14. Blood

HISTOLOGY

BLOOD & HEMATOPOIESIS I

Blood: Specialized CTAll connective tissue consists of cells embedded in a matrix that consists of ground substance and fibers. Blood may thus be described as connective tissue whose matrix consists of free-flowing ground substance (plasma) with no fibers.

Blood: Specialized CTAll of the several blood cell types originate in the connective tissue of bone marrow. Certain white blood cells, notably lymphocytes and monocytes, move freely back and forth between blood and other connective tissues. The chemical composition of plasma is very similar to that of interstitial fluid in ordinary connective tissue.

BloodBloodFormed elementsCells & PlateletsPlasma is an aqueous solution containing proteins (7%), lipoproteins (10%), amino-acids, vitamins, hormones, and inorganic salts. The main blood proteins are: (a) albumins (maintains osmotic pressure of blood)(b) gamma globulins (immunoglobulins or antibodies)(c) fibrinogen (clotting agent)SerumFibrinogen+RBC = 44%WBC = 1%Plasma = 55%

Suitable Slides blood smear - Leishman, Wright's, Giemsa or May-Grnwald-Giemsa stains

Cellular components

Red blood cells erythrocytes (44%)White blood cells (leukocytes) and platelets (1%)

RED BLOOD CELLS erythrocytes

1. Biconcave discs about 7.2m diameter [2.6 Vs0.8](similar to the dimensions of most capillaries), nonnucleated, 2. Acidophilic and are stained a reddish color with eosin. 3. Main Protein is Hemoglobin + O = Oxyhemoglobin4. 120 day life span5. Blood count: males have more per unit volume (5.5 x 106/ul of blood) than females (4.1-6) [3.9-5.5]0.82.6

RED BLOOD CELLS erythrocytes6. Carbonic anhydrase CO2 transportation7. Enzymes of Glycolytic and HMP shunt pathways8. ABO blood group system9. Rh antigens Rh+ vs Rh

Type O blood is the most common blood type, followed by type A, type B, and, the least common blood type, AB. Type O: universal donorno antigens = no clumping

Type AB: universal recipientno antibodies = no clumping

Rh system: inherited independent of ABO system Rh positive = antigen present on RBCs (& no antibodies) Rh negative = no antigen & antibodies will be produced IF exposure occurs Erythroblastosis fetalis (also called Rh disease): hemolysis of RBCs of fetus which can cause anemia or worse; may occur when an Rh negative mother & Rh positive father have an Rh positive fetus

RhoGAM: treatment for Rh disease; contains antibodies specific for Rh positive antigen (a good example of passive immunity) injected within 72 hours after birth of Rh positive baby

O+ 37%, O- 6%, A+ 34%, A- 6%, B+ 10%, B- 2%, AB+ 4%, AB- 1%

Blood typeAntigen presentAABBABA & BOneither A nor B

Blood typeAntigenAntibodyAAanti-BBBanti-AABA & BneitherOneitherboth anti-A & anti-B

Drop of blood in which anti-A antibody was addedDrop of blood in which anti-B antibody was addedBlood typeClumpingNo clumpingANo clumpingClumpingBClumpingClumpingABNo clumpingNo clumpingO

Clinical ApplicationsAnemia: Abnormal low values of hemoglobinPolycythemia or Erythrocytosis3. Erythrocyte membrane deformation cytoskeletal organization -Spectrin

4. Anisocytosis Abnormal variation in cell size (macro and microcytosis)

5. Poikilocytosis altered cell shape (sickling, crenation)

Hemoglobin

composed of globin (made up of 4 highly folded polypeptide chains) + 4 heme groups (with iron) each molecule can carry 4 molecules of oxygen called oxyhemoglobin when carrying oxygen & called reduced hemoglobin when not carrying oxygen can also combine with carbon dioxide & helps transport carbon dioxide from the tissues to the lungs

WHITE BLOOD CELLS - leukocytes Granulocytes neutrophils, eosinophils and basophils

