Transcript ksu-omar-attas-blood

Tissue Chemistry & Biological Fluids
Biochemistry has passed from a state of descriptive to quantifiable science. As
a biochemist, you should always be interested in things about metabolic
sequences:




The description of the enzymes & chemical changes that
comprise the metabolic sequence
The rate at which material can be transformed by the sequence
The amount of material utilized by the sequence among living
things
The nature of the control mechanisms which adjust the amounts
of material utilized by the sequence
2
Roughly, the contributions of the different tissues to the body's metabolism are
proportional to the weights of the tissue and the biological fluids
Wet weight (kg)
Protein content (kg)
Skeletal muscle
30
6.6
Adipose tissue
13.2
0.92
Stomach & intestine
7.25
1.34
Liver
1.6
0.35
Brain
1.36
0.136
Kidneys
0.29
0.05
Heart
0.29
0.06
Adrenals
0.014
?
Blood
6.4
1.02
Skin
4.9
?
Bone
12.0
1.23
3
From the following table…

It is not the sheer mass of tissue which
determines its quantitative contribution to
metabolic activity

Activity of tissue is determined by its enzyme
content
4
The body can be crudely divided into two components:
Circulating Tissues
Biological Tissues
Blood
Cartilage
Water
Bone
Lymph
Skin
Interstitial fluid
Muscles
Cerebrospinal fluid
Liver
5
Vertebrates have evolved 2 principal mechanisms for supplying
their cells with a continuous & adequate flow of oxygen:
A circulating system that actively delivers
oxygen to the cells
 Acquisition of oxygen
 The oxygen carriers in vertebrates are the
proteins hemoglobin & myoglobin

6
Blood

In a normal weight, there is about 5-6 liters of
blood (12%) or 85ml/kg

It circulates as a homogenous suspension of
erythrocytes, leukocytes & platelets in a solution
of proteins, inorganic ions, & low-molecular
weight organic compounds
7
Functions of the Blood
Transport of nutrients
 Exchange of respiratory gases
 Transport of waste products
 Distribution of hormones & other regulatory substances
 Protection against microorganisms
 Acid-base, electrolyte & water homeostasis
 Heat regulation
 Prevention of excessive
hemorrhage by coagulation

8
General Composition


By volume, 40-45% of the blood consists of erythrocytes,
leukocytes & platelets
1 mm3 of blood contains: 5 x 106 RBCs; 5-103 WBCs; 5-105
platelets
RBC
WBC
Platelets
Male Adults
Female Adults
4.5-5.9 x 1012
4.0-5.2 x 1012
cells/L
cells/L
3.9-10.6 x 109
3.5-10.0 x 109
cells/L
cells/L
150-400 x 109 cells/L
9
The Packed Cell Volume
(PCV Hematocrit)
PCV Hematocrit = Volume of Red Cells/ Volume of
whole blood x 100
Expressed as volume of erythrocyte per liter of
whole
blood
 Normal adult males = 41-53; adult females = 3646
 Hematocrit used to determine PCV
 Color of supernatant plasma gives rough idea of
bilirubin content & is often a useful clue about
the nature of anemia:
 White plasma ----- iron deficiency anemia
 Lemon yellow plasma ----- Hemolytic or
10
Megaloblastic anemia

Blood Volume & the Hematocrit




Rarely necessary to have an
accurate blood volume
Hematocrit (HCT) is the
volume percentage of
erythrocytes in whole blood
HCT is obtained by
centrifugation
The specific gravity of
WBC's intermediate between
plasma & RBC, thus forming
"Buffy Coat"
11
Errors in the Estimation of HCT
Usually up to 5% of the apparent RBC mass is
plasma
 HCT differs according to blood source:
- Some particles when centrifuged tend to
accumulate in the center of the tube
- HCT value is affected by movements of
fluid (hydrostatic pressure)

12
Clinical value of HCT

HCT is important in the
diagnosis of anemia

Rough estimation of
blood loss after
hemorrhage
13
Continuation…
Whole Blood

Whole blood – formed elements = plasma

Plasma – Clotting factors = Serum
14
Physical Characteristics

Arterial blood is crimson

Venous blood is darker red

Specific gravity = 1.0351.090 & the viscosity is 5-6
times that of water

Specific gravity of plasma =
1.015-1.035

Ph = 7.3-7.5
15
Erythrocyte Sedimentation Rate
Rate of settling of RBCs after blood is drawn
 In healthy men : 1-3mm/hr; 4-7 mm/hr in
young women
 Low ESR in patients with anemia
 Follows Stoke's Law (settling velocity) with an
equation

