Lecture 7 - White Blood Cells And Platelets Flashcards
Leukocytes
WBCS
only formed elements that are complete cells
critical to our defense against disease.
Diapedia
Process in which leukocytes leave blood and enter the tissues
Leukocytosis
Elevated WBC count
Leukopenia
Decreased WBC count
Granulocytes
major group of leukocytes characterized as large cells with lobed nuclei and visibly staining granules
all are phagocytic
also known as polymorphonuclear cells (PMNs).
( neutrophils, eosinophils and basophils)
Agranulocytes
lymphocytes and monocytes that lack visibly staining granules.
They are also known as peripheral blood mononuclear cells (PBMCs).
(Lymphocytes and monocytes)
Neutrophils
55-70% of all leukocytes
chemically attracted to sites of inflammation and are active phagocytes.
An increased neutrophil count commonly indicates bacterial infection.
Eosinophils
1-4% of leukocytes.
attack parasites in loose connective tissues, and have role in asthma and allergies.
effective against multicellular endoparasites such as worms.
They are also associated with some viral infections.
commonly linked to allergic reaction
Basophils
least numerous type of leukocyte, 0.5-1% of all white blood cells
release histamine to promote inflammation.
associated with multicellular exoparasites such as ticks
commonly linked to allergic reactions.
Lymphocytes ( 3 types)
20-40% of white blood cells
the basis for the adaptive immune response.
T lymphocytes- directly attack virus infected cells and tumour cells.
B lymphocytes- bind antigens and produce antibodies as plasma cells.
Natural killer (NK) cells- similar function to T cells but are part of the innate immune response. W
Monocytes
2–8% of white blood cells
actively phagocytotic macrophages as they enter tissues, and can activate lymphocytes.
common in chronic infections and inflammatory autoimmune diseases.
Leukopoiesis
Formation of WBCS
Regulated by production of interleukins and colony stimulating factors (CSF)
Band cells
Immature granulocytes
Leukemia
Cancer of WBC
clones of single WBC remains unspecialized and divide uncontrollably
How is infectious mononucleosis (MONO) caused?
Epstein Barr virus characterized by excessive numbers of agranulocytes
Platelets
Not complete cells- fragments of bone marrow called megakaryocytes
Lifespan approx. 10 days
What is the function of platelets?
Form temporary seal when blood vessel breaks
Thrombopoietin
Hormone that regulates formation of platelets
Hemostasis
Process of preventing blood loss
Three steps:
1. Vascular spasm
2. Platelet plug formation
3. Coagulation (clotting)
Vascular spasms
immediate vasoconstriction response to blood vessel injury
become more efficient with increased tissue damage.
a temporary mechanism to reduce blood flow until other mechanisms can begin.
Platelet plug formation
Platelets stick to exposed collagen fibres or to each other if collagen not exposed, to form platelet plug
Coagulation (clotting)
Multi step process where blood transformed from liquid to gel
Platelet plugs reinforced with fibrin threads
- formation of prothrombin activator through the intrinsic pathway or extrinsic pathway.
- Prothrombin activator catalyzes prothrombin into active enzyme thrombin
- Thrombin converts soluble fibrinogen into insoluble fibrin which causes plasma to become a gel-like trap to catch formed elements. Thrombin also activates fibrin stabilizing factor to cross-link fibrin into a strong mesh to stabilize the clot.
Intrinsic pathway
all factors necessary are present within the blood
slower clotting pathway that can clot blood but does not seem to play a major role during injuries
Extrinsic pathway
triggered through an endothelium-derived glycoprotein tissue factor (TF)
can occur rapidly by bypassing some steps of the intrinsic pathway.
much more important for clotting blood.
What creates fibrin mesh?
When thrombin catalyzes the reactions that convert fibrinogen to fibrin
Clot retraction
process in which the contractile proteins (myosin and actin) within platelets contract and pull on neighboring fibrin strands, squeezing plasma from the clot and pulling damaged tissue edges together.
typically occurs within 30-60 minutes.
What is repair stimulated by?
platelet-derived growth factor to stimulate endothelial cell division.
Fibrinolysis
removes unneeded clots through the action of the fibrin-digesting enzyme, plasmin.
What are the two factors that limit size of clots as they form?
- Rapidly moving blood disseminates clotting factors before they can initiate a clotting cascade.
- Activated clotting factors are inhibited by other compounds in the blood. For clotting to occur, the concentration of activated clotting factors must overcome a minimum concentration.
As long as the vascular endothelium is smooth and intact, platelets are prevented from clotting.
