Vascular system vessels

Grafts are also frequently employed in the upper part of the body to reconstmct damaged portions of the aorta and carotid arteries. In addition, grafts are used to access the vascular system, such as in hemodialysis to avoid damage of vessels from repeated needle punctures. Most grafts are synthetic and made from materials such as Dacron or Teflon. Less than 5% of grafts utilized are made from biological materials. 

Total peripheral resistance (TPR) is the resistance to blood flow offered by all systemic vessels taken together, especially by the arterioles, which are the primary resistance vessels. Therefore, MAP is regulated by cardiac activity and vascular smooth muscle tone. Any change in CO or TPR causes a change in MAP. The major factors that affect CO, TPR, and therefore MAP, are summarized in Figure 15.3, as well as in Table 15.1. These factors may be organized into several categories and will be discussed as such ... 

Introduction of a water-soluble ionic substance into the vascular system results in an increase in the number of particles in the bloodstream as the contrast substance dissolves. The body possesses several internal regulation systems and, when perturbed by an injection, attempts to restore the concentrations of substances in the blood to their normal or preinjection levels. To re-equilibrate the system, water from the cells of surrounding body tissue moves into the blood plasma through capillary membranes. This transfer of water is an example of osmosis, the diffusion of a solvent (water) through a semipermeable membrane (the blood vessels) into a more concentrated solution (the blood) to equalize the concentrations on both sides of the membrane. To accommodate the increase in... 

HSA is the single most abundant protein in blood (Table 12.7). Its normal concentration is approximately 42 g 1 1, representing 60 per cent of total plasma protein. The vascular system of an average adult thus contains in the region of 150 g of albumin. HSA is responsible for over 80 per cent of the colloidal osmotic pressure of human blood. More than any other plasma constituent, HSA is thus responsible for retaining sufficient fluid within blood vessels. It has been aptly described as the protein that makes blood thicker than water. 

Blood is a unique tissue in that it is (obviously) a fluid. A typical 70 kg adult male has about 51 of whole blood coursing his vasculature at any time. The dynamics of the blood-vascular system are impressive many millions of cells are released from the bone marrow each day a red cell will travel over 250 miles (400 km) during its relatively short life span (120 days), and an endothelial cell lining the lumen of a blood vessel will... 

Normal hemostasis is a balance between excessive and inadequate blood clotting. Overactive blood clotting is harmful because of the tendency for thrombus formation and occlusion of arteries and veins. Vessels may become directly blocked by the thrombus, or a portion of the thrombus may break off and create an embolism that lodges elsewhere in the vascular system. The tendency for excessive thrombus formation in the venous system is usually treated with anticoagulant drugs such as heparin and warfarin. Platelet inhibitors such as aspirin help prevent arterial thrombogenesis. Thrombolytic drugs (streptokinase, t-PA) that facilitate the dissolution of harmful clots may successfully reopen... 

A number of toxicants have effects on the arteries, veins, and capillaries comprising the vascular system. An important factor in vascular toxicity is that toxic substances are transported by blood, which means that they contact the cells making up the structure of the vascular system, which may be adversely affected as a consequence. It is likely that a significant fraction of organ toxicides are actually the result of damage to blood vessels in the organs. 

For the vascular system, Lagana et al. [261] employed a hierarchical methodology for multiscale modeling of pulmonary and coronary perfusions in the cardiovascular system. Essentially, they studied different shunt size effect on the pressure of blood within the vessels. 

Antifoamers are vital in surgery. During operations on heart and large vessels even the smallest bubble of air in the vascular system can block a thin vessel in the brain or other vital organ. Treating medical instruments with silicone liquids greatly facilitates the work of surgeons. 

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