Erectile Dysfunction Prevails With The Aging Of Smooth Muscles
Smooth muscles are spindle shaped and they have one centrally placed nucleus per cell and are usually organized in small clusters of cells. Each cell is separated by fine collagenous, reticular connective tissue. The region around the nucleus is filled with some smooth endoplasmic reticulum and mitochondria. The mitochondria provide the ATP needed for contraction. The smooth endoplasmic reticulum provides a site for calcium storage. The remainder of the cytoplasm includes contractile filaments broken by focal densities. The thin filaments are actin with tropomusin. There is no troponin present in the smooth muscles.
Erectile dysfunction prevails with the aging of smooth muscles warranting treatment with viagra.
In addition there are thick filaments that project the heavy meromyosin heads all along their length. So there is a larger surface area for interaction of the myosin with actin. There are organizational sites called as focal densities which are seen either in the cytoplasm or at the cell membrane and these is for the thick and thin filaments called actin and myosin to interact and be held in register. Desmin or vimentin filaments also bind at these sites which help to hold the filaments together. These intermediate filaments help to relay the contraction and help to shorten the cells. The densities in the membrane are called adherent junctions. The same types of junctions are seen in epithelial cells and it is called as focal adhesions or zonula adherents.
These smooth muscles are found in sheets lining the walls of hollow organs. There are rows of smooth muscles running circularly around the blood vessels, especially prominent around muscular arteries. It can also be seen in the wall of the gastrointestinal tract. The smooth muscles may be organized in 2 to 3 layers. One layer runs around the lumen and the layer runs longitudinally along the length of the organ. In the stomach, there is a layer that runs more diagonally or obliquely. All these works together to propel food along the organ or in the case of the stomach, it helps to churn the food. Very small bundles of smooth muscles are found attached to the hair follicles. These smooth muscle fibers cause the hair to rise on end when we get goose bumps.
Smooth muscles can either receive innervations through autonomic nervous system, or hormones through the blood system can regulate them. Some muscle responds to both types of regulation. Innervations involve nerve endings forming synapses with smooth muscle cells. They are usually in the form of swellings of axons which contain synaptic vesicles. Smooth muscles are involved in a number of disease states. During an asthma attack or an allergic reaction, the smooth muscle of bronchi contract and the airways narrow. Drugs in inhalants that are actually smooth muscle relaxants can relieve this. Lactation depends upon milk production by the mammary gland. However, if the mother is not making enough oxytocin to stimulate myoepithelial cells, the milk will never get into the duct. She may make enough milk, but it will not be able to be secreted because the myoepithelial cells cannot function. Myofibroblasts can actually be found in cases of fibrosis.
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