Where:
Vs is the particles' settling velocity (m/s) (vertically downwards if ρp > ρf, upwards if ρp <
ρf),
r is the Stokes radius of the particle (m),
g is the standard gravity (m/s2),
ρp is the density of the particles (kg/m3),
ρf is the density of the fluid (kg/m3), and
η is the fluid viscosity (Pa s).
16
Continuation…



ESR greatly increased during
menstruation & normal
pregnancy
Increased rate also found in
septicemia & pulmonary
tuberculosis (increased globulin
& fibrinogen content of plasma;
also in elevated cholesterol &
phospholipid levels
Inflammation of various types
that cause cell necrosis will
cause rate of RBC to fall, but
the viscosity remains
unchanged.
17
Continuation…
In alcoholic cirrhosis there is a rise in plasma bile acids &
membrane cholesterol levels may rise by 55%. This has 2 effects:




Cholesterol to phospholipid ratio is increased, reducing membrane flexibility
Increased cholesterol content also raises total lipid present, expanding its
surface area
Increase by 8% in the total lipid is enough to cause formation of spherocytes
(removed from the circulation as a result of alteration in size, shape and
flexibility)
Elevated levels of plasma bile acids (mainly cholic & deoxycholic acids) are
observed in obstructive jaundice with similar consequences for the RBC
membrane
18
Plasma



Straw colored fluid with
specific gravity from
1.015-1.035
Specific gravity of
plasma is related to its
protein content
Contains 90-92% water
19
Continuation…
Blood owes much of its physiological importance to
high water content:


Maintaining blood pressure
Important for heart regulation& in osmotic exchange between
body fluid & compartments
20
Plasma Composition
The solutes of the blood
plasma constitute ≈ 10%
of the volume
 Protein ≈ 7%
 Inorganic salts ≈ 0.9%
 Other organic compounds
≈ the rest other than
proteins.

21
Separation of plasma proteins
Based on the different mobility in an electric
field
Albumin

Electrophoresis – widely used

Isoelectric focusing
Alpha 2
Alpha 1

Beta
Gamma
Immunoelectrophoresis –
separates proteins on the basis of electrophoretic as well
as immunologic properties
22
Albumin & Globulins
Albumin & Globulins



Comprise most of the proteins
in the blood plasma
Colloidal osmotic pressure
(from the proteins of the
plasma) is the force that
opposes the hydrostatic
pressure in the capillaries
Better terminology should be
"potential osmotic pressure"
or "osmotic tendency"
23
Proteins move in electric field by the charge they
carry…
Major fractions include:
Albumin (54-58%)
 α1 globulins (6-7%)
 α2 globulins (8-9%)
 β1- globulins (13-14%)
 Gamma globulins (11-12%)

24
Enzymes of Plasma


Most plasma enzymes do not have metabolic roles in plasma
with the exception of those involved in coagulation
Activity of certain plasma enzymes is useful as index of certain
abnormal conditions:
- Serum amylase – elevated in acute pancreatitis
- Acid phosphatase – in cases of prostatic cancer
- Alkaline phosphatase – in hepatic obstruction and bone
diseases
25
Assay of tissue enzymes in plasma







When organs are damaged part of their
enzyme complement in released into the
plasma.
In a healthy persons, levels of intracellular
enzymes are very low & a result of cellular
turnover
Tissues contain 103-104 times higher content
of soluble enzymes within their cells
Intracellular enzymes released into the
plasma are inactivated & removed within
days
Amount of enzyme released depends on the
concentration of that enzyme & extent of
tissue damage
Knowledge of cellular location of enzyme
provides good clinical information
In practice, enzyme assays are most useful
in detecting damage to the liver, muscles
and blood cells
26
Some enzymes commonly assayed as part of clinical diagnosis
Enzyme
Organ Distribution
Comments
GOT
Widespread but little in red cells
CPK
Widespread but skeletal muscle
is richest source
Mainly liver
Analysis of these enzyme
started clinical enzymology
Monitoring skeletal & heart
muscle disorder
Marker for hepatocellular
diseases
Monitor heart & liver disease
Γ-GT
LDH
Widespread but has distinctive
isoenzyme distribution
Acid phosphatase
Specific activity in prostate gland Monitor prostatic cancer
Alkaline
phosphatase
Widespread in tissues
Diagnosis of bone disease
27
Continuation…
Enzyme assays may also reveal other organ involvement…



