Tunica Adventitia of the Aorta is an Active Vascular Compartment

Abstract

The tunica adventitia has previously been regarded as a passive connective tissue covering that offers only nutritive and physical support to the arterial wall. Recently, however, emphasis has been given to its role in atherosclerosis. Although the normal structure may bear the anatomical basis of these functions, microscopic anatomy of the tunica adventitia in normal arteries is seldom reported. These data are important in understanding disease process and potential areas of intervention. The goat is a suitable model for studying cardiovascular disease and the aorta is frequently afflicted by atherosclerosis. This study, therefore, aimed at describing the structure of tunica adventitia of normal aorta in goat. Materials for the study were obtained from abdominal aorta of 6 healthy young adult male goats (capra hircus) age range 12 – 24 months. Fresh specimens from euthanized animals were fixed in 3% phosphate buffered glutaraldehyde, post fixed in 1% phosphate buffered osmium tetroxide then embedded in durcupan. Ultrathin sections were stained with uranyl acetate counterstained with lead citrate and examined with electron microscope. Some specimens were processed routinely for paraffin embedding and sectioning. They were stained with Mason’s Trichrome and Weigert elastic/Van Gieson stains. The tunica adventitia was fibroelastic with numerous capillaries, arterioles and multiple cell types. The cells were active fibroblasts, phagocytic, perivascular and endothelial cells embedded in the fibrous stroma. These findings suggest that the tunica adventitia of the goat aorta is a metabolically active vascular compartment. These features namely microvasculature and multiple cell populations probably enable it to maintain structural and functional integrity and appropriately respond to vascular injury.

Keywords: Tunica Adventitia, cells, Capillaries, Arterioles, Atherosclerosis