Circulation 1 -physical thrombosis and clotting in wound healing

Question 1

What does the arterial system do?

Answer 1

takes blood away from the heart
oxygenated blood to distal organs and tissues in the body so that they can survive

Question 2

Describe the arterial system?

Answer 2

Goes from the heart and straight into the aorta, which is a large or wide diameter, wide calibre vessel.
As it propagates through the body, it gets smaller and smaller as it branches.
Keeps getting smaller till you get to capillaries and oxygenation occurs here.

Question 3

What cell lines the lumen?

Answer 3

endothelial cell

Question 4

What do endothelial cells sit on?

Answer 4

basal lamina or connective tissue layer

Question 5

What surrounds the basal lamina?

Answer 5

smooth muscle cells

Question 6

What is around smooth muscle cells?

Answer 6

interstitial collagen fibres

Question 7

What does lumen consist of?

Answer 7

red blood cells - carry oxygen
white blood cells - comprise immune mediated cells
platelets
plasma - fluid mixed up of water and numerous proteins other than WBC and RBC …. main constituent of that is clotting factors

Question 8

What is haemostasis?

Answer 8

the cessation of flow of blood either within a lumen or if there’s defect in lumen stopping the flow of blood outside the lumen into the surrounding soft tissues

Question 9

What are the three main steps in haemostasis?

Answer 9

Vasoconstriction- reduces the diameter of the lumen
-reduces blood flow
-limits blood loss

Primary haemostatic process
(initial process of trying to stop blood actually getting through the defect)
-platelet plug formation

Secondary haemostatic process
-Activation of the coagulation cascade
-fibrin meshwork

Question 10

What is the parent cell of platelets?

Answer 10

megakaryocyte

Question 11

Describe the physical appearance of a megakaryocyte?

Answer 11

large cell with many nuclei

Question 12

What kind of division do megakaryocytes go through?

Answer 12

nuclear division but not cell division

Question 13

How do platelets via megakaryocytes enter circulation?

Answer 13

megakaryocytes then produce platelets, which form little clusters on the membrane of the megakaryocytes.
Megakaryocytes in bone marrow sit over the sinusoids of bone marrow and deposit platelets into sinusoids.
-which then enters the circulation

Question 14

Describe primary haemostasis?

Answer 14

when lumen is intact -> inactive and circulate around body

when defect in vessel- contents of vessel gets exposed to tissues and immediately body recognizes that as an abnormal event
Body reacts and platelets bind with collagen fibres and smooth muscle - become activated. Producing diff glycoproteins and molecules.
Platelets start to become sticky and they start to aggregate and stick together.

Question 15

What happens in secondary haemostasia?

Answer 15

activation or the initiation of the coagulation cascade + the activation of clotting factors within that cascade.

Question 16

Where are most clotting factors produced?

Answer 16

in the liver

Question 17

What is the main aim of the coagulation cascade?

Answer 17

convert prothrombin into thrombin- which then converts water soluble molecule , fibrinogen, into an insoluble molecule called fibrin. Fibrin is the ultimate haemostatic endpoint.

Question 18

Describe Extrinsic pathway?

Answer 18

quickest pathway
initial damage to the vessel lumen produces a mol called tissue factor. Tissue factor becomes joined to factor 7 to create a tissue factor 7A complex - which then directly acts on factor 10 , factor 5 to activate their co factors to produce thrombin, fibrin and meshwork.

Question 19

Describe the intrinsic pathway?

Answer 19

initiated by damage to sub endothelial tissue
thrombin can act back into pathway to propagate more conversion of inactive clotting factors to active clotting factors.

Question 20

How is the clotting cascade an amplification system?

Answer 20

so many more molecules of fibrin are produced compared to no. tissue factor mols

Question 21

What is meant by initial damage?

Answer 21

One obvious way is trauma

Trauma leads to 1. Exposure of interstitial collagens (collagens in connective tissue between structures) and 2. Exposure of a molecule called Tissue Factor (=TF)

Answer 22

blood leaks out and plasma comes into contact with interstitial collagen fibres

Contact between plasma clotting factors and interstitial collagen initiates activation

tissue factor produced by smooth muscle and endothelial and initiates secondary phase of haemostasis

Question 23

How do clotting factors become activated?

Answer 23

when come into contact with activator, activates them by allowing them to bind to co factor (12A).
When bound, becomes active complex. Can do the same in next stage of pathway

Question 24

What happens when clotting factor is activated?

Answer 24

Many clotting factors are serine proteases
the serine mol in them is cleaved and allows co factor to bind and that active complex does same thing in next stage of pathway

Question 25

Describe the endpoint of the clotting cascade?

Answer 25

insoluble fibrin strands form a network

Question 26

Difference between thrombus formation and clot formation?

Answer 26

thrombus:
-Occurs in flowing blood
-A pure thrombus is pale cream coloured
-A thrombus consists of platelets and a mesh like network of fibrin strands (although usually also layers of RBCs)
-adherent to the blood vessel wall

clot:
Blood leaks out of a vessel and becomes stationary
within the stagnant blood, next to interstitial collagen- clotting cascade activated
- a clot consists of a network of fibrin strands and red blood cells

Question 27

Why does a thrombus of platelets and fibrin occur in flowing blood?

Answer 27

Platelets have molecules on their surfaces which allow adherence to interstitial collagen, even when blood is flowing past them – the clotting cascade deposits Factor VIII which enhances this further

Question 28

What happens when there is trauma to the skin?

Answer 28

vasoconstriction - limit flow of blood

clotting system- activated by collagen and by stagnant blood- forms clot

May not work v well

activation of platelets

activation of coagulation cascade

to ultimately produce fibrin mesh across vessel

Question 29

What happens after flowing blood has stopped?

Answer 29

production of vascular endothelial growth factors to allow new vessels to be formed into wound area

with production of fibroblasts and oxygen
get granulation tissue (scar tissue formation) — mature fibrous tissue

Question 30

How to removed thrombus?

Answer 30

A blood protein called Plasminogen converts to plasmin, and plasmin cuts up fibrin into smaller fragments, as a way of removing fibrin (in both clots and thrombi). In a thrombus this is sometimes called thrombolysis

Question 31

What is the fibrinolytic system which removes fibrin and stops thrombi from propagating?

Answer 31

In blood there is a fibrinolytic system which removes fibrin and stops thrombi from propagating