Anatomical study of the variation in the branching patterns and histology of the aorta in a South African population
The documentation of variations in branching patterns of the aorta among South African populations is limited. Histological changes in the aortic wall have been documented and may be due to pathology and physiological processes. Whether these changes are solely due to physiological processes such as haemodynamics or pathology is yet to be determined. The present study aims to document the branching patterns of the aorta in a South African population and to distinguishing which particular histological changes in this vessel wall can be associated with haemodynamic forces rather than pathology. Seventy one cadavers from the University of Cape Town MBChB programme were used to document the branching pattern of the aorta. Twenty five random complete aortae with no evidence of macroscopic pathology were collected from Salt River Mortuary and used for histological examination. Seven sections (taken from branching and non-branching sites along the aorta) from each sample were stained with haematoxylin and eosin, alcian blue pH2.5 - periodic Schiff reaction and elastin von Gieson’s for histological analysis using a Zeiss Axioskop Mot upright microscope and Axiovision 4.7 software. Variation in the branching pattern of vessels along the length of the aorta was found in 49% of the cadaver sample. A variety of histological variations of the wall of the aorta in the mortuary sample was noted. Noteworthy variations include the abundance of acid mucopolysaccharide, the increased thickness of the tunica intima, and increased elastin fragmentation of the tunica media at branching sites of the aorta. A pronounced curved ridge-like structure was indentation on the luminal surface at the junction of the arch and descending aorta in 74% of the mortuary sample. The presence of this aortic ridge was association with younger aged individuals (Chi-square 4.57, p=0.56). A high frequency of gross variation in branching patterns of the aorta is present in this cadaver sample, including some rare patterns of variation. Clinically, knowledge of these variations would be relevant and useful to anatomists, radiologists and head, neck, thoracic and vascular surgeons. An explanation for the abundance of acid mucopolysaccharides may be the link between acid mucopolysaccharides and diet, however this needs further investigation. Altered haemodynamic forces created by turbulent flow at branching sites is proposed as the explanation for the increase in the thickness of the tunica intima and increased elastin fragmentation at the branching sites of the aorta, although other factors such as the effects of HIV in the vessel wall of this sample are yet to be determined. This study proposes that the aortic ridge is a result of the closure of the ductus arteriosus.
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