hemostasis

Question 1

define hemostasis

Answer 1

normal state of balance maintained in the blood to control hemorrhage and inhibit thrombosis

Question 2

what is the temporary hemostatic plug made by?

Answer 2

platelets

Question 3

What do platelets do in controlling hemorrhage?

Answer 3

1. adhere to side of vessel
2. activated
3. aggregation

Question 4

what does protein expressed is required for adherence?

Answer 4

von Willebrand factor (vWF)

Question 5

what receptor do platelets bind to vWF on the surface?

Answer 5

glycoprotein

Question 6

how do platelets get activated?

Answer 6

by exposure to subendothelial collagen and thrombin

Question 7

how do activated platelets assume a different shape to better clump and interact with one another?

Answer 7

pseudopods

Question 8

when platelets are activated, what receptor on the surface forms and why?

Answer 8

GPIIb:GPIIIa, and it forms the essential ligand to hold platelets together, with the help of fibrin

Question 9

what is aggregation?

Answer 9

When proteins found in the blood (especially fibrinogen), contact the glycoprotein receptor (GPIIb:GPIIIa), they get sticky

Question 10

what two hormones get released to activate more platelet activation?

Answer 10

Prostaglandin H2 and Thromboxane A2

Question 11

what fuels the platelet activation/aggregation fire when platelet contents are released?

Answer 11

ADP

Question 12

____________ is facilitated through the platelet membrane exposure of certain enzymes and cofactors essential for the clotting cascade

Answer 12

coagulation

Question 13

what starts contracting to solidify the temporary plug?

Answer 13

platelet actinomysin

Question 14

when is the permanent hemostatic plug formed?

Answer 14

when the clotting cascade gets activated and the platelet plug gets made more permanent by the glue known as fibrin. This fibrin clot forms the needed bulk and anchoring mechanism.

Question 15

go in order of what happens to form the permanent hemostatic plug

Answer 15

clotting cascade -> formation of thrombin -> fibrinogen -> fibrin -> permanent hemostatic plug

Question 16

what are the two pathways of the clotting cascade?

Answer 16

intrinsic and extrinsic

Question 17

how does the intrinsic factor start?

Answer 17

Hageman factor (factor XII) contacts endothelial surface

Question 18

how does the extrinsic factor start?

Answer 18

when substances contact factor VII

Question 19

which pathway is faster and gets put into action when damage is deeper?

Answer 19

extrinsic

Question 20

An anticoagulant used for collecting blood for CBC (complete blood count) is EDTA. How does this substance keep the clotting cascade from occurring?

Answer 20

Calcium ions are needed in many parts of the cascade. EDTA binds calcium, making it unavailable. No calcium, no clot.

Question 21

When clotting is measured in the laboratory, is it the extrinsic or intrinsic system that is being measured, and why?

Answer 21

intrinsic

The intrinsic system is activated by exposure to collagen or any negatively charged surface whereas the extrinsic system requires tissue factor, which is not present in a glass tube.

Question 22

Surgical trauma acts via which pathway predominantly?

Answer 22

Tissue factor binds rapidly to Factor VII, starting the extrinsic pathway on a tear.

Question 23

Many rodenticides act by tying up Vitamin K so that the rodents bleed to death. Which factors are involved?

Answer 23

Vitamin K is a necessary cofactor in the carboxylation of glutamate residues which are necessary for functional activity in Factors VII, IX, X and prothrombin. Without Vitamin K, there is massive hemorrhage because none of these factors are functional. Unfortunately, when dogs get into rat poison, their Vit K gets tied up also, and the result is death due to hemorrhage

Question 24

true or false: factors present in blood are usually active

Answer 24

false: inactive

Question 25

true or false: in order for clotting to occur, each factor must be active

Answer 25

true

Question 26

What keeps clotting from happening all the time?

Answer 26

1. Activated clotting factors get removed from the circulation as they pass through the liver. 2. There are quite a few inhibitors present in the plasma.

Question 26

how does the extrinsic pathway inhibitor (EPI) or TFPI prevent coagulation from happening?

Answer 26

binds with Xa and then this complex binds to VIIa/tissue factor and inactivates so the extrinsic pathway can't go nowhere

Question 27

what does antithrombin III inhibit the action of?

Answer 27

thrombin, Xa, and IXa

Question 28

how does heparin prevent clotting?

Answer 28

it converts antithrombin III from a slow to an instantaneous inhibitor of thrombin, Xa and IXa

Question 29

thrombin binds to thrombomodulin on endothelial cells and so activates Protein C. How does that inhibit coagulation?

Answer 29

Protein C inactivates Va and VIIIa and speeds up fibrinolysis.

Question 30

what is the most important molecule in fibrinolysis?

Answer 30

plasmin

Question 31

what does plasmin do?

Answer 31

break down fibrin

Question 32

how is plasmin formed?

Answer 32

from activation of plasminogen

Question 33

the amount of plasmin there is depends on what?

Answer 33

- plasminogen activators, many come from endothelium - streptokinase, made by bacteria, is a powerful plasminogen activator and used to therapeutically break up clots

Question 34

what categories are hemostatic disorders broken into?

Answer 34

- failure of primary hemostasis, which means something wrong with the platelets - failure of secondary hemostasis, which means something wrong with clotting factors

Question 35

true or false: conditions can be both inherited or acquired

Answer 35

true

Question 36

dog has recurrent mucosal surface bleeds. we see ecchymotic hemorrhages on the conjunctiva. What is the most common inherited bleeding disorder in dogs?

Answer 36

Von Willebrand’s disease. need VWF to bind the platelet to the damaged endothelium. Without this, platelets don’t stick. That makes it a primary hemostatic defect

Question 37

hemophilia is an example of what category of hemostatic disorder?

Answer 37

secondary hemostasis

Question 38

what pathway do we want to measure to test hemophilia? and what test can be ran?

Answer 38

intrinsic pathway partial thromboplastin time (PTT) - partial because does not contain tissue factor

Question 39

what test measures the extrinsic pathway of hemophilia?

Answer 39

Prothrombin Time (PT), which measures the EXTRINSIC pathway.

Question 40

what is consumptive coagulopathy?

Answer 40

all of the platelets and clotting factors get used up so fast that the animal cannot control bleeding.

Question 41

dog had amyloidosis, in the kidney, amyloid affects the glomeruli and makes them excessively leaky. How does that impact hemostasis?

Answer 41

If the glomerulus becomes leaky, protein is lost to the outside of the body as it traverses the capillaries in the glomerular filtration apparatus. Antithrombin III is one of the first proteins to be lost. Without antithrombin III, there is too much thrombin around and fibrinogen is readily converted to fibrin in many places where it shoulda just stayed as fibrinogen. Instant clots and way too many of them