Origin of blood cells Flashcards
(45 cards)
Define and describe haematopoiesis
→It is the formation of blood cells.
→STEM CELLS → PROGENITORS → IMMATURE PRECURSORS → MATURE CELLS.
→this is a one way process
→Throughout 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-LYMPHOCYTES make PLASMA CELLS
→MONOCYTES make MACROPHAGES
→MEGAKARYOCYTES make PLATELETS
what are megakaryocytes?
megakaryocytes are large polyploid cells which platelets bud off of
What are the different sites of haematopoiesis throughout a human’s lifetime?
→IN THE EARLY FOETUS: in the yolk sac →IN THE FOETUS: in the liver →IN AN INFANT: throughout the bone marrow →IN AN ADULT: → central skeleton → vertebrae →ribs and sternum → skull → sacrum → pelvis → in the proximal ends of the humerus and the femur
Describe the bone marrow
→The bone marrow is a spongey, jelly-like tissue.
→ It has many blood vessels which bring nutrients and take away new blood cells.
→It is a metabolically active, highly innervated organ.
what are the two different types of bone marrow?
→RED MARROW: where active haematopoiesis takes place
→YELLOW MARROW: where it is filled with fat cells
What is the difference between a bone marrow trephine biopsy and a bone marrow aspiration?
→BONE MARROW TREPHINE BIOPSY: - bone marrow is removed in pieces ( 1 or 2cm core of bone marrow) used to examine the bone marrow architecture
→BONE 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?
→ myelocytes and myeloblasts.
Describe the formation of neutrophils (myelopoiesis)
→myeloblast → promyelocyte → myelocite →metamyelocyte → band → segmented neutrophil (Caps ones are more important)
what are the steps of erythropoeisis?
→ PROERYTHROBLAST → BASOPHILIC ERYTHROBLAST → POLYCHROMATIC ERYTHROBLAST → PYKNOTIC ERYTHROBLAST → RETICULOCYTE →MATURE RED BLOOD CELL As we go along, the nucleus shrinks and the cytoplasm gets pinker
what are the steps of platelet formation?
→ MEGAKARYOBLAST (to the next step, there is only DNA replication, no cell division)
→MEGAKARYOCYTE
→ BLOOD PLATELETS
what do high level of reticulocytes in the blood mean?
→ that the bone marrow is working overtime to produce new red cells
what are the steps of lymphocyte formation?
→STEM CELL
→ forms a COMMON LYMPHOID PROGENITOR
→ forms either a T-LYMPHOCYTE or a B-LYMPHOCYTE
Where does T-Cell formation occur?
→ T-Cell formation occurs in the thymus ( in the chest)
→ The early progenitor migrates to the thymus and T-Cell receptor gene arrangement occurs
→ Positive (check that they work) and negative selection also occur
Where does B-Cell formation occur?
→B-Cell formation occurs in the bone marrow.
→Immunoglobin gene arrangement occurs.
→expression of surface IgM (immunoglobulin)
→The immature B-Cell migrates to the secondary lymphoid organs (lymph nodes) for maturation and antigen selection.
why are progenitors considered undifferentiated?
→undifferentiated because you cannot tell the difference between them morphologically
since they don’t show the characteristics of mature cells.
why are progenitors considered committed?
→they 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?
→Progenitors grow to form colonies of mature cells.
→ from 32 to hundreds or thousands of cells in a colony.
what are some examples of some colony forming units?
→ CFU- G granulocyte progenitor → CFU- GM granulocyte/monocyte progenitor → CFU - E erythroid progenitor → CFU- bas → CFU-eo → CFU - MK megakaryocyte progenitor
why do some erythroid colonies look like they have burst and what are they called?
→ because they are mobile
→ BFU - E (burst forming unit)
What are CSFs?
Factors which were discovered to stimulate colony growth were named Colony Stimulating Factors or CSFs
