A COMPARATIVE STUDY ON THE STRUCTURE AND FUNCTIONS OF AORTA IN MAN AND RUMINANT ANIMALS N. Shakuntala Rao * 1 , K. Sujatha 2 , K Meera 3 , H.R. Krishna Rao 4 . *1 Professor, Department of Anatomy, P.E.S. Institute of Medical Sciences and Research, Kuppam, Andhra Pradesh, India. 2 Assistant Professor, Department of Anatomy, P.E.S. Institute of Medical Sciences and Research, Kuppam, Andhra Pradesh, India. 3  Assistant Professor, Department of Anatomy, P.E.S. Institute of Medical Sciences and Research, Kuppam, Andhra Pradesh, India. 4  Professor and Head, P.E.S. Institute of Medical Sciences and Research, Kuppam, Andhra Pradesh, India Address   for   Correspondence:    Dr.   N.   Shakuntala   Rao,   Professor,   P.E.S.   Institute   of   Medical   Sciences   and   Research,      K uppam,   Andhra   Pradesh   517425,   India. E-Mail: drshakuntala@gmail.com ABSTRACT Background:      In   large   elastic   arteries   the   media   has   elastin   fibres   and   collagen   fibres   to   maintain   pressure   during   the   cardiac   cycles   of   systole   and   diastole. The   contracting   heart   stretches   the   elastin   in   their   walls   and   after   the   ventricle   finishes   contraction   and   the   valve   is   closed   the   walls   of   the   elastic   arteries contract   passively   to   maintain   pressure   for   the   short   interval   between   filling   and   contraction.   In   contrast   to   the   function   of   elastic   arteries   that   maintain pressure   the   muscular   arteries   or   distributing   arteries   have   the   function   of   supplying   blood   to   different   parts   of   the   body   under   varied   conditions.   Since   the domestic   animals   have   a   different   set   of   branches   from   the   aorta   as   was   observed   by   the   authors   in   a   previous   study   comparing   them   with   human   aorta this study was undertaken to study the differences in the histological differences in the aorta of man and domestic animals.  Materials   and   Methods:   The   heart   specimens   of   the   domestic   animals   were   obtained   from   the   local   butcher   who   had   legal   permission   to   sacrifice   the animals   for   sale.   The   heart   was   removed   carefully   along   with   the   arch   and   its   branches   and   processed   for   the   histological   observations   with   use   of   standard histological slide preparation. Results:   It   was   found   that   the   section   of   the   aorta   taken   at   the   origin   had   elastic   fibres   in   the   mediassthe   brachiocephalic   trunk   had   muscle   fibres   arranged in bundles between the elastic fibres and the part of aorta going posteriorly to form the descending aorta also had muscle bundles in the     Conclusion:   The   arrangement   of   muscle   fibres   in   the   anterior   aorta   which   supplies   the   head,neck   upper   limbs   could   be   significant.   The   function   of   aorta   to maintain   pressure   during   the   cardiac   cycle   of   systole   and   diastole   is   taken   care   of   by   the   elastic   fibres.   The   distributive   function   of   supplying   blood   according to   the   needs   of   the   parts   of   the   head   is   probably   served   by   the   muscle   bundles   present.   This   could   be   due   to   the   continuous   adaptation   of   the   animals   to the environment for feeding and locomotion towards and against gravity. 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