Blood system Flashcards
3 Major functions of blood
- Transport substances around the body (e.g. O2, CO2, heat)
- Role in immune response (through phagocytes)
- Coagulation/prevents bleeding (carries platelets, endothelial cells and other substances that are vital in clotting)
What is the composition of blood?
1) Plasma (55%)
- Makes up 1/5 of extracellular fluid
- Comprises
- Water (90%)
- Solutes (10%): Incl. proteins, nutrients, waste products, electrolytes, respiratory gases
2) Cells (45%)
- RBCs or erythrocytes
- WBCs or leukocytes
- Platelets or thrombocytes
3 main groups of plasma proteins
1) Albumins - maintain osmotic pressure, buffer blood, transport insoluble substances
2) Globulins - Mostly antibodies
3) Fibrinogen - precursor of fibrin during blood coagulation
What is the haematocrit/packed cell volume (PCV)?
Is it higher in females or males?
- The amount of red blood cells making up blood
- Higher in males
- What are the 2 types of stem cells in blood cell formation?
- What 3 main types of blood cells do they differentiate into?
- Myeloid stem cell. Differentiates into:
- Erythrocytes/RBCs; and
- Platelets - Lymphoid stem cell. Differentiates into:
- WBCs
Blood cells and their main function
- Neutrophils and eosinophils: immune response (phagocytosis)
- Basophils: Anticoagulant and inflammatory
- Monocytes: transform into macrophages (phagocytic cells)
- Lymphocytes: Secrete antibodies
- Platelets: clotting
- erythrocytes: transport of oxygen (and some CO2)
Physical features of RBCs
- Biconcave disk shape - large SA:V ratio
- allows for efficient diffusion of gases for transport - Flexibility
- for movement through narrow capillaries - Contain large amounts of Hb
- for O2 transport
Production and destruction of RBCs
- How is it controlled?
Erythropoiesis (production)
1. Decrease in RBCs
2. Kidney senses decrease in O2 levels and releases erythropoitin (EPO)
3. Bone marrow stimulated to produce RBCs
- Requires: folic acid, vitamin B12, thymine, iron
Destruction
- Caused by end of life span or excess RBCs
- Broken apart and removed by macrophages
- Bilirubin transported to liver and excreted in bile (if not excreted –> jaundice)
- Other components (AAs, iron) recycled
What is anaemia
- What measurement would you use to determine if someone was anaemic?
- a decrease in conc. of Hb, and thus a decreased O2 carrying capacity of blood
- If Hb conc. was less than normal (approx. 150g/L):
Men = less than 130g/L
Women = less than 115g/L
How does erythropoietin increase performance?
Stimulates erythrocyte production → increased O2 capacity → increase performance
Platelets:
- Structure
- Production (name and stimulus)
- Small, irregular spindels/ oval discs that assume various shapes on contact
- Formation of platelets = thrombopoiesis (stimulated by thrombopoietin)
Platelet function
Haemostasis and blood coagulation:
- Stops/reduces bleeding
- Haemostasis involves co-operation of blood vessels, platelets and the blood coagulation system
Haemostasis stages
Stage 1
- Constriction of blood vessels; stops blood flow to area; immediate and short-lived response
- formation of a platelet plug
Stages 2 and 3
- Formation of blood clot (supported by platelets)
Describe the formation of a platelet plug
- What is damaged?
- What is exposed?
- What forms the platelet plug?
- What is released?
- Tissue/vessel damage
- Collagen exposed due to altered endothelium
- Platelets aggregate, agglutinate and adhere (form platelet plug)
- Mediators released (ADP and thromboxane A2) - becomes more sticky
Describe blood clot formation
1) - Converging of what pathways?
2) - What causes the activation of factor X?
3) - What does factor X activate?
4) - What is next activated?
- The activation of stage 1 provides the source required for activation of stage 2 (precursor)
1) Converging of intrinsic and extrinsic pathway
- intrinsic pathway has all components in the blood
- extrinsic pathway requires substances in the tissue surrounding the blood (thus requires damage to the wall of a blood vessel)
2) Calcium ions catalyse the activation of factor X; cause
3) activation of thrombin (from prothrombin via prothrombin activator complex); cause
4) activation of fibrin (from fibrinogen)
5) Fibrin mesh formed (blood clot): RBCs enmeshed in fibrin ‘net’
