In this article we will discuss about modification of aortic arches in various vertebrates.
Modification in Fishes:
Branches from ventral aorta produce aortic arches, which divide into capillary beds within the gills. The part of the aortic arches delivering blood to the gills is called afferent branchial artery. From the dorsal end of the capillary bed arises another artery, called efferent branchial artery, which joins the dorsal aorta.
The capillary beds partially or completely encircle the gills and empty first into the collecting loop that joins the efferent artery (Fig. 2.43).
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The first afferent artery, which is expected to supply first pharyngeal slit, goes to a vascular sprout adjacent to the first pharyngeal slit. This vessel constitutes the afferent spiracular artery. The dorsal section of the first arch forms the efferent spiracular artery.
The remaining aortic arches (II – VI) complete the circle (Fig. 2.44A). The external carotid artery arises embryo-logically from the anterior end of the ventral aorta and becomes associated with the collecting loop, to carry oxygenated blood to the lower jaw.
The internal carotid artery supplying the brain, receives oxygenated blood from the first fully functional collecting loop (pharyngeal slit II) via the efferent branchial artery (II) (Fig. 2.44B).
