Blood is a fluid substance that circulates in the arteries and veins of thebody. Blood is bright red or scarlet when it has been oxygenated in the lungsand passes into the arteries; it becomes bluish red when it has given up itsoxygen to nourish the tissues of the body and is returning to the lungs throughthe veins and the tiny vessels called capillaries. In the lungs, the blood givesup the carbon dioxide wastes it has taken from the tissues, receives a newsupply of oxygen, and begins a new cycle. This movement of blood is broughtabout by the coordinate activity of the heart, lungs, and blood vessels. Bloodis composed of a yellowish fluid, called plasma, in which are suspended themillions of cells that constitute about 45 percent by volume of whole blood.
Ithas a characteristic odor and a specific gravity between 1. 056 and 1. 066. In anaverage healthy adult, the volume of blood is one-eleventh of the body weight,or between 4. 5 and 6 liters (5 and 6 qt).
A great portion of the plasma iscomposed of water, a medium that facilitates the circulation of the manyindispensable factors of which blood is composed. A cubic millimeter of humanblood contains about 5 million red corpuscles called erythrocytes; 5000 to10,000 white corpuscles called leukocytes; and 200,000 to 300,000 plateletscalled thrombocytes. The blood also carries many salts and organic substances insolution. Blood type, in medicine, classification of red blood cells by thepresence of specific substances on their surface. Typing of red blood cells is aprerequisite for blood transfusion.
In the early part of the 20th century,physicians discovered that blood transfusions often failed because the bloodtype of the recipient was not compatible with that of the donor. In 1901 theAustrian pathologist Karl Landsteiner classified blood types and discovered thatthey were transmitted by Mendelian heredity . The four blood types are known asA, B, AB, and O. Blood type A contains red blood cells that have a substance Aon their surface. This type of blood also contains an antibody directed againstsubstance B, found on the red cells of persons with blood type B.
Type B bloodcontains the reverse combination. Serum of blood type AB contains neitherantibody, but red cells in this type of blood contain both A and B substances. In type O blood, neither substance is present on the red cells, but theindividual is capable of forming antibodies directed against red cellscontaining substance A or B. If blood type A is transfused into a person with Btype blood, anti-A antibodies in the recipient will destroy the transfused A redcells.
Because O type blood has neither substance on its red cells, it can begiven successfully to almost any person. Persons with blood type AB have noantibodies and can receive any of the four types of blood; thus blood types Oand AB are called universal donors and universal recipients, respectively. Otherhereditary blood-group systems have subsequently been discovered. The hereditaryblood constituent called Rh factor is of great importance in obstetrics andblood transfusions because it creates reactions that can threaten the life ofnewborn infants. Blood types M and N have importance in legal cases involvingproof of paternity.
A chemist uses liquid chromatography to analyze a complexmixture of substances. The chromatograph utilizes an adsorbtive medium, whichwhen placed in contact with a sample, adsorbs the various constituents of thesample at different rates. In this manner, the components of a mixture areseparated. Chromatography has many valuable applications, such as determiningthe level of pollutants in air, analyzing drugs, and testing blood and urinesamples. Gas chromatography separates the volatile constituents of a sample, andliquid/liquid chromatography separates small, neutral molecules in solution. Thegoal in conducting a separation is to produce a purified or partly purified formof the desired constituent for analytical measurement, or to eliminate otherconstituents that would interfere with the measurement, or both.
Separation isoften unnecessary when the method is highly specific, or selective, and respondsto the desired constituent while ignoring others. Measuring the pH, or hydrogenion content, of blood with a glass electrode is an example of a measurement thatdoes not require a separation step. QHP 7694 Head Space Sampler is a machinethat equilibrates the sample vials at the desired temperature for the specifiedtime period. A needle then punctures the teflon coated septum at the top of thevial and draws a measured sample of the vapor which it sends to the GasChromatograph. HP 5890 Gas Chromatograph.
This machine takes the vapor from theHead Space Sampler and passes it through a packed column designed specificallyfor alcohol in blood. As the vapor passes through this column, differentcompounds will travel at different rates thus exiting at different times. As theseparated compounds exit, they pass through a Flame Ionizing Device (FID) whichconsists of a hydrogen-oxygen flame and ionizing detectors. The intensity of theionization is measured and sent to the computer for processing. Helium CarrierGas carries the vapors through the Gas Chromatograph. A Power Macintosh 7600 isused for report generation, correspondence and on line communication.
Reportsare printed using a variety of laser printers to insure optimum print quality. Blood samples are quantitatively added to an aqueous solution into which aninternal standard has been added in order to compensate for samplingfluctuations within the Gas Chromatograph. Static head space methodology isemployed in which an aliquot of equilibrated vapor is injected and analyzed by aFlame Ionization Detector in the Gas Chromatograph,which consists of ahydrogen-oxygen flame and ionizing detectors. The intensity of the ionization ismeasured and sent to the computer for processing. Helium Carrier Gas carries thevapors through the Gas Chromatograph. Blood analysis is very important in manydifferent situations.
For example, in forensics, if a bloodstain pattern isobtained, analysis is vital. BPA (Bloodstain Pattern Analysis) may on manyoccasions, clearly define the location of the victim or the assailant byestablishing the actions of either or both. Possible and impossible scenariosmay be established to determine if the victim, witness, orassailant isaccurately describing what took place. Some questions that may be answered are:What type of weapon or impact occurred to cause the bloodstains present? Howmany times was the victim struck ? Where was the victim at the time the injurieswere inflicted? Where was the assailant during and following the assault? Is thebloodstain evidence consistent with the medical examiner findings? Is thebloodstain evidence on the suspect and his clothing consistent with the crimescene? Numerous courts throughout the country have upheld the value andscientific reliability of BPA. Court case information is available upon request. BPA is a valuable asset during and after the initial investigation.
BPA has beenextremely valuable during the establishment of the courtroom trial strategy. Blood analysis can be very important in testing for drugs. If drugs are in yoursystem, your blood can be tested using more sophisticated means than static headspace gas chromatography. You can also use urine tests and breath tests. Urine,however is the least reliable, while blood is the most. DNA Detection is a veryimportant part of blood analysis.
Thanks to a powerful biochemical tool calledpolymerase chain reaction (PCR), it is possible to detect incredibly tinyamounts of particular DNA molecules. Even one single molecule can be enough! DNA(deoxyribonucleic acid) is the central molecule of life. It contains sequencesof information coded along its length. The information tells cells how to buildprotein molecules. PCR uses proteins called enzymes, combined with small piecesof DNA called primers. The primers match the sequence of the target molecule(the one being looked for) and the enzymes make lots more of any matchingmolecules.
The result is that one matching molecule is multiplied into billions!DNA is very important because nobody has the same DNA pattern. Every singleperson’s is different. DNA also lasts forever, it never disappears.Bibliographyhttp://www.letsfindout.com/subjects/body/rfipulma.html http://www.watchtower.org/medical_care_and_blood.htmhttp://www.letsfindout.com/subjects/body/veins.html http://www.encyclopedia.com/articles/01579.htmlhttp://www.letsfindout.com/subjects/body/rfiblood.html “Blood” -Encarta Encyclopedia “Blood Type” – Encarta Encyclopedia”Forensics”- Encarta Encyclopedia
