Haemopoiesis Flashcards
What is haemopoiesis?
The formation of RBCs from pluripotent haematopoietic stem cells. It occurs in the bone marrow
How is the bone marrow related to haemopoiesis?
It occurs in the bone marrow, as it contains uncommitted stem cells. The number of active regions decrease with age.
Active bone marrow is red, inactive is yellow as a result of fat deposition.
25% of bone marrow stem cells are destined to become RBCs, 75% WBC (as they have a shorter life span so more need to be made)
What is the difference between the myeloid line and the lymphoid line?
They are both pathways that form blood cells. The myeloid line forms RBC, platelets, neutrophils, basophils, eosinophils, macrophages.
The only blood cell the lymphoid line forms is lymphocytes
How is haemapoiesis stimulated?
Cytokines (peptide cell signalling molecules).
Erythropoietin
Thrombopoietin
Colony stimulating factors, interleukins and stem cell factors
What is erythropoiesis?
EPO (a glycoprotein) stimulates the production of RBCs with the assistance of several cytokines. EPO is secreted from fibroblasts in the kidneys. The release of EPO is stimulated by a state of hypoxia (low levels of O2).
It acts on bone marrow to increase stem cell turnover, increase the maturation of RBC precursors and increase the rate of RBC release.
How are RBCs made from their precursors?
PHSC (pluripotent haemotopoietic stem cells) becoming committed to becoming a certain cell type (differentiation). The first committed precursor is a proerythroblast/erythroblast. The erythroblast pinches off the nucleus to form a reticulocyte and then the reticulocyte loses its mitochondria and ribosomes and forms an erythrocyte.
What is TPO?
Thrombopoietin - regulates the production of platelets. It is produced mainly in the liver (sometimes in the kidney).
They assist the growth and maturation of megekaryocytes from megakaryoblasts. Megakaryocytes will then form platelets.
What is Leukopoiesis and what stimulates it?
A type of haemapoiesis that forms WBCs (leukocytes).
This is stimulated through colony stimulating factors, made by endothelial cells and fibroblasts in the bone marrow.
What are granulocytes and agranulocytes?
They are both types of white blood cells. Granulocytes have a granulated nucleus e.g. neutrophil, basophil, eosinophil. Agranulated WBCs are monocytes.
What is the WBC count during periods of bacterial infection?
High count with more neutrophils and monocytes
What is the WBC count during periods of viral infection?
A high, low or normal count but with higher proportion of lymphocytes.
What is granulopoiesis?
The development of the granulocytic WBCs (neutrophil, basophil, eosinophil)
The first recognisable cell of granulopoiesis is a myeloblast. The myeloblast will enlarge and differentiate and then form a promyelocyte and then become a specific granulocyte.
What are neutrophils, basophils, eosinophils?
Neutrophil Granulocyte Multi-lobed nucleus Most abundant WBC Granules contain lysosomal enzymes Involved in phagocytosis
Basophils Granulocytes Granules appear blue Contain histamine Involves in allergic reactions
Eosinophils Granulocyte Granules appear red Contain major basic protein (MBP) Fight parasites and viruses Involved in allergic reaction.
What is monopoiesis?
The process of the formation of monocytes (agranulocyte).
The first committed cell is the mono blast, this develops into a promonocyte (a large cell with slightly indented nucleus), this develops into a monocyte.
Monocytes migrate from the bone marrow to peripheral tissue, when stimulated they develop in macrophages.
Macrophages phagocytose pathogens and display the antigens to lymphocytes.
How are lymphocytes made?
Lymphoid line.
Individual cells made via committed precursors. These can develop into pro-T and pro-B cells.
lymphocytes have large nucleus.
