Download Blood histology Dr. Anshu Kacker

BLOOD
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Functions
• Transportation:
– Dissolved or chemically bound matter (O2, CO2, nutrients, metabolites)
– Maintenance of the body temperature
• Regulation:
– Transmission of signals (hormones)
– Maintenance of homeostasis
• Concentration of dissolved substances
• Osmotic and oncotic pressure
• Acid-base balance - buffering the body fluids (maintenance of pH)
• Protection:
– Defense against foreign agents (specific and non-specific immunity)
– Prevention of hemorrhage – Hemostasis.
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Composition of the blood
•
Blood is a specialized C.T.
composed of an extracellular
matrix (ECM) called plasma, and
formed elements (blood cells and
platelets).
•
Blood plasma (55%) - noncellular portion of the blood.
•
Formed elements (45%)
– Red blood cells (erythrocytes)
– Platelets (thrombocytes)
– White blood cells (leukocytes)
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Hematocrit (PCV)
•
•
•
•
Is the fraction of the blood
volume made up of the formed
elements (mainly RBC).
Is determined by the
centrifuging heparinised blood
( blood mixed with anticoagulant)
in a standard calibrated tube of a
small diameter.
After centrifugation the column of
the RBCs and plasma can be
measured.
Three layers are seen:
– Supernatant plasma
– Buffy coat – leukocytes and
platelets
– RBC
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Hematocrit (PCV)
• Values: The hematocrit is
measure of the percent of
RBC’s in blood.
– Males: 40 – 54 vol%
– Females: 38 – 46 vol%
• ↑ in persons living at high
altitudes, in dehydrated state,
polycythemia etc.
• ↓ in anemia, leukemia, bone
marrow failure
• Importance:
– Determines blood
viscosity.
– ↑ Htc → ↑ resistance to
blood flow.
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Plasma
• Plasma is the liquid part of blood that remains after the
cells have been removed, but which still contains clotting
elements.
• Serum is blood from which the cells and clotting
elements have been removed.
• Serum = Plasma - Clotting factors
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Plasma protein
•
Plasma is a pale-yellow fluid containing 90% water, 9% organic
compounds (proteins, hormones etc), & 1% inorganic salts. Its
principal proteins are:
– Albumin: most abundant plasma protein; responsible for 80% of
the total osmotic pressure of the plasma; synthesized in the liver.
– Globulins:
• Alpha globulins: transport bilirubin and steroids.
• Beta globulins: transport iron and copper.
• Gamma-globulins: these are immunoglobulins, or antibodies,
synthesized by plasma cells.
– Fibrinogens: synthesized in the liver; act in blood-clotting;
responsible for most of the viscosity of plasma.
– Complement proteins: Coagulation (blood clotting) is a cascade
of chemical reactions mediated by complement proteins, resulting
in the conversion of fibrinogen into fibrin.
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Albumin
• Albumin have the smallest molecular mass whereas fibrinogen is
the largest.
• Albumin is the serum protein responsible for the maintenance
of colloid osmotic pressure.
• A decrease in osmotic pressure can result from increased protein
loss or decreased protein synthesis.
• Increased albumin Loss:
– Nephrotic Syndrome
• Reduced albumin synthesis:
– Cirrhosis
– Protein malnutrition
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II. Formed Elements
• Blood cells are produced and replaced in blood-forming organs
(mostly bone marrow, in the adult), do not develop or replicate in the
circulation, and have a limited lifespan.
• RBCs and platelets function within the blood vasculature.
• With the exception of the basophil, WBCs exit the vessels and
exert their effects within body tissues.
• The normal proportion of each type of blood cell lies within narrow
limits, as determined by a “Complete Blood Count (CBC)”.
• “Differential leukocyte count" values will help to identify specific
white cell types in blood and in tissues.
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Blood composition: Formed elements
Platelets
Erythrocytes
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Red blood cells
• Red cells are uniform in size and
shape with an average diameter
of 7.2 to 7.9 µm.
• Erythrocytes are anucleate (i.e.
no nucleus), uniformly
acidophilic bi-concave.
• No mitosis, & No organelle.
• Normal RBC should be the size
of a mature lymphocyte nucleus.
• Life span - 120 days.
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Peripheral blood smear
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Biconcave shape of erythrocytes
•
RBC shape is maintained by
a subplasmalemma
cytoskeleton (spectrin, actin,
and band 4.1 protein) that is
connected to the lipid bilayer
by ankyrin.
•
Ankyrin is linked to both band
3 proteins and spectrin
tetramers, thus attaching the
spectrin-actin complex to
transmembrane proteins.
