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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 .
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. Sarcomeres are composed of long, fibrous proteins as filaments that slide past each other when a muscle contracts or relaxes.
Foam cells are very small in size and can only be truly detected by examining a fatty plaque under a microscope after it is removed from the body, or more specifically from the heart. Detection usually involves the staining of sections of aortic sinus or artery with Oil Red O (ORO) followed by computer imaging and analysis; or from Nile Red ...
In 1969, Don Fawcett labelled these cells as ‘peritubular myoid cells’. ‘Peritubular’ refers to their anatomical location: adjacent to the seminiferous tubule. ‘Myoid’ stems from the Greek ‘myo’ (/ˈmʌɪəʊ/), which means relating to muscle. (PTMs resemble smooth muscle cells under an electron microscope). [2]
Structure of muscle fibre (sarcomere) under electron microscope with schematic explanation. By the time Hugh Huxley earned his PhD from the University of Cambridge in 1952 on his research on the structure of muscle, Szent-Györgyi had turned his career into cancer research. [12]
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 ...
The muscularis mucosae, a thin layer of smooth muscle. The epithelium, the most exposed part of the mucosa, is a glandular epithelium with many goblet cells . Goblet cells secrete mucus , which lubricates the passage of food along and protects the intestinal wall from digestive enzymes.
Obliquely striated muscle is intermediate between the other two. The filaments are staggered and this is the type of muscle found in earthworms that can extend slowly or make rapid contractions. [5] In higher animals striated muscles occur in bundles attached to bone to provide movement and are often arranged in antagonistic sets. Smooth muscle ...