vascular physiology Flashcards
artery
thicker walls - varying in diameter - more smooth muscle for contraction - most elastic tissue to maintain the pressure and help maintain the driving pressure from ventricular contraction “resistance”
arteriole
variable resistance, smallest vessel that still has smooth muscle
capillary
no connective tissue, single layer of endothelial cells, all exchange happens, no variable resistance because no smooth muscle - radius is fixed because no smooth muscle
venule
smallest vein
vein
largest diameter of veins, wall thickness can be less not much elastic tissue because it is the volume reservoir “capacitance”
veins vs arteries valves
valves keep it going in one direction to go against gravity and back to the heart prevents no back flow - arteries have no valves because it has high pressure and there is a low pressure in the veins
why are arterioles important
main site of variable resistance in the circulatory system because they have smooth muscle
contribute to more than 60% of total peripheral resistance or resistance to blood flow in the circulatory system - relaxes smooth muscle and wont relate
Metarteriole
allows materials to get around capillaries if the beds are too large. WBC are larger than the size of the capillary
pre-capillary sphincter
At the point where each of the capillaries originates from an arteriole, a smooth muscle fiber encircles the capillary.
pericytes
line the outer surface of the endothelial cell and compromise the adventitia. undifferentiated and serve as support cells. they can differentiate further into smooth muscle, fibroblasts or macrophage cells if needed. important in forming the BBB
paracellular capillary exchange
around the cells through pores between cells
transcellular capillary exchange
fenestrations or pores in the endothelial cell membrane
transcytosis
vesicle-assisted diffusion - small peptides can cross through this process
bulk flow
movement of H2O and dissolved solutes - filtration and absorption
how does most capillary exchange occur
diffusion (paracellular or transcellular) or transcytosis
continuous capillaries
found in muscles, nerves, connective tissues - leaky junctions and transcytosis
fenestrated capillaries
found in GI and kidney - large pores and transcytosis
alterations in capillary exchange can cause
ascites (fluid accumulation in abdominal cavity) and peripheral edema
Hydrostatic (filtration) pressure > osmotic (absorption) pressure
net outward flow, can cause edema in the tissues
Hydrostatic (filtration) pressure < osmotic (absorption) pressure
net inward flow
hydrostatic (filtration) pressure
Pcap - PIF, essentially BP
osmotic (absorption) pressure
osmotic IF - osmotic cap
why doesn’t colloid osmotic pressure change
it is composed of the proteins, this can change if protein is lost in the urine or malnutrition
why is there ankle edema
there is a reduced blood pressure the farther it gets from your heart, if the hydrostatic pressure (BP) is below the osmotic pressure then there will be a net outward filtration and this filtration can go into the tissues causing edema
3 main functions of the lymph system
returns excess fluid from capillary filtration
filters pathogens
transfers lipids from digestive system to circulatory system
why is lymph system a pumpless system
there is a pressure gradient. only flows towards the heart
lymph vessel features that help lymph flow back to the circulatory system
large lymph vessels have smooth muscle
skeletal muscle pump helps lymph flow uphill back towards the heart
some lymph vessels have valves
lymphedema
surgery which the lymph nodes are removed due to diagnosis or cancer (can be breast cancer)
lymphedema treatment
NISAIDs - reduce inflammation
exercise or compression
Central Venous Pressure (CVP)
pressure found in large veins that lead back to the heart (vena cava) driving pressure for venous return to the heart. veins are capacitance vessels that are reservoirs for more than 50% of blood volume in the circulatory system. venous constriction is a mech that blood can be shunted to area of higher need. assess cardiac preload and volume status in critically ill patients, assist in the diagnosis of right-sided heart failure
4 factors that contribute to CVP
- skeletal muscle pump
- respiratory pump
- blood volume
- venomotor- amount oof veins are constricted
venomotor
resting tone generated response to SNS from NE that acts on alpha 1 keeping the veins contracted against the pressure of the blood flowing through them. w/o - blood will pool in the veins bc of their compliance to stretch and expand.
increase in venomotor tone will
increase CVP, EDV, SV, CO, MAP, venous return, preload, arterial pressure- decrease venous compliance, regulated by alpha receptors or vasodialators
