Understanding the Body

The first seven vertebrae, called cervical vertebrae, form the neck. Areas of the spine such as the neck, where flexible, can experience strains and sprains. The shoulder consists of a ball and socket joint where the ball of one bone fits into a hollow crevice of another. The shoulder joint allows movement and rotation of the arms inward, outward, forward, or backward. There are several different tendons attached to bones in the shoulder. Bursar reduces friction and cushions the tendons as they slide back and forth. The spine is a column of approximately 30 bones called vertebrae that run from the neck to the tailbone. These vertebrae stacked on top of one another in a shaped column form spinal joints, which move independently. Health spines contain three natural curves a forward curve in the neck, a backward curve in the chest area, and another forward curve in the lower back. The back s three natural curves should align correctly when ears, shoulders, and hips form a straight line. At the end of the spine, the vertebrae fuse together to form the sacrum and the tailbone. The lower back or lumbar area provides the workhorse capacity of the back. It carries most of the weight and load of the body. Aligning and supporting the lumbar curve properly helps prevent 

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Many work situations, by virtue of the layout of the working station or of the materials used, present a higher than normal risk to health. By understanding the characteristic of the materials in use and the likely reactions of the body the risks to health can be reduced to a minimum. In understanding the body s reaction to chemicals it is necessary to understand how the body functions. 

Before the widespread availability of instrumental methods the major approach to structure determination relied on a battery of chemical reactions and tests The response of an unknown substance to various reagents and procedures provided a body of data from which the structure could be deduced Some of these procedures are still used to supple ment the information obtained by instrumental methods To better understand the scope and limitations of these tests a brief survey of the chemical reactions of carbohydrates is m order In many cases these reactions are simply applications of chemistry you have already learned Certain of the transformations however are unique to carbohydrates... 

A new field of transfusion medicine, cell therapy, has developed with the better understanding of the function of different cell types ia the body. In cell therapy, various malignancies are treated by transfusion of specific cell types from blood. Therefore, more and more specialized methods for separating blood iato the various components are required. 

It is no exaggeration to claim that it was the extensive worldwide body of research on semiconductors from the late 1930s onwards that converted physicists to the recognition that scrupulous control of purity, stoichiometry and crystal perfection, together with characterisation methods that could check on these features, are a precondition of understanding the nature of semiconductors and thus also a precondition of exploiting them successfully - indeed, not only semiconductors but, by extension, many kinds of materials. 

Absorption, distribution, biotransformation, and excretion of chemical compounds have been discussed as separate phenomena. In reality all these processes occur simultaneously, and are integrated processes, i.e., they all affect each other. In order to understand the movements of chemicals in the body, and for the delineation of the duration of action of a chemical m the organism, it is important to be able to quantify these toxicokinetic phases. For this purpose various models are used, of which the most widely utilized are the one-compartment, two-compartment, and various physiologically based pharmacokinetic models. These models resemble models used in ventilation engineering to characterize air exchange. 

In addition to the elimination rate constant, the half-life (T/i) another important parameter that characterizes the time-course of chemical compounds in the body. The elimination half-life (t-1/2) is the time to reduce the concentration of a chemical in plasma to half of its original level. The relationship of half-life to the elimination rate constant is ti/2 = 0.693/ki,i and, therefore, the half-life of a chemical compound can be determined after the determination of k j from the slope of the line. The half-life can also be determined through visual inspection from the log C versus time plot (Fig. 5.40). For compounds that are eliminated through first-order kinetics, the time required for the plasma concentration to be decreased by one half is constant. It is impottant to understand that the half-life of chemicals that are eliminated by first-order kinetics is independent of dose. ... 

These iiicchanisnis can affect the near-term and ultimate fate of a chemical hazard. Recognition of these inechanisms can significantly assist in the identification of a chemical agent as a health hazard. In recent years, the understanding of chemical transport, chemical manipulation in the body, and response by animals luid humans to cheniicals has advtmccd to a point where it is possible to determine whether a chemical is indeed a health hazard. 

The adrenergic dragp produce pharmacologic effects similar to the effects that occur in die body when die adrenergic nerves and the medulla are stimulated. The primary effects of these drugp occur on the heart, the blood vessels, and die smooth muscles, such as die bronchi. A basic knowledge of the nervous system is necessary to understand tiiese drugp and how they work in the body. 

The relative strengths of bonds are important for understanding the way that energy is used in bodies to power our brains and muscles. For instance, adenosine triphosphate, ATP (35), is found in ever)- living cell. The triphosphate part of this molecule is a chain of three phosphate groups. One of the phosphate groups is removed in a reaction with water. The P O bond in ATP requires only 276 kjmol-1 to break and the new P—O bond formed in H2P04 releases 350 kj-mol-1 when it forms. As a result, the conversion of ATP to adenosine diphosphate, ADP, in the reaction... 

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