Agranulocytes lymphocytes and monocytes

~ 60% neutrophils (50% - 70%) ~ 3% eosinophils (>0% - 5%) ~ 0.5% basophils (>0% - 2%) ~ 5% monocytes (1% - 9%) ~ 30% lymphocytes (20% - 40%)

Granulocytes are characterized by: (i) irregular segmented nuclei (ii) specific granules (specific size, staining affinities, ultrastructure) (iii) terminal (fully differentiated) cells.Agranulocytes are characterized by: (i) regular nuclei (round or kidney-shaped)(ii) non-specific granules (also present in other leukocytes)

Processes exhibited by LeukocytesChemotaxis Chemical attraction which stimulates movement of WBC, especially Neutrophils and monocytes, to sites of infectionAmoeboid movement WBC motility in which pseudopodia are extended and the rest of the cell pulled forward in a crawling action along and through the vascular wall.Diapedesis Name for the process in which WBCs flatten and move through the vascular wall into the interstitial tissue

Neutrophils (also called neutrophilic granulocytes, or polymorphonuclear neutrophilic leukocytes, PMNs, or polys) are the most numerous of the leukocytes, about 60% of the white blood cell count.They are about 12 m in diameter in blood smear preparations (about twice the size of red blood cells

PMN LeukocytesNeutrophil granulocytes (or neutrophils) Have a very characteristic nucleus. Divided into 3-5 lobes which are connected by thin strands of chromatin. The number of lobes increases with cell age. Up to 7 lobes can be found in very old neutrophils (hypersegmented cells).Neutrophils also contain two types of granules. Primary granules (or A granules) contain lysosomal enzymes and are likely to be primary lysosomes, although they are larger (0.4 m) than the "ordinary" primary lysosome. Secondary granules (or B granules), the specific granules of the neutrophils, contain enzymes with strong bactericidal actions. The specific granules of neutrophils stain only weakly if they are at all visible - they are "neutral", hence the term neutrophil.

FunctionNeutrophils play a central role in inflammatory processes. Large numbers invade sites of infection in response to factors (e.g. cytokines) released by cells which reside at an infection site. Neutrophils are the first wave of cells invading infection sites. Receptors in their plasma membrane allow them to recognize foreign bodies, e.g. bacteria, and tissue debris, which they begin to phagocytose and destroy. The phagocytotic activity of neurophils is further stimulated if invading microorganisms are "tagged" with antibodies (or opsonised). Neutrophils cannot replenish their store of granules. The cells die once their supply of granules has been exhausted. Dead neutrophils and tissue debris are the major components of pus. Their lifespan is only about one week.

EOSINOPHILS: 10 15 um

Typically with 2 lobes1-4% of leukocytes (150 400 / ul of blood)

3. Short life few days

Granules specific and nonspecific (azurophilic/acidophilic) a. specific: large granules (crystalloid-major basic protein, enzymes) b. nonspecific: lysosomes; hydrolytic enzymes

EOSINOPHILS: 10 15 um

Function: destroy antibodyantigen complexes and parasitic worms

. Release Major Basic Protein involved in killing parasites . Engulf and destroy antibodyantigen complexes

BASOPHILS: 8 12 m

1. Less than 0.5-1% of leukocytes (50 100 / ul of blood)

2. Basophilic granulocytes have a 2 or 3 lobed nucleus. The lobes are usually not as well defined as in neutrophilic granulocytes and the nucleus may appear S-shaped.

The specific granules of basophils are stained deeply bluish or reddish-violet.

4. granules specific and nonspecific (azurophilic)a. specific: large granules (heparin, histamine, Leukotriene) b. nonspecific: lysosomes; hydrolytic enzymes

FunctionsHeparin and histamine are vasoactive substances. They dilate the blood vessels, make vessel walls more permeable and prevent blood coagulation. As a consequence, they facilitate the access of other lymphocytes and of plasma-borne substances of importance for the immune response (e.g. antibodies) to e.g. a site of infection. The release of the contents of the granules of basophils is receptor-mediated.Antibodies produced by plasma cells (activated B-lymphocytes) bind to Fc-receptors on the plasma membrane of basophils. If these antibodies come into contact with their antigens, they induce the release of the contents of the basophil granules.

