Origin of blood cells Flashcards
Define and describe haematopoiesis
βIt is the formation of blood cells.
βSTEM CELLS β PROGENITORS β IMMATURE PRECURSORS β MATURE CELLS.
βthis is a one way process
βThroughout the process of making specialised cells from stem cells, growth factors are added throughout.
Give three examples of precursors and the mature cells that they produce
β Ξ²-LYMPHOCYTES make PLASMA CELLS
βMONOCYTES make MACROPHAGES
βMEGAKARYOCYTES make PLATELETS
what are megakaryocytes?
megakaryocytes are large polyploid cells which platelets bud off of
What are the different sites of haematopoiesis throughout a humanβs lifetime?
βIN THE EARLY FOETUS: in the yolk sac βIN THE FOETUS: in the liver βIN AN INFANT: throughout the bone marrow βIN AN ADULT: β central skeleton β vertebrae βribs and sternum β skull β sacrum β pelvis β in the proximal ends of the humerus and the femur
Describe the bone marrow
βThe bone marrow is a spongey, jelly-like tissue.
β It has many blood vessels which bring nutrients and take away new blood cells.
βIt is a metabolically active, highly innervated organ.
what are the two different types of bone marrow?
βRED MARROW: where active haematopoiesis takes place
βYELLOW MARROW: where it is filled with fat cells
What is the difference between a bone marrow trephine biopsy and a bone marrow aspiration?
βBONE MARROW TREPHINE BIOPSY: - bone marrow is removed in pieces ( 1 or 2cm core of bone marrow) used to examine the bone marrow architecture
βBONE MARROW ASPIRATION: - bone marrow cells are sucked out in a syringe - used to examine cellular morphology
how many red blood cells does adult bone marrow produce?
2x10^11 RBC
how many neutrophils does adult bone marrow produce?
5x10^10 neutrophils
why is haematopoeisis a one way process?
as an anti cancer mechanism
What are the most common cells seen in the bone marrow?
β myelocytes and myeloblasts.
Describe the formation of neutrophils (myelopoiesis)
βmyeloblast β promyelocyte β myelocite βmetamyelocyte β band β segmented neutrophil (Caps ones are more important)
what are the steps of erythropoeisis?
β PROERYTHROBLAST β BASOPHILIC ERYTHROBLAST β POLYCHROMATIC ERYTHROBLAST β PYKNOTIC ERYTHROBLAST β RETICULOCYTE βMATURE RED BLOOD CELL As we go along, the nucleus shrinks and the cytoplasm gets pinker
what are the steps of platelet formation?
β MEGAKARYOBLAST (to the next step, there is only DNA replication, no cell division)
βMEGAKARYOCYTE
β BLOOD PLATELETS
what do high level of reticulocytes in the blood mean?
β that the bone marrow is working overtime to produce new red cells
what are the steps of lymphocyte formation?
βSTEM CELL
β forms a COMMON LYMPHOID PROGENITOR
β forms either a T-LYMPHOCYTE or a B-LYMPHOCYTE
Where does T-Cell formation occur?
β T-Cell formation occurs in the thymus ( in the chest)
β The early progenitor migrates to the thymus and T-Cell receptor gene arrangement occurs
β Positive (check that they work) and negative selection also occur
Where does B-Cell formation occur?
βB-Cell formation occurs in the bone marrow.
βImmunoglobin gene arrangement occurs.
βexpression of surface IgM (immunoglobulin)
βThe immature B-Cell migrates to the secondary lymphoid organs (lymph nodes) for maturation and antigen selection.
why are progenitors considered undifferentiated?
βundifferentiated because you cannot tell the difference between them morphologically
since they donβt show the characteristics of mature cells.
why are progenitors considered committed?
βthey are committed to what they will become when they produce mature cells
Why are progenitors called Colony Forming Units (CFUs) and how many cells can be in a colony?
βProgenitors grow to form colonies of mature cells.
β from 32 to hundreds or thousands of cells in a colony.
what are some examples of some colony forming units?
β CFU- G granulocyte progenitor β CFU- GM granulocyte/monocyte progenitor β CFU - E erythroid progenitor β CFU- bas β CFU-eo β CFU - MK megakaryocyte progenitor
why do some erythroid colonies look like they have burst and what are they called?
β because they are mobile
β BFU - E (burst forming unit)
What are CSFs?
Factors which were discovered to stimulate colony growth were named Colony Stimulating Factors or CSFs