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Blood
-B
lood is unique: it is the only fluid
tissue. It has both solid and fluid
components fluid.
-The fluid part is called plasma, the solid part (the
formed
Elements are the blood cells (red blood cells,
white blood
Cells and platelet).
-If the blood is centrifuged (the heavier formed
elements are pacvked down) and the plasma rise to
the top.
Blood cells
-Most of the cells are erythrocytes (red blood cells
RBCs)
Which function in oxygen transport and it help
carbon dioxide?
Transport.
- At the junction between the formed elements and
the plasma,
There is a whitish layer called the buffy coat (it
contains
Leukocytes (the white blood cells) that act in
various ways to
Protect the body against infection, and platelets
(cell
Fragments that function in the blood clotting
process.
- erythrocytes form about 45% of the blood
volume ( haematocrit), white blood cells and
platelets form less than 1%, plasma form up to
55% of the whole blood volume.
Physical characteristics and volume
- Blood is sticky opaque fluid, has metallic taste
- Oxygenated blood is scarlet color, de
oxygenated (low in oxygen blood) is dull red.
- It is heavier than water, five times thicker (
more viscus)
- It is slightly alkaline (pH between7.34 to
7.45).its temperature is 38° C (higher than
body temperature).
- Blood forms 8% of body weight. Its volume in
healthy males is 5-6 liters.
Plasma
- It is the liquid part of the blood
- 90% of it is water.
- Dissolved in it nutrients, metal ions (salts),
respiratory gasses, hormones, plasma proteins, and
various wastes and products of metabolism.
- Plasma proteins (albumin, globulin and
fibrinogen) they
Function in:1- Albumin (contributes to the osmotic pressure of
the blood)
Which acts to keep water in the blood.
2- Clotting proteins (help prevent blood loss from
injured
Vessels)
3- Antibodies help protect the body from
pathogens).
4-plasma transport substances all around the body.
The formed elements ( RBCs, WBCs, Platelets)
The erythrocytes ( RBCs)
- Are biconcave discs- with depressed centers
- About 5 millions/cmm of blood.
As the RBCs age ,they became more rigid and
begin to fragment, in 100 to 120 days
Functions :
- transport oxygen in the blood to all cells of
the body
- They have no nuclei ( anucleate)
- mature RBCs are full of haemoglobin (Hb), an
iron containing protein, which is the carrier of
oxygen), it bind small amount of carbon
dioxide.
** Although the number is important, the amount
of haemoglobin in the blood is the most
important to the oxygen to be transported in the
blood to tissues.
- each Hb molecule combine with 4 molecules
of oxygen.
- Homeostatic imbalance: A decrease in the
oxygen-carrying ability of the blood,whatever
the reason,is anemia.anemia may be the result
of(1) a lower-than-normal number of RBCs,or
(2) abnormal or deficient hemoglobin content
in the RBCs.
 Sickle-cell anemia,
- the abnormal hemoglobin formed,becomes
spiky and sharp when the oxygen content of
the blood is lower than normal,as during
exercise,anexity,or stressful situations.the
crescent shaped erythrocytes rupture easily.
 -Polycythemia:
is an excessive or abnormal increase in the
number of
erythrocytes,which may result from:
- bone marrow cancer(polycythemia vera),
- normal physiological response(homeostatic) to
high
altitudes,where the air is thinner and less oxygen
is
available(secondary polycythemia).
-The major problem that results from excessive
numbers of RBCs is s increased blood
viscosity,which causes it to flow sluggishly in
the body and impairs circulation.
Leukocytes:
-Leukocytes,or white blood cells (WBCs), are less
numerous than red blood cells,they are crucial to
body defence against disease.they are 4,000 to
11,000 WBCs per cbic millimeter.
-They contain nuclei.
-Leukocytes help defend the body against
bacteria,parasites,and
tumour cells.
-White blood cells,move into and out of the blood
vessels by a
process called diapedesis.
A total WBCs count above 11,000 cells/m m3 is
referred as leukocytosis ,which generally indicates
that a bacterial or viral infection is present.
Leucopenia, is an abnormally low WBCs
count,commonly caused by: drugs as steroids and
anti-cancer agents.
 The excessive proliferation of
abnormal WBCs that occurs in
infectious mononucleosis and
leukemia.
In leukemia, the bone marrow becomes
cancerous,and huge numbers of WBCs are turned
out rapidly.
The newborn WBCs are immature and incapable of
carrying out their normal protective functions.
 Granulocytes, are granules-containing WBCs.
Which include the neutrophils,eosinophils,and
basophils.
Neutrophils,have multilobed nucleus,
phagocytes at sites of acute infection.
Eosinophils have a blue-red nucleus.their
number increases during allergies and infection
by parasitic worms.
Basophils, the rarest of WBCs, contain
histamine-containing granules.histamine is an
inflammatory chemical that makes blood
vessels leaky and attracts other WBCs to the
inflammatory site.
