Lecture 11 Flashcards
Vascular Distensibility
Increase in volume/increase in pressure*original volume
Vascular Compliance
Increase in volume/increase in pressure; also equal to distensibility*volume
Relationship between capacitance and volume and capacitance and pressure
Capacitance is directly proportional to volume and inversely proportional to pressure; much greater in veins than in arteries; capacitance of arteries decreases with age
What happens to the compliance as the amount of elastic tissue increases?
Compliance decreases
What is compliance measuring?
Measure of the ease with which a hollow viscus may be distended (the volume change resulting from the application of a unit pressure differential between the inside and outside of the viscus; reciprocal of elastance
Elastance
Measure of the tendency of a hollow viscus to recoil toward its original dimensions upon removal of a distending or collapsing force
Pulse Pressure
Stroke volume/arterial compliance
Factors that affect pulse pressure
Stroke volume output of the heart (most important determinant) and compliance of the arterial tree
Conditions causing abnormal contours of the pressure pulse wave
Aortic valve stenosis, arteriosclerosis, patent ductus arteriosus, or aortic regurgitation
Aortic Valve Stenosis
Diameter of the aortic valve opening is reduced significantly, and the aortic pressure pulse is decreased significantly
Arteriosclerosis
Hardening of arterial walls
Patent Ductus Arteriosus
Half or more of the cardiac output flows back into the pulmonary artery and lung blood vessels
Aortic Regurgitation
Aortic valve is absent or will not close completely; pressure may fall all the way to 0 between heartbeats
Mean Arterial Pressure
Average arterial pressure with respect to time; not simple average of systole and diastole because a larger fraction of the cardiac cycle is spent in diastole than systole; calculated by adding diastolic pressure and 1/3 of the pulse pressure
Central Venous Pressure
Pressure in the right atrium; regulated by ability of heart to pump blood out of the right atrium or ventricle and tendency of blood to flow into the right atrium
Factors that increase venous return (which increases right atrial pressure)
Increased blood volume, increased peripheral venous pressures due to increased large vessel tone, and dilation of arterioles
Varicose Veins
Defects of the valves of the veins, commonly in the legs
Arterioles
Control blood flow to each tissue; local conditions in tissues control diameters of arterioles; highly muscular until it is lost in metarterioles
Capillaries
Smooth muscle fiber encircles capillary at point where it originates from a metarteriole (referred to as a precapillary sphincter); capillaries in the liver, GI tract, and kidneys have pores
Capillary Wall
Unicellular layer of endothelial cells; thin basement membrane; total wall thickness is .5 micrometers; internal capillary diameter is 4-9 micrometers
Slit Pores
Allow for rapid diffusion of water, water-soluble ions, and small solutes
Plasmalemmal Vesicles
Formed from caveolins; play a role in endocytosis and transcytosis
Most Important Factor in Regulating Vasomotion
Concentration of oxygen in the tissues
Diffusion and Capillary Exchange
Review Slides 40-42 in Lecture 11
Starling Forces
Determine direction of diffusion into or out of a capillary
Factors that Increase Lymph Flow and Interstitial Fluid Pressure
Elevated capillary hydrostatic pressure
Decreased plasma colloid osmotic pressure
Increased interstitial fluid colloid osmotic pressure
Increased permeability of capillaries
Rate of Lymph Flow
Interstitial fluid pressure*activity of lymphatic pump
