牛の多趾症肢の解剖学的所見

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　下腿骨欠損症と多趾症の合併奇形を有する牛(黒毛和種,雄,4日齢)の奇形肢(左側後肢)について解剖学的観察を行った.得られた結果は次のとおりである.　1. 下腿骨および膝蓋骨は欠損し,足根骨は互いに癒合するとともに中足骨とも癒合していた.中足骨は3個の癒合中足骨から成り,遠位外側に小さい中足骨が付着していた.趾列は5列認められ,第二趾以外は中足骨と関節していた.　2. 縫工筋は欠損していた. 下腿骨に起始および停止する筋はdysplasia(異形成)を起こして短縮していた. 趾骨の背側面には,長趾伸筋,第四趾伸筋,短趾伸筋が下走していた.長趾伸筋は第三～五趾の末節骨と第四趾の中節骨に,第四趾伸筋は第五趾の中節骨に停止していた.発達した短趾伸筋は中足骨近位端に起こり,その腱は長趾伸筋腱と癒合していた. 趾骨の掌側面には浅趾屈筋,深趾屈筋が走行し,前者は第三～五趾の中節骨,後者は第一趾および第三～五趾の末節骨に停止した.浅趾屈筋は二腹筋の形態を呈していた.　3. 膝窩動脈から分岐した前脛骨動脈は,中足骨前面を下走し,中足骨近位1/3のところで二分し,第二～四趾に分布していた･伏在動脈は,内転筋の深部を下走したのち,表層に出て中足骨後面を下走し,中足骨近位1/3で外側および内側足底動脈に分岐していた. 外側足底動脈は第五趾の外側と副蹄に,内側足底動脈は第一～四趾および第五趾の内側に分布していた.　4. 坐骨神経から分岐した総腓骨神経は,大腿骨下端部で浅および深腓骨神経に分かれ,浅腓骨神経は第一～五趾に分布していた. 深腓骨神経は短趾伸筋に分布する枝を出したのち,浅腓骨神経と交通していた. 脛骨神経は下腿三頭筋の深部を下走し,屈筋群へ分布する枝を出したのち,表層へ出て外側および内側足底神経に分かれていた. これらの両神経は,中足骨後面を下走し,外側足底神経は副蹄と第五趾に,内側足底神経は第一～四趾に分布していた.Left hindlimb of 4-day-old Japanese blak calf which had congenital malformations such as polydactyly and tibial hemimelia was dissected to be description. The details were reported as follow. 1) The outstanding radiologic feature was congenital agenesis of the tibia and patella. The tarsal and metatarsal bones were intimately fused with one another. The confused metatarsus was attached on the laterodistal end by a small metatarsal bone. These metatarsuses were articulated by four porximal phalanges. 2) The sartorius was absent from the left hindlimb. Muscles that normally inserted on and originated at the tibia were dysplasia and contracted. On the dorasal aspect of the tarsus, metatarsus and digit the extensor digitorum longus was provided with a long tendon which divided into four branches. These tendons inserted on the distal phalanges of the third to fifth digits, and middle phalanx of the fourth digit. The extensor digit IV inserted on the dorsal side of the middle phalanx of the fifth digit. The extensor digitorum brevis was relatively large muscle which arised from the dorsoproximal surface of the metatarsus and the tendons were finally united with the long digital extensor tendon. On the volar side of the metatarsus the flexor digitorum superficialis descended with the flexor digitorum profundus and inserted on the middle phalanges of digits III, IV and V. This muscle had digastric shape that two bellies united by an intermediate tendon. The flexor digitorum profundus inserted to the volar surfaces of the distal phalanges of digits I, III, IV and V. 3) The popliteal artery divided into the cranial and caudal tibial arteries. At the proximal third of the metatarsus the carnial artery which desended along the dorsal surface divided into two arteries supplying the dorsal surfaces of digits II, III and IV. Arising from the femoral artery the saphenous artery coursed from inside of the adductor and appeard on the plantar surface of the metatarsus. It divided into lateral and medial plantar arteries at the proximal third of the metatarsus, the former furnished the dewclaw and lateral side of the fifth digit and the latter furnished the digits I, III and IV and medial side of digit V. 4) Arising from the ischiatic nerve, the common peroneal nerve divided into superficial and deep branches. The superficial fibular nerve supplied dorsal surfaces of each digits. After branching to the extensor digiti brevis, the deep fibular nerve anastomosed with the terminal branch of the superficial fibular nerve. The tibial nerve was one of the two terminal branches of the ischiatic nerves, it gave off musclar branches to the flexor muscles while coursing under the triceps surae, and appeared on the volar surface to divide into the lateral and medial plantar nerves. These nerves coursed plantar surface of the metatarsus toward the digits, the lateral plantar nerve innervated the dewclaw and the fifth figit, the medial plantar nerve supply the digits I, II, III and IV.

牛の多趾症肢の解剖学的所見

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