Blood and Haemopoiesis Flashcards
What is Haemopoeisi?
The process of going from bone marrow to blood full of cells e.g. neutrophils, eosinophils
What are the features of Haemopoietic stem cells?
- Found in the bone marrow.
- Harmopoietic stem cells have the ability to self replicate and differentiate further.
- Haemopoietic stem cells can go on to form common progenitors.
Pg 10
What are the features of common progenitors?
- Common progenitors (myeloid and lymphoid progenitor) have the ability to differentiate into lineage bound. (Cannot go back and undifferentiated, once differentiated they stay doing that function).
- Constantly replicating and differentiating driven by multiple hormones and chemical messengers
E.g. cytokines, interleukins and hormones
Pg 10
What is the concept of selection?
• Not all cells found in the bone marrow will end up in the blood.
• Some will undergo programmed cell death (apoptosis) - quality control, removal of damaged cells
- some are just random
What is Erythropoiesis?
- Process by which erythrocytes are formed
- Common myeloid progenitor is converted to erythrocytes and is regulated erythropoietin.
Pg 12
What are general facts about red blood cells?
- Life span of 120, which is then degraded by the liver/spleen, also damage RBC such as sickle cell are take up.
- Takes 20 seconds for a RBC to circulate around the body once
- 7 um in diameter
What are RBC good oxygen transporter?
- Biconcave shape: Increase surface area for diffusion gases.
- No nucleus/minimal organelles: maximises the oxygen holding capacity
- No mitochondria: ensures that the oxygen isn’t used up (RBC use anaerobic respiration).
- Haemoglobin to increase the affinity of oxygen binding (made from iron)
What occurs in Erythropoiesis?
- Erythroblast starts with a large nucleus, prominent nucleoli and large amounts of RNA and is found in the bone marrow.
- Gradually nucleus shrinks and is removed with majority if RNA and the RBC moved into the peripheral blood.
The erythroblast is purple/blue at the beginning as it contains a lot of RNA and then it because red as the RNA is removed.
Pg 16
What is an reticulocyte?
- The final step/stage before the mature erythrocyte is produced - Once the nucleus is removed (nucleus removed in the step before reticulocyte).
- Only a small amount of RNA is found to help make haemoglobin
- removed in 1-2 days
- High amount of reticulocyte is found in the blood when the body is recovering from blood loss
Pg 16&17
How will the body stimulate more RBC production after blood loss?
- the Kidneys sense tissue hypoxia (low oxygen).
2. Kidney will increase secretion of erythropoietin.
What is Erythropoietin?
- A glycoprotein produced by the kidney to increase levels of red blood cells
- Is produced by the kidneys in response to tissue hypoxia
- Acts to stop programmed cell death (apoptosis) of erythrocyte progenitors
• Made in the liver during fetal life and is taken over by the
kidney around birth
What is Granulopoiesis?
Production of granulocytes e.g. neutrophils (12-15um), basophils(11-14um), eosinophils(10-12um).
- Common myeloid progenitor converted to myeloblast and then to basophils, eosinophils and neutrophils.
- Myeloblast are immature cells and should not be seen in the blood.
Pg 22
What are Granulocytes/Polymorphonuclear cells (polymorphs)?
Polymorphonuclear - nucleus has multiple lobes.
- Sub group of white blood cells- fight infections inflammation.
- Named due to the presence of granules within their cytoplasm.
- All act to mediate inflammatory reactions in the body.
- All act by releasing cytokines, interleukins, leukotrienes etc. which recruit various other immune cells.
What are the features and structure of neutrophils?
• Often first responder and first line of defence against
bacteria.
- Can kill bacteria in multiple ways
- Multilobed nucleus (usually 3-5)
- 3 types of granules
- Most abundant of the granulocytes
What are the function of neutrophils?
• Granules contains lysozomes, matrix metalloproteinases
(MMPs) and gelatinase : break down different component of different pathogens
- Phagocytosis : engulfing pathogens and breaking them down by their enzymes
- The middle person i.e signalling and antigen presentation: in inflammatory /immune response they will release messengers to signal to other immune cells.
