Myocyte shearing, myocardial sheets, and microtubules

Skeletal muscle cells, also called muscle fibers, are distinctly elongated, multi-nucleated, slender biological units. They are packed with specialized structures designed to facilitate their primary function, which is contraction.
The muscle sarcolemma is a plasma membrane enclosing each muscle cell that conducts electrical signals called action potentials. The sarcolemma extends into the cell to form T-tubules, ensuring the neural impulses are uniformly distributed across the entire muscle...

Actin and myosin or actomyosin filaments also play a significant role in cells other than those involved in muscle contraction (which occurs within the sarcomere of muscle cells). The mechanism of non-muscle cell contractile bundles was first observed in Dictyostelium and Acanthamoeba. In non-muscle cells, two bundles are commonly found: stress fibers and actomyosin adherence belts. These contractile bundles are smaller and less organized than the ones found in muscle cells. They  are held...

Cardiac muscle, or myocardium, is a specialized type of muscle found exclusively in the heart. Its unique structural and functional characteristics enable the heart to perform its vital role of pumping blood throughout the body continuously and rhythmically. The cardiac muscle cells, or cardiomyocytes, possess an endomysium and perimysium but do not have an epimysium.
Compared to skeletal muscles, cardiac muscle cells are small and mostly have a single nucleus. Additionally, they are usually...

Blebs are a type of membrane protrusion formed by the internal hydrostatic pressure of the cytoplasm. Blebs are observed in several cell types, including fibroblasts, immune cells, and single-celled organisms like the amoeba. The primary function of blebs is cell locomotion and apoptosis, but they are also found during necrosis and cell division. The life cycle of a bleb comprises an initiation phase followed by the expansion and retraction phases.
Blebbing Through the Matrix
In multicellular...

Complex microtubule structures are present in resting cells and in dividing cells. In resting cells, they are responsible for maintaining the cellular architecture, tracks for intracellular transport, positioning of organelles, assembly of cilia and flagella. They mediate the bipolar spindle assembly for chromosomal segregation and positioning of the cell division plate in dividing cells. The formation of microtubule complex structures depends on the cell type, cell stage, and cell function.

Microtubules are hollow cylindrical filaments having a diameter of approximately 25 nm and a length that varies from 200 nm to 25 μm. GTP-bound tubulin subunits form αβ-heterodimers for microtubule assembly. These core building blocks interact longitudinally, polymerizing into protofilaments. The protofilaments then interact with one another through lateral bonding forces to form stable cylindrical microtubules. These cylindrical filaments are dynamic as they undergo repeated assembly and...