I. Smooth muscle cells contain the contractile proteins actin (so-called "thin fibers") and myosin ("thick fibers") as components of their cytoplasmic structure. These function in concert ("sliding filament theory") to generate contraction in response to synaptic input from motor neurons.
II. Podocytes, which are cells within Bowman's capsule of the kidney that contain foot processes that interdigitate and wrap around glomerular capillaries creating slits through which filtrate passes. These slits are further covered by diaphragms containing various proteins that help ensure the passage of small molecules (e.g., urea) but the retention of large macromolecules (e.g., albumin or immune globins).
