Diffen âº Science âº Biology âº Microbiology. Fraternal twins are âdizygotic,â meaning that they developed from two different eggs fertilized by two different sperm cells, while identical twins are âmonozygoticâ i.e., they developed from a single fertilized egg that split.
A T-tubule (or transverse tubule) is a deep invagination of the sarcolemma, which is the plasma membrane of skeletal muscle and cardiac muscle cells.These invaginations allow depolarization of the membrane to quickly penetrate to the interior of the cell.ransverse tubules are invaginations of the sarcolemma. Though the invaginations are normally perpendicular to the length of the fiber, many T-tubules can lie axial to the long-axis of the fiber, both wrapping around and running alongside myofilament bundles.
These cells can be replaced when smooth muscle is injured by trauma, surgery or disease. While during regeneration of skeletal muscle, only nearby precursor or satellite cells become activated and are the source of new muscle tissue, all smooth muscle cells have the ability to divide and form new smooth muscle.he cells in multi-unit muscles can function independently of each other, while the muscle cells of single-unit muscles work together as a unit. An example of multi-unit muscle cells are the cells that constrict or dilate the iris of the eye.