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- • consist of leaflets or cusps made of
- endothelial & connective tissue.
- •purpose: to prevent backflow of blood from the ventricle through the AV valves into the
- •The mitral valve is on the left, and the
- tricuspid is on the right.
•close passively, are fairly thin–they actually require a minimal amount of backflow for them to close,
- •The av valves have papillary muscles–that
- attach to the vanes of the valve–their attachments are the chordae tendineae,
- they have that parachute appearance.
- •When the ventricles contract, the
- papillary muscles also contract. That
- pulls the vanes of the valves inward toward the ventricle so that the backflow
- doesn’t push them into the atria.
- •The contraction of the papillary muscles
- is not what closes the valves, but rather the backflow of blood which closes
- the valves.
- •If there is papillary muscle
- dysfunction–like in a rupture, or paralysis of the papillary muscle–if that
- happens the valve would bulge back into the atria. There could be anything from a small leak to full-blown cardiac failure if that were to occur.
In contrast to AV valves, the semi lunar valves:
- •Are heavier, and because they areheavier, more backflow is needed for a longer period of time for them toclose.
- •Because the pressure in the aorta andpulmonary artery are high, the valves actually snap closed.
- •The openings of the semilunar valves are smaller than the AV valves.
- •Because the openings of the semilunar valves are smaller, the velocity of blood going through those valves isgreater.
- •Since the velocity is greater, thosevalves ( semilunar) are subject to much more mechanical abrasion.
- •The semilunar valves do not have the samepapillary muscle & chordae tendineae support, so they need to be heavierand strong, but they also need to be pliable to handle the stress of that highvelocity flow.
Normal aortic valve area =
Normal mitral valve area =
- Normal aortic valve area =
Normal mitral valve area = 4-6cm2
Stenosis vs Regurgitation
- There are 2 types of deficiencies
- or defects:
1.Stenosis = narrowed opening,
- usually because of fibrosis with calcification. This
- decreases the cross-sectional area, and ultimately what happens is the cusps
- fuse together, which limits the ability of the valve to open at all.
- 2.Insufficiency/regurgitation (effectively the same thing): the
- leaflets do not seal completely.
- Consequently, the blood will go from the distal to the proximal
- chamber. Again, we’ll talk about valve
- insufficiency/valve regurgitation as being essentially the same thing (using
- the terms interchangeably).
•Ohm’s Law & Poiseuille's Law come into play, in the case of the stenotic valve in
particular, because stenosis will increase
resistance to flow.
Because Resistance is inversely related to the
radius of the valve to the 4th power,
If the average valve radius is decreased by half?
the resistance is increased 16-fold
Q = ΔP pie r4 / 8 nl