Remember mast cells?

1. Binding of antigens (to IgE) releases specific granules

2. Histamine vasodilation, smooth muscle contraction, etc.

3. Heparin anticoagulant

SizeNuclear configGranule distribGranule content

MONOCYTES: 12 25 um

1. Kidney or C shaped nucleus; no specific granules; "pale blue" cytoplasm2. Life span few days in circulation / months in tissues

3. 3% of leukocytes (200 800 / ul of blood)

4. Granules: nonspecific (azurophilic) lysosomes

MONOCYTES: 12 25 um

Function is to become tissue macrophages after migration:

1. avid phagocytes (dead cells, antigens, bacteria)

2. produce cytokines initiate inflammation, etc.

3. antigenpresenting cells

4. foreign body giant cells (multinucleated)

LYMPHOCYTES: 5 18 um

a. 25 30% of leukocytes (1500 2500 /ul of blood)

b. Life span months to years

c. Round, dense nucleus; no specific granules; small, "blue" cytoplasm [may be large or small]

d. Granules: nonspecific (azurophilic) - lysosomes

LYMPHOCYTES: 8 18 um

Function: immune response (B cells, T cells, null cells)

1. B-cells become plasma cells produce antibodies

2. T-cells kill viral cells, produce cytokines

3. Null cells stem cells, natural killer cells

PLATELETS: 2 4 um

No nucleus; never had oneCell fragments from megakaryocytes Hyalomere: outer region, hardly stains, peripheral tubular system, increases surface area4. Granulomere: dense core with granules and few organelles, stains bluish5. Granules: alpha, delta, lambda (lysosomes) a. alpha: fibrinogen, platelet derived growth factor,[PDGF], etc. b. delta: calcium, serotonin, ATP, etc. c. lambda: lysosomal (hydrolytic) enzymes Count: 250,000 500,000

Platelets assist in hemostasis, the arrest of bleeding.

Serotonin is a potent vasoconstrictor. The release of serotonin from thrombocytes, which adhere to the walls of a damaged vessels, is sufficient to close even small arteries.

Platelets, which come into contact with collagenous fibers in the walls of the vessel (which are not usually exposed to the blood stream), swell, become "sticky" and activate other platelets to undergo the same transformation. This cascade of events results in the formation of a platelet plug (or platelet thrombus).

Finally, activating substances are released from the damaged vessel walls and from the platelets. These substances mediate the conversion of the plasma protein prothrombin into thrombin. Thrombin catalyzes the conversion of fibrinogen into fibrin, which polymerizes into fibrils and forms a fibrous net in the arising blood clot.

Platelets captured in the fibrin net contract leading to clot retraction, which further assists in hemostasis.

PLATELET FUNCTION

Some AnomaliesInappropriate clotting: Thrombus - clot formed in an intact vessel, possibly due to: roughened vessel walls (atherosclerosis) slow-moving blood (e.g., in varicose veins) = small quantities of fibrin form & accumulate Embolus - 'moving' clot = piece breaks-off from a thrombus.

Excessive bleeding: Hemophiliagenetic 'defect' inability to produce certain factor(s) Thrombocytopenia abnormally low platelet count most persons have idiopathic thrombocytopenia (= unknown cause) while in others it's an autoimmune disease

Identify the cells, their size, their granules and their function:

Identify the cells, their size, their granules and their function:

Identify the cells, their size, their granules and their function:ABCD

NORMAL BLOOD CELL COUNT

********************RDW :red cell distribution width. 11% - 14%, MCV: mean cell volume 80 100fl, MCHC:32 36% or g/dl, MCH:27 31pg