Centripetal Developing from the outside inwards so the youngest structures are at the center.
Centripetal Developing from the outside inwards so the youngest structures are at the center.
向心的：从外向内的一种发育方式，新生的结构在中央处。
Centripetal Developing from the outside inwards so the youngest structures are at the center.
向心的：从外向内的一种发育方式，新生的结构在中央处。