•
Within the bilayer are various
integral proteins, such as
glycophorins, ion channels,
and band 3 protein.
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RBC cytoskeleton
•
The biconcave shape
provides erythrocytes with a
large surface-to-volume ratio,
thus facilitating gas
exchange.
•
Shape, along with the fluidity
of the plasma membrane,
allows the erythrocyte to
deform readily, and are able
to pass through the smallest
capillaries.
•
The cytoskeleton of
nonerythroid cells consists of
Actin, alfa-Actinin and
Vinculin.
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Hereditary spherocytosis
•
•
•
•
Mutation in spectrin that
renders the protein incapable of
binding to band 4.1 protein, thus
destabilizing the spectrin-actin
complex of the cytoskeleton.
Such RBC adopt a spherical
shape and are osmotically fragile.
In a blood smear, the affected
cells lack the pale area in the
center because they are
spherical.
These fragile cells are prone to
rupture, leading to anemia
Spleen is the principal site for the
removal of worn-out rbcs,
individuals with spherocytosis
show splenomegaly.
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Hereditary elliptocytosis
• Deficiency in band 4.1
proteins results in elliptical
erythrocytes.
• Erythrocytes are unable to
adapt to changes in their
environment (e.g., osmotic
pressure and mechanical
deformations), which results in
premature destruction of the
cells, or hemolysis.
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Reticulocytes
•
Reticulocytes are immature red blood
cells still retain residual nuclear
material, few mitochondria & Golgi
complex.
•
Less than 1% of circulating red blood
cells.
•
Stain with basic dyes cytoplasm shows
blue precipitates.
•
Increase proportion of reticulocytes in
the bloodstream.
– hemorrhage
– exposure to high altitudes
– bone marrow pathology
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White blood cells
• Five types of leucocytes are normally present in the
circulation.
• These are divided into two main groups based on their nuclear
shape and cytoplasmic granules.
• Within the C.T. they act in cellular and humoral immune
responses to foreign agents.
• On the basis of the presence and type of granule in their
cytoplasm and the shape of the nucleus, white blood cells are
classified into two groups:
– Granulocytes
– Agranulocytes
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Peripheral blood cells
A. Erythrocytes; B. Large Granular Lymphocyte;
C. Neutrophil; D. Eosinophil; E. Neutrophil;
F. Monocyte; G. Platelets; H. Lymphocyte;
I. Band Neutrophil; J. Basophil
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• Granulocytes - these cells have
multilobulated nuclei and contain primary
and secondary (specific granules).
– Neutrophils (polymorphs)
– Eosinophils
– Basophils
• Agranulocytes (Mononuclear leucocytes)
these cells have non-lobulated nuclei and
contain primary or azurophil granules.
Agranulocytes do not have specific granules.
– Lymphocytes and Monocytes.
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Differential leucocyte count
• In general, leucocytes number between 6,000 and 10,000 cells/mm3
in blood.
• In an acute infection (as for example, appendicitis), the cell number
may rise to 20,000 or 40,000/mm3.
• The relative proportion of leucocytes in the blood (differential count)
is usually constant within an individual:
– Neutrophils (50%-70%) of total leukocytes
– Lymphocytes (20%-30%)
– Monocytes (3%-8%)
– Eosinophils (2%-4%)
– Basophils (0-1%)
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White Blood Cells
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Neutrophils
•
These cells constitute 50–70% of
circulating leucocytes.
•
The cytoplasm of a neutrophil
contains three kinds of granules,
reflect the various phagocytotic
functions of the cell.
•
They are 12–15 mm in diameter,
with a nucleus consisting of 2–5
(usually 3) lobes linked by fine
threads of chromatin.
•
Neutrophils with more than five
lobes are called hypersegmented
(in Vitamin B12 or folate
deficiency).
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Neutrophil granules
•
Primary (azurophilic) granules
1. Myeloperoxidase
2. Phospholipase A2
3. Lysozyme
4. Acid hydrolases
5. Elastase
6. Defensins
7. Bacterial permeability
increasing protein (BPI)
•
Secondary (specific) granules
1. Phospholipase A2
2. Lysozyme,
3. NADPH oxidase
4. Leukocyte alkaline
phosphatase (LAP)
5. Collagenase
6. Lactoferrin
•
Tertiary granules:
– Phosphatases and
metalloproteinases
(gelatinases &
collagenases)
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Band Neutrophil
•
•
Juvenile neutrophils
Non-lobulated nucleus
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Functions
• Under normal conditions, 90% of the neutrophils are in the bone
marrow, 2–3 % are circulating and the rest are in the tissues.
