tl;dr Higher activation energy required to activate slip-systems Ductile and brittle are relative terms, since the deformation of a material and the corresponding mode of failure depends on many conditions in addition to crystal structure such a...
Skin cells live about two or three weeks. Colon cells have it rough: They die off after about four days. Sperm cells have a life span of only about three days, while brain cells typically last an entire lifetime (neurons in the cerebral cortex, for example, are not replaced when they die).
Muscle cells come in many different types, but most have an average life span of about 25 years. This includes cardiac cells, skeletal cells, and smooth muscle cells. Most of these contain protein filaments that aid in the contraction and relaxation of muscles, which is what produces movement.