Blood Flashcards
What are the characteristics of blood?
Viscosity- thicker and flows slower
Temperature- higher than tissues, redistributes
Alkaline - pH 7.35-7.45 (arterial more alkaline due to less CO2)
Functions of blood
Clotting
Immune response
Transport -nutrient, gasses, wastes, hormones, heat
Regulation - water, electrolytes, temp and acidity
How does blood maintain a relatively stable pH?
Buffering
Carbonic anhydrase coverts CO2 to H2CO3
CO2 + H2O <==> H2CO3 <==> H+ and HCO3-
Hemoglobin binds H+
How do plasma proteins maintain water balance?
Starlings forces.
Colloid osmotic pressure promotes reabsorption of fluid from tissues.
Prevent excessive loss of plasma proteins
What are the classes of plasma proteins?
Albumins
Globulins
Fibrinogen
Function of albumins
Major contributor to ontonic pressure of plasma
Important in transport of fatty acid
What are the types of Globulins and what is their main function?
Transport globulins- binding hormones or small molecules for transport in the body
Immunoglobulins- antibodies in immune response
What is the function of fibrinogens?
Blood clotting
Where are albumins and fibrinogens produced?
Liver
Where are immmunoglobulins produced?
Lymphocytes
What are the primary differences between blood plasma and interstitial fluid?
Concentration of dissolved proteins
Levels of respiratory gases
What is the process of producing formed elements of the blood called?
Haemopoiesis or hematopoiesis
Where does hematopoiesis take place?
Bone marrow
All formed elements in blood are derived from what type of cell?
pluripotent hematopoietic stem cell
The pluripotent hematopoietic stem cell can differentiate into which two types of cells?
Lymphoid stem cell
Colony forming unit
A colony forming unit can form what types of cells?
Erythrocytes
Leukocytes
Megakaryocytes (platelets)
How are erythrocytes formed?
CFU-S differentiates into CFU-E, produces hemoglobin.Under the influences of erythropoietin CFU-E develops into a recticulocyte (no nucleus). Recticulocytes leave the bone marrow. Recticulocyte loses ER, mitochondria, and ribosomes to become a mature RBC.
CFU-GM forms what types of cells?
Granulocytes and Monocytes
= basophils, eosinophils, neutrophils, monocytes.
CFU-M forms what types of cells?
Megakaryocytes which form platelets (influenced by thrombopoietin)
Lymphocyte stem cells form what?
T lymphocytes and B lymphocytes
What are the characteristics of RBC?
Flat
Biconcave
Disc-shaped
The characteristics of the RBC allows for what functions?
High surface area for diffusion of O2
Narrow shape for diffusion of O2 between exterior and interior of cell (Ficks Law)
Bending of cell to travel through capillary
Ficks Law
Diffusion rate is proportional to the partial pressure of O2, proportional to SA of diffusion, and inversely proportional to thickness of the membrane (distance travelled)
Describe the process of erythrocytes degradation
RBC have no nucleus and cannot replace enzymes. Membrane proteins are degraded over time and the integrity of the plasma membrane decreases. RBC travel through narrow vessels of spleen and membrane ruptures. Macrophages phagocytose RBC and hemoglobin is recycled
What is anemia?
Reduction below normal isn’t he O2 carrying capacity of blood and is characterized by a low number of RBC
What is a hematocrit?
Ratio of RBC volume to total volume of blood
Aka Packed cell volume
What are the 3 causes of anemia?
Decreased rate of erythropoiesis
Excessive loss of erythrocytes
Deficiency in hemoglobin concentration of RBC
Anemia due to a deficiency of a factor required for erythropoiesis
Nutritional anemia
What nutritional factors may be lacking in nutritional anemia?
Iron- not enough for Hb synthesis
Folic Acid- critical for stem cell division and maturation of RBC
What type of anemia results from an inability to absorb vitamin B12?
Pernicious anemia
B12 required for development of RBC
Intrinsic factor lacking preventing sufficient absorption from GI tract
What is aplastic anemia?
Failure of bone marrow to produce adequate amounts of RBC
Toxic chemicals
Radiation exposure
Bone marrow cancer
Renal anemia is caused by what?
Erythropoietin(stimulant for RBC production) is not released from the kidney
A substantial blood loss causes what kind of anemia?
Hemorrhagic anemia
An immunohemolytic disease would cause what type of anemia?
Haemolytic anemia
- autoimmune disease
Anemia resulting from low RBC would have what effect on the circulatory system?
Decrease in blood viscosity -> decreased total peripheral resistance -> increased flow -> increased venous return and preload
Cardiac hypertrophy
Heart failure
Law of LaPlace
What is Polycythemia
Excess amount of circulating RBC
In polycythemia, what happens to hematocrit?
Increase in RBC
70% hematocrit (same total volume, higher percentage being RBC)
What two conditions can cause and elevated hematocrit?
Polycythemia
Dehydration
Elevated hematocrit in dehydration is due to what?
Decreased plasma volume
Amount of RBC remains the same
Increased blood viscosity
Primary polycythremia
Tumor-like condition where bone marrow is producing excessive RBC
Secondary polycythremia
Physiological response
Erythropoietin released by kidney in response to low O2 in tissues. (Often seen in at high altitudes)
What effect can polycythremia have on the CVS?
