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Blood
Introduction
•
Blood is a collection of cells that have been
specialized to perform a set of tasks within an
organism.
• For this reason, doctors and scientists consider
blood a tissue and not a fluid.
• Blood consists of two distinct elements:
1. Plasma, the fluid portion of the blood (55% of
blood)
2. Cells, the solid portion of blood (45% of blood)
Red Blood Cells (Erythrocytes)
• Make up 44% of blood.
• These are specialized cells for oxygen transport.
Without them plasma could only carry 2% of the
oxygen that normally travels through our bodies.
• Red blood cells are in the shape of a biconcave
disk with no nucleus. They are packed with 280
million molecules of hemoglobin, an ironcontaining molecule that binds with oxygen.
• Hemoglobin is able to bind with four oxygen
molecules, however it commonly binds with two,
due to space issues.
White Blood Cells (Leukocytes and
Lymphocytes)
• Make up about 1% of blood's volume.
• All white blood cells contain nuclei and appear
colourless.
• They play many roles in fighting off infection and
protecting the body from pathogens.
• Two of the most important disease fighting white blood
cells are leukocytes and lymphocytes.
• Leukocytes engulf and digest pathogens. They are part
of the body's innate immune response (generalized
response of the body to infection).
• Lymphocytes are part of the body's acquired immune
response. They recognize and remember specific
pathogens and fend them off if they attack again.
Macrophage (Leukocyte)
Neutrophil (Leukocyte)
B Cell (Lymphocyte)
Platelets
• They are not cells. They
are fragments of larger
cells that broke apart in
the bone marrow.
• They contain no nucleus
and break down
relatively quickly.
• They help the blood to
clot and protect the body
from excessive blood
loss after an injury.
Steps in Blood Clotting
1.
A blood vessel is ruptured. (first step triggered by an injury)
2.
Substances released by the broken vessel attract platelets to the site.
3.
As the platelets collect, they rupture and release certain chemicals.
4.
These chemicals combine with clotting agents in the blood plasma
creating thromboplastin, an enzyme.
5.
Thromboplastin reacts with calcium in the blood and prothrombin, a
protein produced by the liver to produce thrombin.
6.
Thrombin reacts with fibrinogen to produce fibrin.
7.
Fibrin, an insoluble material, forms a mesh of strands around the injury
that traps escaping blood cells and forms the clot.
Plasma
•
Carries numerous proteins that are
important to many body processes.
1. Fibrinogen is used in blood clotting.
2. Serum Albumin in maintaining blood
pressure and blood volume.
3. Serum Globulin contains antibodies that
fight against infection and disease.
• Plasma also plays a role in the removal
of carbon dioxide from the body
The Rhesus Factor
• All blood also contains the Rhesus factor.
If you have the protein then you are Rh +.
If you don't have the protein then you are
Rh -.
The Rhesus Factor
• Rh-factor problems occur when an Rhnegative person comes in contact with Rhpositive blood for the second time. The
first time there is contact the Rh-negative
person will create antibodies against the
Rh-positive blood. The second time there
is contact, the blood will agglutinate and
block blood vessels which could be fatal.
The Rhesus Factor
• Rh-negative mothers with a second Rhpositive baby already have the antibodies
to destroy the fetus' blood, so they are put
on medication to prevent her antibodies
from crossing over into the placenta and
attacking the fetal blood.