Blood Anatomy
Forensics, 4th hour
Blood
Parts of Blood
Plasma
The Plasma is the liquid part of blood that carries nutrients and hormones throughout the body. The Plasma makes up about 55% of blood tissue. Plasma should not be confused with Serum. When blood clots, the solid clot separates from the liquid components. This liquid part of clotted blood is called Serum.
RBC, Platelets, WBC
Red Blood Cells
Platelets
White Blood Cells
White Blood Cells are abbreviated WBC but they are technically the Leukocytes (Leuko = white, cyte = cell). There are 5,000 to 10,000 WBC per microliter of blood (5,000 per 1 millionth of a liter). The WBC are the only blood cell that contains a nucleus and thus DNA.
WBC obviously belong to the circulatory system, but they are also part of the immune system. Their main function is to fight disease and foreign invaders - anything from a virus to a splinter to a donated organ. There are many different types of WBCs. In general, once a foreign substance (an Antigen) enters the body, WBC identify it, surround it, and destroy it. Once the WBC has encountered a foreign Antigen, it secretes an Antibody. The Antibody is a protein that has a specific shape that fits like a key into the lock of the foreign Antigen. If the foreign substance invades the body a second time, the WBC can very quickly check their database by using the Antibodies. The image below shows RBC, WBC, and the two together to compare sizes.
RBC is far right, Platelets surround red blood cells in center photo, WBC Left
Presumptive Blood Tests
One of the jobs of a forensic scientist is to determine if a substance is blood. Kastle was the first to develope a presumptive blood test in 1903.
Phenolphthalein Test
The Phenolphthalein Test is also known as the Kastle Meyer Test. A positive test produces a pink color. However, it can produce false positives in the presence of many body fluids including saliva or pus as well as other non human substances.
Luminol Test
The Luminol Test uses UV light to cause blood to glow blue when sprayed with Luminol. Interestingly, this blood test works best with older blood. The older the blood the more it glows. Luminol can also give false positive results in the presence of many heavy metals.
Other Confirmatory Tests
Many of these tests also do not rule out the possibility of another animal's blood as a source. There are other chemicals that can be used to confirm if the blood is from human or another animal.
This is Blood Anatomy
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