Red blood cells
Carry respiratory gases such as oxygen and carbon dioxide, contains hemoglobin
White blood cells
Fight disease and foreign elements.
Platelets
Help blood clot and repair damaged vessels
Plasma
Liquid containing antibodies, hormones, clotting factors, and nutrients
Antigen
On the surface of some red blood cells, provokes an immune response
antibody
Y-shaped protein molecule that binds to the molecular shape of specific antigens
hemoglobin
iron containing protein in red blood cells, binds to oxygen in the lungs, transports oxygen to cells in all body tissues
What type of cells engulf and digest foreign elements?
white blood cells
What type of cells secrete antibodies?
white blood cells - specifically, B-lymphocytes
What component of the blood can be used for DNA profiling and why?
white blood cells because they have nuclei
Give the 4 components of blood in order of percentages, from least to greatest.
white blood cells, platelets, red blood cells, plasma
What type of evidence is blood type?
class evidence
How is blood type helpful as evidence?
It is used to EXCLUDE suspects.
agglutination
clumping of red blood cells
Who discovered the 3 blood types?
Karl Landsteiner in 1901
What determines a person's blood type?
the presence or absence of antigens
Adult humans have _____ liters (______ quarts) of blood.
5.5 liters or 6 quarts
The heart pumps _____ liters of blood hourly.
300 liters
What type of test is used to determine blood type?
an antibody reaction test
If you have Type A blood, then the antigen on the surface of your red blood cells is the _______________________ .
A antigen
If you have Type B blood, then the antigen on the surface of your red blood cells is the _______________________ .
B antigen
If you have Type AB blood, then the antigens on the surface of your red blood cells are the _______________________ .
A and B antigens
If you have Type O blood, what antigens are on the surface of your red blood cells?
There are no antigens on Type O red blood cells.
List the blood types in order of frequency, from least common to most common.
Type AB (3%)
Type B (12%)
Type A (40%)
Type O (45%)
What additional antigen was discovered from research on rhesus monkeys?
the Rh factor
When something foreign enters a body, our immune system responds. What is this response called?
the antigen-antibody response
What is one aspect of antibodies that contributes to agglutination?
Its Y shape promotes clotting.
If a person's blood is mixed with antibodies that bind to the A antigen, but no clotting occurs, then do they have A antigens on their red blood cells?
No. No clotting means that the person does not have that particular antigen.
If Type A blood occurs in 42% of the population, and Rh- occurs in 15% of the population, what are the chances of a person having Type AB- blood?
0.42 x 0.15 = 0.063
0.063 x 100 = 6.3
6.3% of the population has A- blood type.
What does it mean when we say blood is cohesive?
The molecules of blood are attracted to each other; in other words, blood tends to stick together
What are the small secondary droplets of blood around a main droplet called?
satellites
When a drop of blood hits a surface the splatter may have elongated extensions around the edges called _______________.
spines
The tendency of blood to stick to other surfaces is called _____________.
adhesion
If blood is dropped straight down at a 90 degree angle, what shape will it make on the surface where it lands?
circular
If blood is released at an angle that is NOT 90 degrees, what shape will it take upon landing?
elliptical
At a crime scene, can elliptical blood drops inform investigators about the direction the blood was traveling?
yes, the pointed end "points" in the direction the blood was moving
A cast-off blood pattern is often made by what?
a weapon
The smaller the angle of impact (example 10 degrees), the ________________ the blood droplet.
more elongated
A bloody shoe print is an example of a _________________ pattern.
transfer
A bright red blood splatter on the wall that appears to have been sprayed under some pressure is called _______________________.
an arterial gush
Blood blown out of the mouth or nose is called __________________.
expired blood
A door is covered in blood but behind the door the wall is clean. This is an example of a ________________________ pattern.
shadowing or void
Blood ______________________ after it leaves the body, giving investigators a way to estimate the age of the blood deposit.
congeals (thickens)
A technique called _______________________________ can be used to calculate the height above the floor where the injury took place (from a 2 dimensional view).
area of convergence
The location of the blood source as viewed in 3 dimensions
area of origin
How can the angle of impact be calculated?
1. measure width and length of blood droplet
2. Divide the width by the length
3. take the inverse sine of that ratio
What does a fine mist spatter pattern (drops < 1mm) indicate?
high velocity impact, such as a shotgun
What do blood drops 1 - 4 mm in size indicate?
medium velocity, beatings/stabbings
What do blood drops 4 - 6 mm in size indicate?
low velocity, impact with a blunt object such as a bat
What chemical reveals blood even after it has been washed away many times?
Luminol
What test is used to see if a sample is actually human blood?
ELISA test (enzyme linked immunosorbent assay)
Can bloody clothes from a crime scene be stored in plastic containers?
No; they should be dry, packaged, and refrigerated/frozen at the lab
Can different bloodstained items from a crime scene be placed in the same paper bag?
No, each item needs its own package, always labelled completely.
What do the size and shape of blood stains tell us?
1. directionality
2. speed
3. angle of impact
4. the nature of the wound
5. perhaps the source of blood
Blood-spatter analysis can _____________________ eyewitness testimony.
confirm or refute