Musculoskeletal System | Smooth Muscle

Smooth muscle is involuntary and non-striated, primarily found in the walls of hollow organs such as the intestines, blood vessels, and the bladder. Its contractions are controlled by the autonomic nervous system, allowing for functions such as peristalsis (moving food/liquids thru) in the digestive tract and regulation of blood flow.

No sarcomere because their protein filaments are arranged differently

This unique arrangement allows smooth muscle to contract in a more sustained and efficient manner, contributing to the prolonged contractions necessary for functions like maintaining blood pressure and facilitating digestion.

dense bodies are made of a protein primarily called alpha-actinin. Alpha-actinin is the primary protein that makes up these dense bodies.

These dense bodies are scattered all throughout the actual smooth muscle cell. What's important is that these dense bodies are anchored to the plasma membrane by these pink proteins. These pink proteins are basically anchoring the actual dense bodies to the smooth muscle cell membrane. There are many proteins that make up that structure, but basically, what it's doing is there are these attachment plaques, these integrin proteins that are actually on the inner cytosolic side of the smooth muscle cell, and these attachment plaques are what these dense bodies are connecting to.

Structures

Intermediate filaments: composed of two primary proteins: one is called vimentin, and the other one is called desmin.

Vimentin: A type of intermediate filament protein that provides structural support and stability to the smooth muscle cells.
Desmin: Another intermediate filament protein that plays a role in maintaining the integrity of the muscle cell structure and facilitating contractile function.