Cardiovascular- Heart (general info) Flashcards
Tissues of the heart
Pericardium
Epicardium
myocardium
Endocardium
What is the pericardium?
fibrous protective sac enclosing heart
What is epicardium?
inner layer of pericardium
What is myocardium?
heart muscle, the major portion of the heart
What is endocardium?
smooth lining of the inner surface and cavities of the heart
4 chambers of the heart
R and L atriums
R and L ventricles
What is the R atrium?
receives blood from systemic circulation, from the superior and inferior vena cavae
What is the R ventricle?
receives blood from the RA and pumps blood via the pulmonary artery to the lungs for oxygenation; the low pressure pulmonary pump
What is the L atrium?
receives oxygenated blood from the lungs and the 4 pulmonary veins
What is the L ventricle?
receives blood from the LA and pumps blood via the aorta throughout the entire systemic circulation; the high pressure systemic pump. the walls of the LV are thicker and stronger than the RV and form most of the L side and the apex of the heart.
Name the valves. Why are the important?
Provide 1 way flow of blood
Atrioventricular valves: tricuspid valve and bicuspid valve
Semilunar Valves: pulmonary valve and aorta valve
Info about Atrioventricular valves
Prevent backflow of blood into the atria during ventricular systole
anchored by the chordae tendineae to papillary muscles
valves close when ventricular walls contract
What is the tricuspid valve?
three cusp or leaflets
right heart valve
What is the bicuspid valve?
also called the mitral valve
2 cusps or leaflets
left heart valve
Info about semilunar valves
Prevents backflow of blood from aorta and pulmonary arteries in ventricles during diastole
Function of pulmonary valve
prevents R backflow
Function of aortic valve
prevents L back flow
4 components of cardiac cycle
1- The rhythmic pumping action of the heart
2- Systole
3- Diastole
4- Atrial contraction
Explain systole
The period of ventricular contraction
End systolic volume is the amount of blood in the ventricles after systole
About 50 mL
Explain Diastole
The period of ventricular relaxation and filling of blood
End-diastolic volume is the amount of blood in the ventricles after diastole
About 120 mL
Explain atrial contraction (atrial kick)
Occurs during the last third of diastole and completes ventricular filling, comprising last 20%-30% of end diastole volume
2 points of note: coronary circulation
1- Distribution of blood supply is variable from individual to individual
2- Myocardial oxygen supply and myocardial oxygen demand (MVO2) should be in balance in order to maintain a given activity level without ischemia
General info about coronary arteries
arise directly aorta near aortic valve; blood circulates to myocardium during diastole
Info about R coronary artery
Supplie R atrium. most of R ventricle, and in most individuals, the inferior wall of L ventricle, AV node and bundle of His
Supplies SA node 60% of the time
Info about L coronary artery (LCA)
Supplies most of the L ventricle
2 major divisions: L anterior descending (LAD) and Circumflex
Info about L anterior descending
Supplies the L ventricle and the interventricular septum, and in most individuals, the inferior areas of the apex
It may also give off branches to the R ventricle
Info about circumflex (LCx)
Supplies blood to the lateral and inferior walls of the L ventricle and portions of the L atrium
Supplies SA node 40% of the time
Info about coronary veins
Parallel arterial system
The coronary sinus receives venous blood from the heart and empties into the R atrium
What is the conduction system of the heart?
There are specialized conduction tissues that allow rapid transmission of electrical impulses throughout the myocardium (normal sinus rhythm, NSR)
Structures of the conduction system
SA node
AV node
Bundle of His
Purkinje tissue
Explain the Sinoatrial node
1- Located at junction of superior vena cava and R atrium
2- Main pace maker of the heart, initiates the impulse at rate of 60-100 beats per minute
3- Has sympathetic and parasympathetic innervation affecting both heart rate and strength of conduction.
Explain Atrioventricular node
1-Located at the junction of the R atrium and the R ventricle
2- Has sympathetic and parasympathetic innervation
3- Merges with bundle of His
4- Intrinsic firing rate of 40-60 beats per minute.
Explain Purkinje tissue
1- R and L bundle branches of the AV node are located on either side of intraventricular septum
2- Terminate in purkinje fibers, specialized conducting tissue spread throughout the ventricles.
2 Points about the conduction system of a normal heart beat
1- Origin is in the SA node; impulse spreads throughout both atria, which contract together
2- Impulse stimulates AV node, is transmitted down the bundle of His to the purkinje fibers; impulse spreads throughout the ventricles, which contract together (atrial kick)
3 points about myocardial fibers
1- Muscle tissue: striated muscle fibers with more numerous mitochondria; exhibits rhythmicity of contraction; fibers contract as a functional unit (sliding filament theory of contraction)
2- Myocardial metabolism is essentially aerobic, sustained by continuous O2 delivery from coronary arteries
3- Smooth muscle tissue is found in the walls of blood vessels.
What is stroke volume (SV)?
The amount of blood ejected with each myocardial contraction
Normal range is 55-100mL/beat
It is influenced by L ventricular end diastolic volume, contractility, and afterload
What is L ventricular end diastolic volume (LVEDV)?
the amount of blood left in the ventricle at the end of diastole,also known as preload. The greater the diastolic filling (preload), the greater the quantity of blood pumped (Frank-Starling Law)
What is Frank-Starling Law?
The greater the diastolic filling (preload), the greater the quantity of blood pumped.
Define contractility in the context of hemodynamics?
The ability of the ventricle to contract
What is afterload?
The force the LV must generate during systole to overcome aortic pressure to open the aortic valve.
What is Cardiac Output (CO)?
The amount of blood discharged from the R to the L ventricle per min.
Average adult at rest - normal range is 4-5L per min
Determined by HR x SV = CO
How is cardiac index determined?
Cardiac output divided by body surface area
Normal range is 2.5- 3.5 L/min
What is L ventricular end diastolic pressure (LVEDP)?
pressure in the L ventricle during diastole
Normal range is 5-12 mm Hg
What is ejection fraction?
percentage of blood emptied from ventricle during systole; a clinically useful measure of LV function
How is EF calculated?
SV/LVEDV
Norms for EF
Normal EF averages >55%
The lower the EF , the more impaired the LV
What is atrial filling pressure?
the differences between atrial and venous pressures
Factors that affect atrial filling pressure
1- R atrial filling pressure is decreased during strong ventricular contraction, and atrial filling is enhanced
2- R atrial filling pressure is affected by changes in intrathoracic pressure; decreases during inspiration and increases during coughing or forced expiration
3- venous return increases when blood volume expands and decreases during hypovolemic shock
Diastolic filling time ______ with increased heart rate and with heart disease.
decreases
What does myocardial oxygen demand (MVO2) represent?
The energy cost to the myocardium
* MVO2 increases with activity and with HR and/or BP
How is MVO2 measured?
Clinically measured by the product of heart rate and systolic BP, known as the rate pressure produce