Increase RBC -> increase viscosity -> increased total peripheral resistance -> increase afterload -> more work for heart ->
Cardiac hypertrophy
Heart failure
Law of LaPlace
Hemoglobin structure
4 nonprotien haem groups
Porphyrin ring
How are platelets produced
In bone marrow. CFU-M forms megakaryocytes. Shedding of cytoplasm making platelets. The remaining nucleus of megakaryocyte is engulfed my macrophage.
What is platelet production called?
Thrombopoiesis
What is thrombopoietin and what does it do?
Peptide hormone that accelerates platelet production and stimulates megakaryocytes production.
What is the function of platelets?
Transport chemicals- clotting factors
Form platelet plug
Contraction- actin and myosin filaments to reduce clot size
What are the three responses to tissue injury that maintain hemostasis
Vascular spasm
Platelet plug formation
Clotting/coagulation
What happens in vascular spasm?
Cutting/damage to vascular wall triggers contraction of smooth muscle
Slows blood flow and minimizes blood loss
What changes can be seen in the endothelium during vascular spasm
Contract and exposure of underlying basement membrane
Release of chemical factors
Contraction of blood vessels
Become sticky- opposing endothelial walls stick together
What is the process of platelet plug formation
Damaged endothelial wall with exposed collagen of basement membrane
Platelets bind to collagen and vonWillenbrand factor
Platelets change shape and extend projections
Synthesize clotting factors
What molecules do platelets produce?
ADP Thromboxane A2 Serotonin Ca2+ Platelet derived growth factor
What role does ADP play in the platelet plug?
Stimulus for platelet aggregation and change in shape
Released by damaged endothelium and activated platelets
Projections and sticky platelets
What role does thromboxane play in the platelet plug?
Stimulates ADP release, platelet aggregation, and contraction of smooth muscle
What role does serotonin play in the platelet plug
Assist thromboxane in vasoconstriction
What role does Ca2+ play in platelet plug?
Aggregation and clotting
What role does platelet derived growth factor play in the platelet plug?
Promote vessel repair- stimulate division of endothelial, smooth muscle, and fibroblast cells
How is platelet plug formation regulated
Positive feedback - ADP, thromboxane and Ca2+ feedback to stimulate each other
Prostacyclin limits platelet growth
What enzyme converts fibrinogen to fibrin?
Thrombin
What is the purpose of fibrin?
Forms a network covering injured tissue. Seal of damaged blood vessel
Where are most procoagulants produced?
Liver
What are procoagulants?
Precursors to an enzyme that are converted to active forms by a clotting factor
What is the functions of anticoagulants?
Prevent clotting
What do coagulants do?
Convert inactive molecules in clotting to active forms
Why is vitamin K important to clotting process?
Vitamin K must be present in liver to synthesize 4 clotting factors (prothrombin, proconvertin, christmas factor, stuart-proper factor)
At what steps of fibrinogen to fibrin formation is Ca2+ involved?
Prothrombin is converted to thrombin by prothrombinase and Ca2+.
Thrombin converts fibrinogen to fibrin
Fibrin converted to fibrin fibers by thrombin and Ca2+
What initiates the intrinsic pathway of clotting?
Exposure of blood to collagen fibers
What initiates extrinsic clotting pathway?
Trauma to vessel wall causing release of tissue factor (thromboplastin)
Exposure of blood to collagen causes activation and release of what? (Intrinsic clotting pathway)
Activation of factor XII and release of platelet phospholipids
How is coagulation regulated
Positive feedback- formation of thrombin from factors VIII and V, thrombin activates factors and production of thrombin
Negative feedback- thrombin produces protein C which prevents its formation by deactivating factors
What is the purpose of clot retraction?
Pull edges of damaged tissue together
Reduces size of damaged area making it easier for fibroblasts and smooth muscle to complete repairs
The process of clot removal is called…
Fibrinolysis
What converts fibrin into soluble fibrin fragments?
Plasmin
What turns plasminogen into plasmin?
Plasminogen activator
What activates plasminogen activator?
Thrombin inhibits plasminogen activator inhibitors (i-PA). Active PA can convert plasminogen to plasmin
What factors prevent clotting from occurring all the time?
Smoothness of vessel wall
Substance on inside of wall
Thrombomodulin
What is the purpose of thrombomodulin?
Sequesters thrombin and activates protein C (prevent thrombin formation)
Name anticoagulants
Prostacyclin
Tissue plasminogen activator
Anti-thrombin III
Heparin
How does prostacyclin inhibit clotting?
Released by healthy endothelial cells
Opposes ADP platelet stimulation -> no platelet aggregation
What is the action of anti-thrombin III?
Inhibits production of several procoagulants, including thrombin
How does Heparin inhibit clot formation?
Released by basophils, mast cells, and endothelial cells.
Increased activation of anti-thrombin III (anticoagulant )
How does Warfarin decrease clotting?
Block the use of vitamin K in the liver
Decreased synthesis of clotting factors