Smooth Muscle
Smooth muscle forming the contractile wall of inner hollow organs and vessels is composed of bundles or sheets of fusiform cells that measure in length between 20 μm in blood vessel walls and approximately 200 μm in the wall of the intestine; smooth muscl
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eas extending from the regions close to the nuclear poles, as shown in the micrograph in panel A in the uppermost smooth muscle cell sectioned longitudinally. Dense areas and dense bodies providing the platforms for the anchoring of actin filaments are conspicuous in the interior of the cells (asterisks) and are attached to the plasma membrane. Each smooth muscle cell is sheathed by a basal lamina (arrowheads in panel B), the constituents of which, such as type IV collagen, laminin, and proteoglycans, are products of the muscle cell. Both micrographs show groups of caveolae that occupy large areas of the smooth muscle cell surfaces. In smooth muscle cells, caveolae may be closely apposed to membranes of the endoplasmic reticulum (cf. panel A in Fig. 63). It is assumed that there may be analogies to the T- and L-systems in striated muscle fibers. Studies with vascular smooth muscle of the ferret aorta have revealed that the muscle cell contractility is regulated by caveolin-1. Smooth muscle cells are surrounded by fine connective tissue, the endomysium, where an axon is visible embedded in a network of collagen fibrils (C) and neighbored by a process of a fibroblasts (F). The axon is bare of a glial cell sheath (cf. Fig. 180) and contains abundant small synaptic vesicles (arrows) accumulated close to the plasma membrane. Transmitters released from the axon have to diffuse across some distance to reach the muscle cell surface (“synapse á distance”).
References Baron CB, Coburn RF (2004) Smooth muscle raft-like membranes. J Lipid Res 45:41 Bolton TB, Prestwich SA, Zholos AV, Gordienko DV (1999) Excitationcontraction coupling in gastrointestinal and other smooth muscles. Annu Rev Physiol 61:85 Isshiki M, Anderson RGW (2003) Function of caveolae in Ca2+ entry and Ca2+-dependent signal transduction. Traffic 4:717 Je H-D, Gallant C, Leavis PC, Morgan KG (2004) Caveolin-1 regulates contractility in differentiated vascular smooth muscle. Am J Physiol Heart Circ Physiol 286:H91
Magnification: ×10,300 (A), ×52,000 (B) M. Pavelka, J. Roth, Functional Ultrastructure: Atlas of Tissue Biology and Pathology, Third Edition, DOI 10.1007/978-3-7091-1830-6_28, © Springer-Verlag Vienna 2015
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Smooth Muscle
CADASIL CADASIL stands for Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leukoencephalopathy and is the most common form of hereditary stroke. This disease has an average age onset of 45 years and presents with migraine, repeated strokes, white matter changes, and progressive dementia. CADASIL is caused by mutations in the Notch3 gene found on human chromosome 19q12 that is located within the epidermal growth factor repeats of the Notch3 protein. Notch3 mutations entail either loss or gain of cysteine residues. Notch proteins regulate cell fates or are involved in controlling signals for cell proliferation and maturation. A characteristic feature of CADASIL is a systemic arterial vasculopathy affecting the smooth muscle fibers of small arteries. It has been proposed that vascular
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