Blood Webquest Notes

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Blood

“Out damned spot! Out, I say

Here’s the smell of the blood still,

All the perfumes of Arabia will not

Sweeten this little hand. Oh, Oh, Oh!”

—William Shakespeare’s Lady Macbeth, in Macbeth

Unknown Stains at a Scene

Questions to be answered:

•Is it blood?

•Is it human blood?

•Whose is it?

•Determine blood type.

•What caused the blood spatter?

•Determine the method(s) in which blood may have been deposited.

Introduction

Blood typing

can provide class evidence; whereas

DNA profiling

can provide individual evidence.

Blood Characteristics

Whole blood

carries cells and

plasma

—the fluid with hormones, clotting factors, and nutrients.

Shown below:

Red (Erythrocyte) blood cells

carry oxygen to the body’s cells and carbon dioxide away.

Platelets

aid in blood clotting and the repair of damaged blood vessels.

White (Leukocyte) blood cells

fight disease and foreign invaders and, alone, contain cell nuclei.

Erythrocyte Platelet Leukocyte

Blood Typing

What are the four types of blood?

• A, B, AB, and O

What do we use to identify the blood types?

• ABO Blood Typing

What is the population distribution in the

US?

Type Percent

O 45

A

B

AB

40

11

4

Blood Typing

What is the difference between the types?

Antigen

cells are located on the red blood cell.

Antibody

—are proteins secreted by white blood cells that attach to antigens to destroy them, located outside the red blood cell.

Agglutination

—clumping of red blood cells; will result if blood types with different antigens are mixed

Blood Group A

•Has

A antigens

on the surface of red blood cells and

B antibodies

in blood serum.

• The

B antibodies

will attack and destroy

Type B blood cells when they are introduced into the body.

•Can give blood to A and AB, can received blood from O and A

Blood Group B

•Has

B antigens

on the surface of red blood cells and

A antibodies

in blood serum.

• The

A antibodies

will attack and destroy Type

A blood cells when they are introduced into the body.

• Can give blood to B and AB; can receive blood from O and B

Blood Group AB

Has both A + B antigens on the surface of red

• blood cells + NO A or B antibodies in blood serum.

Will not reject or attack any blood types =

Universal Recipient

Can give blood to AB, can receive blood from A, B,

O, and AB

Blood Group O

•Has

NO A or B antigens

on the surface of red blood cells but has

BOTH A + B antibodies

in blood serum.

•Will not “provoke” and attack by any antibodies

=

Universal Donor

• Can give blood to A, B, O, and AB; can receive blood from O

Blood Groups

Type

A

B

AB

Universal Acceptor

O

Universal Donor

Antigen

A

Antibody

B

Can Give

Blood To

A, AB

Can Get

Blood From

O, A

B

A and B

Neither

A nor B

A

Neither

A nor B

A and B

B, AB

AB

A, B, O, AB

O , B

A, B, O, AB

O

11

Rh Factor

A certain blood protein was discovered while studying Rhesus Monkeys called: Rh

• If this protein is present in your blood, you are: Rh

+

(positive).

• If your blood lacks this protein, you are:

Rh

-

(negative).

* This is why we have positive (O

+

) and negative (B

-

) blood types!

Presumptive Tests for

Blood Determination

Kastle-Meyer color test

—a mixture of phenolphthalein and hydrogen peroxide; the hemoglobin will cause the formation of a deep pink color if blood is present

Hematest® tablet

—reacts with the heme group in blood causing a blue-green color

Luminol test

—reaction with blood to produce light

Human vs Animal Blood

Microscopic observation

RBC in animal has a nucleus

RBC in human no nucleus

Frog Blood

Human Blood

Human vs Animal Blood

Precipitin test

Blood is injected into a rabbit; antibodies are formed; the rabbit’s blood is extracted as an antiserum; the antiserum is placed on sample blood. The sample will react with human proteins if human blood is present. This test is very sensitive and requires only a small amount of blood.

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