Detailed Comparative Anatomy of the Extrinsic Cardiac Nerve Plexus and Postnatal Reorganization of the Cardiac Position and Innervation in the Great Apes: Orangutans, Gorillas, and Chimpanzees

Abstract

To speculate how the extrinsic cardiac nerve plexus (ECNP) evolves phyletically and ontogenetically within the primate lineage, we conducted a comparative anatomical study of the ECNP, including an imaging examination in the great apes using 20 sides from 11 bodies from three species and a range of postnatal stages from newborns to mature adults. Although the position of the middle cervical ganglion (MG) in the great apes tended to be relatively lower than that in humans, the morphology of the ECNP in adult great apes was almost consistent with that in adult humans but essentially different from that in the lesser apes or gibbons. Therefore, the well-argued anatomical question of when did the MG acquire communicating branches with the spinal cervical nerves and appear constantly in all sympathetic cardiac nerves during primate evolution is clearly considered to be after the great apes and gibbons split. Moreover, a horizontal four-chambered heart and a lifted cardiac apex with a relatively large volume in newborn great apes rapidly changed its position downward, as seen in humans during postnatal growth and was associated with a reduction in the hepatic volume by imaging diagnosis and gross anatomy. In addition, our observation using a range of postnatal stages exhibits that two sympathetic ganglia, the middle cervical and cervicothoracic ganglia, differed between the early and later postnatal stages. Anat Rec,

Developmental Morphology and Topography of the Components of the Cervical Sympathetic Trunk in Sheep (Ovis aries) During the Fetal Period

“…In this study, bilateral CCG was constantly noted in all specimens which is concordant with findings of all reported anatomical studies in the adults and fetuses of animals and humans (Hara et al, ; Pospieszny and Bruzewicz, ; Kawashima, ; Kawashima and Sato, ; Nourinezhad et al, ).…”

“…In accordance with findings of Kawashima and Sato () in lorisiformes and Kawashima et al () in the New World monkeys as low primates, the term “accessory middle cervical ganglion” (aMG) is reserved for a grossly visible independent ganglion which is situated immediately cranial to the main MG. The reported incidence of the aMG in the fetal sheep is almost similar to that in the lorisiformes (having most primitive morphology) rather than New World monkeys.…”

“…Conversely, evolutionary anatomical studies of the cardiac innervation in humans and primates also seem to support the conclusion above (Kawashima et al, ; Kawashima and Sato, ). They described that the SCG acquired gradually communicating branches with the cervical nerves in conjunction with their development in size in the primate linage from lorisiformes (having the most primitive morphology) to humans.…”

“…Waites () in the fetal and newborn sheep, illustrated only two middle cervical ganglia in his diagram: an upper and lower middle cervical ganglion, somewhat similar to that of this study. In this respect, without consideration of the existence of the vertebral ganglion, double middle cervical ganglion (humans by Axford,; Werte, 1959, 1962; Saylam et al, ) or multiple ones (great apes by Kawashima and Sato, ; the sheep by McKibben and Getty, ) were noted.…”

Evolutionary Anatomy and Phyletic Implication of the Extrinsic Cardiac Nervous System in the Philippine Tarsier (Tarsius syrichta, Primates) in Comparisons With Strepsirrhines and New World Monkeys

“…To increase our understanding of primate evolution, we have conducted detailed submacroscopic anatomical studies of the autonomic cardiac nervous system in Strepsirrhini (Kawashima and Thorington, ; Kawashima et al, 2013), New World monkeys (Kawashima et al, ), Old World monkeys (Kawashima et al, ), gibbons (Kawashima et al, ), great apes (Kawashima and Sato, ), and humans (Kawashima, ; Kawashima and Sasaki, ). These studies suggest that the primate autonomic cardiac nervous system preserved its evolutionary history in close alignment with its phylogeny, but that somatic structures such as the skeleton, muscles, and their innervation had been modified for functional adaptations.…”