There are two main types of bone. Compact bone, which makes up most of the bone of arms and legs, is very dense and hard on the outside. The structural units of compact bone are osteons, elongated cylinders that act as weight-bearing pillars, able to withstand any mechanical stress placed on the bone. The center of each osteon contains a hollow canal that acts as a central passageway for blood vessels and nerves.
- compact bone [kəmˈpækt - bəun] n.密质骨
- make up [meik - ʌp] v. 组成
- dense [dens] adj.密集的
- osteon [ˈɔstiɔn] n.骨单位(密质骨构造的基本单位)
- elongated [ˈi:lɔŋɡeitid] adj. 被拉长的
- cylinder [ˈsilində] n.圆柱体
- pillar [ˈpilə] n. 柱状物
- withstand [wiðˈstænd] v.经受, 承受
- canal [kəˈnæl] n. 导管
- passageway [ˈpæsidʒwei] n.出入口