CPK (Creatinine phosphokinase) &
LDH1 (Isoenzyme of LDH) indicate
amounts of myocardial infarct. If no
further damage occurs, levels return to
normal.
Congested liver can be due to inefficient
pumping of the right side of the heart.
Most patients with metastatic prostatic
carcinoma have elevated plasma
phosphatase levels. RIA is used for the
detection of this enzyme.
28
Erythrocytes
Circulating erythrocytes are derived from erythropoietic cells (or erythron), the
precursors of erythrocytes. RBCs arise from mesenchymal cells present in bone
marrow
Major functions
Transport of oxygen from the lungs to the tissues
 Controls blood pH (CO2) is converted to
bicarbonate by carbonic anhydrase = major buffering
system)
 RBCs lack nucleus & other organelles;
utilizes anaerobic metabolism

29
30
Structure & Composition



RBC s have a biconcave
disc shape (6-9 µm in
diameter; 1 µm thick; 22.25 µm at the periphery)
Most of the solid matter is
hemoglobin ( the
conjugated protein
responsible for the red
color of the blood)
Behaves like an osmometer
31
The Erythrocyte Membrane



Composed largely of protein (49%) & lipid (43%) with a small
amount of carbohydrate (8%)
Has a cytoskeleton which controls the shape of the membrane &
limits the lateral mobility of some intrinsic proteins
Some of the protein is glycoprotein covalently linked to CHO
(Sialic acid)
32
Membrane Changes in Diseases
Mature RBCs synthesize very little lipids but:
Sphingomyelin
Phosphatidylcholine
Cholesterol
in the outer half of the bilayer
those in plasma lipoproteins
exhanges freely with serum cholesterol
The important factor that affects this
exchange is the activity of the
plasma enzyme LecithinChoelsterol Acyl Transferase
(LCAT) – responsible for the
formation of majority of esterified
cholesterol and is inhibited by bile
acids
33
Erythropoiesis



During gestation, erythrocytes are
formed in various tissues occurring
successively in:
Yolk sac – main site for the 1st
weeks of gestation
Liver & Spleen - from 6 weeks to
6-7 months & can continue to
produce until about 2 weeks after
birth
Lymph Nodes
34
Continuation…
From 6-7 months of fetal life onwards… the bone marrow is the only source of
new blood cells
35
Continuation…

Erythroid cells in the bone marrow
are called normoblast (a large cell
with dark blue cytoplasm, a central
nucleus with nucleoli & slightly
clumped chromatin
Reticulocytes



A reticulocyte stage results when the nucleus is
finally extruded from the late normoblast. In this
stage it still contains some ribosomal RNA and can
still synthesize Hb
Reticulocytes spends 1-2 days each in the
circulation & bone marrow before it matures
mainly in the spleen when RNA is completely lost
A single pronormoblast usually gives rise to 16
mature red cells
36
Substances needed for
erythropoiesis
The bone marrow requires many precursors to synthesize new cells:
 Metals: Iron, manganese, cobalt

Vitamins: B12, folate, ascorbic acid

Amino acids

Hormones
37
Hemolysis




Maybe produced by substances that
dissolve or change the state of
membrane lipids (ether,
chloroform, bile salts & soaps) .
Certain biological toxins
(venomous snakes & hemolytic
bacteria)
Physical forces (UV rays, freezing,
thawing)
Aging – this is why whole citrated
blood cannot be used after 5-7 days
38
Red Cell Metabolism
The components required for these include:
1.
2.
3.
4.
ATP – maintenance of membrane function
2,3 –diphosphoglycerate (2,3 – DPG) to
modulate O2 affinity
NADPH – to prevent hemoglobin denaturation
NADH – to maintain the heme in the Fe(II)
state
39
Continuation…



