1. Leukocytes (WBCs)
Leukocytes:
The only blood components that are complete cells
Less numerous than RBCs
/ul of blood (on average)
Can leave capillaries via diapedesis
Diapedesis is prompted by endothelial cell adhesion molecules (CAMs)
In tissue (loose connective or lymph), they mount inflammatory or immune response
They move through tissue spaces (ameboid)
Classified as:
Granulocytes
Agranulocytes

2. Percentages of Leukocytes
Figure 17.9

3. Granulocytes Granulocytes: Contain cytoplasmic granules
Granules stain specifically (acidic, basic, or both) with Wright’s stain
Include:
Eosinophils (acidic)
Basophils (basic)
Neutrophils (both)
Larger and usually shorter-lived than RBCs
Have lobed nuclei
All are variably phagocytic cells

4. Neutrophils Most numerous of WBCs (50-70%)
Have two types of granules that take up both acidic and basic dyes
Have multilobed nucleus (3-7 lobes)
Increase exponentially during acute infection
Active phagocytes
Contain potent antimicrobial proteins (defensins)
They are the “bacteria slayers” of the body

5. Eosinophils Eosinophils: Account for 2–4% of WBCs
Red stained bilobed or 8-shaped nuclei
Have large acidophilic, lysosome-like granules
Lead the body’s attack against parasitic worms
Lessen severity of allergies by phagocytizing immune complexes

6. Basophils Account for 0.5-1% of WBCs U- or S-shaped nuclei
Functionally similar to mast cells
Have large, purplish-black (basophilic) granules
Produce histamine (contained in granules)
Histamine is:
An inflammatory chemical
Acts as a vasodilator
Attracts other WBCs

7. Agranulocytes Agranulocytes: Lack visible cytoplasmic granules
Found in bloodstream but much more abundant in lymphoid tissues
Include:
Lymphocytes
Monocytes
Lymphocytes & Monocytes are:
Structurally similar
Functionally distinct and unrelated cell types

8. Lymphocytes Lymphocytes: Types of lymphocytes:
Account for 25% or more of WBCs
The smallest of the leukocuyes (RBC size)
Have large, dark-purple, circular nuclei
Have a thin rim of blue cytoplasm
Found mostly enmeshed in lymphoid tissue
A small proportion circulatse in the blood
Types of lymphocytes:
T cells:
Function in immune response
Act directly against grafts, tumors and virus-infected cells
B cells
Give rise to plasma cells, which produce antibodies

9. Monocytes Monocytes: account for 3–8% of leukocytes
are the largest leukocytes
abundant pale-blue cytoplasms
purple-staining, U- or kidney-shaped nuclei
leave the circulation and enter tissues,
Once in tissues, they differentiate into macrophages
Increase dramatically in number during chronic infections

10. Macrophages Macrophages: Are in-tissue-differentiated monocytes
They are:
Highly mobile
Actively phagocytic
Activate lymphocytes to mount an immune response

11. Leukocytes
Figure 17.10

12. Leukopoiesis Is the production of WBCs
Stimulated by chemical messengers (glycoproteins) from:
Bone marrow
Mature WBCs
Chemical messengers include
Interleukins (number naming, e.g., IL-1, IL-2)
Colony-stimulating factors (CSFs); (named fater the cell type they stimulate, e.g., granulocyte-CSF )
All leukocytes originate from hemocytoblasts

13. Accumulated lysosomes
Stem cells
Hemocytoblast
Myeloid stem cell
Lymphoid stem cell
Committed
cells
Myeloblast
Myeloblast
Myeloblast
Monoblast
Lymphoblast
Developmental
pathway
Promyelocyte
Promyelocyte
Promyelocyte
Promonocyte
Prolymphocyte
Accumulated lysosomes
Eosinophilic
myelocyte
Basophilic
myelocyte
Neutrophilic
myelocyte
Granules appearance; division stops
Eosinophilic
band cells
Basophilic
band cells
Neutrophilic
band cells
Nuclei arc
Eosinophils
Basophils
Neutrophils
Monocytes
Lymphocytes
(a)
(b)
(c)
(d)
(e)
Nuclear segmentation
Leaving bone marrow
Enetring circulation
Agranular leukocytes
Some
become
Granular leukocytes
Some become
Figure 17.11

