Haemotology Flashcards
How much blood does the average human have
5L
How much of the blood is plasma
55%
What are the three main type of cells in blood
White blood cell, red blood cells, platelets
What are the main components of plasma
Water, Albumin, Globulin, Fibrinogen, regulatory proteins and other solutes
What is Haematopoiesis
The process in which blood cells are formed
What can the common lymphoid progenitor produce
Natural killer cells and B/T lymphocytes
What does the common myeloid progenitor produce
Red blood cells, non-lymphocyte white blood cells and Megakaryocytes
What is erthyropoiesis
The process or erythrocytes being produced (red blood cells)
What are the first two cells in erthyropoiesis
Hemocytoblast (stem cell) and then Proerythroblast (committed cell)
What is the developmental pathway in erthyropoiesis
Early erythroblast (ribosomes being synthesised), late erythroblast (haemoglobin accumulation), normoblast (nucleus size reducing and then being ejected), Reticulocyte (Nucleus ejected but some organelles remain).
What is the significant feature of an erythrocyte compared to a reticulocyte
All organelles have been ejected from the cell
What minerals and molecules are needed for erythropoiesis
erythropoietin, iron, vitamins B9, B12, Intrinsic factor (helps absorb vitamin b12) and amino acids
Where does erythropoiesis occur
In the fetus occurs in yolk, then liver and spleen and later in bone marrow, in children occurs in all bone marrow then in adults it occurs in red bone marrow
Why is the biconcave shape of the red blood cell important
Increases surface area, allows the cells to deform and flex - aiding them to navigate tight blood cells
Where are red blood cells broken down
Macrophages break them down mainly in the spleen, liver and lymph nodes.
What is Hb broken down into
Heme-iron-ferritin/iron+transferrin and globin-amino acids
What is the structure of HbA
4 Haem groups with a central iron atoms (2 α groups 2 β groups), each one binded to a separate globin chain
What is the difference in RBC in someone with iron deficiency with red blood cells
Hypochromic (pale RBCs) and Microcytic (small RBCs)
What is megaloblastic anaemia
B12 or B9 (folate) deficiency anaemia
What is the difference between blood in megaloblastic anaemia
Macrocytic cells (larger), reduced Hb conc. and hypersegmented neutrophils
Why does megaloblastic anaemia cause macrocytic cells
Red blood cells don’t divide sufficiently making less but larger cells
Why might IF affect megaloblastic anaemia
Lack of intrinsic factor prevents b12 from being absorbed properly causing this form of anaemia
How are platelets formed
Myeloid stem cells differentiate into megakaryocytes which produce platelets.
What three substances affect the rate of platelet formation
Thrombopoietin accelerates platelet formation and increases megakaryocyte numbers
Interleukin-6 stimulates platelet formation
Multi-CSF promotes megakaryocyte formation and growth
What happens to the smooth muscle in a blood vessel that has been cut
A vascular spasm occurs which constricts the blood vessel and potentially helps to temporarily seal the vessel. This occurs for for approx 30 mins
What chemicals are released by endothelial cells in hemostasis
ADP, tissue factor, prostacyclin and endothelins
What do endothelins do
Accelerate local cell division of endothelial cells, smooth muscle and fibroblasts while also stimulating smooth muscle contractions
Why does the endothelial plasma membrane become ‘sticky’
It may help partially ‘seal’ the wound and it also helps reduced blood flow and increase likelihood of platelets attaching
How does collagen exposure affect platelets
Exposed collagen fibres in the surrounding basement membrane will help platelets to adhere and activate. This causes the release of thromboxane, serotonin and platelet phospholipids.
How does ADP, thromboxane and serotonin aid in haemostasis
They all stimulate vasoconstriction which reduces blood flow and therefore loss, while Thromboxane and ADP also aid platelet aggregation which forms the primary haemostatic plug.
What is platelet aggregation
As more platelets begin to adhere it is described as aggregation as they build up and eventually form the haemostatic plug.
How does tissue factor and phospholipids produced by platelets aid in stabilising the haemostatic plug
They triggers the blood coagulation cascade which causes thrombin to form which in turn converts fibrinogen (soluble) into fibrin (insoluble fibres)
Why is the extrinsic pathway triggered
When tissue is damaged the endothelial will begin to begin to release tissue factor which then starts the extrinsic pathway
How is the intrinsic pathway triggered
Tissue factors in the blood are activated by exposure to endothelial collagen fibres
Describe the extrinsic pathway
TF-III with the aid of CF-VII will form Factor VII TF complex which will then bind to Factor X creating FXa
(TF - Tissue Factor)
(CF- Clotting Factor)
Describe the intrinsic pathway
Activated pro enzymes (FXII) will combine with PF-3 and CF-VIII/CF-IX with the aid of calcium ions to form FX activator complex which in turn activates FX into FXa
(TF - Tissue Factor)
(CF- Clotting Factor)
(PF- platelet factor)
What is the common pathway and describe it
FXa in combination with FVa as a co-factor will form prothrombinase. This turns prothrombin into thrombin which will then turn fibrinogen into fibrin. Fibrin is an insoluble rigid polymer which stabilises a haemostatic plug.
How does calcium and vitamin K deficiencies impair blood clotting
Ca2+ is necessary in both pathways so a low concentration will slow clotting, Vitamin K is necessary for production of certain clotting factors in the liver including prothrombin.
How is clotting controlled
Anticoagulants in the plasma such as antithrombin which inhibits thrombin and other factors alongside Heparin released by basophils and mast cells which acts as an accelerators co-factor for antithrombin.
Why is fibrinolysis important and how does it occur
It is important to break down the fibrin in a clot and is undertaken by plasmin an enzyme which comes from plasminogen.
How are blood groups inherited
A and B groups are codominant where as O is recessive, this is because A and B are the presence of antigens on the surface of the red blood cells.
What antibodies for blood groups are naturally produced
The antibodies produced are all the antigens that are NOT present on the red blood cells (with the exception of Rhesus)
Why is the Rhesus (D) blood group significant
It signifies the presence of the D antigen on the Red blood cells however an Rh- individual does not naturally produce antibodies unless they have been exposed to Rh+ RBCs prior. This can happen in pregnancy or transfusions.
What are four major characteristics of white blood cells
Phagocytosis in Neutrophils, eosinophils and monocytes. Attraction to specific chemical stimuli. Ability to move in and out of blood vessels, and ability to undergo amoebic movement.
Describe the function of neutrophils
50-70% of all white blood cells, distinctive nucleus with 2-5 lobes and a granular cytoplasm. They act as the first line of defence for bacteria as mobile phagocytic cells.
What are the functions of eosinophils
Granular cytoplasm with a bilobular nucleus. Release cytotoxic compounds e.g. NO or enzymes. They can cause allergies and asthma but are vital for parasitic infections. Will also help with bacteria, Protozoa and debris.
What is the function of basophils
> 1% of WBCs. Very large granules with a S shaped nucleus. Secrete histamine and heparin responsible for the inflammatory response
What is the function of monocytes
Very large cells with a horseshoe shaped nucleus but an a granular nucleus. They act as phagocytes in tissue (tissue macrophages)
What is the function of lymphocytes
Smallest white blood cells. They have a crucial role in adaptive immune response (not innate) and circulate around lymphatic system and blood.
