Lecture 11: Arterial venous lymphatic systems Flashcards
Vascular distensibility equation
VD= Increase in volume/ Increase in pressure X original volume
Vascular distensibility in arteries vs veins
Veins are 8x more distensible than arteries
Pulmonary vein distensibility is same as systemic veins
Pulmonary arteries are 6x more distensible than systemic arteries
Vascular compliance equations
VC= Increase in volume/Increase in pressure VC= VD x Original volume
Capacitance describes the
Distensibility of blood vessels - how volume changes in response to a change in pressure
Capacitance is directly proportional to _______ and indirectly proportional to ______
Directly proportional to volume, indirectly proportional to pressure
Capacitance is much greater for ______ than for ______
Greater for veins than for arteries
The greater the amount of elastic tissue in a blood vessel…
The higher the elastance
The lower the compliance
Vascular compliance is the
Total quantity of blood that can be stored in a given portion of the circulatory system
Pulse pressure equation
PP= Stroke volume/arterial compliance
Factors affecting pulse pressure
Stroke volume output of the heart (most important factor)
Compliance of the arterial tree
Conditions causing abnormal contours of the pressure pulse wave
Aortic valve stenosis
Arteriosclerosis
Patent ductus arteriosus
Aortic regurgitation
Aortic valve stenosis
Diameter of the aortic valve opening is reduced significantly, and the aortic pulse pressure is decreased significantly
Blood flow through the aortic valve is diminished
Patent ductus arteriosus
Half or more of the cardiac output flows back into the pulmonary artery and lung blood vessels
Diastolic pressure falls very low before next heartbeat
Aortic regurgitation
The aortic valve is absent or will not close completely
Aortic pressure may fall all the way to 0 b/w heartbeats
The progressive reduction of the pulsations in the periphery=
Damping of the pressure pulses
Mean arterial pressure equation
MAP= Diastolic pressure + 1/3 pulse pressure
Central venous pressure equals
Pressure in the right atrium
Factors that regulate right atrial pressure
Ability of the heart to pump blood out of the right atrium/ventricle
Tendency of blood to flow into the right atrium
Factors that increase venous return/right atrial pressure
Increased blood volume
Increased peripheral venous pressures due to increased large vessel tone
Dilation of arterioles
Arterioles
Small arterioles control blood flow to each tissue
Local conditions in tissue control diameters of arterioles
Arterioles are highly muscular
Capillaries
Smooth muscle fiber encircles capillary at point where it originates from a metarteriole (referred to as a precapillary sphincter)
Capillary wall
Unicellular layer of endothelial cells
Thin basement membrane
0.5um thick
Internal capillary diameter 4-9um
Vasomotion
Cyclical opening and closing of precapillary sphincters
Slit pores
Capillaries
Intercellular clefts- spacing of 6-7nm
Allow for rapid diffusion of water, water-soluble ions and small solutes
Plasmalemmal vesicles
In capillaries
Formed from caveolins
Play a role in endocytosis and transcytosis
Some capillaries in these organs have pores
Liver, GI tract, kidneys
Most important factor regulating vasomotion
Concentration of oxygen in the tissues
These lipid soluble substances can diffuse readily through the capillary cell membranes
Oxygen
Carbon dioxide
Non lipid soluble diffuse through pores/clefts
Rate of water diffusion through capillary is __x faster than flow of plasma within capillary
80x faster
Passage of substances through interstitium is mostly through ________ rather than ________
Through diffusion rather than flow
-This is due to large number of proteoglycan filaments in interstitium
Rivulets
Occasionally form in interstitium and allow fluid flow
Starling forces determine
Direction of diffusion into or out of a capillary
Four types of starling forces
Capillary pressure (outward force)
Interstitial fluid pressure (inward force)
Capillary plasma colloid osmotic pressure (inward force)
Interstitial fluid colloid osmotic pressure (outward force)
Net filtration pressure
Sum of all four starling forces
Capillary filtration coefficient
Takes into consideration the number and size of pores
Filtration= NFP x Kf (Kf=Capillary filtration coefficient)
Lymph flow reaches maximum when
Interstitial pressure rises slightly above atmospheric pressure
Factors that increase lymph flow (and also 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 X activity of lymphatic pump
