Haemopoiesis Flashcards
What ability do haemopoietic stem cells have?
They have ability to self replicate and differentiate further
What are progenitors limited by in terms of differentiation?
They are lineage bound so have a set number of cells they can become.
What is the haemopoietic cell replication driven by?
Constant replication and differentiation driven by multiple hormones and chemical messengers.
What does selection refer to in terms of haemopoietic replication?
Not all cells made in the marrow will enter the blood.
Some undergo programmed cell death (apoptosis)
Up to 40% survival rates in certain stages of rbc synth
What is erythropoiesis?
The formation of red blood cells.
What regulatory hormone is used in erythropoiesis?
Erythropoietin is the regulatory hormone to rbc’s
How long is the life span of a red blood cell and what happens to them after this?
120 days then they are degraded by the liver/spleen.
Broken down earlier if damaged (ie sickle cell anemia)
What structural specialisations do rbc’s have that improve their ability’s as oxygen transporters?
Biconcave shape-increase SA for gas diffusion
No nucleus + minimal organelles-maximise O2 holding
No mitochondria-ensure O2 isn’t used up by RBC (they respire anaerobically)
Heamoglobin-increases affinity of O2 binding
What are the 3 main cell types n the process of erythropoiesis? Where are these cells found?
Erythroblast-bone marrow
Reticulocyte-peripheral blood
RBC-peripheral blood
How does an erythroblast become a reticulocyte?
Erythroblast starts off with large nucleus, prominent nuclei and large amounts of RNA.
Gradually the nucleus shrinks and is removed with the majority of RNA
This forms a reticulocyte
What is some key info regarding reticulocyte.
Final step before mature erythrocytes (RBC’s)
Only small amount of RNA-helps make heamoglobin
After 1/2 days the RNA is removed
How can reticulocyte be used as a clinical marker?
If there is a high amount in the blood this means a lot of them have been produced quickly.
This shows attempted recovery from blood loss so can be useful clinically to establish blood loss has occurred in prev hours/days.
How does the body stimulate an increase in RBC synthesis?
The kidney senses hypoxia in tissues. It then increases its secretion of erythropoietin hormones (this increases RBC synth)
What is Erythropoietin?
A glycoproteins produced by the kidney to increase the level of RBC’s.
It’s produced in response to tissue hypoxia
Acts to stop apoptosis or erythrocyte progenitors meaning a higher % f them reach the blood
(During foetal life its made in the liver, taken over by kidney after birth)
What is granulopoiesis?
The synthesis and release of granuloctyes into the blood
What are granulocytes in general ?
A sub group of WBC’s they fight infection + Inflammation
Have granules in cytoplasm
Mediate inflammation in body
Release cytokines, interleukins, etc to recruit immune cells
What 3 cells do granulocytes consist of?
Neutrophils
Basophils
Eosinophils
Describe the make-up of a neutrophil.
A multilobule nucleus (stains blue)
3 types of granules in cytoplasm
Most abundant granulocyte
What is the function of a neutrophil?
Kill bacteria in multiple ways
Granules contain lysosomes, MMPs and gelatinise
Perform phagocytosis
Signal and antigen presenting role
Form Neutrophil Extracellular traps (a DNA net catches pathogens, killing some bacteria and gathering others together for easier phagocytosis)
Respiratory burst (rapid release of oxidative free radicals to kill bacteria by damaging DNA)
What is G-CSF (granulocyte-colony stimulating factor)?
Secreted by multiple immune cells and endothelial cells
Usually released in response to inflammation
Acts on bone marrow to increase number of circulating neutrophils
Increases speed at which neutrophils mature as well as heir numbers ( increase in 80% by 12 hours)
What is a basophils?
They release histamine to trigger inflammation
Mediate hypersensitivity reactions (asthma)
Have a bilobule nucleus
Many purple granules (stain by basic dye)
Granules contain histamine and heparin
What does histamine do?
Causes vasodilation of an area
Making it hot and swollen
It increases the number of immune cells ABLE to reach the site
What does Heparin do?
It’s a blood thinner and is neede to reduce the risk of dangerous clots forming due to the vasodilation caused by histamine
What are eosinophils?
They phagocytose pathogens.
Fight parasitic worms and have an inflammatory role
Have many granules
2 nuclear lobes
Granules are spherical and acid loving (stain red)
