Circulation 1 Flashcards
Describe the structure of an artery.
- Endothelial cell lines lumen.
- Endothelial cells make basal lamina to sit on.
- All around the basal lamina are smooth muscle cells.
- -Around smooth muscle cells are interstitial collagen fibres.
- Inside the lumen contains Red blood cells, white blood cells, platelets (white in colour, very small)
look at notes for diagram
What are platelets not normally exposed to?
Interstitial collagen fibres around the vessel
What does the lumen also contain?
Plasma:
- water, numerous proteins and other molecules
- remove RBC, WBC, Platelets are you are left with plasma
- contains clotting factors
- serum is plasma without clotting factors
What is serum?
plasma without clotting factors
Where are clotting factors mainly produced?
Liver, but also by endothelial cells
How are clotting factors named?
a Roman numeral eg Factor VIII
What are clotting factors described and what do they do?
- They are an amplification system/clotting cascade, resulting in thrombin production from prothrombin
- thrombin, in turn converts Soluble Fibrinogen into insoluble fibrin strands
- Fibrin forms a mesh of strands
What is meant by initial damage?
trauma.
What does initial damage lead to?
- Exposure of interstitial collagens
2. Exposure of a molecule called Tissue Factor (TF)
What does trauma result in?
- Defects in vessels.
- Blood leaks out and serum comes into contact with interstitial collagen fibres.
- Plasma clotting factors can now be activated as they contact interstital collagens
- Tissue factor is also released from smooth muscle cells.
- Tissue factor can now bind to a particular clotting factor and initiate the clotting cascade.
How are clotting factors activated?
- Blood leaks out and serum comes into contact with interstitial collagen fibres.
- Plasma clotting factors can now be activated as they contact interstital collagens
What are the structure of many clotting factors?
- Many clotting factors are serine proteases - = they have a serine amino acid in them and they cleave other clotting factors to form the active molecule
What are platelets and where are they produced?
- Produced in bone marrow From cell called a megakaryocyte
- Megakaryocyte = Large cell with many nuclei
- Bud off as fragments from cytoplasmic extensions
Why are megakaryocytes large cells with many nuclei?
Undergoes nuclear division but not cell division so get huge cell with many nuclei
What is the function of platelets?
- Trauma to vessel Exposure of platelets to interstitial collagen
- Platelets adhere together try to form bridge to close gap
- Coagulation:
• Solidification of blood which is:
• 2 types: Thrombus formation and clot formation
What is thrombus formation/thrombosis?
- Occurs in flowing blood and stops bleeding from gaps in vessels
- A pure thrombus is pale cream coloured
Why does thrombus of platelets and fibrin occur in flowing blood?
- 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
How to remove thrombus?
- Fibrinolytic system:
- 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).
What is the fibrinolytic system Called in a thrombus?
-In a thrombus this is sometimes called thrombolysis
What is the fibrinolytic system normally in balance with?
-The clotting system.
What Is the function of the finbrinolytic system?
Plasmin generation, at the site of injury, limits the extent of the evolving thrombus.
What is clot formation?
- Think of black pudding. Blood leaks off a vessel and becomes stationary/stagnant.
- Within the stagnant blood, sitting next to the interstitial collagen, the clotting cascade is activated.
What is haemostats?
stopping bleeding in normal skin with wound
Describe the beginning stages of the activaiton of the clotting system, in a clot.
- Vessel in the skin is surrounded by collagen.
- Trauma i.e. cut to skin disrupts one side of the vessel.
- Blood, including red blood cells, leaks out.
Describe the process of when clots do not work perfectly
- The clotting system is activated by Collagen and by the Stagnant Blood, forming a clot.
- But this may not work perfectly and the wound may continue to bleed.
- The vessel vasoconstricts to decrease blood loss.
- A platelet and fibrin thrombus forms to bridge the gap between the ends of the vessel adjacent to flowing blood.
- The skin now stops bleeding- haemostasis has been achieved.
What are the advantages of any wound due to trauma?
- Vasoconstriction helps reduce bleeding
- Clot formation occurs in space around vessel and may fill void of wounded tissue
- Thrombus forms in flowing blood and stops bleeding from gaps in vessels
What can grow in the area of wound?
- New vessels can grow called granulation tissue.
- The capillaries that grow in granulation tissue can oxygenate the area of wound and keep it alive.
What physiological mechanisms is thrombosis and clotting normal in?
Wound healing and stopping bleeding during menstruation.
What does a thrombus consist of?
consists of platelets, red blood cells and a mesh like network of fibrin strands
What does a clot consist of?
A network of fibrin strands and platelets, red blood cells.
What does thrombus do?
Stops bleeding from gaps in vessels
