Lecture 8: The Buffy-Coat Leukocytes and Platelets

leukocytes

white blood bells; part of the immune system

nuclei and organelles

what two structures do WBCs have that other formed elements don’t?

<1%

what percent of blood volume do WBCs account for?

diapedesis

process that leukocytes complete in which they can move out of the vessel into infected tissue

granulocytes and agranulocytes

what are the two categories of leukocytes?

neutrophils, eosinophils, and basophils

which leukocytes are granulocytes?

lymphocytes and monocytes

which leukocytes are agranulocytes?

50-40%

relative abundance of neutrophils

2-4%

relative abundance of eosinophils

0.5-1%

relative abundance of basophils

25-45%

relative abundance of lymphocytes

3-8%

relative abundance of monocytes

leukopoiesis

leukocyte formation

hemocytoblast

the stem cell for all leukocytes

myeloid stem cell

the cell that arises from the hemocytoblast that is the stem cell for RBCs, platelets, granulocytes, and monocytes

lymphoid stem cell

the stem cell that arises from the hemocytoblast that is the stem cell for T lymphocytes, B lymphocytes, and natural killer cells

RBCs, platelets, eosinophils, basophils, neutrophils, and monocytes

which formed elements arise from the myeloid stem cell?

T lymphocyte, B lymphocyte, and NK cells

which formed elements arise from the lymphoid stem cell?

neutrophils

professional phagocytes that target bacteria and some fungi and kill them after engulfment; multilobed nucleus and highly motile

enhance inflammation (attract other lymphocytes) and antimicrobial molecules

what are the functions of the fine granules in a neutrophil?

eosinophil

defense against parasitic worms that are too large to be phagocytosed; bilobed nucleus; role in allergic response and asthma

enzymes and toxins and chemicals that mediate inflammation

what are the functions of the course granules in eosinophils?

basophils

course granules contain histamine which acts as a vasodilator and attracts other WBCs to site of infection

T, B, and NK

what are the types of lymphocytes?

t-lymphocytes

T cells: kill infected cells and direct activities of other immune cells

b-lymphocytes

B cells; antibody production

natural killer cells (NK)

nonspecific defenses

monocytes

develop into macrophage upon entry into the tissues; phagocytose bacteria, debris, and dead cells; activate other immune cells by presenting antigens; u-shaped nucleus

leukemia and mononucleosis

what two disorders are caused by overproduction of leukocytes?

leukemia

cancer of WBCs; uncontrolled division leading to overproduction of abnormal cells

mononucleosis

caused by Epstein-Barr virus; high numbers of lymphocytes, many of which are atypical

leukopenia

under production of leukocytes commonly caused by medications, autoimmune disorders, or bone marrow dysfunction; leukocytes lack protective membranes

platelets

cell fragments that contain granules with clotting factors and enzymes

megakaryocyte

the larger cell in which platelets are formed from

thrombopoietin

the hormone that controls platelet formation

hemostasis

the stoppage of blood flow that occurs in response to damage of a blood vessel

vascular spasm, platelet plug formation, coagulation, clot retraction, and thrombolysis

what are the 5 steps of hemostasis?

vascular spasm

contraction of smooth muscle leading to vasoconstriction, which significantly reduces blood loss

direct injury, chemical release, and local nociceptors

what three things activate vascular spasm?

platelet plug formation

positive feedback loop that temporarily seals the break in the vessel by platelets becoming “sticky” and adhering to tissue at the site of injury

von Willebrand factor (vWF)

what substance binds platelets?

release contents of their granules to attract more platelets

what do platelets do once they have been activated?

coagulation phase

protein called fibrin converts the platelet plug to a more solid mass

Vitamin K and calcium

what are the two clotting factors the coagulation phase relies on?

intrinsic pathway

all necessary factors are in the blood

extrinsic pathway

requires a factor outside of the blood called the tissue factor

factor x

in the intrinsic pathway, what factor do exposed collagen fibers activate?

tissue factor

in the extrinsic pathway, what factor do subendothelial cells display?

common pathway

once factor x has been activated, what do the intrinsic and extrinsic pathway merge into?

3

how many phases are in the common pathway?

generation of prothrombin activator

what is the first phase of the common pathway?

conversion of prothrombin to thrombin

what is the second phase of the common pathway?

thrombin converts soluble fibrinogen to insoluble fibrin

what is the third phase of the common pathway?

clot retraction

actin and myosin in the platelets contract drawing the edges of the vessel closer together

thombolysis

end goal is fibrinolysisfi

fibrinolysis

the breakdown of the fibrin clot by plasmin

tissue plasminogen activator

what activates plasminogen?

endothelial cells

what cells release tPA?

themboembolic conditions

undesirable clot formation

thombus

clot in an undamaged blood vessel

embolus

clot in a blood vessel that breaks away from the vessel wall

emoblism

embolus that obstructs the blood vessel

hemophilia

hereditary bleeding disorder; clotting pathway does not function properly = prolonged bleeding upon even minor injury