BLOOD AND BLOOD SPLATTER

Chapter 8

Composition of Blood

Blood is a tissue that circulates around through the body.

There are 3 types of cells in blood:1. Red blood cells2. White blood cells3. Platelets

Composition of blood

All of these cells are suspended in a liquid called plasma.

It is similar to saltwater in composition.

Carries dissolved proteins (antibodies, hormones, clotting factors) and nutrients (glucose, amino acids, salts and minerals).

Composition of Blood

1. Red blood cells (erythrocytes)Carry respiratory gases (O2 and

CO2)Hemoglobin in the red blood cells is

an iron-containing protein that binds to O2 in the lungs and transports the O2 to cells in all the tissue in the body.

Also responsible for the color red in blood.

5-6 million per mm3 of blood.

Composition of blood

2. White blood cells (leukocytes)Fight disease and foreign invaders.The white blood cells attack

invaders and concentrate where the infection is.

They engulf and digest the invaders.Other white blood cells secrete

proteins known as antibodies, and assist in immune response.

White blood cells continued

Only type of blood cell that contains a nucleus.

Only type used as a source for DNA profiling.

Dr. Alec Jeffreys used in 1982 for DNA profiling.

Types: Basophil, Eosinophil, lymphocyte, neutrophil, and monocyte.

5,000-10,000 per cubic mm of blood

Composition of blood

3. Platelets (thrombocytes)Aid in blood clotting and are

involved in repairing damaged blood vessels.

Discovered by Sir William Osler.250,000-400,000 per cubic mm of

blood

*

Components of blood for greatest to least in percentage

1. plasma2. Red blood cells3. Platelets4. White blood cells (unless sick)

Presumptive Tests For Blood

Kastle-Meyer Indicator testHow does the Kastle-Meyer Indicator

test detect for blood?1. In the presence of Heme, hydrogen peroxide breaks down into water and oxygen (free radical).2. The free oxygen (radical) readily combines with the phenolphthalein in the Kastle-Meyer reaction.

Presumptive Tests For Blood

3.Once the phenophthalein is oxidized, the phenophthalein turns pink. If it does not turn pink, then there was no Heme to break down the hydrogen peroxide. Therefore, no blood was present.

Presumptive Tests For Blood

Reaction: H2O2 + Heme → H2O + O2

How do you run a Kastle-Meyer Test ?1. Looking for peroxidase in the red stain.2. First you apply 2 drops of de-ionized water to

the cotton swab. Rub the moistened swab on the blood stain.

3. Add 2 drops of ethyl alcohol to the cotton swab. This helps to expose the hemoglobin molecules.

4. Add 2 drops of phenolphthalein to the moistened cotton swab. The phenolphthalein serves as the oxygen acceptor. If phenophthalein is oxidized it will produce a pink color.

5. Lastly, add a drop or two of hydrogen peroxide to the cotton swab. If the stain contains blood, then the peroxidases of the Heme in the blood will start to decompose the hydrogen peroxide.

Presumptive Tests For Blood

6. Check for pink color. You may also see some foaming action on the cotton swab. It is important to check the results within the first 30 seconds.

Animal or Human Blood

Animal blood will produce a positive reaction using the Kastle Meyer Test

To determine if the blood is human, it is necessary to produce antihuman antibodies.

Injecting some human blood into different animals-a rabbit for example- does this.

When human blood is injected into the rabbit, the rabbit produces antihuman antibodies or antiserum.

Animal or Human Blood

To perform the precipitin test, a sample of the suspected human blood is placed in the depression of a gelatin-coated depression slide.

Antihuman antibodies or antiserum is placed on the opposite side of the depression slide.

After applying an electric current, the protein molecules in the two samples migrate toward each other, forming a precipitin line where the proteins combine (antigen and antibodies).

Animal or Human Blood

A precipitin is an antibody that precipitates its specific antigen and removes it from the blood.

Blood Spatter

3 Things act on falling blood along with the force of gravity.

Cohesion, adhesion and surface tensionGravity pulls downward on blood and

causes the blood droplet becomes longer than it is wide.

Blood is said to be cohesive. This means that a blood mixture is attracted to similar blood mixtures and tends to stick together and not separate as it falls.

Blood Spatter

Basically the blood pushes toward the center of the drop.

Combining the effect of gravity and the cohesive nature on falling blood gives a net effect of maintaining the bloods circular or round appearance.

When blood falls on a flat surface it will still have a curved surface (again because of its cohesive nature).

The surface of blood is elastic and gives the blood spatter a spherical appearance.

Blood Spatter

If any of the blood does overcome cohesion and separates from the main droplet of blood, it will form small secondary droplets called satellites.

If blood falls on a porous surface (wood, ceiling tile) it may form extensions on the outer edge of the blood droplet known as spikes.

Blood Spatter

Surface tension is an elastic characteristic along the outer edge of a liquid caused by the attraction of like molecules.

Cohesion is a force between two similar substances.

Adhesion is a force between 2 unlike surfaces.Example- blood and surface of wall