Vascular smooth muscle: excitation, contraction and relaxation
Neil Herring, David J. Paterson in Levick's Introduction to Cardiovascular Physiology, 2018
The tunica media (middle coat) of arteries, arterioles, venules and veins consists mainly of vascular smooth muscle (VSM) cells (vascular myocytes). These are small, spindle-shaped cells, varying in length from ~70-200 gm long by ~4 gm wide at the centre and wrapped helically around the vessel (Figure 1.11). Changes in their contractile tension (tone) cause the vessel to constrict or dilate as required. There are substantial differences in the way contraction is regulated in different blood vessels, making this a tricky subject for teacher and student alike. Nevertheless, two principles apply to nearly all vessels: (1) contractile tension is governed primarily by cytosolic Ca2+concentration; and (2) contractile tension is also regulated by changes in sensitivity to Ca2+. Other key features, often contrasting sharply with cardiac contraction, are as follows.
The transport and exchange systems: respiratory and cardiovascular
Nick Draper, Helen Marshall in Exercise Physiology, 2014
There are five basic subgroups of blood vessels; arteries, arterioles, capillaries, venules and veins. The walls of these vessels enclose the inside space through which blood flows, commonly known as the vessel lumen. Blood vessel walls are composed of three distinct layers; the tunica intima, tunica media and tunica externa (also known as tunica adventitia) (Figure 6.22). The layer surrounding the vessel lumen, the tunica intima, minimises resistance to blood flow as it provides a smooth surface. The tunica media is composed primarily of smooth muscle and elastin and hence, plays a pivotal role in the vasoconstriction (reduction in lumen diameter) and vasodilation (increase in lumen diameter) of blood vessels. This middle layer provides the mechanical strength of the blood vessel. The external layer, the tunica externa, is a collagen fibre protective layer which also functions to attach the vessel to surrounding structures.
The Kidney (KI)
Narda G. Robinson in Interactive Medical Acupuncture Anatomy, 2016
Clinical Relevance: Pseudoaneurysms sometimes develop after orthopedic surgery. In the case of anterior cruciate ligament reconstruction, arteries affected include the medial inferior genicular artery and popliteal artery.11 When acute, these vascular lesions can cause sudden bleeding into the joint cavity. Acute and voluminous hemarthrosis usually presents with a pulsatile mass within the first few weeks after surgery, although a pseudoaneurysm may develop after ten weeks. Their growth may compress nerves and nearby veins, potentially leading to deep vein thrombosis and occasionally amputation. A pseudoaneurysm differs from a true aneurysm by not involving all layers of an artery. Instead, a collection of blood forms between the two outer layers of an artery, the tunica media and the tunica adventitia. Pseudoaneurysms occur more frequently following total knee arthroplasty, but also after several other types of orthopedic interventions, including arthroscopic meniscectomy and the aforementioned anterior cruciate ligament reconstruction.
Targeting VCAM-1: a therapeutic opportunity for vascular damage
Published in Expert Opinion on Therapeutic Targets, 2023
Mayarling F Troncoso, Magda C Díaz-Vesga, Fernanda Sanhueza-Olivares, Jaime A Riquelme, Marioly Müller, Luis Garrido, Luigi Gabrielli, Mario Chiong, Ramon Corbalan, Pablo F Castro, Sergio Lavandero
The cardiovascular system includes the heart and blood vessels that pump and deliver blood throughout the body. Blood vessels are structured in three layers: the tunica intima, media, and adventitia. The tunica intima, or inner layer, comprises endothelial cells (EC) in contact with the blood. The tunica media or medial layer is formed mainly by vascular smooth muscle cells (VSMC) and the extracellular matrix, such as collagen and elastin, that regulates vascular tone and the integrity of vessels. In capillaries, the medial layer does not contain VSMC, but pericytes form a thin wall that facilitates the transport of blood components [3]. The adventitia layer, or outer layer, comprises fibroblasts, nerves, and small arteries (Vasa vasorum) that deliver nutrients to this layer [4].
Vitamin D deficiency and androgen excess result eutrophic remodeling and reduced myogenic adaptation in small cerebral arterioles in female rats
Published in Gynecological Endocrinology, 2019
Leila Hadjadj, Éva Pál, Anna Monori-Kiss, Réka Eszter Sziva, Ágnes Korsós-Novák, Eszter Mária Horváth, Rita Benkő, Attila Magyar, Péter Magyar, Zoltán Benyó, György L. Nádasy, Szabolcs Várbíró
In our model, anterior cerebral arteries of vitD deficient testosterone treated animals showed a geometrical remodeling typical for chronic hypertension (Figure 2(A, B)). It is interesting to note that this remodeling occurred without significant change in measured mean arterial pressure. In vitD deficient and T treated group, higher wall thickness values were accompanied by higher elastic fibers density and a reduction of inner radii (Figure 4(A, B)). Increased wall thickness could be the result of two different compensatory mechanisms. Growth of the muscle mass of the tunica media can be observed as an adaptation to higher blood pressure values. Reorganization of cellular and noncellular elements could cause wall thickness changes and narrowing of arteriolar lumen [13,14]. This second phenomena could possibly explain the lower tunica media values of both vitD deficient groups. These changes could increase vascular reactivity, thus enhancing peripheral resistance and alteration in myogenic tone, which is typical in diabetes mellitus and obesity [15,16]. As no significant difference could be observed in arteriolar cross-sectional area values, we conclude, that these results may be interpreted as a possible eutrophic remodeling, which is a typical vascular alteration in hypertension [14,17,18].
Histopathological and ultrastructural study of carotid atherosclerotic plaques: a study of four cases
Published in Ultrastructural Pathology, 2021
Ru Yong-xin, Zhang Xue-bin, Dong Shu-xu, Zhang Yongqiang, Li Ying, Liu Jing, Gao Ying-dai, Shang Hong-Cai, Brian Eyden
The observation that all of the cells in the basal bands were positive for α-SMA is liable to allow the misinterpretation of a whole basal band as part of the tunica media stripped off together with an atherosclerotic plaque during the operation. Combining H&E, Congo red and α-SMA staining, every basal band included two parts with distinct patterns:- layers of d-VSMCs organized in elastin networks as normal tunica media at the bottom; and layers of irregular cells with common features of myofibroblasts and VSMCs inside the former part. The existence of d-VSMCs demonstrated that tunica media was affected during atherosclerosis.18,19 The layers of irregular myoid cells inside the affected tunica media confirmed that the cells were derived from MMSCs and constructed a pseudo-media.20,21 In case 2, the hemorrhage between the pseudo-media and the affected tunica media hinted at a reasonable mechanism of sporadic aortic aneurysms and dissections in cardiovascular diseases.22