![掌骨[II] - 手部MRI - 轴 - e-Anatomy](https://cdn.imaios.cn/i/imaios-images/web/images/eanatomy/modules/hand-mr/images/v1/4c1c47972a830cfc35481b6a5a132f0ba3c4879edcd3813f4a8bd16a67ebe023?ar=640:670&auto=format,compress&bg=000000&fit=crop&p64=MTk4LDQ0MA&t=5o6M6aqoW0lJXQ&tf=Tm90byBTYW5zIFND&tx=198&ty=440&w=350&wk=1&s=005b8ecb0791d45315872a593fb419f3)
掌骨[II]
Os metacarpale [II]
定义
第二掌骨（os metacarpale II；示指掌骨）是其余四块掌骨中最长的一块，其底部也是最大的。
其底部向上并向内侧延伸，形成一个突出的嵴。底部呈现四个关节面：上面三个，尺侧一个。上面的关节面中，中间的关节面最大，从侧面看呈凹形，从前向后呈凸形，与小多角骨形成关节；外侧关节面小而扁平，呈卵圆形，与大多角骨形成关节；内侧关节面位于嵴的顶端，细长而狭窄，与头状骨形成关节。尺侧的关节面与第三掌骨形成关节。桡侧腕长伸肌止于底部背侧面，桡侧腕屈肌止于底部掌侧面。
參考資料
This definition incorporates text from a public domain edition of Gray's Anatomy (20th U.S. edition of Gray's Anatomy of the Human Body, published in 1918 – from http://www.bartleby.com/107/).
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