Table 2.

Correlation between the ratio of intramural collagen to elastin (C:E) and the in vivo axial prestretch of common carotid arteries from multiple species. Note, too, that smaller values of C:E correlate with higher values of the mean heart rate (beats per minute), emphasizing the important role of elastin in cyclically distended arteries. Indeed, elastin is absent in arteries within invertebrates or primitive vertebrates having low pulse pressures, presumably because elastic fibers enable large arteries to “damp out the pulsatile flow and blood pressure” (Faury, 2001) and they confer arteries with the “properties of elastic recoil and resilience” (Mathieux and Weiss, 2005). Data from Cox (1975), van Loon et al. (1977), Weizsacker et al. (1983), Lacolley et al. (2001), Jackson et al. (2002), and Gleason et al. (2007). Collagen and elastin contents are not listed for the human data because age was not specified for the in vivo stretch data.