The predominant metabolic fuel is glucose where they
serve as gluconeogenic precursors
The 2 ATP molecules are utilized in the ion pump in the
cell membrane
Failure to produce enough ATP results in an ability to
maintain ionic balance leading to accumulation of Ca2+
and shape change
40
41
Continuation…



2,3 DPG is a metabolite unique to the RBC. At a
concentration of 4-5mM, it is almost equimolar to
Hb
20-25% of 1, 3 DPG pass to 2, 3 DPG by mutase,
therefore ATP yield decreases from glucose
2,3 DPG depends on the relative rates of the mutase&
phosphatase reactions
42
Glutathione
Can be used for the removal of H202.
 This reaction protects the membrane from
oxidative damage.
 A deficiency of any enzyme of the glycolytic,
phosphogluconate or GSH-GSSG pathway may
seriously compromise the energy dependent
maintenance of membrane integrity.

43
Hereditary Hemolytic Anemias
Have been associated with deficiencies of the following enzymes:




Enolase enzyme – deficiency leads to decreased ATP required to
maintain the biconcave shape of RBC
Glucose-6-P-Dehydrogenase – deficiency may result in
increased hemolysis & severe hemolytic anemia
Pyruvate Kinase - deficiency may lead to bizarre model which
is extremely fragile and readily hemolyzed
Other enzymes such as hexokinase,glucose –
phosphoisomerase, phosphofructokinase, triose phosphate
isomerase, 2-3 diphosphoglycerate dismutase
44
Erythrocyte Destruction
Senescent erythrocytes are
engulfed primarily in the
reticuloendothelial cells of the
spleen
 Free hemoglobin is released and
binds to plasma proteins (e.g.
haptoglobin)
 Complex is transported to liver
where Hb portion is split
 Heme portion is transported to
plasma & converted to bilirubin;
excreted in the bile
 Iron is released & stored in the
liver for reuse

45
Hemoglobin

1 liter of blood usually contains 150g of hemoglobin;
each gram can combine with 1.34ml of oxygen
46
Continuation…

1 liter of blood can carry
200ml of oxygen, 87 times
higher than plasma alone.

Each RBC contains ≈ 640
million Hb molecules
47
Hemoglobin Structure



The 4 chains are held
together by non-covalent
bonds
There are 4 binding sites
for oxygen
The Hb molecule is
nearly spherical; packed
together in a tetrahedrical
way
48
Continuation…

1.
2.
3.
4.
5.
The amino acid sequence of hemoglobin is known for 20 species.
However there are 9 positions in the sequence that contain the
same amino acid in nearly or all species studied. These conserved
positions are especially important for the function of
hemoglobin:
Some of them are involved in oxygen binding sites
Stabilizing the molecule via forming H-bond between the helix
Some (e.g. GLY) for easy contact between the chains
Some (e.g. PRO) to terminate the elix
The non-polar residues (Alanine, Isoleucine) are important because
reversible oxygenation of heme group depends on its location where it is
protected from water.
49
Continuation…

Normal hemoglobin is of several types containing 4 sub-units
made up of various combinations of 4-5 different related peptide
chains
Hemoglobin
Structure
Stage of Life
% in Adult
Gower I
ζ2ε2
0-5 weeks embryo
None
% in
Newborn
Up to 40
Gower II
α2ε2
None
Up to 35
Portland
ζ2γ2
None
Up to 35
Fetal (F)
α2γ2
4-13 weeks
embryo
4-13 weeks
embryo
Newborn & adult
< 1.0
80
A1
α2β2
Newborn & adult
97
20
A2
α2δ2
Newborn & adult
2.5
< 0.5
50
Biosynthesis of Hemoglobin



It has been estimated that there are 30 trillion
erythrocytes in the circulating blood & ≈ 3 million/sec
are destroyed
Globin moiety is formed from amino acids from the
body pool in amounts of about 8g/day in the normal
adult
14% of the amino acids from an average daily protein
intake are used for globin formation
51
52
Availability of Fe++
Total body content of iron is about 2-6g & is not
excreted in this form
 Found in porphyrin ring of the heme complex
 The first type of compounds (Hb, myoglobin,
cytochromes,catalase) are associated with the
physiology
 The second type is concerned with absorption,
transport & storage of iron

