Contractility and motility of muscle and non-muscle cells

Abstract

Almost any unicellular organism is able to actively move or to generate force, i.e., to exhibit motility and contractility. Most multicellular organisms have, however, developed specialized cells, muscle cells, to fulfill their needs for locomotion and force generation. Functionally and morphologically, three different muscular tissues can be distinguished: (i) Skeletal muscle which performs voluntary movement by moving skeletal elements, (ii) cardiac muscle, which in a life-long restless action pumps blood into the vascular system, and (iii) a vast number of different smooth muscles which shorten slowly and are able to sustain long-term contractility. Additionally, a fourth contractile cell type is found around the endpieces of certain exocrine glands, the so-called myoepithelial cells. These cells have a spider-like appearance and help to transport the secretory product by the contraction of their numerous cytoplasmic extensions.