• Neutrophils to survive in an anaerobic environment is highly
advantageous, since they can kill bacteria and help clean up
debris in poorly oxygenated regions, eg, inflamed or necrotic
tissue.
• Neutrophils constitute a defense against invasion by micro
organisms, especially bacteria.
• Dead neutrophils, bacteria, and semi digested material form a
viscous, usually yellow collection of fluid called pus.
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Eosinophils
•
Eosinophils constituting only 2–4%
of leukocytes in normal blood.
•
Diameter of 12–15 mm and
contains a characteristic bilobed
nucleus.
•
Azurophilic granules are
lysosomes, contain lysosomal acid
hydrolases and hydrolytic enzymes
that function in destruction of
parasites and hydrolysis of
antigen–antibody complexes
internalized by the eosinophil.
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Eosinophils (specific granules)
• Specific granules of eosinophils contain a crystalloid body.
• Crystalloid body contain four major proteins:
1. Major basic protein (MBP), for the intense acidophilia of the
granule. MBP is localized in the crystalloid body.
2. Eosinophil cationic protein (ECP)
3. Eosinophil peroxidase (EPO) and
4. Eosinophil-derived neurotoxin (EDN)
• MBP, ECP, and EPO have a cytotoxic effect on protozoans and
helminthic parasites.
• EDN causes nervous system dysfunction in parasitic
organisms.
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Eosinophil
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Functions
• Phagocytosis of antigen/antibody complexes in asthma, hay fever
and other allergies.
• Destruction of invading parasites - their numbers rise sharply during
allergic reactions or parasitic infections. Eosinophils are activated by
interactions with IgG, IgA, antibodies and have receptors for IgE,
which is important for destruction of parasite.
• Counteracting the effects of basophils - eosinophils produce
substances that break down products released by basophils:
– Histaminase - anti-histamine
– Arylsulfatase (which neutralizes leukotrienes secreted by
basophils and mast cells )
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Basophils
• Less than 1% of blood
leukocytes.
• They have bilobed nucleus but
this is usually obscured by
numerous densely basophilic
(deep blue) specific granules.
• Structural and functional
similarities with tissue mast cells.
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Basophil
• Heterochromatin is in a peripheral
location, and euchromatin is centrally
located
• The basophil plasma membrane
possesses numerous high-affinity Fc
receptors for IgE antibodies.
Electron micrograph and
Light microscopic
appearance of a basophil
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Basophil function
• Basophils participate in certain specific types of immune
reactions because they have surface receptors for IgE.
When activated, they release their vasoactive substances.
• The basophil's specific granules contain:
– Heparin, a powerful anticoagulant.
– Histamine, which quickly and drastically increases the
permeability of blood vessels, causes vasodilation, and causes
smooth muscle contraction in bronchi.
– Leukotrienes or Slow-Reacting Substance of Anaphylaxis
(SRS-A), for the slow, sustained contraction of smooth muscle.
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Lymphocytes
• Lymphocytes are the smallest cells in the white cell
series, being only slightly larger than erythrocytes.
• They are the second most common leucocytes in
circulating blood and make up 20-50% of the
differential white cell count.
• Lymphocytes are characterized by a round, densely
stained nucleus and a small amount of pale
basophilic, non-granular cytoplasm.
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Lymphocytes
• The amount of cytoplasm depends upon the
state of activity of the lymphocyte, and in
circulating blood there is a predominance of
'small' inactive lymphocytes (6-9 μm in
diameter).
• 'Large' lymphocytes (9-15 μm in diameter) make
up about 3% of lymphocytes in peripheral blood.
• Large lymphocytes represent activated B or T
lymphocytes. ONLY cells that leave and re enter
circulation.
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Lymphocytes
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Types of lymphocytes
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Types of lymphocytes
• T cells:
– Th (T helper) cells: activate
and regulate T and B cells.
– CD8+ cytotoxic T cells:
virus-infected and tumor cells.
– Regulatory (suppressor) T
cells: Returns the functioning
of the immune system to
normal after infection;
prevents autoimmunity.
• B cells:
– Precedes plasma cells
and releases antibodies.
• Natural killer cells: acts on
virus-infected and tumor
cells.
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Monocytes
• Monocytes are the largest of the white cells (up to 20 μm in
diameter) and constitute from 2 to 10% of leucocytes in
peripheral blood.
• They are motile phagocytic cells and are the precursors of
macrophages found in peripheral tissues and organs.
