<span>Muscle cells are uniquely adapted to contractile function due to three main things. FIrst, they have a large capacity for storage of readily available glycogen to use for work. Second, they contain the actin and myosin cross-bridge cycling structure to perform a contraction of a muscle fiber. Finally, each fiber has central nervous innervation to control contraction and relaxation of the muscle fibers.</span>
Karyotypes describe the chromosome count of an organism, so all the chromosomes would be in front of you, and it'd be easy to tell if there are 2 or 3 chromosome 21.
