Platelets and Coagulation Flashcards
What is the maturation process of Megakaryocyte?
PPSC-myeloid stem cell-megakaryoblast-megakaryocyte
What is Thrombopoietin?
stimuli for PPSC’s to differentiate into megakaryocyte
What is the source of TPO?
uncertain but involves liver, endothelial cells and fibroblasts
What signals the release of platelets to increase amount in blood?
negative feedback
What is Endomitosis?
nucleus divides inside itself
What is the Platelet Parent Cell?
megakaryocyte
What is the result of Endomitosis?
large, multinucleated cell with abundant cytoplasm (nuclei fuse together resembling one large, multilobed nucleus)
Where do most Megakaryocyes reside?
bone marrow
but some colonize the lungs and produce platelets
What are Invaginations?
infoldings that develop into plasma membrane that divide marginal cytoplasm into little compartments which break off and enter bloodstream as platelets
How many platelts form from 1 megakaryocyte?
1,000-5,000
Where are platelets stored?
spleen
released as needed
How long do platelets circulate in the blood before being destroyed by macrophages (dogs)?
5-8 days
What is the concentration in blood?
RBCs>PLTs>WBCs
True or False: Platelets have a greater variety of functions than any of the true blood cells
True
Platelets are (bigger or smaller) compared to a RBC
smaller
What animal’s platelets stain lighter than others?
horses
How long do platelets circulate in cats?
1 day
What shape are platelets while in circulation?
discoid
have numerous, small, purple/pink granules scattered throughout the cytoplasm
What kind of platelets are occasionally seen in blood smears?
giant platelets
What happens to a platelet when it becomes activated?
centralization of granules
develop dendritic processes
What is the normal range in dogs?
200,000-500,000
What is the normal range in cats?
300,000-700,000
What is the normal range for all species?
100,000-800,000
What is the concentration of platelets in horses?
lowest normal concentration
What is the concentration of platelets in cattle?
highest normal concentration
When will animals bleed spontaneously?
if platelet concentration is less than 10,000-50,000
What do 90% of all bleeding disorders result from?
abnormalitites in platelet number or function
What is an adequate number of platelets to see during a differential count?
8-10/hpf
What should you do if it appears that the # of platelets on a blood film is decreased
perform a manual platelet count
Where should you check for platelet clumps during a manual platelet count?
body of smear
feathered edge
blood tube
When can platelet clumping occur?
common in cats
result of needle stick to draw blood
can occur in-vitro (low ratio of anticoagulant to blood)
How do you perform a platelet estimation?
using hemocytometer (acetic acid) count during blood film evaluation
What are the 2 methods of Platelet Estimation?
direct
indirect
Direct Method of Platelet Estimation
count 10 HPFs and determine the average (7-21=adequate), multiply by 20,000 to determine the estimated # of platelets per microliter
Indirect Method of Platelet Estimation
while performin differential count, keep track of platelet # then divide by 100. Multiply by total WBC count to determine total # of platelets
What are the primary functions of platelets?
maintenance of vascular integrity secrete vasoconstrictors platelet plug formation secrete procoagulants and calcium secrete growth factors to help repair damaged vessels initiate fibrinolysis secrete cytokines that attract neutrophils and monocytes to sites of inflammation limited role in phagocytosis
Maintenance of Vascular Integrity
line endothelium of vascular system and release endothelial growth factor into endothelial cells
What vasoconstrictor is secreted by platelets?
thromboxane
What initiates the formation of a platelet plug?
damaged blood vessel
What procoagulants are secreted by platelets?
