8.0 CONNECTIVE TISSUE: BLOOD
Upon completion of this lecture, students will be able to:
a) Define and use properly the following words: Specialized circulating connective tissue,
Erythrocytes, Biconcave disk, Reticulocytes, Polychromatophilic erythrocytes, HowellJolly (H-J) bodies, Erythrocyte refractile (ER) bodies (HEINZ bodies), Anisocytosis,
Poikilocytosis, Crenation, Rouleaux formation, Leukocytes (WBCs),
Monomorphonuclear, Lymphocytes, Nuclear/cytoplasmic ratio, Humoral and cellular
immunity, B-cell, Plasma cell, T-cell, Monocytes, Euchromatic nucleus, Phagocyte,
Polymorphonuclear, Granulocytes, Neutrophil, Polymorphonuclear leukocyte (PMN),
Segmented Neutrophil, Band Neutrophil, Eosinophils, Acidophilic granules, Lobulated
nucleus, Basophils, Platelets, Thrombocytes, Megakaryocyte, New Methylene Blue,
Punctate, Dohle Bodies, Heterophil.
b) Describe and associate basic structure/function for all structures listed above and
recognize important species differences.
c) Identify by microscopy the cells, organelles, tissues, and organs listed above.
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I.
INTRODUCTION
A. Connective tissues consist of cells separated by an abundance of intercellular material
(fibers and ground substance). CT is found in every organ; it surrounds all the other
tissue types, and is a general classification for: cartilage; bone; blood; adipose tissue
and lymphatic tissue (tissues of the immune system)
B. Blood is a specialized circulating CONNECTIVE TISSUE in an extracellular matrix
called "PLASMA".
C. Blood makes up 7-8% of the total body weight.
D. Blood is composed of CELLS & PLASMA.
E. Components of blood pass through blood vessels
1. plasma fluid passes into the interstitium and then into the lymphatic system
2. cells (white cells only) move by diapedesis (extravasation) between the
endothelial cells and into the interstitium
3. Plasma
a. contains the clotting factors and fibrinogen;
4. Serum
a. Serum = the fluid collected after allowing blood to clot
b. contains no fibrinogen
5. STAINS: Romanowsky stains are used for most blood cell studies. This
procedure involves fixing the cells on a slide with alcohol and then staining with
metachromatic dye (blue-purple).
a. For reticulocytes (an immature red blood cell) in the blood, vital stains
(for live cells) are used and the cells are not killed before staining.
F. CELLS OF BLOOD
1. Erythrocytes (RBC)
2. Leukocytes (white blood cells)
3. Platelets
II.
CLASSIFICATION OF CONNECTIVE TISSUES
A. Supporting connective tissue (also covered in Gross Anatomy)
1. Cartilage & Bone
2. support for soft tissues of the musculoskeletal system
B. Connective Tissue Proper
1. Loose (areolar, reticular)
2. Dense (Regular, irregular)
3. lies beneath epithelia, binds tissues & organs together
C. Specialized connective tissue
1. Adipose tissue
2. Lymphatic tissue (defense of body)
3. Embryonic (Mucous, mesenchyme)
4. Blood (liquid extracellular matrix)
III. ERYTHROCYTES
A. General Information
1. Biconcave disk shape provides for better gas diffusion and flexibility in
squeezing through capillaries
2. In most species, RBC's are devoid of organelles (exceptions are avian and
lower vertebrate species which have nucleated RBCs)
B. Structural variations:
1. Reticulocytes are immature RBC's that enter the blood.
a. They are stained with vital stains.
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b. slightly larger in size (macrocytic)
2. Polychromatophilic erythrocytes
a. similar to reticulocytes if they are macrocytic
b. stained deep blue with metachromatic stain due to an abundance of
ribosomes and polyribosomes in the cytoplasm
3. Howell-Jolly (H-J) bodies
a. are RBCs with remnants of nuclear material, which are normally removed
in the spleen without destroying the RBC (1% of feline & equine blood)
4. Erythrocyte refractile (ER) bodies (HEINZ bodies)
a. are pale areas at the periphery of the cell resulting from oxidation of
hemoglobin in lungs (increased by toxins).
b. Feline more susceptible (Heinz body hemolytic anemia)
5. Anisocytosis (not same size)
a. macrocytes and microcytes
b. Normal ranges in size of RBCs:
c. Goat, sheep = 4-5 µm
d. horse, ox, cat, pig = 5-6 µm
e. dog = 7 µm
6. Poikilocytosis (variation in shape)
7. Crenation is the shrunken appearance of RBCs (ball with spikes),
a. normal in pig blood due to the artifact of Romanowski stain.