53
Iron Absorption





No iron absorption takes place in
the stomach
Stomach acid is essential for iron
reduction
Duodenum contains "apoferritin"
(converts Fe ++ to Fe+++)
Ferritin may then act as an iron
store or transported to the serosal
side where it is released in the
ferrous form
In the blood, iron is bound by
specific α-1 Globulin (transferrin)
Iron is stored in the liver & bone marrow in 2 forms: Ferritin & Hemosiderin
(agglomeration of ferritin molecules)
54
Transport of Oxygen


If arterial blood is
analyzed for its oxygen
content, it is found to
contain 18-20% volume
Hb is an allosteric
protein: the binding of
additional O2 Hb enters
the binding of
additional O2 to the
same Hb molecule
55
Continuation…

The sigmoidal property of the
curve is believed to be due to
heme-heme interactions

Heme-heme interaction means
binding at one heme facilitates the
binding of oxygen at the other
hemes on the same tetramer & vice
versa
56
Cooperative Property



When environmental oxygen levels are high, partially saturated
hemoglobin molecules exhibit enhanced affinity for binding
additional oxygen molecules, a specialized behavior referred to
as cooperativity.
Hb has the capacity to bind between 1 and 4 O2 molecules,
ranging from fully "desaturated" Hb (deoxyHb) to fully
"saturated" Hb (oxyHb).
As part of this process, Hb also serves to replenish the "oxygen
stores" maintained by myoglobin (Mb), the O2-binding protein in
muscle which releases its oxygen in response to high levels of
muscle activity.
57
2, 3 Bispospoglycerate (2,3 –DPG)






Is very important for long-term regulation of Hb affinity to
O2
2,3 BPG shunt is a pathway derived from glycolysis.
Competition with oxygen for binding site on ß-subunits
Hypoxia stimulates 2,3 BPG synthesis, i.e. improve O2
release
2,3 DPG binds electrostatically to β- subunits through Lys
82, His 143 & N-term. The juxtaposition of these groups
is favorable for 2,3-DPG binding only in the T-state.
DPG stabilizes the deoxyHb by cross-linking the β chains. In other
words, DPG shifts the equilibrium to tense form.
58
Clinical Significance of DPG





It has been approved that DPG levels decrease from 4.5mM to 5.0mM
Ill patients may take longer time to regain DPG when blood is
transfused
Inosine can be converted to DPG inside RBC. Inosine can now be used
to preserve integrity of stored blood
In hypoxia (e.g. emphysema), airflow in the bronchioles is blocked so
the pressure increases as DPG increases. DPG levels lead to 27%
increase in the amount of oxygen due to pressure changes. (Also in
high altitude adaptations)
Fetal Hb has high affinity to transfer oxygen from maternal to fetal
circulation. HbF binds DPG less strongly than does HbA &
consequently has higher oxygen affinity.
59
Life span of RBCs





RBCs have a limited life span of 120
days
The "Red Cell Theory of
Aging" is based on observed Ca2+
that occurs in old erythrocytes
Ca2+ rises to 0.5mM, enough to
activate transglutaminase present in
cell membrane
Transglutaminase form cross-links by
creating iso-peptide bonds
Red cells with cross-linked membrane
proteins are less flexible & are removed in
the circulation by the spleen
60
RBC Destruction



Hemoglobin from senescent
erythrocytes (phagocytosed in the
reticuloendothelial cells of the
spleen) are transported to the liver
bound to the plasma protein
haptoglobin
The globin portion is reused as
amino acids & the heme moiety is
converted to several steps to the bile
pigments
Bilirubin, Urobilin & Stercobilin
are colored (BILE PIGMENTS)
61
Continuation…
The pigments (biliverdin & bilirubin) are
extracted in bile

The iron of heme is removed & the process,
bound to plasma transferrin & either recycled
as new hemoglobin or stored in the liver as
ferritin

In the liver, bilirubin, either from Hb or from
other hemoporteins is transported bound or
loosely associated with plasma albumin
In the small intestine…

Conjugates with glucoronic acid to form
bilirubin diglucoronide which is water soluble
& is readily excreted by means of the bile into
the intestine

Hydrolysis in the intestine by a β-glucoronidase
into bilirubin & glucoronic acid

Reduction of bilirubin by bacterial floral action
to colorless D or L- Urobilinogen

