1' dia

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HISTOLOGY 1.7. THE BLOOD
Blood is a fluid connective tissue that
circulates through vascular channels to carry
nutrients and oxygen to the cells and waste
products to the excretory organs and carbon
dioxyde to the respiratory organ. Total volume in
percentage of body weight large domestic
animals 8-11 common laboratory animals 6-7
Components cellular (blood corpuscles)
erythrocytes platelets (thrombocytes) leu
kocytes neutrophils eosinophils
granulocytes basophils lymphocytes
agranulocytes monocytes ECM 1./
plasma 91-92 water 8-9 solutes inorganic
ions, electrolytes organic proteins
(albumins,globulins) glucose lipids,
etc. 2./ fibers fibrinogen dissolved in plasma
fibrin (clothing)
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Microscopic preparation of blood for light
microscopic studies
An evaluation is often needed to assess general
health, or to diagnose haematologic and some
other diseases. Blood test is used for this
purpose. For light microscopic observation one
drop of blood is enough spread onto the surface
a slide. The blood film is air-dried, fixed in
methanol and stained with Giemsa
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• Blood corpuscles
• Erythrocytes (red blood cells)
• Non-nucleated biconcave discs dog, cow, sheep.
• Shallow concavity horse, cat
• Flat shape pig, goat
• Size and number also varies among species

SEM image of blood LM image of a blood smear
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1. RED BLOOD CELLS (ERYTHROCYTES) Size 7 mm
the largest (in dog) 4.1 mm the smallest (in
goat) Number in 1 mm3 of blood in the range of
N x 106 (depending on size) Origin red bone
marrow Life span some months only (120
days) Destruction in the spleen Poikilocytosis
variation in shape (goat, deer) Rouleaux
formation adherence to each other, forming long
chains Howell-Jolly bodies small, round,
pyknotic DNA fragments (remnants of the
nucleus) Reticulocyte immature red blood cell
with residual ribosomes
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Rouleaux formation
Howell-Jolly bodies (arrows)
Poikilocytosis
Reticulocyte (arrow)
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Fine structure of erythrocytes Mature
erythrocyte lacks nucleus and cell organelles. It
is a membrane-bound container of hemoglobin
(33-36 ) some enzymes and electrolytes in
water. Biconcave shape is maintained by spectrin
at the internal surface of the membrane
TEM
Main function of the erythrocytes to carry
oxygen to the cells and to carry carbon dioxyde
from the cells to the respiratory organ
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Molecular structure of hemoglobin
Heme-part
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2. Leukocytes (white blood cells)
(5000-9000/mm3) 2.1. Polymorphonuclear
granulocytes 2.1.1. Neutrophils (55-60
) 2.1.2. Eosinophils (1-3 ) 2.1.3.
Basophils (0-0.7 ) 2.2. Mononuclear
agranulocytes 2.2.1. Lymphocytes
(25-33) 2.2.2. Monocytes (3-7 )
2.1.1.
2.2.1.
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2.1.1. Neutrophils The most segmented nuclei
(4-5 lobes) Size 10-12 mm Amount
3000-6000/ml Moderately stained pale
granules Function phagocytosis
(microphages) Origin red bone marrow Life span
some hours (7-8)
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• 2.1.1. Neutrophils
• Ultrastructure
• Two types of granules
• Specific lysosyme,
• lactoferritin, alkaline
• phosphatase
• Azurophilic lysosomal
• enzymes (acidic phos-
• phatase, peroxidase,
• etc.)
• Neutrophils are able to
• migrate through capillary walls (see the image)
  to the site of bacterial
• infection.
• There they phagocyte the bacteria.
• Pus phagocyted bacteria and hundreds of
  thousands dead neutrophils.

Endothelial cell
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2.1.2. Eosinophils Bilobed nuclei (spectacle
form in human) Bright red eosinophilic
granules (species-specific) Size 10-12
mm Amount 300/ml Origin red bone marrow Life
span 8-12 days Function Control of allergic
reactions Moderate phagocytotic activity Defense
against parasitic worms
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2.1.2. Eosinophils Fine structure Specific
granules are heterogeneous from species to
species (various crystal structures inside). Conte
nt of specific granules lysosomal
hydrolases, major basophilic protein MBP,
eosinophilic cationic protein ECP,
eosinophil-derived neurotoxin, antihistamin, slow
reacting substance SRS)
TEM
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2.1.3. Basophils U- or kidney-shaped
nucleus Large purple granules Size 10 mm Amount
very rare Origin red bone marrow Function They
share common features with the CT mast
cells. Their granules contain histamine
(allergic reactions, anaphylaxic shock), heparin
(anticoagulant).
Human
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2.2.1. Lymphocytes Large nucleus, thin
cytoplasmic rim Size 7-12 mm (large-medium-small)
Origin red bone marrow No stained granules in
the cytoplasm (except small azurophilic
ones) Types B- and T-lymphocytes
(morphologically not distinguishable) null-cells
(somewhat smaller size) Function defence -
immunity
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2.2.2. Monocytes Large kidney-shaped eccentric
nucleus No granules in the cytoplasm except
azurophilic small granules Size up to 17
mm Origin red bone marrow Function 1-2 days
circulation in the blood, then enter the CT and
trasform into macrophages (see there)
TEM
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3. Platelets (thrombocytes) Minute colorless
anucleate corpuscles Thin biconvex discs Size
2-3 mm Number 150.000-300.000/ml Origin
megakaryocytes Function blood clothing
TEM
TEM
LM
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Blood clothing
Thromboplastin Prothrombin Thrombin Fibrinog
en Fibrin
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The avian blood Erythrocytes are nucleated
ovoid cells Thrombocytes are nucleated ovoid
cells Granulocytes are called heterophils (arrows)