A forensic investigation can involve the analysis of body fluids, including saliva, for evidence of toxins and both prescription and illicit drugs. Obtaining a saliva sample is far less obtrusive and
Saliva is a clear liquid that is made and is present in the mouth, where it has a number of functions. It wets food and makes the food easier to swallow. As well, specialized proteins that are present in saliva trigger chemical reactions that begin to break apart chemical bonds in the food (the proteins are generically termed enzymes). This begins the process of digestion, whereby the food is converted to a form that can be utilized by the body to provide energy. For example, the salivary enzyme alpha-amylase initiates the breakdown of starch into its constituent maltose sub-units.
In addition to wetting the food, saliva also wets the tongue, which aids the various receptors on the surface of the tongue in differentiating the different tastes of foods. Washing of saliva over the surface of teeth, and the presence of antibacterial enzymes, helps keep teeth clean and helps lessen the chance of infections.
Saliva production lessens during sleep. The resulting build-up of bacteria on the teeth and in the mouth produces the characteristic objectionable morning breath. Even though production lessens during sleep, the production of saliva is a round-the-clock affair. Every day, 2 pints (approximately 1 liters) of saliva are produced. This large volume is secreted by three pairs of salivary glands located in the mouth.
Within each gland a cluster of cells called the acinus secrete the salivary fluid. The fluid contains water, electrolytes (minerals such as sodium, potassium, and calcium that are present in body fluids and cells, and whose concentrations are important in maintaining proper body function), mucus (a slippery, jelly-like substance that helps coat and protect cells) and the aforementioned enzymes.
From the acinus, the fluid collects in ducts within each salivary gland. Here, the composition of the fluid is changed. Most of the sodium is reabsorbed and potassium and bicarbonate ions are added. The latter is particularly important in ruminant animals like cows, since, when swallowed, it helps counteract the corrosive action of the large quantity of acid that is produced in the forestomachs.
From the collecting ducts, the saliva passes to larger ducts, which ultimately merge to form a single large duct, from which the saliva empties into the mouth.
Most animals, including humans, have three pairs of salivary glands that are located on either side of the mouth in three different locations. They differ in the nature of the saliva that is produced.
The parotid glands are located near the upper teeth, in a broad area underneath the earlobe. The secreted saliva is watery and reminiscent of the serum portion of blood; indeed, it is described as being serous. Submaxillary (or submandibular) glands are located on the floor of the mouth, underneath the back portion of the tongue. The saliva produced by these glands is a mixture of serous and mucus portions. Finally, the sublingual glands are located on the floor of the mouth in the region of the chin. Sublingual saliva is predominantly mucous in composition.
In addition to the three pairs of glands, hundreds of small glands called minor salivary glands are located in the lips, inside of the cheeks, and throughout the remainder of the mouth and throat.
Saliva can be of forensic significance because traces of drugs that are circulating in the body can be present in saliva. The composition of the saliva accurately mirrors the proteins that are present in both the blood and the urine. Thus, testing of saliva, which is easier and less obtrusive than obtaining a blood or urine sample, can be used to reveal the presence of prescription and illicit drugs.
Similar tests are being refined that will enable the detection of viral and bacterial infections as well as diseases such as cancer. These tests are based on the presence of signature proteins that are unique to the maladies, such as antibodies, from the microorganism or cancerous cells.
For example, an antibody-based saliva test for the human immunodeficiency virus (HIV; the accepted cause of acquired immunodeficiency syndrome) is available for clinical use. No home-use tests are officially approved as of yet, although a number of nonsanctioned and independently evaluated tests are available through Internet-based companies.
Promising preliminary research results published in February 2005 have shown that aberrant genetic material (deoxyribonucleic acid; DNA) and the messenger ribonucleic acid (mRNA) that helps process the genetic information into a protein from cancerous cells can also be detected in saliva. In the future, forensic analysis of saliva may help determine if the subject has (or did have) cancer.
SEE ALSO Barbiturates; Illicit drugs.
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