Page 104 - Tailoring Electrospinning Techniques for Regenerative Medicine - Marc Simonet

CHAPTER 5
Figure 5.2 Hemodynamic parameters that apply on the aortic valve (transvalvular pressure di erence, cardiac output and heart rate) and its diameter during development from neonate to adult. The data for this graph was obtained from several databases, among which the National Heart Lung and Blood Institute, MedScape and literature.23
6.4.2 Structure and composition of semilunar heart valves
Fibrous load-bearing tissues, such as heart valves, can be considered as composite materials, mainly consisting of cells and extracellular matrix, organized to perform a specialized function. Mechanical functioning is determined by the organization and composition of the extracellular matrix (ECM) as well as the interactions between the matrix and the cells. The ECM is composed of a network of fibrous proteins, predominantly collagen and elastin, embedded in a gel of proteoglycans, glycoproteins and water. It provides mechanical support and
anchorage to the cells and guides and restricts mechanical deformation of the tissue. The collagen fibers provide tensile strength to the tissue, whereas the elastin fibers give the tissue its resilience. The hydrated gel provides resistance when the tissue is compressed. These tissues are rich in collagen and their strength mainly depends on collagen architecture, i.e. collagen fiber length, fiber diameter, fiber organization (e.g. alignment), and fiber cross- linking.26,27
The main load-bearing parts of the valves are the leaflets. At first sight, these may look like simple structures, but they are complex and mechanically
102