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Smooth muscle is grouped into two types: single-unit smooth muscle, also known as visceral smooth muscle, and multiunit smooth muscle. Most smooth muscle is of the single-unit type, and is found in the walls of most internal organs (viscera); and lines blood vessels (except large elastic arteries), the urinary tract , and the digestive tract .
Skeletal muscles are composed of tubular muscle cells (called muscle fibers or myofibers) which are formed during embryonic myogenesis. Muscle fibers contain numerous tubular myofibrils . Myofibrils are composed of repeating sections of sarcomeres, which appear under the microscope as alternating dark and light bands.
Vascular smooth muscle cells also play important roles during development, e.g. driving osteocyte differentiation from undifferentiated precursors during osteogenesis. [1] Arteries have a great deal more smooth muscle within their walls than veins, thus their greater wall thickness. This is because they have to carry pumped blood away from the ...
Their function is to regulate blood flow before it enters the capillaries and venules by the contraction and relaxation of the smooth muscle found on their walls. The second sector is the capillary sector, which is represented by the capillaries, where substance and gas exchange between blood and interstitial fluid takes place.
In the skin, smooth muscle cells such as those of the arrector pili cause hair to stand erect in response to cold temperature or fear. [19] Smooth muscle cells are spindle-shaped with wide middles, and tapering ends. They have a single nucleus and range from 30 to 200 micrometers in length. This is thousands of times shorter than skeletal ...
This layer functions to mechanically transport fluid and since the basement membrane on which it rests is discontinuous; it leaks easily. [2] The next layer is that of smooth muscles that are arranged in a circular fashion around the endothelium, which by shortening (contracting) or relaxing alter the diameter (caliber) of the lumen.
Muscle tissue functions to produce force and cause motion, either locomotion or movement within internal organs. Muscle is formed of contractile filaments and is separated into three main types; smooth muscle, skeletal muscle and cardiac muscle. Smooth muscle has no striations when examined microscopically. It contracts slowly but maintains ...
Tracheomalacia may involve hypotonia of the trachealis muscle. [6]The trachealis muscle may become stiffer during ageing, which makes the whole trachea less elastic. [7]In infants, the insertion of an oesophagogastroduodenoscope into the oesophagus may compress the trachealis muscle, and narrow the trachea. [8]