Heart Wall - Tissue Functioning and Remodeling in the Circulatory and Ventilatory Systems - page 304

Tabl e 6. 5. Structural elements of heart valves, with the 3 layers: (1) the ventricularis (rich in
elastin); (2) the central spongiosa; and (3) the fibrosa (with packed collagen). Forces applied on the
valve leaflets (pressure, shear, tension, and bending) are borne by structural rearrangement (fiber
reorientation, folding, uncrimping, and compaction). Collagen and elastin fibers cooperate. Align-
ment of packed collagen bundles transfers forces between the cusps and the wall. Corrugations of
the cusp face in front of the wall (fibrosa) help size and shape changes during the cardiac cycle.
Microscopic collagen foldings (crimps) enable lengthening from low stresses. The anisotropic
behavior is responsible for required differences in radial and circumferential extensibility. Cusp
coaptation prevents valve prolapse. The trileaflet semilunar ventriculoarterial valves are inserted
and supported by aortic and pulmonary roots. The atrioventricular valves are inserted on an
annulus. Chordae tendineae and papillary muscles maintain the atrioventricular valve closed during
blood ejection from the ventricles into the corresponding arteries (Source: [ 587 ]).
Component

Function

Cells Interstitial cells synthesize and remodel ECM

(fibroblasts, smooth myocytes, myofibroblasts)
Valvular endothelial cells regulate the behavior
of flowing and mural cells

Matrix Elastin fibers extend in closed valve

and shrink in open valve
Collagen fibers maintain coaptation in closed valve
Proteoglycans associate with matrix fibers
for stress accommodation

Blood vessels Valve cusps are avascular

Nutrient/waste transport from heart cavity
and myocardial vessels

Nerves Regulation of coordinated activity

of heart components

free edge

fibrosa

spongiosa

ventricularis

Fig. 6.3 Ventriculoarterial valve layers, according to the internal collagen network of the valve
leaflets: fibrosa, spongiosa and ventricularis from the wavy arterial face to the smooth ventricular
face. Collagen fibers provide strength, elastin fibers elasticity and proteoglycans swelling. Collagen
architecture is mediated by mechanical loading.