Bone Marrow Structure and Function Flashcards
Where is blood made?
In the bone marrow
What is bone marrow creation called?
Haemopoiesis
What happens in the bone marrow?
Cells differentiate and proliferate
What cells do RBCs come from?
Pluripotent haemopoietic stem cells
What cell types can be made via pluripotent haemopoietic stem cells?
WBCs, RBCs, Platelets
What influences the proliferation and differentiation of pluripotent haemopoeitic stem cells?
Cytokines and regulators
Metals
Vitamins
Why do RBCs look brown on a slide and WBCs look purple?
Staining
What is the most active tissue in the body? Why?
The bone marrow; They make blood from when we are fetuses until we die and they continuously produce RBCs and WBCs indefinitely.
Where is blood produced in utero?
During the first 3 months the yolk sac starts the production of blood
During month 3 to month 7 the liver is the primary site of haemoppoiesis.
The spleen produces blood from the 3rd month to the 7th month as well
The bone marrow is another site that starts producing blood at 4 - 5 months and becomes fully active by the 7th or 8th month
What stage does the bone marrow become fully active?
7 - 8th month
Which bone marrow produces the most blood?
Vertebral bone marrow. After birth the rest of the bones decrease production of blood.
Can haemopoietic stem cells renew themselves?
Yes and they are pluripotent so they can differentiate into many cell types.
What percentage of bone marrow cells are CD34+?
1% of BM cells
What are blasts?
Morphologically distinguishable immature cells
How long does granulopoiesis usually take?
7 days approximately
What are the stages of erythropoiesis?
Proerythroblast
Basophilic normoblast
Polychromatic normoblast
Orthochromatic normoblast
Reticulocyte
RBC
What kind of bone is contained within the bone marrow?
Trabecular bone (small thin pieces of bone that give bone marrow a framework)
How do blood cell precursors organize themselves in bone marrow?
Immature cells adhere to matrix due to presence of adhesive proteins so they are located at edges.
Mature cells lose adhesive properties and are released into the middle of the bone marrow.
What stains are used for bone marrow microscope images?
3 micrometers thick and stained with Haemotoxilin and eosin
What does the amount of fat in our bone marrow tell us?
More fat is present in bone marrow with older age.
When baby is born there is no fat
By 80 years of age only 20% will be cellular and 80% will be fat.
Cellularity of bone marrow = 100 - age of person
What is a sign of healthy bone marrow?
Lots of variation of WBCs.
In leukemia there are lots of similar looking WBCs
What are the contents of normal bone marrow?
Erythropoiesis: 20% of RBC production (proerythroblasts - maturing erythroblasts - late forms)
Granulopoiesis (60% of BM)
Lymphocytes are 15%
Megakaryocytes are <0.1%
Other cells include plasma cells and macrophages
What do megakaryocytes do?
They produce platelets which make our blood clot
Into what do pluripotent stem cells differentiate initially?
Myeloid stem cells
Lymphoid stem cells
Which immune cell comes from myeloid stem cells?
Monocytes and macrophages
What do growth factors regulate?
Differentiation of stem cells
Number of cells being produced in the bone marrow
Can affect the function of a cell
What kind of cells can growth factors act on?
Some act on primitive cells
Some act on later cells
Where is erythropoeitin (EPO) produced?
Kidneys
What does EPO do?
Affects pluripotent stem cells to produce more red blood cells.
It increases production of RBCs
What happens to EPO during haemorrhage?
It increases
What do G-CSF, GM-CSF do?
Control leucocyte production
What does the kidney produce EPO in response to?
Decreased oxygen
What happens to EPO production in patients with renal failure?
It is lowered so they must be given EPO exogenously
What does IL-3 do?
Acts on early stem cell and is broad in specificity
What does thrombopoeitin do?
Acts on megakaryocytes to produce platelets
How do cytokines exert their function on cells?
They stimulate a secondary messenger system which acts on the nucleus.
What growth factors act on stem cells?
IL-3
Stem cell factor
How can haemopoiesis be assessed?
Blood count
Bone marrow examination
Some growth factors can be measured
What questions do we ask in bone marrow examinations?
How many cells are present?
Are the cells in the right place?
Which cells are present?
Do the cells look normal?
