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The muscle fiber cells are arranged in 5 to 7 layers of circular and longitudinal smooth muscle with about 50μ in length and contain well-marked, rod-shaped nuclei, which are often slightly curved. Separating the tunica media from the outer tunica externa in larger arteries is the external elastic membrane (also called the external elastic ...
Sympathetic nerve fibers travel around the tunica media of the artery, secrete neurotransmitters such as norepinephrine into the extracellular fluid surrounding the smooth muscle (tunica media) from the terminal knob of the axon. The smooth muscle cell membranes have α and β-adrenergic receptors for these neurotransmitters.
Smooth muscle differs from skeletal muscle and cardiac muscle in terms of structure, function, regulation of contraction, and excitation-contraction coupling. However, smooth muscle tissue tends to demonstrate greater elasticity and function within a larger length-tension curve than striated muscle. This ability to stretch and still maintain ...
The tunica intima is well developed, with many smooth muscle cells in the subendothelial connective tissue, and often shows folds in cross section because of the vessel’s contraction with loss of blood pressure at death. Between the intima and the media lies the internal elastic lamina, usually better defined than the elastic laminae of the ...
The tunica media may (especially in arteries) be rich in vascular smooth muscle, which controls the caliber of the vessel. Veins do not have the external elastic lamina, but only an internal one. The tunica media is thicker in the arteries rather than the veins. The outer layer is the tunica adventitia and the thickest layer in veins. It is ...
As referenced in the explanation of smooth muscle physiology, smooth muscle within the tunica media is innervated by the autonomic nervous system. The autonomic nervous system (ANS) controls essential involuntary body functions and originates as nerves leaving the brain stem or spinal cord; it contains both sensor and motor nerves. [2]
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 ...
Vasomotion is the spontaneous oscillation in tone of blood vessel walls, independent of heart beat, innervation or respiration. [1] While vasomotion was first observed by Thomas Wharton Jones in 1852, the complete mechanisms responsible for its generation and its physiological importance remain to be elucidated.