Blood system Flashcards
function of blood
transport, immune response, coagulation
composition of blood plasma
- 90% water
- 10% solutes including plasma proteins, nutrients, waste products etc
3 groups of plasma proteins
- albumins - maintain osmotic pressure; hormones, coagulation factors
- globulins - antibodies
- fibrinogen - blood clotting
cells in blood
- erythrocytes (RBCs)
- leukocytes (WBCs)
- Thrombocytes (platelets)
types of WBCs
- granulocytes
- monocytes
- lymphocytes
types of granulocytes
- neutrophils
- basophils
- eosinophils
what does blood transport
O2, nutrients, CO2, hormones, phagocytic cells, antibodies, coagulation factors
function of neutrophils
cellular defence - phagocytosis
function of basophils
anticoagulation and inflammatory response
function of eosinophils
cellular defence and anti-inflammatory
function of monocytes
aggressive phagocytosis of bacteria, debris etc
function of lymphocytes
humoral defence - secrete antibodies
features of neutrophils
- 65% of blood cells
- multilobed nucleus
- small pink staining granules
features of basophils
- <1% of blood cells
- 2-lobed nucleus
- large purple stained granules
features of eosinophils
- 2-5% of blood cells
- 2-lobed nucleus
- large orange stained granules
features of monocytes
- 3-8% of blood cells
- horse-shoe shaped nucleus
- steel blue colour
features of lymphocytes
- 25% of blood cells
- round nucleus
- little cytoplasm
features of RBC
- Biconcave disc shape for large surface area: volume ratio
- Flexibility for movement though narrow capillaries
- Contain large amounts of Hb- 1/3 of weight of RBC
features of RBC production (erythropoiesis)
- stimulated by erythropoietin (EPO)
- requires folic acid, vit B12, thymine, iron
- controlled by homeostatic mechanism with EPO
- helped by testosterone
- decrease in RBC sensed by kidneys
destruction of RBCs
- life span = 120 days
- break apart in capillaries
- fragments removed by macrophages
- iron recycled in bone marrow, amino acids to produce more proteins, bilirubin pigment transported to liver and excreted in bile
anaemia definition and causes
- A reduction in the concentration of Hb (reduced O2 carrying capacity of blood- insufficient to supply tissues)
causes:
- decreased production of RBCs
- increased destruction of RBCs
- severe bleeding
3 components of haemostatic response to injury
- Blood vessels vasoconstrict (stage I haemostasis)
- Platelets form the platelet plug (stage I haemostasis)
- Coagulation cascade: sequential series of chemical reactions of clotting factors, resulting in the formation of a fibrin clot (stage II and III haemostasis)
stage 1 haemostasis
- Vessel damage
- altered endothelial surface
- exposure of sub-endothelium
- platelets get activated and begin to aggregate (form platelet plug)
- activated platelet release mediators (e.g. ADP, thromboxane A2) that activate more platelets (platelet plug gets bigger) and constrict blood vessels
stage 2 of haemostasis
- Prothrombin, prothrombin activator and calcium to be released, which produces thrombin which combines with fibrinogen to make fibrin (the spider-web like mesh stuff that holds all platelets together)
- intrinsic or extrinsic pathways
intrinsic pathway
- Intrinsic pathway already has everything (clotting factors) in blood
- clotting factors XII, XI and IX
extrinsic pathway
- Extrinsic pathway requires tissue factor (from sub-endothelium) to be activated
- clotting factor VII
common pathway
- Pathways join to form a common pathway at production of “Activated factor X”
- factor X converts prothrombin to thrombin, which then converts fibrinogen to fibrin (forming a clot)
- Ca2+ is essential for the common pathway
haemophilia A
absence of factor VIII
haemophilia B
absence of factor IX
haemophilia C
absence of factor XI
opposing clot formation
- Endothelial surface is normally smooth – prevents platelets adhering
- Prostacyclin (from endothelium) inhibits aggregation
- Nitric Oxide (from endothelium) vasodilates and inhibits aggregation
- Tissue Factor Pathway Inhibitor (from endothel.) binds TF/VIIa complex & inhibits extrinsic pathway
- Thrombin is inhibited via antithrombins
- Warfarin – drug that impair liver’s use of vitamin K – slow down clotting
- Aspirin - inhibits platelet aggregation
dissolving blood clots
- fibrinolysis (occurs simultaneously with clot formation)
- Plasminogen and particularly t-PA (tissue Plasminogen Activator) incorporated into the Blood clot
ABO blood group
- RBCs have membrane proteins (antigens) that are genetically determined and inherited
- We have naturally occurring antibodies to antigen that is not present on our own Red blood cells
- AB has antigens A and B so neither antibodies
- O has antigens for neither A nor B so both antibodies
blood transfusions
- Type O = universal donor
- Type AB = universal recipient
rhesus system for blood type classification
- based on presence of D antigen - individuals with D antigen are rhesus positive (85% of population)
- No pre-formed natural antibodies (these develop slowly so does not affect developing Rh+ foetus in Rh- mother)
- if another Rh+ foetus born, can fix this by giving mother anti-D antibody at first delivery to prevent antibody development
