The Nature of
Blood
Serology
Slide 001
What Forensic Serology?
• Forensic serology is the application of the
study of blood, semen, saliva and other
body fluids to legal matters.
Slide 002
What is Blood?
• A mixture of cells, enzymes, proteins (all
organic…living) and inorganic substances.
• It has fluid AND solid components.
Slide 002
PLASMA
- This is the fluid component.
- It is composed of mainly water.
- Accounts for about 55% of total blood
volume.
- It is a clear, straw-colored liquid that
carries the blood cells and various
hormones, and nutrients through the
body.
The Solid Portion of Blood
- Cells that are suspended in the plasma:
- Erythrocytes (RBC)
- Leukocytes (WBC)
- Platelets (involved in clotting)
- 45% of total blood volume
Serum (add to noteguide)
- When Blood clots, RBC are attaching to a molecule
called fibrin.
- If you were to centrifuge the clotted blood, you would
be left with serum on top and the solid clotted
material on the bottom.
- The difference between plasma and serum?
- Serum: no fibrin
- Plasma: fibrin
Serum (add to noteguide)
RBC
WBC and Platelets
Duties
– RBC:
- They transport oxygen from the lungs to the
rest of your body tissues.
- And remove CO2 by transporting it back to the
lungs.
– WBC: part of the immune system.
– Platelets: part of the clotting
mechanism.
Duties
How is Blood Made?
- Blood cells are produced in the bone marrow.
- Bone marrow is a jellylike substance inside the
bone.
- In children, the marrow of most of the bones
produces blood.
- In adults, only the marrow of certain bones -- the
spine, ribs, pelvis, and some others -- continues to
make blood.
- Bone marrow that actively produces blood cells is
called red marrow, and bone marrow that no longer
produces blood cells is called yellow marrow.
Stem Cells
- The body has a feedback system that tells it
when to make new red blood cells.
- If there are too few red blood cells circulating,
bodily oxygen levels are low.
- The kidneys produce a hormone called
erythropoietin, which stimulates the stem cells
in the marrow to produce more red blood cells.
Stem Cells
How Does the Body Know When to
Make More?
- All blood cells come from the same kind of stem cell (a
cell that has the potential to turn into any kind of blood
cell).
- These stem cells are called pluripotential hematopoietic
stem cells.
- The different kinds of blood cells have different "life
spans“.
- Red blood cells last about 120 days in the bloodstream.
- Platelets about 10 days.
- White blood cells can last anywhere from days to
years.
Making History - 1901
- Karl Landsteiner
- Discovered Blood Types
- Won the Nobel Prize
- Out of his work came the A-B-O blood typing system.
- 1937: Rh factor was discovered