lecture 4 - blood Flashcards
what are the functions of blood?
transport, maintain body temp, controls pH, regulation of body fluid electrolytes, regulates blood clotting, removes toxins from the body
what are erythrocytes?
red blood cells
what are leukocytes?
white blood cells
what are thrombocytes?
platelets
what are blood constituents?
55% plasma, 1%WBCs, 44%RBCs
what is plasma?
90% water, transports materials carried in the blood, waste products, dissolved gases
why do erythrocytes have an indented, disc shaped cells?
efficient o2 transport
what is the erythrocytes structure/function?
transports o2 in the haemoglobin they contain
what are globins?
4 protein chains - alpha, beta, gamma and delta
what is haemoglobin?
goes red when combined with o2 and blue when deoxygenated
what is sickle cell anaemia?
RBCs trapped within small blood vessels and blocks them - deprives the downstream tissues of 02
what are the steps involved in haemostasis?
1) vascular spasm (blood vessel constriction)
2) formation of platelet plug
3) blood coagulation
- platelets have a role in all these steps
what is blood vessel constriction?
The smooth muscle layer surrounding a cut or torn blood vessel immediately constricts slowing blood flow through the defect and minimizing blood loss
Damaged cells and platelets at cut site release potent vasoconstrictors such as serotonin
As the ends of the endothelial (inner) surfaces are pushed together (by this spasm) they become sticky and adhere to each other
what is the platelet plug?
Platelets stick to each other using von Willebrands factor, Causes a rapid build up of platelets at the site of injury so that a platelet blocks the site
what is blood coagulation (clotting)?
conversion of fibrinogen (a large soluble plasma protein) into fibrin (an insoluble thread like molecule)
what are the 2 control processes which inhibit coagulation?
1) anti-thrombin – inhibits many of the clotting factors and especially thrombin – its activity is enhanced by heparin which is normally present on endothelial cells
2) thrombomodulin – proteins C and S - endothelial cells also express thrombomodulin that can bind thrombin, this binding eliminates thrombins coagulant effects and also activates protein C – in addition to these controls which try to slow or prevent clot formuation there is a whole system for fibrinolysis – breakdown of a fibrin clot
what is thrombus?
blood clot within a vessel/ heart
what is embolus?
detached mass able to travel in a vessel
what is embolism?
the lodging of an embolus
what is thrombo-embolism?
blockage by a thrombus that has travelled
what are blood groups?
Blood groups are inherited. An individual almost always has the same blood group for life but it may change due to infection, malignancy, autoimmune disease
what is the clinical relevance of ABO groups?
Because mismatching of blood groups will result in a haemolytic transfusion reaction, donated blood must be carefully matched before any transfusion, Patients with group AB are ‘universal recipients’, Patients with blood group O are ‘universal donors’