Anatomy Of The Metacarpus, Phalanges And Sesamoids Of Bactrian Camel, Yak, Cattle, Yak-Cattle Hybrid And Buffalo

Fourteen specimens of the metacarpus and digits of the forelimb of the adult Bactrian camel were examined by means of radiograph, computerized tomography(CT),gross anatomy and morphometry. The large metacarpal are fused by the metacarpalⅢandⅣ.Its index of width/length and thickness/length shape index was 11.66% and 9.9%,respectively,which was approximately slender and long shaft.Two digits,the third and fourth,were fully developed.Each digit had three phalanges and two proximal sesamoid bones.Under the phalanges of the forefoot,it was a well-developped digital pad which had three fat cushions(central,axial and abaxial)and an elastic fibrous cushion each digit.The gaps of metacarpophalangeal and proximal interphalangeal joints in radiograph were approximately 0.6-0.8cm and 0.4-0.6cm wide respectively.The area of proximal articular facet in digital joints was much larger than that of the corresponding distal end.The relative density of phalanges in digitⅢwas slightly larger than in digitⅣ,but the weight and volume of phalanges in digitⅢwas slightly smaller than in digitⅣrespectively.The relative density of axial proximal sesamoid was slightly smaller than that of the abaxial.The weight and volume of axial proximal sesamoid were larger than of the abaxial respectively. The distal half of proximal phalanx and middle phalanx were obviously oblate.The difference was found to be highly significant (P＜0.01)in respect of volume of the proximal and middle phalanx. Difference found to be significant(P＜0.05)in respect of height of the abaxial distal articular facet palmarly in proximal phalanx,area of proximal articular facet in the middle and distal phalanx.The bones of 24 metacarpus were collected from apparently healthy,middle size,female and adult yak,cattle,Yak-Cattle(Y-C) hybrid and buffalo(3 for each species,3 right and 3 left).The mean maximal traverse width of the base of the metacarpal(Mc.)Ⅲ+Ⅳ(large metacarpal bone)was the most in cattle(6.90cm),the smallest in yak(5.23cm),and intermediate type in buffalo(6.34cm) and Y-C hybrid(5.87cm).The mean maximal traverse width of the head of the Mc.Ⅲ+Ⅳwas the most extensive in buffalo(7.09cm), the narrowest in yak(5.36cm),and intermediate type in cattle(6.63cm) and Y-C hybrid(6.24cm).The index of width/length of the Mc.Ⅲ+Ⅳwas the largest in buffalo(21.26%),the second in yak(20.88%), the third in Y-C hybrid(20.14%),and the smallest in cattle(17.44%). The index of thickness/length was the largest in yak(14.49%),the smallest in cattle(12.56%).The mean maximal length of the Mc.Ⅲ+Ⅳwas the largest in cattle(21.33cm),the smallest in yak(14.08cm). The mean area of proximal articular facet of the Mc.Ⅲwas larger than that of the Mc.Ⅳ.The mean area of proximal articular facet of the Mc.Ⅲ,Ⅳwas the most in cattle,the second in yak,the third in Y-C hybrid,and the smallest in buffalo.The mean area of articular facet of the distal Mc.Ⅲ,Ⅳwas the same pattern.The mean relative density of the Mc.Ⅲ+Ⅳwas the most in Y-C hybrid(1.82), intermediate type in cattle(1.70)and buffalo(1.49),and the smallest in yak(1.44).The mean length of the Mc.Ⅱin yak was 1.50cm.In Y-C hybrid,the Mc.Ⅱfused partly with the Mc.Ⅲ+Ⅳ,which had also clear vestige.In cattle,the Mc.Ⅱfused almost with the Mc.Ⅲ+Ⅳwhich sometimes had clear vestige.In buffalo,the Mc.Ⅱhad disappeared.The bones of 96 digits were collected from apparently healthy, middle size,female and adult yak,cattle,Y-C hybrid and buffalo(3 for each species,3 right and 3 left).Preliminary analysis showed that differences were not significant(P＜0.05)on the means of all measurements from the left and right sides,the digitⅢ&Ⅳ,the digitⅡ&Ⅴ.The phalanges and sesamoids of digitⅢ&Ⅳin the yak was the least in density:proximal phalanx(1.20),middle phalanx (1.20),distal phalanx(1.27),axial proximal sesamoid(1.22),abaxial proximal sesamoid(1.31),distal sesamoid(1.02).The largest mean densities were of the proximal phalanx in the Y-C hybrid(1.34), middle phalanx in the buffalo(1.41)and distal phalanx in the cattle (1.41).The axial proximal sesamoid was the densest in the Y-C hybrid(1.34).The abaxial proximal and distal sesamoids were the densest in the cattle(1.43,1.24).The phalanges of digitⅡ&Ⅴin the mean density were the least in the cattle(1.03,0.95)and the densest in the Y-C hybrid(1.92,1.32).For phalanges of digitⅢ&Ⅳin the yak,cattle and Y-C hybrid,the order of the decling trend of density was as follows:the distal phalanx＞middle phalanx＞proximal phalanx;but in the buffalo,the middle phalanx＞proximal phalanx or distal phalanx.The order for sesamoid was as following: the abaxial phalanx＞axial proximal sesamoid＞distal sesamoid.The proximal phalanx of digitⅡ&Ⅴin the mean density was larger than the middle phalanx.The results indicated that the unique structures of the metacarpus and phalanges and sesamoids of forelimb for these five species could cooperated well with other parts of manus.All of these could morphologically support the heavy body and well adapted to the corresponding environments.