Pg 26 - 27
- Neutrophil Extracellular traps (NETS)
- Respiratory burst - make free radicals that can damage the DNA of certain pain pathogens(bacteria) and cause cell death
What is Granulocyte-colony stimulating factor (G-CSF)?
- Secreted by multiple immune cells in the body and endothelial cells
• Usually released in response to inflammation
• Acts on the bone marrow to increase the number of circulating
neutrophils
• Increases the speed at which neutrophils mature as well as the numbers
What is the structure and function of Basophils?
Structure
• Bilobed nucleus (cannot be seen as granules cover the surface of the cell)
• Purple granules (stained due to basic dye)
• Granules contain histamine and heparin
Function
• Release histamine to trigger inflammation: Histamine causes vasodilation and increases the number of cell and blood to a certain area, that’s why inflamed areas get hot
• Mediate hypersensitivy reactions (eg asthma).
Pg 29
What is the structure and function of eosinophils?
Structure
• Granules contain
- antihelminthic proteins such as major basic protein and eosinophilic cationic protein
- Cell component destroying enzymes (eg phosphlipases and acid hydrolases)
• 2 nucleur lobes
• Spheric granules- eosinophilic (acid-loving) granules
Function
• Phagocytose pathogens
• Fight parasitic worms and have a role in inflammation/allergy?(anti-inflammatory)
What occurs in Granulopoiesis?
All 3 lineages go through the process of:
• Nuclear condensation and lobulation
• Formation/increased numbers of granules
How are monocytes and macrophages produced?
Common myeloid progenitor converted to myeloblast converted to monocyte converted to macrophage
Pg 3x
What is the structure and function of a monocyte/macrophage?
Structure
- Largest of all the mature blood cells
- Unilobular horseshoe shaped nucleus
Function
- Monocyte in the blood, macrophage in the tissue.
- First line of defence
- Phagocytose pathogens, cell debris and senescent cells.
- Present foreign antigens
Pg 32-33
What is Thrombopoiesis?
Formation of thrombocytes.
- Common myeloid progenitor and regulated by Thrombopoietin to megakaryocytes and then goes into thrombocytes.
Pg 37
What are the structures and functions of thrombocytes (platelets)?
Structure • 2-3 µm in size • Biconvex shape • No nucleus- just cytoplasm • However, contains vast amount of proteins and clotting factors • Have special receptors on surface which causes platelet aggregation (gpIIb/gpIIIa)
Function
• Function to stop bleeding and mediate haemostasis
Pg 38-39
What occurs in thrombopoiesis?
- Upregulated by Thrombopoietin from the liver
- Megakaryocyte breaking down which eventually form 2000-3000 platelets
Pg 40
What is lymphopoiesis?
Process of the production of lymphocytes.
- B lymphocyte
- T Lymphocyte
- Natural killer cell
- Common lymphoid progenitor o natural killer cell or small lymphocyte
- Small lymphocyte to T or B lymphocyte
- B lymphocyte to plasma cell
Pg 41
What are the functions of B cells?
- Main function revolves around production of antibodies
- Each B cell is specific to a specific antigen
- Can activate T cells
- Play a part in humoral adaptive immunity
- Maturation occurs in the bone marrow and then in:
- Intestines (peyers patches)
- Spleen
- Lymph nodes
What are the functions of T lymphocytes (T cells)?
- Kill virus-infected cells, neoplastic cells and transplanted tissue
- Carry out cell-mediated immunity
- Activate B cells to make antibodies using IL 4
- Large nucleus with small rim of cytoplasm
- Proliferation and activation caused by IL 2
- Microscopically indistinguishable from B cells (6-9µm)
Where do T cell migrate to ?
- T cells start off in the bone marrow or fetal liver and then migrate to the thymus to mature.
- Once matured they will migrate to secondary lymphoid organs where they will wait to be activated.
Pg 44
What is plasma and what does it contain?
- Water component of the blood.
- The supporting medium for circulating blood cells
Consist of:
- 92% Water
- 8% Protein
- Ions (Na,K,Cl, etc.)
Protein component hugely important
- Albumin (liver)
- Clotting factors (liver)
- Hormones, cytokines, antibodies
Pg 47-48