• Monocytes are characterized by a large, eccentrically placed
nucleus; nuclear indentation tends to become more
pronounced as the cell matures, so as to give a kidney shape
appearance.
• Cytoplasm stains pale greyish blue, contains numerous small
purple stained lysosomal granules and cytoplasmic vacuoles
which gives a 'frosted-glass' appearance.
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Monocyte
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Monocyte
• Monocytes migrate to peripheral tissues where they assume
the role of macrophages.
• Monocyte-macrophage system (mononuclear phagocyte
system), consisting of circulating monocytes, their bone marrow
precursors, and tissue macrophages both free and fixed
(histiocytes).
• Monocytes respond by chemotaxis to the presence of factors
from damaged tissue, microorganisms and inflammation by
migration into the tissues and differentiation into macrophages;
with their capacity for phagocytosis.
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Platelets
• Blood platelets (thrombocytes) are nonnucleated, disk like
cell fragments 2–4 mm in diameter that participate in clot
formation.
• Platelets arise from megakaryocytes, extremely large cells
that are found in the bone marrow.
• Megakaryocytes have a single, large, highly lobulated
nucleus. They arise in turn from megakaryoblasts by the
process of endomitosis, in which nuclear division
occurs without cytoplasmic division and the nucleus
will become polyploid.
• In stained blood smears, platelets appear in clumps.
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Hyalomere and Granulomere region
•
The hyalomere contains actin and myosin, which enable the platelets to
contract.
•
The granulomere contains three types of granules ( α, δ, λ )
– 1. The alfa (α ) granules contain factors that are involved in repair of
blood vessels, aggregation of platelets, and coagulation of blood.
• These factors include fibrinogen, platelet-derived growth factor,
platelet thromboplastin, and coagulation factors V and VIII.
– 2. Dense (δ) bodies contain factors that are involved in
vasoconstriction, platelet aggregation, and platelet adhesion. These
factors include ADP, ATP, ionized calcium, histamine, epinephrine, and
serotonin storage (produced mostly by enteroendocrine cells of the
gut).
– 3. The λ granules contain lysosomal enzymes, participate in the
removal of blood clots.
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Platelets
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Platelets
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Platelet function
• Platelets play a crucial role in blood clotting (coagulation).
– Maintenance of vascular integrity. Upon activation,
they are able to increase their surface area by severalhundred fold . This enables them to spread across
gaps torn in the endothelium and to stick to endothelial
walls, temporarily sealing leaks in vessels until the
tissue can regenerate .
– Release of blood clotting factors.
– Clot retraction and dissolution.
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Complete Blood Count
• Screens for anemia and infection
• Total RBC, WBC & platelet counts;
differential WBC; hematocrit and
hemoglobin measurements
• Normal hemoglobin range
– infants have 14 to 20 g/100mL of blood
– adult females have 12 to 16 g/100mL of
blood
– adult males have 13.5 to 18g/100mL of
blood
White cell count in disease
• Raised neutrophil count (neutrophilia) indicates an acute
inflammatory response and is seen in bacterial infections.
• Raised eosinophil count (eosinophilia) is seen in response to allergy
and in infections with certain parasites.
• Raised lymphocyte count (lymphocytosis) is seen in response to viral
infections.
• Malignant tumors can form from the bone marrow cells that make
white blood cells, termed leukaemias. In these conditions it is
common to find a very raised white cell count corresponding to
circulating malignant cells.
• Reduction in white cells in the blood may indicate defective function
of the bone marrow.
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Anemia
• Low RBC count,
• Decreased hemoglobin in peripheral blood
• Etiology:
– Loss of blood (hemorrhage)
– Insufficient production
• Lack of iron, vitamin B12
– Increased destruction due to intrinsic
factors
– Hemolytic Anemia
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Anemia
• Results in:
– ↓ oxygen-carrying capacity of the blood → hypoxia → vasodilation
– ↑ in pulse and respiratory rates (effort to supply sufficient oxygen
to tissues)
– ↓ exercise & cold tolerance
– Pale skin (↓ red colored oxy Hb)
– ↑ fatigue and lassitude (lack of energy)
– ↓ blood viscosity → ↓ peripheral resistance → ↑ blood flow, venous
return and CO and work load on the heart
• Etiological classification:
–
–
–
–
Nutritional
Aplastic
Hemorrhagic
Hemolytic
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Clinical features
• Symptoms:
– Tiredness
– Easy fatiguability
– Generalized muscular
weakness
– Lethargy
– Headache
• Signs:
–
–
–
–
–
Pallor
Retinal hemorrhages
Menstrual disturbances
Mild proteinuria
Anorexia, flatulance
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