Prenatal growth and development of the modern human labyrinth

Abstract

The modern human bony labyrinth is morphologically distinct from that of all other primates, showing derived features linked with vestibular function and the overall shape of the cranial base. However, little is known of how this unique morphology emerges prenatally. This study examines in detail the developing fetal human labyrinth, both to document this basic aspect of cranial biology, and more specifically, to gain insight into the ontogenetic basis of its phylogenetically derived morphology. Forty-one post-mortem human fetuses, ranging from 9 to 29 weeks gestation, were investigated with high-resolution magnetic resonance imaging. Quantitative analyses of the labyrinthine morphology revealed a number of interesting age-related trends. In addition, our findings show that: (1) the prenatal labyrinth attains an adult equivalent size between 17 and 19 weeks gestation; (2) within the period investigated, shape changes to all or most of the labyrinth cease after the 17-19-week size maturation point or after the otic capsule ossifies; (3) fetal cochlea development correlates with the surrounding petrosal morphology, but not with the midline basicranium; (4) gestational age-related rotations of the ampullae and cochlea relative to the lateral canal, and posterior canal torsion are similar to documented phylogenetic trends whereas other trends remain distinct. Findings are discussed in terms of the ontogenetic processes and mechanisms that most likely led, in part, to the emergence of the phylogenetically derived adult modern human labyrinth.

Reconstruction of breastfeeding and weaning practices using stable isotope and trace element analyses: A review

“…First, the petrous part of the temporal bone starts to ossify by approximately 18 gestational weeks (Jeffery and Spoor, 2004) and the inner layers of the petrous bone experience hardly any further turnover after 2 years of age (Frisch et al, 2000) in humans. Jørkov et al (2009) performed carbon and nitrogen isotope analysis on petrous bone collagen from medieval human skeletons in Denmark and revealed that diet in the fetal stages and early years of life can be reconstructed using adult petrous bones.…”

Vestibular Evoked Myogenic Potentials in Preterm Infants

“…In utero, each otic vesicle differentiates to a superior vestibular part and an inferior cochlear part, and the vestibular apparatus develops earlier than the cochlear part. The human fetal labyrinth reaches its adult equivalent size at between 17 and 19 weeks of gestation and is fully encapsulated by bone a few weeks later [Jeffery and Spoor, 2004]. Meanwhile, the number of nerve fibers increases: 40000-42000 nerve fibers are present in the fetal central nerves by 38 weeks.…”

The labyrinthine morphology of Pronycticebus gaudryi (Primates, Adapiformes)

“…Primates, and in particular anthropoids, exhibit a well documented general evolutionary trend towards increased encephalization during the Cenozoic (Jerison 1973(Jerison , 1979Radinski 1977), that is toward increasing their relative brain size. Evolving larger brain size implies modifications of the morphology of the braincase, and has a potential impact on the otic capsules and the surrounding petrous bone (Jeffery and Spoor 2004). The coronal orientation of the petrous bone has been shown to correlate with relative brain size in primates (Spoor 1997), which may influence the geometry of the labyrinth, and in particular the relative position of the semi-circular canals and the orientation of the cochlea.…”

“…The coronal orientation of the petrous bone has been shown to correlate with relative brain size in primates (Spoor 1997), which may influence the geometry of the labyrinth, and in particular the relative position of the semi-circular canals and the orientation of the cochlea. Also, in modern humans, the petrous bone is wedged between the cerebral temporal lobe and the cerebellum (see for instance Jeffery and Spoor 2004). This configuration is found in other extant primate species, such as Otolemur garnetti, Tarsius syrichta and Callithrix jacchus (see Fig.…”