Factors XII and XIII, PF1, PF2, PF3, PF4
What is PDGF?
platelet derived growth factor
stimulates fibroblasts and smooth muscle to multiply and repair damaged vessels (and strengthen and seal vessel while repairs take place)
What is fibrinolysis?
dissolution of blood clots
What does fibrinolysis stimulate?
secretion of tissue plasminogen activator(TPA) which converts plasminogen to plasmin
What is Hemostasis?
arrest/stoppage of blood loss from vessels
What is the process of Hemostasis dependent upon?
integrity of blood vessels
adequate # of normal circulating platelets
presence of adequate coagulation factors
Why is the liver essential to coagulation?
synthesizes clotting factors
produces bile which is essential for utilization of vitmin k
Which factors require vitamin K for activation?
Factors II, VII, IX, X
What are the 3 stages of Hemostasis?
primary
secondary
tertiary
What are the stages of Primary Hemostasis?
vasoconstriction
platelet adhesion
platelet aggregation
What happens during Platelet Adhesion?
platelets attach to exposed endothelial lining (due to positive charge)
What prevents platelets from sticking to normal endothelium?
negative charge
prostacyclin
What factor is necessary to bind platelets?
vonwillebrands factor
What synthesizes VonWillebrand’s factor?
megakaryotes and endothelial cells
What happens during Platelet Aggregation?
as platelets adhere to one another, they continue to change physically to promote increased aggregation
granules are released
other platelets are attracted to site by chemicals released to site by chemicals released from platelet granules
What are the steps during Secondary Hemostasis?
coagulation factors (protein) are activated includes intrinsic, extrinsic and common pathways
What is the ultimate goal of Primary Hemostasis?
formation of platelet plug
What is the ultimate goal of Secondary Hemostasis?
fibrin formation
What is the Extrensic Pathway?
occurs outside vessel wall when shed blood contacts tissue debris. Factor 3 is embedded in plasma membrane of most cells and is released by trauma to the endothelium
What is the Intrinsic Pathway?
triggered by effects of abnormal surfaces on components normally present in blood
What are the steps during the Tertiary Hemostasis?
clot retraction occurs after 30 minutes
PDGF secreted to initate tissue repair
TPA converts plasminogen to plasmin to initiate clot dissolution
What is Coagulopathy?
any disorder of blood coagulation (bleeding diathesis/tendency)
may involve defects or deficits in vasculature, platelets or clotting factors
can be aquired or genetic
What is Genetic Coagulopathy?
inherited/congenital
manifest at young age
usually associated with a SINGLE coagulation factor
What is Aquired Coagulopathy?
may occur at any age
often involve MULTIPLE coagulation factors
How are Coagulopathies categorized?
according to the stage of hemostasis that they affect
When should you suspect a Hemostatic Disorder?
increased length of bleeding time after venipuncture
evidence of intra/subdermal bleeding or bleeding into body cavities, joints, etc.
family history of diathesis
history of prolonged bleeding
What are the types of Defects of Primary Hemostasis?
quantative
qualitive
What are the types of Quantative defects of primary hemostasis?
thrombocytopenia
thrombocytosis
What are causes of Thrombocytopenia?
decreased production
increased rate of destruction
activation/utiliaztion
consumption/sequesterization
What are the most common infectious diseases that cause Thrombocytopenia?
ehrlichiosis toxoplasmosis FeLV haemobartonellosis FIV FIP
What are the causes of Thrombocytosis?
bone marrow disorders
disorders secondary to disease states
splenic contractions
What are the types of Qualitative defects of primary hemostasis?
vonwillebrand disease
thrombocytopathy
vascular causes of bleeding
True or False: vWF is a congenital Hemostatic condition
True
Decreased or Deficient vWF=
decreased platelet adhesion, decreased aggregation
What are clinical signs of VonWillebrand’s disease?
mucus membran hemorrhage
hematuria
GI bleeding
epistaxis
What breeds are predisposed to VonWillebrand’s disease?
doberman pinscher #1 german shepherd dog golden retriever chesapeake bay retriever poodle welsh corgi
What is Thrombocytopathy?
disease of platelets
What does Thrombocytopathy result from?
defective granules
True or False: Thrombocytopathy can be congenital or aquired
True
What are the causes of Thrombocytopathy?
