I forgot to include the following statements. Thank you very much for your help!

1) A camp instructor was thrown out of his raft and hit his head on the rock. 2) Though he lost consciousness, two of his students called the emergency services.
3) An ambulance was immediately sent from the hospital. When it arrived, the instructor recovered (came round, woke up). He was taken to hospital.
4) His arm was x-rayed and he was diagnosed (??) a broken arm. He had it put in a cast.(In the picture he is sitting on his bed. His right arm is in a cast and he has a bandage on his head)
5) As he had a minor head injury, he was kept in hospital for 24 hours for observation. He is expected to return home (to be discharged) today.
6) Chaucer mention the plants whose life source have such a powerful liquid that it (? is "it" necessary?) makes the flowers sprout.
7) He injured (wounded/broke/hurt) his right arm when he fell off his raft.
Can you say "he was injured in his arm.

1, 2, 3 - OK

4 - add "with" after "diagnosed"

5 - "in the hospital"

6 - Chaucer mentions ... that it makes...

7 - Your choices are fine as is. But, no, you would say "he injured his arm."