Comparative anatomy and development of the carotid‐basilar arterial trunk in vertebrates

Abstract

In order to assess general patterns of vertebrate hindbrain vasculature, we dissected a wide taxonomic range of latex‐injected specimens. Examinations of distantly‐related taxa including cyclostomes, elasmobranchs, actinopterygians and sarcopterygian tetrapods demonstrated a conserved suite of hindbrain vascular features including: 1) the origin and branching of cerebral (internal) carotids; 2) the ontogenetic origins of the basilar artery from paired precursors; and 3) the presence of a quasi‐segmental series of transverse basilar artery branches that extend circumferentially around the brainstem, giving off penetrating vessels. The major exception to this general pattern is found in teleosts, in which a series of midline segmental central arterial stems arise from the basilar artery and branch into intramural vascular trees within the sub‐ependymal zone of the hindbrain. The restriction of penetrating arteries to a series of dominant medial segmental stems in teleosts is derived relative to other vertebrates and may be part of a set of key innovations in this group. Phylogenetic analysis suggests that paired basilar arteries are primitive for jawed vertebrates, with unpaired basilars arising independently in chondrichthyes, teleosts and tetrapods. The hypothesized independent development of unpaired basilar arteries may represent convergence towards similar neurovascular functional designs. Given the highly dissimilar body plans and lifestyles of these groups, the overall conservation of hindbrain macrovasculature likely results from the primitive, shared similarity of embryonic brain development.Grant Funding Source: None