1-NSAIDs
myeloproliferative disorders
rare congenital diseases
What are the reasons for aquired Vascular bleeding?
scurvy
Cushing’s
What are the reasons for congenital Vascular bleeding?
Ehlers-Danlos syndrome
Marfan Syndrome
What are clinical signs associated with Primary Hemostasis?
chronic bleeding prolonged bleeding petechiae purpura ecchymoses epistaxis melena
What are clinical signs of Secondary Hemostasis?
delayed bleeding
rebleeding
hemorrhaging into body cavities
hematoma formation
What are the 2 types of Secondary Hemostasis?
congenital
aquired
What is Congenital Secondary Hemostasis?
congenital clotting factor deficiencies of virtually all known coagulation factors have been described
What are the types of Aquired Secondary Hemostasis?
rodenticide toxicity
hepatic disease
DIC
What are the common active ingredients of rat poision?
coumarin
dicoumarol
warfarin
What clotting factors does the liver synthesize?
I, II, V, VII, VIII, IX, X, XI, XII
What is Disseminated Intravascular Coagulopathy?
syndrome that results from a pathologic condition that involves accelerated activation of plaatelets, coagulation proteins and plasmin
What are conditions associated with DIC?
systemic infections (septicemia, endotoxemia) pancreatitis trauma (systemic inflammatory response syndrome) infectious diseases burns severe shock neoplasia (exposes subendothelial collagen) envenomation (activates factor X) heatstroke heartworm disease secondary to hepatic disease sometimes considered idiopathic
What are the 3 phases of DIC?
peracute phase (hypercoaguable) acute phase (consumptive) chronic phase
What are the c/s of Peracute Phase?
may have few or no overt CS
What are the c/s of the Acute Phase
venipuncture oozing
modest to severe hemorrhage
absolute inability to form a clot
What are c/s of Chronic Phase?
if animal survives=chronic
no c/s of oozing blood
What kind of prognosis does DIC have?
grim
What is the treatment for DIC?
supportive care (target organs where microemboli may cause ischemia)
fluid therapy (balanced electrolyte solutions IV to maintain effective circulating blod volume)
coagulation factor replacement (transfusion with heparin rich fluid)
administration of IV heparin
close monitoring
What are defects of Tertiary Hemostasis?
uncommon
excessive fibrinolysis
fibrinolysis
What starts the Extrinsic Pathway?
when blood contacts tissue debris or damage
Extrinsic Pathway
damage occurs outside vessel wall-> (releases) thromboplastin->(activates) proconvertin->(activates) stuart-prower factor->(activates) prothrombin activator (with labile factor)-> (converts) prothrombin->(into) thrombin->(converts) fibrinogen->(into) fibrin->fibrin clot <- fibrin stabilizing factor
What starts the Intrinsic Pathway?
blood contacting abnormal surfaces
Intrinsic Pathway
damage occurs inside vessel wall-> (activates) hageman factor->(activates) PTA factor->(activates) christmas factor->(activates) antihemophilic factor->(activates)stuart-prower factor->(activates) prothrombin activator (with labile factor)-> (converts) prothrombin->(into) thrombin->(converts) fibrinogen->(into) fibrin->fibrin clot <- fibrin stabilizing factor
Thromboplastin
factor III
“tissue factor”
when comes in contact with blood, becomes activated
Proconvertin
factor VII
“stable factor”
enzyme
Hageman Factor
factor XII
located inside platelet granules
PTA Factor
factor XI
Christmas Factor
factor IX
Antihemophiilic Factor
factor XIII
Stuart-Prower Factor
factor X
Prothrombin Activator
only happens when labile factor is present, F3, Ca
Prothrombin
factor II
globulin
Thrombin
factor IIa
Fibrinogen
factor I
Fibrin
factor Ia
Fibrin Stabilizing Factor
factor XIII
Labile Factor
factor V
