Function of the RBCs, WBCs, platelets and Bone Marrow Flashcards
What is haematopoiesis?
Formation of blood components
It includes the processes of erythropoiesis, thrombopoiesis, and granulopoiesis.
What regulates erythropoiesis?
Erythropoietin (EPO) synthesized by kidneys
EPO stimulates the formation of erythrocytes.
What is thrombopoiesis?
Formation of thrombocytes/platelets
It is regulated by thrombopoietin (TPO) synthesized by the liver.
What are the steps involved in thrombopoiesis?
- Pluripotent stem cells stimulated by TPO to differentiate into megakaryocytes
- Megakaryocyte develops extra cytoplasm and forms pro-platelets
- Platelets bud off from pro-platelets into circulation
The megakaryocyte remains in the bone marrow.
What regulates granulopoiesis?
Granulocyte colony stimulating factor (GCSF) synthesized by endothelium
GCSF stimulates the formation of granulocytes.
What are hematopoietic stem cells?
Multipotent stem cells capable of differentiation or self-renewal
Their differentiation is influenced by growth factors and the microenvironment.
What is the differentiation timeline for blood cell types?
Takes 2-3 weeks and occurs in different areas as age increases
Initial formation in foetus occurs in the yolk sac, then lymph nodes, liver, and spleen.
Where does haematopoiesis occur in infants and children?
In red marrow, which is present in all bones
Red marrow is responsible for the formation of blood cells.
Where does haematopoiesis occur in adults?
In red marrow of axial bones: sternum, vertebrae, ribs, pelvis, proximal long bones, cranial
All other bones develop yellow marrow.
What do haematopoietic stem cells differentiate into?
Myeloid or lymphoid stem cells
Myeloid stem cells further differentiate into various blood cell precursors.
What do myeloid stem cells differentiate into?
Megakaryoblasts, proerythroblasts, monoblasts, myeloblasts
Myeloblasts further differentiate into granulocytes: neutrophils, eosinophils, basophils.
True or False: Erythropoiesis occurs primarily in the liver.
False
Erythropoiesis is regulated by EPO from the kidneys.
What do lymphoid stem cells differentiate into?
Lymphoblasts, which further differentiate into NK cells, T lymphocytes, and B lymphocytes.
What is a multipotent hematopoietic stem cell also known as?
Hemocytoblast.
What are the two paths a remaining cell can take after division?
Myeloid stem cell or lymphoid stem cell.
What are the products of myeloid stem cells?
Megakaryoblast, proerythroblast, reticulocyte, myeloblast, monoblast, basophil, neutrophil, eosinophil, monocyte.
What are the products of lymphoid stem cells?
Lymphoblast, natural killer cell, small lymphocyte, T lymphocyte, B lymphocyte, plasma cell, macrophage.
Where do myeloblasts and lymphoblasts remain?
In the bone marrow; they should never enter peripheral blood circulation.
What can cause Bone Marrow Failure (BMF)?
Stress can cause yellow marrow to revert back to haematopoiesis.
What is extramedullary hematopoiesis?
Formation of blood components outside the bone marrow, e.g., in the liver and spleen.
What condition can cause myelofibrosis?
It causes red bone marrow to become filled with fibrotic tissue, leading to haematopoiesis occurring elsewhere.
What is self-renewal in the context of hematopoietic stem cells?
The ability to maintain proliferation and block differentiation, increasing the number of hematopoietic stem cells.
What is self-renewal in haematopoietic stem cells?
Self-renewal allows haematopoietic stem cells to maintain their ability to proliferate and block differentiation, increasing their numbers.
What is the normal blood volume in males and females?
Normal blood volume is 5-6 litres in males and 4-5 litres in females, increasing by ~50% during pregnancy.
What are the components of centrifuged blood?
In centrifuged blood:
- Top: 55-60% volume plasma
- Middle: Less than 1% volume WBCs and platelets (buffy coat)
- Bottom: 40-45% volume RBCs
What happens to cell lineage counts with overactive and failed stem cells?
Overactive stem cells cause cell lineage counts to increase, while failed stem cells cause cell lineage counts to decrease.
What is the structure of bone marrow?
Bone marrow is soft, spongy, and flexible.
What does a bone marrow trephine biopsy show?
A bone marrow trephine biopsy shows cells with pink/orange cytoplasm and purple nuclei, dispersed around large white circles (fat spaces in bone marrow).
What does a bone marrow aspirate reveal?
A bone marrow aspirate shows individual cells in more detail but cannot show bone marrow architecture.
