Haemostasis Flashcards
define haemostasis
the arrest of bleeding AND
the maintenance of vascular patency
what is formed in primary haemostasis?
a platelet plug
what is formed in secondary haemostasis?
fibrin clot
is a platelet plug or fibrin clot more secure?
fibrin clot
what happens to stop formation of the fibrin clot?
fibrinolysis
name the 4 stages of haemostasis
primary
secondary
fibrinolysis
anticoagulant defences
biggest cell in the bone marrow?
megakaryocyte
describe the relationship between platelets and megakaryocytes
formed in the cytoplasm of megakaryocytes and “bud” off
when should you stop aspirin before surgery? why?
7 -10 days before
this is the mean life span of platelets
when endothelial cells are damaged what attracts the platelets to adhere to them?
collagen
von willebrand factor
what happens to platelets after they adhere to damaged endothelial cells?
release chemicals that cause them to aggregate (stick together)
causes of failure of the platelet plug?
vascular
reduced function/number of platelets
VWF deficiency
what vitamin is responsible for making collagen? what effect does this have on clotting and why?
C
no collagen = no signal for platelets to adhere to the wall
what happens in ITP (immune thrombocytopaenic purpura)?
antibodies stick to platelets and cause them to be removed -> thrombocytopaenia
commonest inherited bleeding disorder?
VWF deficiency
VWF affects __% of the popn
1%
signs of failure of the platelet plug in patients
lower limb purpura (gravity pushes platelets down = more leaking)!! blood blisters in mouth epistaxis GI bleed conjunctival haemorrhage menorrhagia intracranial haemorrhage if severe
Ix primary haemostatic problems
platelet count
phospholipids tend to be __vely charged
negatively
what forms the surface of the platelet plug and why?
calcium
the neg charged phospholipids within the platelet attract positively charged Ca
what does the “a” mean on a clotting factor?
activated form
what is released from damaged endothelium?
tissue factor
what is the first clotting factor to respond to tissue factor?
factor 7
factor _ and _ form prothrombin
5 and 10
what clotting factors are needed to form factor 5 and 10
TF
factor 7
VIII
IXa
haemophilia A is a deficiency of what CF?
8
haemophilia B is a deifciency of what CF?
9
clotting factors are made..
in liver
causes of failure of fibrin clot formation?
single CF deficiency
multiple CF deficiency
increased fibrinolysis
give an example of a multiple CF deficiency
DIC
what enzyme breaks fibrin down?
plasmin
plasmin is formed from..
plasminogen
Hx questions in bleeding disorders?
bleeding/bruising duration previous surgery/dental extraction menstrual history DH FH
prothrombin time measures what CF formation?
TF
VIIa
activated partial thromboplastin time measures what CF formation?
VIII
IXa
name the 2 ways in which factor 10a can be formed
combine factor 8 and 9a
combination of tissue factor and factor 7
what CFs are involved in the initiation phase
7
TF
10
what CFs are involved in the amplification phase
5
8
9
10
what activates factor 8 and 9
thrombin
protein _ switches off CFs to stop haemostasis
protein c
what does thrombin bind to when it senses haemostasis has been achieved and what effect does this have?
thrombomodulin
stops haemostasis
name the deficiency in thrombophilia?
naturally occuring anticoagulants
name the body’s naturally occurring anticoagulants
protein C
serine protease inhibitors
causes of thrombocytosis
bone marrow disease
splenectomy
inflammatory disease
what cancers can present as thrombocytosis
LEGO-C lung endometrial gastric oesophageal colorectal
