head of ulna

例句：

1. 1. The ulna is the longest bone in the human arm.
   尺骨是人类手臂中最长的骨头。
2. 2. The doctor examined her ulna and found no fractures.
   医生检查了她的尺骨，发现没有骨折。
3. 3. The ulna runs from the elbow to the wrist.
   尺骨从肘部到手腕延伸。