"Internal skeleton" refers to a framework of bones or hard structures inside the body of an organism. It provides support, protection, and shape to the body, allowing for movement and performing various functions. Full definition
Fig. 7 The small internal skeleton of the sea hare, about 1 1/2» across. (AmbergrisCaye.com)
Paclitaxel targets a part of the cell's internal skeleton called microtubules and stabilizes the structure so that the cell can not rapidly grow and divide. (sciencedaily.com)
Axons are stretchy due in part to their flexible internal skeleton. (discovermagazine.com)