骨髄

1. Origins, structure, and basic meaning

• Structure: 骨髄 (こつずい) is bone marrow, the tissue found within bones. The examples present its function and anatomical location.
• Basic usage: A doctor explains marrow function with a diagram; a class identifies where it is located.

2. Common pitfalls and similar expressions

• What the tissue does and where the tissue is located
  • 骨髄の働き concerns function, while 骨の内部にある identifies location. Bone marrow is not the same as the entire bone.