17. Hemostasis and blood coagulation: phases. Platelet role in hemostasis and blood clotting.

Question 1

What are thrombocytes and conc in blood

Answer 1

also called platelts, are cell fragments that help form blood clots

200x10^9 /L in blood

Question 2

Disease associated with:

Low thrombocytes in blood
normal count but impaired function

Answer 2

Theombocytopenia= less than 100x10^9 /L

Thromasthenia

Question 3

Composition of thrombocyte

Answer 3

Bright periphery=hyalomere
Centre granular zone=granulomere

Question 4

What are some organelles of platelet

Answer 4

Dense granules= has ATP/ADP, GTP/GDP, Ca2+

Mitochondria= for ATP

a granules= has fibrinogen, plasma facotrs V, albumin, fibronectin

Lysosomes

Contractile microfilaments=myosin, actin, tropomyosin

Question 5

can platelets reproduce

Answer 5

no bc no nuclei

Question 6

What do they have membrane receptors for

Answer 6

fibrinogen, ADP, thombin, collagen, Von Willebrand factor

Question 7

How are platelets involved in clotting

Answer 7

React to injury site
Form plug
Release thromboxane A2 and prothrombonin
Activates intrinsic/extrinsic pathways

Question 8

What enzyme does platelets contain for prostaglandin synthesis

What stimulates the regeneration of smooth muscle, fibroblast, endothelial

Answer 8

thromboxane A2

Platelet derived growth factor

Question 9

Formation of platelets (thrombocytopoesis)

What is it reg by

Answer 9

Derived from prothrombocytes (megakaryocytes)
Turn into platelets in pulmonary capillaries

Reg= cytokines, Interleukin 3,6,11, thrombopoietin

Question 10

How long do platelets last until it is degraded by phagocytes

Answer 10

5-11 days

Question 11

What is hemostasis

Answer 11

Stops blood flow and controls hemorrhage from injured blood vessel

Question 12

What are the phases of blood coagulation

Answer 12

1. Vascular Vasoconstriction: at injury, smooth muscle contracts to decrease blood flow. Von willebrand factor released to increase platelet adherance
2. Aggregation: platelets change shape and volume help them adhere to each other. Mediated by fibrinogin
3. Coagulation: Clumped togtehr platmelts undergo viscous metamorphosis + release substances. CASCADE- intrinsic or extrinsic
4. Antithrombotic mechnaism: plaminogen to plasmin (triggered by heparin) breaks clot

Question 13

Extinsic pathway vs intrinsic pathway

Answer 13

extrinsic= in the tissues/ blood.
Requires Tissue Factor and Factor VII

Intrinsic= occurs in injured vessels
Requires clotting factors 12, 11,9,8 and ca2+

Question 14

Intrinsic pathway

Answer 14

factor 12, factor 12a, factor 11, factor 9, factor 9a, “w factor 8” factor 10, factor 10a

Question 15

extrinsic pathway

Answer 15

Tissue factor, factor7, factor 7a, factor 10, factor 10a

Question 16

hat does factor 10a acivate

Answer 16

prothrombin to thrombin

thrombin activates fibrinigen to fibrin

Factor 13 activates stable fibrin grid

thrombin activates factor 5a-process faster