62
Urobilinogen
First part is reabsorbed & excreted in the urine as oxidized
orange-yellow pigment L-Urobilin
 Second part is reduced in the intestine to L-Stercobilinogen &
excreted as an oxidized pigment L-Stercobilin in the feces
(Faecal urobilinogen)
Urinary urobilin is increased if…
 Hemolysis is excessive when large amounts of bilirubin enter the
bowel & are converted to stercobilinogen
 There is liver damage (impairs re-excretion of normal amounts of
urobilinogen into the bile)

63
Erythrocyte Abnormalities
A large number of human diseases are associated with
abnormal function of the erythrocytes including
Altered rates of erythrocyte production &
destruction
 Defects in iron or heme metabolism
 Combination of these conditions

These diseases are called ANEMIAs…
64
Nutritional Deficiency
Anemia


Hematopoietic precursor cells are particularly sensitive
to any insult that impairs DNA synthesis. This leads to
appearance of characteristic megaloblasts corresponds to normoblasts (characterized by increased
ratio of RNA to DNA). The cause can be deficiencies in
metal traces, folic acid & vitamin B12
Larger amount of hemoglobin than other proteins, &
constant daily losses of Hb must be replaced by
resynthesis
65
Continuation…



Iron-deficiency – lack of dietary iron or excess blood
loss (e.g menstruation)
Folic acid deficiency – its deficiency leads to
megaloblastic anemia as it is a co-factor for a variety
of reactions to 1-carbon metabolism (synthesis of
purines & thymines)
Vitamin B12 deficiency – deficiency leads to
pernicious anemia. Based on malabsorption of
Vitamin B12 due to failure of the gastric mucosa to
secrete adequate intrinsic factors
66
Hemolytic anemias

Anemias associated with increased destruction of erythrocytes,
characterized by shortened life span of cells

Isoimmune hemolytic disease – in newborns; caused by
transplacental transfer of maternal blood-group Abs
capable of reacting with fetal erythrocytes

Hereditary spherocytosis - associated with the presence
of spherical erythrocytes that are more fragile to hypotonic
solutions; nature of defect unknown
67
Continuation…

Paroxysmal nocturnal hemoglobinuria – erythrocytes
are abnormally sensitive to lysis by complement

Sickle Cell anemia – abnormal Hb, HbS aggregates on
deoxygenation & the aggregates deform the shape of
the cell, rendering susceptible to lysis

Thalassemias – caused by defective synthesis of α & β
globin chains
68
Sickle Cell Anemia
1.
2.
3.
4.
5.
6.
Characterized by the sickle-cell or crescent shape of the erythrocytes
when the oxy HBs is converted to deoxy HbS at low PO2.
At intracellular concentrations, molecules of deoxy HbS aggregate to
form filaments on tubules of indeterminately high molecular weight
The sickle-cell causes severe anemia since they have increased
mechanical fragility
Sickle cells also impede blood flow through capillaries
It is genetically transmitted
Vigorous physical activity at high altitude, air travel in unpressurized
plane, & anesthesia can be potentially hazardous to a person with this
disease
69
Characterization of HbS

HbS has between 2 & 4 more net + charges per molecule than
net HbA
A


S
pI of Oxy Hb
6.87
7.09
= 0.22
pI of deoxy Hb
6.88
6.91
= 0.23
Non-polar residue on the outside of HbS (due to Val) causing
low solubility
Sticky patch on the outside of its β chains & are present on both
deoxy HbS & oxy HbS but not on HbA
70
Thalassemias

Normally the rates of synthesis of the α & β chains of Hb must
be virtually identical.
α-Thalassemia


In α-Thalassemia, there is deficiency in α chains & hence β
chains precipitate; β- thalassemia is the reverse
Results from deletion of the α-globulin gene (Homozygotes with
α-Thalassemia exhibit a syndrome known as hydrops fetalis)
71
Continuation…
β- thalassemia
 β- thalassemia are heterogenous
 β- globin gene is deleted
 β- globin gene remains intact & β- globin
mRNA is synthesized but not translated
 In many β- thalassemia, the β- globin gene is
present but very little β- globin mRNA is
produced
72
Blood Groups


Isoagglutinins (blood group substances) are found on the erythrocyte surfaces
& are responsible for the major immunological reactions of erythrocytes
(Blood Types)
Surface of RBCs carry antigens (agglutinogens), the plasma carry
agglutinins
73
Continuation…

