Regional Variation in the Microscopy and Tensile Strength of the Linea Alba in the Male Goat (Capra Hircus)

Abstract

The linea alba (LA), a midline tendinous structure formed by the interlocking anterior abdominal wall aponeurotic fibers, acts as a passive tensile band that prevents sagging of the lower abdomen. The microstructure and the strength of these fibres would thus be expected to reflect on the forces that act on the linea alba. This study was undertaken to establish the histomorphology, morphometry and tensiometric characteristics of the linea alba of the goat so as to elucidate on the elements that are responsible for maintaining the integrity of the wall. Tissues resected from the linea alba in six male goats and prepared for routine light microscopy and stained with Weigert resorcin–fuchsin stain revealed three distinct laminae namely a superficial, intermediate and deep. The superficial lamina of goat epigastric linea alba, which was closely apposed to the overlying elastic tunica flava abdominis (deep fascia), was made up of predominantly obliquely aligned collagen bundles, an intermediate lamina comprising longitudinally aligned collagen bundles and a deep lamina consisting of transversely oriented collagen fibres. When exposed to longitudinal traction, the epigastric LA on average was the stiffest at 35 N/mm² with an elastic coefficient 350 N/mm² while the hypogastric LA was the weakest at 26.5 N/mm² with an elastic coefficient 217 N/mm² respectively. In conclusion, the epigastric LA was well suited for longitudinal load strength to support the compound stomach during grazing while the relatively elastic hypogastric LA was most suited for allowing a degree of midline sagging during browzing. The variations noted in tensiometry suggest that the hypogastric linea alba is more compliant to stretch but more predisposed to tearing than the epigastric line alba especially when exposed to sudden violent force or trauma.

Keywords: linea alba, histomorphology, tensile strength, collagen fibers, elastic fibers