FOM Flashcards
(31 cards)
What is the process of manufacturing blood?
- haematopoiesis
Where does haematopoiesis occur?
- foetal: yolk sac, liver and spleen
- after birth: bone marrow
- adult: normally confined to central skeleton
What are the roles of stromal cells?
- secret extracellular molecules to EMC, GFs, adhesion molecules
- provide support for stem cells and keep them viable
Why are stem cells critical in haematopoiesis?
- able to self-replicate, proliferate and differentiate
What is the process of the producing RBC?
- erythropoiesis
What is the GF important in erythropoiesis?
- erythropoietin
- produced in the kidney
Describe RBC membrane structure
- lipid layer: phospholipids + cholesterol
- proteins: membrane integral proteins which attach carbohydrates and membrane skeleton
- carbohydrates: attached to external surface (determine blood groups)
What are the five major classes of WBC?
- neutrophil
- lymphocytes
- monocytes
- eosinophil
- basophil
Characteristics of neutrophils
- mobile in tissue, chemotactic and phagocytotic
- rich in toxins and enzymes for bacterial killing
What does neutrophil maturation involve?
- involves progressive acquisition of granules and lobulation of nucleus
Characteristics of monocytes
- phagocytose and destroy pathogens and cellular debris
- process and present antigens to cells of immune system
- produce cytokines governing haematopoiesis, inflammation and other cell processes
Characteristic of lymphocyte
- undergoes differentiation and proliferation into B cells and T cells
What is leukaemia?
- malignant disorders of blood and bone marrow
- acute: marrow replaced by immature malignant blast cells. Unable to perform functions of normal ones
What is haemostasis?
- body’s normal physiological response for the prevention and stopping of bleeding/haemorrhage
What are the functions of platelets in haemostasis?
- adhesion: attach to vessel via interaction with endothelium wall. activation
- aggregation: attach to each other
- degranulation and amplification: release granule content
What are the steps of haemostasis?
- vessel wall vasoconstriction. Prevent blood flow to area
- platelets. Initial platelet plug.
- Coagulation cascade. Stable haemostatic plug
Structure of platelets
- membrane: lipid bilayer. Phospholipids need for activation of factors
- cytoplasm: contains enzyme COX (cyclo-oxygenase) promotes degranulation
What is primary haemostasis?
- sub endothelium is exposed. Platelet adhesion, aggregation and cascade is triggered
- vessel wall contracts
- effectiveness relies on normal quality of blood vessel, quality and function of platelets
What segments form the coagulation cascade?
- extrinsic
- intrinsic
- common
Describe the extrinsic pathway of coagulation cascade
- TF in cell surface found outside blood vessels but not on circulating blood cells or endothelium
- Factor VII forms complex triggering Factor X
- triggers common pathway
Describe the intrinsic pathway of the coagulation cascade
- surface damage of vascular endothelium leads to exposure of clotting factors to negatively charged sub endothelial surfaces
- Factor XII, FXI, FIX, FVIII
- Factor IXa combines with FVIIIa, platelet membrane phospholipids and Ca ions to produce thrombin
- activates common pathway
Describe the common pathway of coagulation cascade
-activation of FX to FXa via extrinsic or intrinsic
- leads to formation of thrombin and fibrin
- FVa combines with FV platelet membrane phospholipids and Ca ions to produce thrombin
- thrombin converts fibrinogen to fibrin
Ways of avoiding excess of thrombosis
- coagulation inhibitors
- fibrinolysis: reversal. Fibrin destruction
How does the ABO blood groups relate to RBC membrane?
- membrane contains carbohydrates attached to external surface.