8. Rouleaux formation is the stacking of RBCs like coins.
a. Normal in horse, seen also in feline.
b. Increased incidence in dog or cat suggests and increase in total plasma
protein concentrations of globulins or fibrinogen which causes RBC
stickiness
9. Life-span of RBCs:
a. they live for about 120 days and
b. then are removed in the spleen, bone marrow and liver by macrophages.
c. Iron is salvaged and sometimes appears as hemosiderin.
IV. LEUKOCYTES (WBCs)
A. General Information
1. Monomorphonuclear: Lymphocytes, Monocytes, plasma cells
2. Polymorphonuclear: Neutrophils, eosinophils, basophils
B. MONOMORPHONUCLEAR
1. LYMPHOCYTES
a. sometimes the most numerous leukocyte in some species (e.g., bovine)
b. small & large types are found
c. mostly roundish dense nucleus (feline small lymphocytes sometimes has
an indented nucleus)
d. has a more euchromatic nucleus than neutrophils
e. high nuclear/cytoplasmic ratio
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f. humoral and cellular immunity is provided by the lymphocyte
g. Types B & T
h. B becomes reactive (immunocyte in the blood), a precursor to the
PLASMA CELL (in the tissues), seen when there is chronic antigenic
stimulation (eg, parasitic infection)
2. MONOCYTES
a. large irregular shaped nucleus (oval to horseshoe);
b. large amounts of blue-gray cytoplasm
c. euchromatic nucleus
d. largest cells in the blood (up to 25 µm)
e. Major phagocyte (along with neutrophil)
C. POLYMORPHONUCLEAR, granulocytes
1. NEUTROPHILS
a. called neutrophilic granulocyte, polymorphonuclear leukocyte, PMN,
heterophil
b. smaller more condensed (heterochromatic) & segmented nucleus (3-5
lobes)
c. small primary granules are lysosomes (azurophilic or blue)
d. small Specific granules are bactericidal enzymes (pink to purple)
e. Mature cells called Segmented Neutrophil
f. Immature cells called Band Neutrophil (C-shaped nucleus); less
condensed nucleus
2. EOSINOPHILS
a. unique, has large acidophilic granules (very large in horse)
b. 2-3 lobed nucleus (larger than segments of PMN nucleus)
c. heterochromatin
d. not to be confused with Mast cell (large oval nucleus) stained with H&E;
however, when the Mast cell is stained with toluidine blue, the granules are
deep blue
3. BASOPHILS
a. Usually least numerous and even rare (except rabbit, bird & guinea pig)
b. Less heterochromatic nucleus than Neutrophil, but segmented
c. Specific granules reddish purple to dark purple (heparin, histamine, ECF)
d. Functions are not understood
e. Hyperlipidemia causes an increase in Basophils
V. PLATELETS (THROMBOCYTES in bird)
A. General information
1. fragments of membrane-bound cytoplasm from the megakaryocyte of the bone
marrow
2. found in clusters
3. stain pale blue centers and have small purple granules
4. Mammals (functions in the clotting process)
5. Birds (phagocytic function); thrombocytes are nucleated cells with pale blue
cytoplasm
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VI. SPECIES VARIATION
A. CANINE
1. largest erythrocyte seen in common species: 7 mm diameter, distinctive central
pallor
B. FELINE
1. HJ bodies
2. Erythrocyte refractile bodies (Heinz bodies) are easily seen with supravital stain
New Methylene Blue (NMB)
3. eosinophil granules often rod-shaped
4. RBCs may show Rouleaux formation
5. Reticulocytes
6. Aggregate (macrocytic & polychromatic)
7. Punctate (RBC size & color; but New Methylene Blue stain visualizes the RER)
8. "Dohle Bodies" are irregular blue staining bodies in the cytoplasm of neutrophils
(indicates toxicity in other species)
C. EQUINE
1. rapid Rouleaux formation (very few single erythrocytes)
2. No reticulocytes (very important, because in anemic situations one ascertains
whether the bone marrow is responding on the basis of the number of
reticulocytes in the blood)
3. Thus, in the horse other means of assessment must be used, such as bone
marrow biopsy.
4. Eosinophil granules are very large
D. BOVINE
1. No Rouleaux formation
2. Anisocytosis is normal
3. Lymphocytes are more common than neutrophils (called a "lymphocytic lead")
E. OVINE (SHEEP) and CAPRINE (Goat)
1. smallest erythrocytes
2. lymphocyte may be most common leukocyte
F. PORCINE
1. Crenation of erythrocytes is common
2. lymphocytes may be more common than neutrophils
G. AVIAN and FISH
1. large nucleated oval erythrocyte ... more bluish
2. Heterophil = Neutrophil
3. Eosinophils are rare
4. Thrombocytes are nucleated but smaller than erythrocyte and have little
cytoplasm
H. RABBIT
1. Heterophil = Neutrophil = Pseudoeosinophil = Amphophil
2. has numerous intracytoplasmic eosinophilic granules
3. Basophils are common (2-7%)
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