Regional Differences in the Tunica Media of the Uterine Artery of Domestic Pig (Sus Scrofa Domesticus): Basis for Uterine Blood Flow Regulation

Abstract

This study aimed at describing the structure of tunica media of the uterine artery of domestic pig, since this structure influences the pattern of blood flow and reproductive performance. Specimens were obtained from main trunk, broad ligament segment and the terminal portion of twelve healthy adult domestic pigs (Sus scrofa domesticus) age range 6 – 18 months. They were fixed in 10% formaldehyde solution, and routinely processed for paraffin embedding and sectioning. Seven micron thick sections were stained with Hematoxylin & Eosin, Mason’s Trichrome and Weigert resorcin fuchsin counterstained with Van Gieson stains. Tunica media comprising predominantly smooth muscle occupied approximately fifty percent (50%) of the volume of the entire wall with vasa vasora present deep into its inner zone. It showed zonal and regional variation in that in the main trunk and broad ligament segments was divided into inner two thirds having   predominantly circular smooth muscle orientation while outer third was  preponderantly fibroelastic with longitudinally disposed smooth muscles. The terminal segment had only circular layer. Density of vasa vasora  declined distally. The predominantly muscular tunica media of the uterine artery in pigs shows zonal and regional suggesting segmental   differentiation of function. The main trunk of this artery, due to its  additional longitudinal layer of smooth muscle may be involved in  regulation of blood flow to the uterus depending on the functional  demands of the uterus.