Agranulocytes :lack visible cytoplasmic granules
(lymphocytes,
monocytes)
 Lymphocytes,have larg dark purple nuleus that
occupy most of the cell volume,play an
important role in immune response
 Monocytes, are the largest of the WBCs with
more abundant cytoplasm and intended nucleus.
When they migrate into the tissues ,they change
into macrophages ,which are important in fighting
chronic infection like tuberculosis.
Platelets:
Platelets are fragments of bizarre multinucleate
cells called megakaryocytes.
The normal platelets count in blood is about
300,000/m m3
Platelets are needed for the clotting process.
Hematopoiesis(blood cell formation)
-occur in the red bone marrow
-all the formed elements arise from a common
type of:
stem- cell,the hemocytoblast.
-The rate of erythrocyte production is controlled by
a hormone
called erythropoietin.
-The kidney play a major role in producing this
hormone.
-When blood levels of oxygen begine to decline for
any reason,
the kidneys release erythropoietin which
stimulate the bone
marrow to form more RBCs.
The formation of leukocytes and platelets is
stimulated by hormones as clony stimulating
factors(CSFs) and interleukins.
Hemostasis:
Hemostasis or stopping of blood flow,which
involve three major phases,platelet plug formation,
vascular spasms , and coagulation,or blood clotting.
1.platelet plug formation.
Platelets are repelled by an intact endothelium,
but when it is broken, so that the underlying
collagen fibers are exposed, the platelets become
sticky and attach to the damaged site so a platelet
plug or white thrombus is formed.
2. vascular spasms occur. The anchored platelets
also release serotonin which causes the blood
vessels to go into spasms.
These spasms narrow the blood vessel at that point,
decreasing blood loss until clotting occur.
3.Coagulation events occur with the formation of
fibrin threads.
disorders of hemostasis
abnormal clotting
 A clot that develops and persists in unbroken
blood vessel is called a thrombus.
If a thrombus forms in the blood vessels suppling
the heart(coronary thrombosis),a fatal heart attack
occur.
 If a thrombus breaks away from the vessel wall
and floats freely in the blood-stream, it
becomes an embolus.
For example, a cerebral thrombus may cause a
stroke.
Bleeding disorders
The most common causes of abnormal bleeding
are:
1.
platelet
deficiency(thrombocytopenia) and
2. deficits of some of the clotting
factors as in hemophilia.
Thrombocytopenia: results from insufficient
number of circulating platelets.
This is evidenced by many small purplish
blotches, called petechiae, on the skin
-When the liver is unable to synthesize its usual
supply of clotting factors, abnormal and often
severe bleeding episodes occur.
-If vitamin K(needed by the liver cells to produce
the clotting factors) is deficient, the problem is
easily corrected with vitamin K supplements.
Hemophilia : is hereditary bleeding disorders
that result from a lack of any of the factors
needed for clotting.
o In hemophilia, even minor trauma results in
prolonged bleeding and can be lifethreatening.
Hemophiliacs are given a transfusion of fresh
plasma or injections of the purified clotting
factor they lack.
Blood group and transfusions
The whole blood transfusions are routinely given
to replace severe blood loss and to treat severe
anemia or thrombocytopenia.
Human blood groups
The plasma membranes of RBCs, like those of
all body cells, carry genetically determined
proteins (antigens),which identify each person as
unique.
An antigen is a substance that the body recognize
as foreign; it stimulates the immune system to
release antibodies.
Binding of the antibodies causes the RBCs to
clump, a phenomenon called agglutination.
The ABO blood grouping are based on which of
the two antigens, type A or type B, a person
inherits.
-Absence of both antigens results in
type O
blood.
-Presence of both antigens leads to
type AB.
-The possession of either A or B
antigens yields
type A or B blood, respectively.

In the ABO blood group, antibodies are
formed during infancy against the ABO
antigens not present on your own RBCs.
 A baby with neither the A or the B antigen
(group O)
forms both anti-A and anti-B antibodies,while
those with
type A antigens (group A) form anti-B
antibodies and so on.
The Rh blood group are so called because one
of the eight Rh antigens(agglutinogen D) was
originally identified in Rhesus monkeys.
Rh+(rh positive),meaning that the RBCs carry
the Rh antigen.
Anti-Rh antibodies are not
automatically formed and present in the
blood of Rh- (Rh negative) individuals.
 If an Rh- person receives mismatched blood
(that is Rh +),his or her immune system
becomes sensitized and begins producing
antibodies (anti-Rh+ antibodies) against the
foreign blood type.
 In pregnant Rh- women who are carrying
Rh+ babies. The first such pregnancy
usually results in the delivery of a healthy
baby but she will form anti-Rh + antibodies
unless treated.
 If she is not treated and becomes pregnant
again with an Rh + baby, her antibodies will
cross the placenta and destroy the baby
RBCs., producing hemolytic disease of the
newborn.
 The baby is anemic and becomes hypoxic.
 Brain damage and even death may result
unless fetal transfusions are done before
birth to provide more RBCs for oxygen
trnsport.