扬子鳄附肢的组织发生

Histogenesis of the Limb of Chinese Alligator

本文在２２例扬子鳄胚胎中观察了附肢的组织发生过程。孵化第６天，前、后肢芽形成处的组织开始向外隆起。第８天，前、后肢芽突出呈乳状。第１４天，前、后肢芽基部的中胚层浓缩，开始形成肱骨、股骨软骨原基。第１６天，前肢的桡骨、尺骨及后肢的胫骨、腓骨软骨原基出现，软骨原基周围的骨骼肌亦开始分化。第１８天，肱骨、股骨、桡骨、胫骨、腓骨均发生明显的软骨化，前肢尺骨尚未发生软骨化，后肢跖软骨原基形成。第２０天，前肢掌骨原基及后肢的第１、２、３趾骨原基出现。第２４天，前肢第１、２、３、４指骨原基清晰，后肢第１、２、３、４趾骨基节软骨化明显，趾肌开始分化。第３０天，前、后肢的指（趾）骨均发生明显的软骨化，前肢掌骨以上诸骨和后肢跖骨以上诸骨的软骨化趋于成熟，其周围的骨骼肌已较发达。本文着重讨论了扬子鳄附肢组织发生的规律和特点。

This paper described histogenesis of the limb of Alligator sinensis based upon 22 embryos ranged from day 2 to day 30.The lateral plate tissue at presumptive fore and hindlimb buds elevated a little at 6th day and projected as mammashaped buds at 8th day.The mesoderm at base of limb buds condensed and began to form humerus and femur cartilage anlagen at 14th day.At 16th day,the cartilage anlagen of radius,ulna,tibia and fibula appeared,while the skeleton muscle around them also started to differentiate.At 18th day,the cartilage formation of humerus,femur,radius,tibia and fibula were all visible,but not the ulna,and metatarsus anlagen of hindlimb had formed.The metacaroal anlagen of forelimb and 1-3 phalanges anlagen of hindlimb emerged at 20th day.At 24th day,the phalange anlagen of 1-4 forelimb fingers were distinct,and cartilage formation occured in the base phalanges of 1-4 digits in which muscle of digit began to differentiate.At 30th day,cartilage formation happened in all phalanges of fore and hindlimb,Nearly matured cartilage and skeleton muscle appeared in forelimb from metacarpal to humerus and hindlimb from metatarsus to femur.This paper discussed the characteristics of histogenesis of limb emphatically in Alligator sinensis.