Download ppt

Blood & Blood Spatter
Chapter 8
Composition of Blood
• Three components
– Red blood cells (erythrocytes)
– White blood cells (leukocytes)
– Platelets (thrombocytes)
• Suspended in liquid called plasma
– Carries antibodies, hormones, clotting
factors, nutrients (glucose, amino
acids, salts, minerals)
Composition of Blood
Blood Cells
• RBC – carry respiratory gases
(oxygen & carbon dioxide)
– Hemoglobin – iron-containing protein
that transports oxygen
• Responsible for red color of blood
• WBC – fight disease and foreign
elements
• Platelets – involved in blood clotting
and repairing damaged blood
vessels
Leukocytes (WBC)
• Only blood cells with a nucleus &
DNA
– Used for DNA profiling
• Some are phagocytes (engulf
foreign cells) and some release
antibodies (proteins that “label”
foreign cells for destruction)
• Basophils, eosinophils, neutrophils,
lymphocytes (B&T cells), monocytes
Types of WBC
Elements of Blood
Blood Typing
• Class evidence
– Excludes a person as a suspect
– Largely replaced by STR analysis using
DNA from WBCs (why?)
• Blood from one person does not always
freely mix with blood from another
– Agglutination occurs when mixing some
blood types (clumping that leads to
death)
– Antigens on RBC identify a blood type –
“name tags” that cause an immune
response when foreign to the body
A & B Antigens
• A & B antigens determine ABO blood
group
– Act as nametags on RBC for
identification
– Antibodies bind to foreign antigens
• Type A: RBC have A antigens
• Type B: RBC have B antigens
• Type AB: RBC have both A & B
antigens
• Type O: RBC have no antigens
Antigens & Blood Types
Rh Antigens
• Additional protein antigen on RBCs
– Presence or absence determines Rh
blood group
• Rh antigen present: Rh+ blood type
• Rh antigen absent: Rh- blood type
Antigen-Antibody
Response
• B-lymphocytes are
WBC that secrete
antibodies
– Y-shaped protein
molecules that bind to
specific antigens,
fitting together like a
puzzle piece
– Bind to foreign
substances (viruses,
bacteria, RBC of a
foreign blood type)
Agglutination
• Y-shaped antibody arm fits with the
foreign antigen of a RBC, second arm
can fit with another antigen on another
RBC
– Causes clumping
– If occurs in a blood transfusion, clumping
can cause blood to cease flow due to
obstruction, resulting in death
• used to test blood to determine blood
types
– Mix antibodies with unknown blood to
determine when agglutination does and
does not occur
Agglutination
Agglutination
No Agglutination
Agglutination
Blood
Typing
Tests
Probability
Type
Percent
Fraction
A
42%
42/100
B
12%
12/100
AB
3%
3/100
O
43%
43/100
Rh+
85%
85/100
Rh-
15%
15/100
Multiply to get the probability of A+, A-, B+, B-, etc.
Example: A+ (.42 x .85 = .357 or 35.7%)