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Cardiovascular System:
Published in Michel R. Labrosse, Cardiovascular Mechanics, 2018
The tunica media is the middle layer of the vessel wall. It is made up of both smooth muscle and connective tissue and shows the greatest variation among the blood vessels of the circulatory system. When the smooth muscle contracts in vasoconstriction, there is a decrease in radius, an increase in resistance, and a resulting decrease in blood flow. The external elastic lamina forms the outer portion of the tunica media. The tunica externa (or adventitia) is made up of collagen and elastin fibers, which contribute to the mechanical properties of the blood vessels. It also helps anchor the vessels to the surrounding tissue. In the larger vessels, there are small blood vessels (the vasa vasorum) that supply the outer layers of the blood vessel wall with oxygen and nutrients. A weakened area of the wall with less connective tissue reinforcement may result in a region of expansion (a “bulge”) known as an aneurysm. This could be a result of a genetic defect (such as Marfan’s syndrome) or a disease state such as atherosclerosis and syphilis. If the wall becomes further stretched, it may result in rupture. Surgery is often done to repair this and prevent further rupture. This will be discussed further in Chapter 6.
The response of endothelial cells to endogenous bioelectric fields
Published in Ze Zhang, Mahmoud Rouabhia, Simon E. Moulton, Conductive Polymers, 2018
The primary capillary networks that develop via vasculogenesis in the embryo are modified, extended, and pruned by angiogenesis so that the functional requirements for each tissue in terms of energy, material and oxygen delivery, and waste removal are provided. In the normal mature state, no cell will be more than 50–100 microns away from a blood vessel (Alberts et al. 2002). The physical processes by which nutrient and waste exchange occurs in the vascular system require an intricate balance between large-diameter vessels under high pressure, smaller low-pressure capillary networks, and the control of blood flow as the demand of various tissues varies on a minute-to-minute basis. The mature organism develops a rich array of vessels, all of which are modifications of the basic vessel developed during vasculogenesis. With the exception of the capillary networks, virtually all blood vessels, including arteries and veins, end up comprising three layers: The tunica intima, which is the endothelial cell layer surrounded by its basal lamina. In the small capillaries, there may be pericytes included in an inconsistent pattern.The tunica media is formed by SMCs that are recruited by the endothelial cells to surround the intima. These SMCs produce an extracellular matrix (ECM) composed of glycosaminoglycans and the connective proteins elastin and collagen, which provide elastic compliance and tensile strength to the vessel. The SMCs both provide the structural integrity needed by any vessel larger than a capillary and impart the capacity of the vessel to constrict and dilate in response to endothelial stimuli such as nitric oxide (NO), and also to neurogenic stimuli and hormonal stimuli such as epinephrine.Finally, the outer layer of the vessel is a connective tissue layer, the tunica externa.
Acid and enzymatic extraction of collagen from Atlantic cod (Gadus Morhua) swim bladders envisaging health-related applications
Published in Journal of Biomaterials Science, Polymer Edition, 2020
Rita O. Sousa, Ana L. Alves, Duarte Nuno Carvalho, Eva Martins, Catarina Oliveira, Tiago H. Silva, Rui L. Reis
The main part of the fish by-products resulting from the fisheries and food processing industries is still directed for fish silage, fishmeal and oil production, mainly used for animal feed [3,4]. Nevertheless, cod by-products have already been used, for example, for the extraction of collagen [5,6] and fish leather production from skin, the extraction of calcium phosphates such as hydroxyapatite from bones [7], the isolation of enzymes from liver, as well as other valuable compounds from viscera or muscle [4]. In this project, swim bladders were removed from salt-cured cod (Gadus morhua) and used to extract fish protein - collagen. The swim bladder or air bladder is an internal gas-filled organ that contributes to the ability of many bony fish (but not cartilaginous fish) to control their buoyancy, avoiding the waste of energy in swimming. Additionally, the swim bladder functions as a resonating chamber, to produce or receive sound and it is evolutionarily homologous to the lungs [8,9]. The swim bladder consists of three main layers: tunica externa, submucosa, and mucosa. The tunica externa is composed of a dense layer of connective tissue [9], being a potential source for the production of collagen.
Drug carrier three-layer nanofibrous tube for vascular graft engineering
Published in Journal of Biomaterials Science, Polymer Edition, 2019
While not presented here, the mechanical properties and biocompatibility of the prepared SF/PU/SF three-layer nanofibrous tube still need to be further studied in clinical experiments. Since natural arteries and veins are comprised of three distinct layers, i.e. tunica intima, tunica media and tunica externa, it can be expected that a bionic three-layer nanofibrous tube is able to provide closer natural vessel properties (e.g., mechanical properties and biocompatibility) than existing one-layer SF/PU vascular graft.