what 2 mediators are released by normal endothelial cells, in order to prevent clotting?
NO and PGI2
List the 4 steps of haemostasis
vasoconstriction and platelet plug (1); Coagulation-->fibrin(2); fibrinolysis; repair
What is the parent cell in thrombopoeisis, and what tells it to develop?
Megakaryocytes, under the influence of thrombopoetin
How long does megakaryocyte maturation take?
2-10 days, depending on the species
describe the look of Megakaryocyte
8-32 nuclei, with a huge cytoplasm and red/purple granules
Describet he look of a platelet
small packets of granules with a pale bue cytoplasm
List the four ways platelet numbers are affected
production in BM or spleen; consumption; redistribution into or out of spleen; destruction by macros in the spleen or liver
Why woudl a platelet by normally destroyed in the spleen/liver?
if carrying ABs or compliment
Explain what happens during primary haemostasis
vasoconstriction due to neurogenic reflex and mediators, platelets adhere to subendothelial collagen (Von Will. factor may help to bridge), platelets release granules which tell others to change shape and agregate, platelets contract together to form plug
what compound is released by a newly shaped platelet, to tell others to aggregate?
PRIMARY HAEM. DISORDERS: defects in numbers and function of platelets
What 5 conditions may result in thrombocytosis?
splenectomy, neoplasia, inflammation, haemolytic disease, and iron deficiency
What 3 dog breeds may give falsely low thrombocytopenia?
KingCharles (has microplatelets that may not be coutned), Greyhounds and Shiba Inus (have naturally lower counts)
At what level of platelets does spontaneous bleeding occur?
<25x10(9) cells/L, or higher if there's a demand eg surgery or trauma
List four reasons thrombocytopenia may be due to decreased production?
Bone Marrow Pnahypolasia/bovine neonatal pancytopenia, pure megakaryocytic hypolasia, myelophthisis, or infectious agents
Explain the clinical presetation of Bone marrow Panyhypoplasia
Due to damaged stem cells. You see neutropenia first, then thrombocytopenia, then non-regenerative anaemia
What is the cause of Pure Megakaryocytic hypoplasia?
immune-mediated, against megakaryocytes
What is myelophthisis?
Neoplasia or fibrous tissue occupying the space of the bone marrow
What is the most common cause for increased consumption, resulting in cytopenia?
DIC- vasculitis and edocarditis causes altered eno cells, or exposed subendothelial collagen
Why disease woudl cause icnreased sequestration, resulting in thrombocytopenia?
spelnic neoplasia, causing congestion or enlargements
What is the most common cause of increased destruction of platelets in dogs, leading to thrombocytopenia?
Idiopathic Immune-mediated thrombocytopenia
what are 5 causes of thrombocytopathy (normal numbers, but abnormal function?)
Drugs, uraemia, DIC, Liver disease, and hyperglobulinaemia (plasma cell myeloma)
List 2 drugs that can cause thrombocytopathy, and how so?
COX inhibitors inhibit coxegenase for 6 hours. Usually okay, but if another underlying problem (VWD or thromb'penia) then can bleed. B-lactam ABs and calcium-channel blockers (barbiturates) can impain platelet activation.
How does DIC impair platelet function?
There are increased numbers of Fibrin Degradation Products (FDP) that bind and swith off the platelets
How does Liver disease impain platelet fucntion?
If diseased, it may not be clearing the FDP properly, so they bind and turn plaetels off