Evolution of aortic arches in aves

Presented by:m.Jhansi lakshmi

M.Sc zoologyuom

Introduction

• Phylogenetic modifications with in this basic pattern of arteries and veins are largely correlated with functional changes.

• In transition from water to land gills gave rise to lungs.

• In some fishes and certainly in tetrapods, cardinal veins become less involved in blood return.

• In various adult vertebrates the arterial system appears to be different from their embryonic aortic arches.

• Studies of development shows that they are built on the same fundamental plan.

• There is a progressive reduction in number of aortic arches in vertebrate series.

• Tetrapoda- reduction in number of aortic arches DONOT break up into afferent and efferent parts because true internal gills are ABSENT.

• In all tetrapoda the first and second arches disappear.

• The number of primitive aortic arches and branchial arches from which they run are still debated.

• The number of aortic arches varies in living forms.

• Nevertheless only upto six pairs customarily appear during embryonic development.