Platelets Flashcards
Platelets are not cells but are _
fragments
What are platelets
membrane bound pieces of cytoplasm
Platelets lack a _ but contain _
nucleus; granules
Megakaryocytes form in the _ _ from PPSC due to chemical, thrombopoitetin
bone marrow
What two mechanisms are platelets formed by
budding off surface of megakaryocyte and cytoplasm of megakaryocyte splits off
_ is a chemical which is usually associated with a platelet
Thrombopoietin
When the thrombopoietin is release (becomes free thrombopoietin) it stimulates the _ _
bone marrow
How long do platelets last in circulation
10-14 days
Spleen stores _ of total platelets
1/3
Platelet functions
1.Form platelet plug in primary hemostasis
2.Stimulate secondary hemostasis
3.Stimulate neovascularization
What is hemostasis
maintenance of blood volume
3 components of hemostasis
- Vascular integrity
2.Platelet number and function
3.Coagulation factors
Why are cat platelet counts difficult
because they are large and hard for machine to differentiate from RBCs
What is the normal range for platelets?
200,000-500,000 plt/uL for all species
What is the term for less than normal range of platelets
thrombocytopenia
What is the term for greater than normal range of platelets
thrombocytosis
When would you HAVE to use a platelet estimate because a count won’t work?
platelet clumping
If less than 7 plt/field (without clumping on feathered edge)= appears _
decreased
Secondary hemostasis occurs in the _
liver
If greater than 21plt/field = appears _
increase
How should platelets be examined
-Monoloayer
-100x (oil)
-5-10 fields to judge
If platelets consistently the same size as RBCs or even bigger- can use one of these terms:
-Megaplatelet
-Large platelet
-Giant platelet
If membrane irregular = _ _
reactive platelet
Some stimulus causes increased surface area for _ and _
adhesion and aggregation
Decreased production of platelets indicates
bone marrow toxins or infections
Increase utilization (consumption) indicates
blood loss; DIC
Increased destruction of platelets indicates
Immune-mediated problem
Increase sequestration of platelets indicates
-Splenomegaly, endoteoxemia, hepotmegaly, hypothermia
Most common cause of thrombocytosis
traumatic venipuncture
Thrombocytosis can also occur with
excitement (splenic contraction), elevated glucocorticoids, splenectomy, fractures
Why is MPV not useful in cats
cats have larger platelets
Breed that usually has increase MPV
cavalier King Charles spaniels
increased MPV can also be expected with ,, or _
increased loss, destruction, or consumption
High MPV indicates adequate _ _ response; however, normal or low does not predict a low _ _ response
bone marrow
What is plateletcrit or thrombocrit
measure of the percentage of the total blood volume comprise of platelets
How is plateletcrit or thrombocrit determined
multiplying total plt count by MPV
Plateletcrit or thrombocrit is normally less than _ in most mammals
1%
