Arterial, veinous and lymphatic systems Flashcards
What is vascular compliance?
=Increase in volume/ increase in pressure
= distensibility X original volume
Total quantity that can be stored in a given portion
Relation between capacitance, volume and pressure
Capacitance directly proportional to volume
Capacitance inversely proportional to pressure and to elastance
Compliance between veins and arteries
Greater for veins than arteries
Capacitance of arteries decrease with age
What is elastance?
Measure of the tendency of a hollow viscus to recoil towards original dimensions after removal of a distending or collapsing force
Major factors that affect pulse pressure
Pulse pressure= stroke volume/arterial compliance
Stroke volume output of the heart
Compliance
Conditions causing abnormal contours
Aortic valve stenosis
Atherosclerosis
Patent ductus arteriosis
Aortic regurgitation
Characteristics of Aortic valve stenosis
Diameter of aortic valve reduced
Aortic pressure reduced
Less blood flow
Characteristics of patent ductus arteriosis
Half or more of the cardiac output flow back into pulmonary artery and lung
Diastole pressure falls very low before next heartbeat
Characteristics of aortic regurgitation
Aortic valve absent or not completely close
Aortic pressure might fall to 0 between heartbeats
What is damping of the pressure?
Pressure lessen as blood moves through arteries due to compliance and resistance
What is mean arterial pressure ?
Average arterial pressure with respect to time
Closer to diastolic pressure
=diastolic pressure + 1/3 pulse pressure
What is central venous pressure
Pressure in the right atrium
Regulated by:
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 veinous return(increase right atrial pressure)
Increased blood volume
Increased peripheral venous pressure due to increased large vessel tone
Dilation of arterioles
Microcirculation and capillary system
Main control system to autoregulate blood flow
Small arterioles control blood flow to each tissue
Local conditions in tissues control diameter of arterioles
arterioles are highly muscular
Muscularity lost in metarterioles
What is vasomotion?
Cyclical opening and closing of precapillary sphincters
Regulated by concentration of oxygen in tissues
Role of diffusion in exchange of substances between blood and interstitial fluid
Lipid soluble diffuse through capillary cell membranes (O2, CO2)
Non lipid soluble diffuse through pores
Rate of water diffusion faster than flow of plasma
What is interstitium?
Spaces between cells (1/6 total volume of body)
Contain collagen fibers which provide most of tensional strenghts
Proteoglycan filaments thin coiled (98% hyaluronic acid, 2% protein), can not be seen in light microscope
What are the Starling forces?
Forces that determine direction of diffusion into or out of capillary
Papillary pressure (Pc)–>outward force
Capillary plasma colloid osmotic pressure(Pip)–>Inward force
Interstial fluid pressure (Pif)–>Inward force
Interstial fluid colloid osmotic pressure (pi if)–>outward force
What is net filtration pressure?
Sum of all Starling forces
=Pc+PIif-Pip-Pif
What is filtration?
=coefficient of filtration X net filtration pressure
Negative pressure in interstitial space due to lymph vessels contracting and pumping fluid into circulation
Filtration at end of capillaries
At arterial end plasma filters into the interstitial space
At venous end absorption is favored
Lymphatic system
Salvage proteins in the interstitial fluid into circulation
Without it oncotic pressure will increase and cause blood loss from capillaries
Lymphatic return
One way valve
Reaches maximum when interstitial pressure above atmospheric pressure
Increase lymph flow also increases interstitial fluid pressure
Factors that increase lymph flow
Elevated capillary hydrostatic pressure
Decreased capillary 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
What is vascular distensibility?
Increase in volume/(increase in pressure X original volume)
