Lesson 1: hemostasis

Hemostasis

property of circulation that maintains blood as a fluid within the blood vessels and prevents excessive bleeding upon injury

what are the three major components of the hemostatic system?

blood vessels

platelets

coagulation factors

what are blood vessels involved with during hemostasis?

• vessel rupture

• tissue and vessel contraction

• endothelial cell functions

what are platelets involved with during hemostasis?

• formatino of temporary plug and the solid gel clot 

• clot solidification/retraction 

• clot/plug dissolution 

• vessel tone and tissue repair

what are coagulation factors involved with in hemostasis?

• formation of solid gel clot

• fibrinolysis

what are RBCs, monocytes, and lymphocytes involved with in hemostasis?

• are a physical mass for clot 

• helps with initiation of clotting

• wound healing 

what are the three stages of hemostasis?

• primary hemostasis

• secondary hemostasis

• fibrinolysis 

what components are in primary hemostasis?

blood vessels and platelets

what components are in secondary hemostasis?

coagulation factors

what are the steps of hemostasis?

1. trauma to vessel

2. exposure of basement membrane

3. vessel contracts (reduce blood flow)

4. primary hemostasis (temporary platelet plug formed)

5. secondary hemostasis (stable fibrin gel clot forms)

6. fibrinolysis 

7. repair of vessel

what are three main characteristics of the hemostatic system?

• continuosly operates 

• has checks and balances 

• is a part of the overall host defense system 

what components are on the outer layer of a generic blood vessel?

smooth muscle cells and fibroblasts 

what components are in the lumen of a blood vessel?

• endothelial cells 

• RBCs

• platelets

where is the basement membrane?

inbetween the endothelial cells and smooth muscle cells and fibroblasts layer

what is another name for the basement membrane?

collagen

what role does collagen/basement membrane play in coagulation?

activator of coagulation 

what roles do fibroblasts play in coagulation?

creates collagen and helps with stability of outer layer 

arterioles

• prominent smooth muscle cells

• thicker collagen and ECM 

• main function: vasoconstriction (controls blood pressure)

• hemostatic area after injury 

• “small artery”

venules

• very little smooth muscle cells

• thing collagen and ECM 

• hemostatic site after traumatic injury 

• regulates vascular permeability 

• mainly involved with a platelet plug 

• “small veins”

capillaries

• smalles blood vessel 

• no smooth muscle cells or collagen 

• has endothelial cell monolayer and pericytes 

• connects arterioles and venules 

• mainly involved with platelet plug

platelets

derived from megakaryocytes

*fragments of the cell’s cytoplasm 

what roles do platelets play in hemostasis?

• physical mass for plug (primary)

• cofactors

• reaction surface 

• vessel repair 

• growth factor that stimulates mitosis of endothelial cells

• releases substances for dilation and constriction

coagulation cascade

reactions that occur in a connected fashion to ultimately create a blood clot; product becomes an activator 

zymogen

inactive precursor that can be activated by enzymes; inert coagulation factors

plasma clotting factors

proteins in the blood that participate in coagulation cascade

cofactor

coagulation components that work together 

*required for certain zymogen to be turned into serine proteases

inhibitor

prevents coagulation

example: endothelial cells

protease

break specific bonds through hydrolysis to regulate clotting and dissolution (mainly serine proteases)

thrombosis

formation of a clot in abnormal conditions within a blood vessel; hyperactive clotting factors

fibrinolysis

breakdown of fibrin

coagulation factors

• necessary for fibrin clot (secondary)

• procoagulants 

• circulate in inactive forms but are activated during hemostasis

• 15 types

how do zymogens get turned into proteases?

1. some sort of stimulus 

2. cofactor comes in and helps 

3. the active protease then becomes the stimulus for another zymogen

hypercoagulation

clot formation is over active

clot inhibition is under active 

examples of hypercoagulation

stroke

myocardial infarct

hear attack 

deep vein thrombosis 

hypocoagulation/bleeding

clot formation is underactive

clot inhibition is overactive 

examples of hypocoagulation

hemophilia

vonWillebrands 

thrombocytopenia 

which coagulation factors serve as serine proteases?

• Factor II (prothrombin)

• Factor VII (proconvertin)

• Factor IX (plasma thromboplastin component)

• Factor X (stuart factor)

• Factor XI (plasma thromboplastin antecedent)

• Factor XII (hageman factor)

• Factor PK (fletcher factor)