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Forensics Class #5

Plasma

the liquid portion of whole blood containing proteins, enzymes, clotting factors, electrolytes and various types of cells.

Leucocytes (leukocytes)

white blood cells; a high number is often an indicator of disease since they defend the body against infectious disease and foreign materials.

Erythrocytes

red blood cells; carries oxygen from the lungs to the body tissues, color comes from hemoglobin

Platelets

tiny cells involved in blood clotting

Serum

the yellowish liquid remaining after whole blood is allowed to clot; it contains most of the proteins and enzymes of plasma but none of the cells or clotting factors.

Antigens

important molecules that instigate immune reactions within the body and help determine your blood type; any substance that causes your immune system to produce antibodies against it.

Putrefaction

decay caused by bacterial growth within cells (decomposing animal proteins, this rotting causes a strong odor)

Presumptive test

a test which indicates a likelihood (presumes) that blood is present but doesn't establish it as fact.

Confirmatory test

more expensive and time consuming tests that prove blood is present

Luminol

a chemical used to reveal latent blood in extremely small amounts even if the area has been cleaned (unless cleaned with bleach). Its chemical reaction with hemoglobin produces light (luminescence). It can detect blood in dilution up to 1 in 5 million.

Fluorescein

reveals blood like luminol but thicker (sticks better to walls) and bleach doesn't interfere with its results.

Exsanguination

bleeding to death

Centrifuge

a device that rapidly spins a test tube of blood causing the cells to settle at the bottom with the plasma left on top

Viscosity

a measure of thickness; Blood viscosity is a measure of the resistance of blood to flow, the more viscous the blood, the harder the heart must work to move it around.

Velocity

a measure of speed

Surface tension

an elastic-like property that holds liquid together in a spherical shape. Example: Beading of rain water on the surface of a waxed car. Water adheres weakly to wax and strongly to itself, so water clusters into drops. Surface tension gives them their near-spherical shape because a sphere has the smallest possible surface area to volume ratio.

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