Cardiovascular Flashcards
Layers of the Heart
Pericardium: fibrous covering around heart holding it in place, providing physical protection and a barrier to infection
Myocardium: muscular portion, forms walls of atria and ventricles
Endocardium: thin three layered membrane lining the heart
what is between the visceral and parietal layers
pericardial cavity, a portential space containing 30-50 mL of serous fluid. this minimizes friction as the heart contracts and relaxes. Also the site of pericarditis and hemopericardium
AV Valves
supported by papillary muscles, which project form the walls of the ventricals, and chordae tendineae, which attach to the valve.
Chordae tendineae
cordlke structures that support AV valves and prevent eversion into the atria during systole
Fibrous Skeleton
provides structural support and isolating force for electrical impulse
What happens when excess blood enters the heart
the atria is distended, excess blood is pushed back into the veins.
Cardiac cycle
Systole and diastole:
Sys: period in which ventricles contract.
Dias: ventricles relax and fill with blood.
electrical activity precedes mechanical events
Semilunar valves opening
signal the onset of the ejectrion period. sixty percent of stroke volume is ejected during the first quater of systole, 40% ejected during the next two quaters of systole
Closure of the AV valves
first sound, healds the onset of of systole
S2
blood from the large arteries flows back toward the ventricles, causing the aortic and pulmonic valves to snap shut
The last third of the cardiac cycle
atrial contraction and accounts for 20% of the filling of the ventricles
what is the difference between end diastolic and end systolic volumes
stroke volume
Cardiac output
the efficiency of the heart is measured by this. HR x SV = CO
Cardiac REserve
the maximum percentage of increase in CO above normal resting level
Preload
volume of blood pumped per heartbeat. largely determined by venous return
AFterload
the pressure it must generate to pump the blood out of the heart. systemic arterial pressures main source of afterload on the left heart.
Cardiac Contractility
the ability of the heart to change its force of contraction without changing its resting diastolic length
Frank-Starling mechanism
the change in preload. briefly an increase in venous return to the heart increases the filled volume of the ventricles, which stretches the muscle fibers thereby increasing their preload.
The greater the amount of volume of blood in the heart before contraction, the greater the volume of blood ejected from the heart
Changes in ventricular inotropy (contractility)
alter the rate of ventricular pressure development (heart failure)
Pulmonary circulation
moves blood throught he lungs and creates a link with the gas exchange function of the respiratory system. right heart, pulmonary artery carries venous blood. and pulmonary veins are the only ones that carry arterial. low pressure, low resistance, short system
Systemic circulation
all other tissues of the body. includes the coronary system. left heart, brain and tissues, veins from the lower body merge to form the inferior vena cava and those from the head and upper extremities form the superior vena cava.
Composition of blood vessels
Tunica externa- outermost layer. primarily loosely woven collagen fibers that protect the blood vessel and anchor it to surrounding structures
Tunica media: largely smooth muscle that constricts to control diameter
tunica intima: single layer of flattened endothelial cells. prevents platelet adherence and blood clotting
Venous System
veins are capable of enlarging and storing large quantities of blood. when blood is lost, veins constrict. valves prevent retrograde flow.
heat syncope
think of a sudden decrease in muscle support to venous system, after running or strenuous exercise. think of marathoners laying down after race
Microcirculation
the nutrient flow is blood flow through capillary channels designed for exchange of nutrients and metabolites. blood flow bypasses the capillary bed moving through an arteriovenous shunt which directly connects an arteriole and a vein.
Nonnutrient flow
does not allow nutrient exchange. common in the skin and are important for heat exchange and temperature regulation
blood pressure
stroke volume times heart rate times peripheral vascular resistance