Primary Defense

It is also important to assure that corrosion, erosion, or other damage has not affected the system to the point that it can no longer safely contain the design pressure. Maintaining mechanical integrity once the system has been placed in service is discussed later in this chapter. 

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The gastrointestinal tract (GIT) is a highly specialized region of the body whose primary functions involve the processes of secretion, digestion, and absorption. Since all nutrients needed by the body, with the exception of oxygen, must first be ingested orally, processed by the GIT, and then made available for absorption into the bloodstream, the GIT represents a significant barrier and interface with the environment. The primary defense mechanisms employed by the gut... 

The fourth type of geosynthetic is a GM or an FML. It is the primary defense against escaping leachate and is of crucial importance. 

Individuals with defects in cellular immunity are prone to fungal, protozoal, and viral infections, such as Candida albicans, cytomegalovirus, and Pneumocystis carinii, since cell-mediated immune responses are the primary defenses against these types of infection. Because of the role of cell-mediated immunity in tumor surveillance, these individuals will also demonstrate an increased incidence of malignancy if they survive long enough. 

Aplysia with chemical defenses in their tissues but without ink were consumed at a similar rate to those without toxins (20% vs. 12%), whereas those without toxins in their tissues, but with ink exhibited much greater survival (71%), suggesting that the excretion of ink may be the primary defense of these sea hares when being consumed by slow-moving predators like sea anemones.45 Pennings42 also found that ink from some (but not all) sea hares could deter predators, however he found no evidence that the metabolites responsible for defense were diet derived. Sea hares also secrete opaline when attacked by predators, although the function of this secretion has yet to be unambiguously determined.44... 

The innate nonadaptive mucosal defense system of the airways of healthy individuals is a highly efficient primary defense for the elimination of... 

The route of exposure determines both the initial physiological barrier faced by the xenobiotic and its initial metabolic fate. Two of the primary defense mechanisms against xenobiotics are barriers, such as skin and membranes, and the biotransformation or breakdown of toxic compounds to nontoxic products. Xenobiotics must elude these defense mechanisms in order to reach the target tissue and cause damage. 

The skin serves as a barrier between humans and their environment and therefore functions as a primary defense mechanism against infections. The skin consists of the epidermis, the dermis, and subcutaneous fat. The epidermis is the outermost, nonvascular layer of the skin. It varies in thickness from approximately 0.1 mm on most areas of the body to a maximum of 1.5 mm on the soles of the feet. 

Conversion of superoxide anion to hydrogen peroxide and O2 (dismntation) by superoxide dismutase (SOD) is often called the primary defense against oxidative stress because superoxide is such a strong initiator of chain reactions (Fig 24.14). SOD exists as three isoenzyme forms, a Cn -Zn form present in the cytosol, a Mn form present in mitochondria, and a Cn -Zn form found extracellnlarly. The activity of Cu -Zn SOD is increased by chemicals or conditions (snch as hyperbaric oxygen) that increase the prodnction of snperoxide. 

Oxide layers formed on metals at high temperature are the primary defense against high-temperature corrosion. The formation of oxide layers at high temperature is... 

Infection—The risk of infection is high with chemical bums because the body s primary defense against infection-causing microorganisms (the skin) is damaged or destroyed. 

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