Quick Facts
Smooth muscle is a type of muscle without transverse striations in its constituent fibers; it is found in the walls of the viscera and blood vessels and in the dermis and is not under voluntary control (Dorland, 2011).
Related parts of the anatomy
Structure
Smooth muscle is a type of non-striated involuntary muscle, which generally forms the supporting tissue of blood vessels and hollow internal organs, such as the stomach, intestine, and bladder. Smooth muscle is found within the tunica media, the middle layer, of the artery wall. There is a larger amount of smooth muscle in the walls of arteries than veins, hence their greater wall thickness.
There are no striations in vascular smooth muscle, this is due to their lack of sarcomeres and unsymmetrical arrangement of cytoskeletal fibers when compared with skeletal muscle. Fibers in smooth muscle are smaller than those of striated muscle and their cells are spindle shaped with a single central nucleus.
Anatomical Relations
Smooth muscle surrounding the blood vessels is innervated predominantly by the sympathetic division of the autonomic nervous system (Mescher, 2013).
Function
Arterial smooth muscle is responsible for changing the volume of blood that passes through the artery as well as the local blood pressure. This is achieved through vasoconstriction or vasodilation resulting in changes of lumen diameter. This vascular smooth muscle also provides the artery with structural integrity giving support to the vessel at high pressure.
List of Clinical Correlates
- Hypertension
References
Dorland, W. (2011) Dorland's Illustrated Medical Dictionary. 32nd edn. Philadelphia, USA: Elsevier Saunders.
Mescher, A. (2013) Junqueira's Basic Histology: Text and Atlas. 13th edn.: McGraw-Hill Education.
