3B-1 Blood.pdf

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Learning Objectives 

Explain blood biochemistry and blood typ

Conduct blood spatter analysis to find source of blood and reconstruct past ev

Identify the various blood spatter pattern

1

3

4

Describe the methods used in tidentification and individualisation of blo

2

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Blood 

Fresh

Old & dried

Obvious

Obvious?

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Whose blood is it? 

Show up invisible stainsIs it blood?1

3

Is it human blood?

Can we use blood spatterpatterns to reconstruct events? 

4

2

Blood 

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Blood Composition 

Fresh frblood p

Fluid portion of blood

55% by weight

Transport system

8% of body weight

Blood plasma

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Blood Composition Left to right: erytthrombocyte, le

Blood cells

Oxygen transport

Red blood cells / erythroc

8% of body weight

Blood plasma

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Blood Composition Left to right: erytthrombocyte, le

White blood cells / leukoc

Immune response

Blood cells Red blood cells / erythroc

8% of body weight

Blood plasma

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Blood Composition Left to right: erytthrombocyte, le

Clotting response

Platelets / thrombocytes

White blood cells / leukoc

Blood cells Red blood cells / erythroc

8% of body weight

Blood plasma

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Erythrocytes 

7.8 microns in diameter

No nucleus

Biconcave

No DNA Red bloo

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Erythrocytes 

Principle function

4 oxygen moleculeson each protein

Oxygen transport

Red bloo

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Antigens 

Proteins on surface of red blood cells

Over 100 rare antigens

30 commonly occurring antigens

Responsible for blood typing

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Blood transfusion 

Must be given blood of the right type

Early days Some people fine aftera blood transfusion

Some people fell ill or dieafter a blood transfusion

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Karl Landsteiner 

Karl Land

Developed the A-B-Oblood typing system

Won the 1930 NobelPrize in Medicine

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A-B-O Blood Types 

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A-B-O Blood Types 

Occurrence of blood types vary

Blood Type Percentage (%)

O 40

A 25

B 30

AB 5

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Blood Types & Personality 

No

Is your blood typethe key to true love?

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Blood Types & Personality 

“I  am type B and

have the tendency

to be simplistic and

straightforward at

times.” - Ryu Matsumoto

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Antibodies 

20% of bloodplasma volume

Immunoglobins

Produced as part ofimmune response

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Antibodies 

Antigen binding sites

Bind to “alien” objects 

Extremely specific

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Serum Antibodies 

Antibodies corresponding to surface antige

Anti-A antibodies

Anti-B antibodies

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A-B-O Blood Types 

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Blood typing system 

Many different antigens 

A-B-O system based on A and B antige

Less common antigens 

D antigen / rhesus antigens 

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Rhesus antigens 

Rhesuspositive

With D antigen Without D antig

Rhesusnegative

85% of population 15% of populat

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Blood Type Distribution in Singapore 

Blood Type Percentage (%)

O+ 34

O- 6

A+ 21

A- 4

B+ 25.5

B- 4.5

AB+ 4

AB- 1

Want to indivievidence

Blood types not individuali

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Bio-Identification 

Individualisation of blood type?

More complex blood typing 

Inferior to DNA fingerprinting 

Blood sample  Individualise it 

Extensive research before 1990 

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Bio-Identification 

Cannot be used to prove guilt 

Can be used to establish innocence 

Blood type not individualised

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Bio-Identification 

Crime scene Type A blood found

Established innocence 

Suspect is type B blood

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Bio-Identification 

Does not prove guilt 

Suspect is type A blood

Require further evidence 

Crime scene Type A blood found

Suspect is type B blood