Blood is a fluid substance that circulates in the arteries and veins of the
body. Blood is bright red or scarlet when it has been oxygenated in the lungs
and passes into the arteries; it becomes bluish red when it has given up its
oxygen to nourish the tissues of the body and is returning to the lungs through
the veins and the tiny vessels called capillaries. In the lungs, the blood gives
up the carbon dioxide wastes it has taken from the tissues, receives a new
supply of oxygen, and begins a new cycle. This movement of blood is brought
about by the coordinate activity of the heart, lungs, and blood vessels. Blood
is composed of a yellowish fluid, called plasma, in which are suspended the
millions of cells that constitute about 45 percent by volume of whole blood. It
has a characteristic odor and a specific gravity between 1.056 and 1.066. In an
average 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 is
composed of water, a medium that facilitates the circulation of the many
indispensable factors of which blood is composed. A cubic millimeter of human
blood contains about 5 million red corpuscles called erythrocytes; 5000 to
10,000 white corpuscles called leukocytes; and 200,000 to 300,000 platelets
called thrombocytes. The blood also carries many salts and organic substances in
solution. Blood type, in medicine, classification of red blood cells by the
presence of specific substances on their surface. Typing of red blood cells is a
prerequisite for blood transfusion. In the early part of the 20th century,
physicians discovered that blood transfusions often failed because the blood
type of the recipient was not compatible with that of the donor. In 1901 the
Austrian pathologist Karl Landsteiner classified blood types and discovered that
they were transmitted by Mendelian heredity . The four blood types are known as
A, B, AB, and O. Blood type A contains red blood cells that have a substance A
on their surface. This type of blood also contains an antibody directed against
substance B, found on the red cells of persons with blood type B. Type B blood
contains the reverse combination. Serum of blood type AB contains neither
antibody, 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 the
individual is capable of forming antibodies directed against red cells
containing substance A or B. If blood type A is transfused into a person with B
type blood, anti-A antibodies in the recipient will destroy the transfused A red
cells. Because O type blood has neither substance on its red cells, it can be
given successfully to almost any person. Persons with blood type AB have no
antibodies and can receive any of the four types of blood; thus blood types O
and AB are called universal donors and universal recipients, respectively. Other
hereditary blood-group systems have subsequently been discovered. The hereditary
blood constituent called Rh factor is of great importance in obstetrics and
blood transfusions because it creates reactions that can threaten the life of
newborn infants. Blood types M and N have importance in legal cases involving
proof of paternity. A chemist uses liquid chromatography to analyze a complex
mixture of substances. The chromatograph utilizes an adsorbtive medium, which
when placed in contact with a sample, adsorbs the various constituents of the
sample at different rates. In this manner, the components of a mixture are
separated. Chromatography has many valuable applications, such as determining
the level of pollutants in air, analyzing drugs, and testing blood and urine
samples. Gas chromatography separates the volatile constituents of a sample, and
liquid/liquid chromatography separates small, neutral molecules in solution. The
goal in conducting a separation is to produce a purified or partly purified form
of the desired constituent for analytical measurement, or to eliminate other
constituents that would interfere with the measurement, or both. Separation is
often unnecessary when the method is highly specific, or selective, and responds
to the desired constituent while ignoring others. Measuring the pH, or hydrogen
ion content, of blood with a glass electrode is an example of a measurement that
does not require a separation step. QHP 7694 Head Space Sampler is a machine
that equilibrates the sample vials at the desired temperature for the specified
time period. A needle then punctures the teflon coated septum at the top of the
vial and draws a measured sample of the vapor which it sends to the Gas
Chromatograph. HP 5890 Gas Chromatograph. This machine takes the vapor from the
Head Space Sampler and passes it through a packed column designed specifically
for alcohol in blood. As the vapor passes through this column, different
compounds will travel at different rates thus exiting at different times. As the
separated compounds exit, they pass through a Flame Ionizing Device (FID) which
consists of a hydrogen-oxygen flame and ionizing detectors. The intensity of the
ionization is measured and sent to the computer for processing. Helium Carrier
Gas carries the vapors through the Gas Chromatograph. A Power Macintosh 7600 is
used for report generation, correspondence and on line communication. Reports
are printed using a variety of laser printers to insure optimum print quality.
Blood samples are quantitatively added to an aqueous solution into which an
internal standard has been added in order to compensate for sampling
fluctuations within the Gas Chromatograph. Static head space methodology is
employed in which an aliquot of equilibrated vapor is injected and analyzed by a
Flame Ionization Detector in the Gas Chromatograph,which consists of a
hydrogen-oxygen flame and ionizing detectors. The intensity of the ionization is
measured and sent to the computer for processing. Helium Carrier Gas carries the
vapors through the Gas Chromatograph. Blood analysis is very important in many
different situations. For example, in forensics, if a bloodstain pattern is
obtained, analysis is vital. BPA (Bloodstain Pattern Analysis) may on many
occasions, clearly define the location of the victim or the assailant by
establishing the actions of either or both. Possible and impossible scenarios
may be established to determine if the victim, witness, orassailant is
accurately describing what took place. Some questions that may be answered are:
What type of weapon or impact occurred to cause the bloodstains present? How
many times was the victim struck ? Where was the victim at the time the injuries
were inflicted? Where was the assailant during and following the assault? Is the
bloodstain evidence consistent with the medical examiner findings? Is the
bloodstain evidence on the suspect and his clothing consistent with the crime
scene? Numerous courts throughout the country have upheld the value and
scientific reliability of BPA. Court case information is available upon request.
BPA is a valuable asset during and after the initial investigation. BPA has been
extremely valuable during the establishment of the courtroom trial strategy.
Blood analysis can be very important in testing for drugs. If drugs are in your
system, your blood can be tested using more sophisticated means than static head
space 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 very
important part of blood analysis. Thanks to a powerful biochemical tool called
polymerase chain reaction (PCR), it is possible to detect incredibly tiny
amounts of particular DNA molecules. Even one single molecule can be enough! DNA
(deoxyribonucleic acid) is the central molecule of life. It contains sequences
of information coded along its length. The information tells cells how to build
protein molecules. PCR uses proteins called enzymes, combined with small pieces
of 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 matching
molecules. The result is that one matching molecule is multiplied into billions!
DNA is very important because nobody has the same DNA pattern. Every single
person’s is different. DNA also lasts forever, it never disappears.
Bibliography
http://www.letsfindout.com/subjects/body/rfipulma.html http://www.watchtower.org/medical_care_and_blood.htm
http://www.letsfindout.com/subjects/body/veins.html http://www.encyclopedia.com/articles/01579.html
http://www.letsfindout.com/subjects/body/rfiblood.html “Blood” –
Encarta Encyclopedia “Blood Type” – Encarta Encyclopedia
“Forensics”- Encarta Encyclopedia