14. Leukocytes Disorders Leukocytosis: Leukopenia: Leukemia:
WBC count over 11,000/mm3
Normal response to bacterial or viral invasion
Leukopenia:
A decrease in WBCs number below 4000/mm3
Leukemia:
Cancerous conditions of the lymphoid tissues
Characterized by:
Uncontrolled proliferation of abnormal WBCs
Reduction in:
RBC number
Platelets number

15. Platelets Platelets function: Platelets: Their granules contain:
Fragments of megakaryocytes
Blue-stained outer region
purple granular center
Their granules contain:
Ca2+, enzymes, platelet-derived growth factor (PDGF), and other substances
Platelets function:
Form a plug temporarily sealing broken blood vessels

16. Genesis of Platelets The stem cell for platelets is the hemocytoblast
The hormone regulating genesis is called thrombopoietin
The sequential developmental pathway is as shown:
Stem cell
Developmental pathway
Hemocytoblast
Megakaryoblast
Promegakaryocyte
Megakaryocyte
Platelets
Figure 17.12

17. Hemostasis A series of reactions to stop bleeding
Three phases occur in rapid sequence:
Vascular spasms:
Immediate vasoconstriction
Platelet aggregation:
Plug formation
Coagulation:
Blood clotting

18. Platelet Plug Formation
Upon damage of endothelium of blood vessels:
Collagen fibers exposed
Platelets adhere tenaciously to exposed fibers
Endothelial cells synthesize a large plasma protein (von Willebrand factor)
Protein factor bridges & stabilizes platelets-collagen binding
Platelets:
Swell
Form spiky processes
Become sticky
Granules of swollen platelts break
They release several chemicals

19. Platelet Plug Formation (cont’d):
Release chemicals include:
ADP:
A potent aggregating agent
Causes more platelets to stick and release their contents
Thromboxane A2:
Enhances vascular spasms
Enhances platelets aggregation
Serotonin:
Functions similar to Thromboxane
A platelet plug is formed within one minute

20. Coagulation: A set of reactions in which blood is :
Transformed from a liquid to a gel
It follows two pathways:
Intrinsic (endothelium)
Extrinsic (tissue)
The final three steps of these reactions involve:
Formation of prothrombin (plasma protein) activator
Prothrombin is converted into thrombin (an enzyme)
Thrombin polymerizes fibrinogen (soluble plasma protein) into fibrin (insoluble form)
Insoluble fibrin forms a mesh
The mesh traps RBCs (starting clotting)

21. Figure 17.13a

22. Clot Retraction and Repair
Involves the stabilization of the clot:
By squeezing serum out of fibrin strands
Thru the contraction of platelets proteins (actin & myosin)
Repair:
Rebuilding of blood vessel wall:
Involves Platelet-derived growth factor (PDGF)
PDGF stimulates the division of :
Smooth muscle cells
Fibroplast cells (connective tissue patch)
Restoration of endothelial lining:
Involves Vascular endothelial growth factor (VEGF)
VEGF stimulates endothelial cells multiplication

23. Hemostasis Disorders (Thromboembolytic Conditions):
Thrombus:
A clot that develops and persists in an unbroken blood vessel
Thrombi can block circulation, resulting in tissue death
Coronary thrombosis:
Thrombus in blood vessel of the heart
Can lead to fatal heart attack

24. Hemostasis Disorders (Thromboembolytic Conditions):
Embolus:
A thrombus that breaks away from a vessel wall & freely floats in the blood stream
When trapped by narrow vessels it results in embolism
Pulmonary emboli:
Emboli that become trapped in the lungs
Can impair the ability of the body to obtain oxygen
Cerebral emboli:
Emboli that become trapped in the brain
May cause a stroke

25. Prevention of Undesirable Clots
Substances used to prevent undesirable clots:
Aspirin:
Inhibits thromboxane A2, therfore,
Interfers with platelet aggregation & plug formation
Heparin
An anticoagulant
Used clinically for pre- & postoperative cardiac care
Warfarin
An anticoagulant found in rat poison
Interfers with Vit K production of some procoagulants
Used for those prone to atrial fibrillation

26. Assigment Chapter 17 List the chapter-indicated diagnostic blood tests
Explain the diagnostic use of each test