APK 2105C Lecture Notes - Lecture 32: Smooth Muscle Tissue, Mean Arterial Pressure, Aorta

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Chapter 14, Lecture 3
Vessels & Blood Pressure
Review of the vessels
o Lumen
o Endothelium
Only layer in capillaries
Allow for diffusion
o Smooth muscle
Veins have less smooth muscle than arteries
o Connective tissue
o Arterioles have highest ability to generate resistance against blood flo
o Arteries are both stiff and flexible
o Artery arteriole capillary venule vein
Arteries are both stiff (collagen) and flexible (elastic)
Have lots of smooth muscle in them
Very elasticgood for blood flow
Lots of collagen in walls of arteriesmore than in veins
o Collagen is very strongadd stiffness to artery walls
Vein has larger lumen
Blood vessels and pressure
o Blood vessels expand when pressure inside it increasecontracts when
pressure falls
Degree of distention depends on transmural pressure
Dependent on pressure inside and outside the vessel
o Ex: if pressure outside is high, won’t be able to expand as
much when pressure increases inside
o Elasticity acts to push back on pressure trying to expand
the vessel
More important in arteriesmore elastic
o Compliance = change in volume per unit change in transmural pressure
The ease with which a vessel expands
If walls are very stiff, generates lots of pressure inside (arteries)
Arteries have low complianceveins have higher
Compliance = change in volume / change in (pressure inside pressure
outside)
o Arteries = pressure reservoir
Low compliance from collagen, elasticity
Wall stores pressure and help maintain BP
Takes a lot of transmural pressure to get them to distend
o Arterial BP
Systolic BP (SBP) = max pressure in aorta occurs
Diastolic BP (DBP) = min pressure in the aorta occurs
Mean arterial pressure (MAP) = average pressure in the aorta during a
cardiac cycle
MAP = (SBP + DBP + DBP) / 3
MAP = [SBP + (2 x DBP)] / 3
At rest, we spend more time filling our hearts
o Measuring BP
Best way is inter-arteriolydirect method
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