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Fourth Digit (fourth + digit)

Distribution by Scientific Domains

Life Sciences	100%

Selected Abstracts

Growth and maturation of metatarsals and their taxonomic significance in the jerboas Allactaga and Jaculus (Rodentia: Dipodidae)

ACTA ZOOLOGICA, Issue 2 2005
A. A. B. Shahin
Abstract The development of metatarsals in Allactaga tetradactyla, Jaculus jaculus jaculus and J. orientalis was studied and their taxonomic significance was elucidated. The five metatarsals, as a rule, are developed and ossified in the three species, but variation in the fate of the first and fifth metatarsals was found. Ossification begins in the median part of the metatarsals; however, it appears in the distal part of the digits' phalanges, beginning with the third phalanx. The first metatarsal appears just distal to the entocuneiform and develops as a small, separate bone located either in close contact with the distal end of the entocuneiform in A. tetradactyla or completely fused with it, forming a compound bone, in both of J. j. jaculus and J. orientalis. The second, third and fourth metatarsals differentiate distal to the mesocuneiform, ectocuneiform and cuboid, respectively, and fuse with one another into a single long cannon bone in all species. Nevertheless, the fifth metatarsal differentiates ventro-lateral to the head of the fourth metatarsal and ossifies ventral to the head process of the developing cannon bone. The fifth metatarsal either extends to articulate with the phalanges of the fourth digit in A. tetradactyla or persists as a separate, small bone in both of J. j. jaculus and J. orientalis. On this basis, it is concluded that J. jaculus and J. orientalis are both distinct congeneric species and are somewhat more distant from A. tetradactyla. [source]

Innervation of the Pelvic Limb of the Adult Ostrich (Struthio camelus)

ANATOMIA, HISTOLOGIA, EMBRYOLOGIA, Issue 5 2010
T. El-Mahdy
With 24 figures Summary The pelvic limb of the ostrich is innervated by the lumbar and sacral plexuses. The lumbar plexus gave rise to several nerves (N.s) including, N. coxalis cranialis, lateral and cranial femoral cutaneous N.s, N. femoralis, cranial, caudal and medial crural cutaneous N.s, and N. obturatorius. The remaining nerves emanated from the sacral plexus. The N. iliotibial, N. ischiofemoralis, N. iliofibularis, and N. coxae caudalis were distributed in the thigh, while the N. ischiadica, which terminated as the tibial and fibular N.s that innervated the leg and foot. The tibial N. gave rise to the parafibular N. then divided to form the Nn. suralis medialis and lateralis. The N. suralis medialis continued as the N. metatarsalis plantaris medialis. The parafibular N. continued as the N. plantaris lateralis, which terminated as the R. digitalis of the fourth digit. The fibular N. terminated as the superficial and deep fibular N.s. The superficial fibular N. continued as the N. metatarsalis dorsalis lateralis and divided into two digital N.s to the third and fourth digits. The deep fibular N. crossed the ankle joint and continued as the N. metatarsalis dorsalis medialis that continued as the R. digitalis of the third digit. In general, the innervation of the pelvic limb of the ostrich was similar to the pelvic limbs of several different species of domesticated birds, including the chicken. We discuss the few differences as well as appropriate sites to perform nerve blocks for the lateral and medial dorsal and the lateral plantar N.s. [source]

Meta-analysis of digit ratio 2D:4D shows greater sex difference in the right hand

AMERICAN JOURNAL OF HUMAN BIOLOGY, Issue 5 2010
Johannes Hönekopp
Objectives: Our aims are, first, to describe the sex difference in the length ratio of the second and fourth digits (2D:4D), which likely reflects prenatal testosterone levels in humans. Second, to infer the loss of reliability observed in 2D:4D based on self-measured finger lengths. Methods: We used random-effects meta-analysis of 2D:4D based on expert-measured finger lengths (116 samples with 13,260 females and 11,789 males). Results: We find a moderate sex difference (with lower 2D:4D for males), which shows substantial heterogeneity (which is unrelated to age). The sex difference is moderated by the type of finger length measurement and by hand. Measurement involving the distortion of soft tissue leads to a significantly larger sex difference than finger length measurement avoiding this. The sex difference in 2D:4D is larger in the right hand than in the left. The reliability of self-measured 2D:4D in the BBC internet study, by far the largest study on 2D:4D, is estimated to be 46% of that of expert-measured 2D:4D. Conclusions: Right-hand 2D:4D might be a better indicator of prenatal androgenisation than left-hand 2D:4D. The view that 2D:4D has allometric properties (Kratochvil L, Flegr J. 2009. Differences in 2nd to 4th digit length ratio in humans reflect shifts along the common allometric line. Biol Lett 5:643,646.) is not supported. Bone lengths contribute to the sex difference in 2D:4D. In addition, there might be a sex difference in fingers' soft tissue, which should be investigated. Because of measurement unreliability, correlations between 2D:4D and variables of interest are about one-third smaller in the BBC internet study than in studies in which 2D:4D is based on expert-measured finger lengths. Am. J. Hum. Biol. 22:619,630, 2010. © 2010 Wiley-Liss, Inc. [source]