Outline the process of haemopoiesis
1) Proliferation: Starting with a stem cell, the cell divides into two. One to replace the original stem cell (self-renewal) and one that differentiates.
2) Differentiation: Haemopoietic progenitor will first differentiate to form either a myeloid blast (RBC, WBC, platelets) or a lymphoid blast (immunoresponse cells) -The progenitor will differentiate into a certain cell type under the influence of a particular cytokine. e.g. erythropoietin will cause differentiation into RBCs whilst thrombopoietin into platelets
N.B. Erythropoiesis is controlled by partial pressure of O2. decreased pO2 stimulates erythropoietin
What type of nucleus do neutrophils have?
Multi-lobed
What type of nucleus do eosinophils have?
Bi-lobed
What type of nucleus do basophils have?
Bi/Tri lobed
What type of nucleus do monocytes have?
Kidney shaped
What type of nucleus do lymphocytes have?
Deep staining
What is the function of neutrophils?
- they migrate out of circulation to infections site
- partake in phagocytosis
- granulocyte colony stimulating factor (G-CSF) increases neutrophil production
What is the function of eosinophils?
- capable of phagocytosis
- release cytotoxic particles to damage larger particles
What is the function of basophils?
-mediate acute inflammatory reactions using heparin and histamine
What is the function of monocytes?
- they migrate out of cells to become macrophages in many organs of the body
- capable of phagocytosis and they interact with T-cells
What is the function of lymphocytes?
B cells: humoral immunity/ stimulated by antigens which causes them to transform into plasma cells which secrete immunoglobins
Helper T cells: express CD4 on surface
Killer cells, permit the transformation of B cells into plasma cells
Describe the structure and function of erythrocytes
- biconcave disc
- 4 globin chains (2 alpha, 2 beta)
- each molecule carries a haem
- carries oxygen to tissues
- carries carbon dioxide to the lungs
Describe the structure and function of reticular cells
- synthesis reticular fibres and surround them with cytoplasm (structural function)
- Direct B and T lymphocytes to specific regions within the lymphatic tissues
Describe the structure and function of platelets
- small round blue particles produced by megakaryocytes in the bone marrow
- complex surface membrane
- cytoplasm contains alpha and dense granules
- alpha granules: contains fibrinogen and Von Willebrand’s factor
- Dense: contain ADP and Ca2+
- involved in the clotting cascade, they adhere to damaged cell walls and aggregate together
- 8/9 day lifespan
Describe some features of red blood cells
- 120 day lifespan
- Biconcave and flexible to facilitate passage through microcirculation
Describe the process of red blood cell destruction and catabolism
- red blood cells broken down to release haemoglobin in blood
- haemoglobin broken down to release haem
- haem converted into bilirubin in plasma
- plasma bilirubin taken up by liver
- from the liver, bilirubin can go to the kidney, where urobilogen is excreted via urine
- from the liver it can also go to the gall bladder, then the small intestine, then the large intestine where stercobilin is excreted
