressure (the upper number) — indicates how much pressure your blood is exerting
against your artery walls when the heart beats.
Diastolic blood pressure (the lower number) — indicates how much pressure your blood is exerting
against your artery walls while the heart is resting between beats.
Normal BP – 120/80
Hypertension: >140/90
Hypotension: <90/60
The EKG
Electrocardiogram (ECG or EKG from the German word Elektrokardiogram) is a test that records
the electrical activity of the heart.
-
Measures the rate and regularity of heartbeats, as well as information about the heart anatomy.
Interpreting an EKG
P wave – atrial depolarization (contraction)
QRS complex – depolarization of the right and left ventricles
T wave – repolarization of the ventricles
PR interval – time for the cardiac impulse to travel from SA node through the AV node
QT interval – beginning of QRS complex to end of T wave. Prolonged QT interval is a risk for
ventricular tachyarrythmias and sudden death
ST segment – segment where the ventricles are depolarized
THE WIGGER DIAGRAM
End-diastolic volume - the amount of blood in each ventricle at the end of ventricular diastole (the
start of ventricular systole) 130 ml
End-systolic volume - the amount of blood remaining in each ventricle at the end of ventricular
systole (the start of ventricular diastole)
50 ml
Stroke volume (SV) - the amount of blood pumped out of each ventricle during a single beat, which
can be expressed as EDV – ESV = SV
130ml – 50ml = 80 ml
Ejection fraction - the percentage of EDV represented by the SV
The stroke volume divided by the EDV or 80/130 = 62%
A simple model of Stroke Volume
Stroke volume of the heart can be compared to the amount of air pumped from an old-fashioned
bicycle pump. The amount varies with the amount of handle movement. The extent of the upward
movement corresponds to the EDV; extent of the downward movement corresponds to the ESV
Cardiac Output – the amount of blood pumped by each ventricle in 1 minute
CO = SV x HR
If the stroke volume is 80 ml/beat and the heart rate is 75 bpm
CO = 80ml/beat x 75 bpm
CO = 6000 ml/min (6 L/min)
The EDV is affected by:
1. Filling Time – the duration of ventricular diastole
2. Venous return – the rate of blood flow over this period
The ESV is affected by:
1. Preload – the degree of stretching experienced during ventricular diastole, which is directly
proportional to the EDV
The Frank-Starling Principle (Straling’s Law of the Heart): increases in EDV results in
a corresponding increase in stroke volume
- Relationship between fiber length and force of contraction
- increase blood in heart  inc. ventricular distention  inc. contraction  inc.
SV  inc. CO
2. Contractility – the amount of force produced during a contraction at a given preload
3. Afterload – the amount of tension the contracting ventricle must produce to force open the
semilunar valve and eject blood
- The greater the afterload, the longer the period of isovolumetric contraction, the
shorter the duration of ventricular ejection, and the larger the ESV
Or
- As afterload increases, the stroke volume decreases
- increases in arterial pressure (HYPERTENSION) increases afterload