ABO system is more complicated than the outline given. The ABO groups
actually have 6 groups:
A1
A2
B
AB
A2B
O
The following rules must be observed in blood transfusion:
• If the recipient's ABO group is known, give blood of the same group if possible
• Give Blood group O if the ABO group is unknown
• If the recipient's blood group is AB, neither antibodies are found are found in plasma so
any red cells can be given
74
Rhesus Groups

The term Rhesus (Rh) blood group system refers to the 5 main Rhesus
antigens (C, c, D, E and e) as well as the many other less frequent Rhesus
antigens. The terms Rhesus factor and Rh factor are equivalent and refer to
the Rh D antigen only. Rh + gene is the dominant gene; Rh – is the recessive
gene
Genotype
Symbol
Rh(D) status
cde/cde
rr
-
CDe/cde
R1r
+
CDe/CDe
R1R1
+
cDE/cde
R2r
+
CDe/cDE
R1R2
+
cDE/cDE
R2R2
+
75
Blood Coagulation

Injury to a blood vessel initiates a
series of reaction involving 3
separate processes:
1.
The damage end contracts
Platelets begin to adhere to the
injured endothelium & form a
plug
Blood clot formation
2.
3.
76
Clotting
Must be initiated rapidly when the vascular system is damaged but must occur when the
circulatory system is intact





When the vessel is punctured or cut, the
endothelium brings blood into contact
with sub-endothelial collagen
Platelets at the site of injury are
influenced to stick
As the platelets aggregate they release
vasoactive amines (serotonin &
epinephrine) & prostaglandin
metabolites (thromboxane A2) which
stimulate vasoconstriction
The plug is called thrombus & it is a
major chemical defense against blood
loss
The actual blood clotting processes that
lead to a proper clot are set into motion
by 2 mechanisms: intrinsic & extrinsic
77
pathways:
The Coagulation Cascade
78
The Intrinsic (Intravascular system)


A.
B.
C.
D.
So termed because all factors involved are present in the vascular system
The 3 factors involved lead to the activation of factor X & in turn to the
conversion of prothrombin to thrombin
The Hageman factor binds to collagen or to vasoactive peptide
such as Kallikrein, resulting to a proteolytically active form
XIIa
XIIa activates XI by hydrolyzing an internal peptide bond
In the presence of Ca2+, IX is activated to IXa. This activation is
vitamin K dependent.
In the final step factor X is converted to Xa by IXa in the
presence of VIII (hemophilia A factor), platelet phospholipids
and Ca2+ ions
79
The Extrinsic (Extravascular system)

The factors involved are
supplements of the
intrinsic to ensure more
rapid coagulation

Factor VII is converted
to active form VIIa by
factor III in the presence
of Ca 2+
80
Conversion of factor II (Prothrombin) to
factor IIa (Thrombin)

The rest of the reactions are common in both
patrhways

Factor Va, platelets, phospholipids & Ca 2+ to
promote the reaction
81
Conversion of Factor I
(Fibrinogen) to factor Ia (Fibrin)




By thrombin, ARG-GLY in α-A & β-B chains of fibrinogen is
released in a form of fibrinopeptide A & B from NH2 terminal
ends of the chains.
The gamma chain is not affected
Factor VIIIa (the fibrin-stabilizing factors FSF is present in
human platelets & in plasma
Factor VIIIa (fibrinoligase) is a trans glutaminase that catalyzes
the formation of cross-linked peptide bonds
82
Continuation…

Once the clotting cascade is initiated, mechanisms must operate
to prevent clotting from spreading throughout the intravascular
system.

Plasmin & fibrinolysin prevent such spread & dissolve any clots
that do form.

Plasmin is derived from inactive plasminogen in a reaction that
requires blood & tissue factors including factor XIIa & Kallikrein
83
ANTICOAGULANTS
In vitro…
 A number of substances prevent coagulation [oxalate,
fluoride, citrate, EDTA – they precipitate Ca 2+ and
bind to it]
 Bile salts are inhibitors of thromboplastin
 Dicumarol – is an antagonist of vitamin K by impairing
its biosynthesis
 Heparin – is a complex polysaccharide β- diglucoronic
acid & α-D-glucosamine
84