Phase 1 Haematology notes Flashcards
(104 cards)
Haemopoiesis
- production of blood cells that occurs in the bone marrow
- In embryos (yolk sac)
- In foetus (spleen)
- Bone marrow near end of pregnancy
–>Extensive bone marrow distribution in the skeleton in infants
where are rich sources of bone marrow
Main tissue: pelvis, sternum, skull, ribs and vertebrae
Where we take a trephine biopsy
Bone marrow found in the parietal region (not at proximal or distal ends)
5 major lineage pathways arise from haemopoietic stem cells in bone marrow
Myeloid
1) Erythrocytes
2) Myeloblast: basophiles, neutrophils, eosinophils, monocytes/ macrophages
3) Megakaryocyte-> platelets
Lymphoid
4) B
5)T cells
Hormones
- Erythropoietin- secreted by the kidney stimulates RBC production
- Thrombopoietin- produced by liver and kidney regulates production of platelets
Growth and development of megakaryocytes
- Transcription factors
- Interactions with non-haemopoietic cell types (e.g. endothelial cells)
Reticuloendothelial system (RES)
- Part of the immune system made up of monocytes in the blood and network of tissues which contain phagocytic cells
- Remove damage and dying cells from the circulation
- Main organs:
o Spleen and liver
o TES cells in spleen dispose of blood cells, in particular old red cells
- Back pressure- portal hypertension in liver disease e.g. cirrhosis
- Over work (red or white pulp)
-> Immune problems
-> Have to remove lots of RBC - Expanding as infiltrated by cells
->Cancer cells e.g. Leukaemia
->Other cancer metastases
->TB - Expanding as infiltrated by other material (sarcoidosis (granulomas)
NEVER NORMAL TO HAVE A LARGE SPLEEN
why can hypersplenism cause a low blood count
low blood counts can occur due to pooling of blood in enlarged spleen
- MUST AVOID contact sports and vigorous activity
- Risk of rupture if spleen is enlarged and no longer protected by rib cage
When patients are hypo splenic you can see the lack of function of the spleen ->doesn’t clear RBC properly- will see irregular blood films
Erythrocytes
Function
- Deliver oxygen o tissue
- Carry haemoglobin
- Maintain haemoglobin in its reduced ferrous state
- Main osmotic equilibrium
- Generate energy
- 120 days life
structure of RBC
Biconcave
- Flexible
- Carry lots of oxygen
- No nucleus or mitochondria
Haemoglobin
Haemoglobin
- Tetramer of 2 pairs of globin chains each with own haem group
- Globin gene clusters on Ch 11 and 16
- Different globin chains combine to form diff haemoglobins with diff properties
- Switch from fetal to adult Hb at 3-6 months of age
- Exists in 2 configuration
o Related binding (R state)- oxyhaemoglobin
o Tight binding (T state)- deoxyhaemoglobin
Changes in components in the membrane can make the cell less flexible
Will breakdown easily
- Spleen recognised cell as abnormal and removes from circulation
- RBC turnover increase and anaemia (haemolytic anaemia)
- Can be hereditary or acquired
Degradation of haem
- Stercobilin makes faeces brown
- Urobilin- yellow wee
haemotology terminology
Neutrophils
- First-responder phagocyte
- Most common white cell
- Essential part of innate immune system
- Circulate in bloodstream & invade tissues – live for 1-4 days
maturation of neutrophils
Maturation controlled by hormone G-CSF, a glycoprotein growth factor & cytokine which:
* Increases production of neutrophils
* Speeds up release of mature cells from BM
* Enhances chemotaxis
* Enhances phagocytosis and killing of pathogens
Recombinant G-CSF is routinely administered in cases when more neutrophils are needed e.g. a patient with severe neutropenia and sepsis after chemotherapy
neutrophilia
increase in absolutes no. of circulating neutrophils
Only those cells in circulating pool are actually measured in a blood count (not in tissue). Haemorrhage brings more cells out from marginated pool
Causes:
- Infection
- Tissue damage
- Smoking
- Drugs
- Myeloproliferative disease
- Acute inflammation
- Cancer
- Cytokine s (G-CSF)
- Metabolic disorders
- Endocrine disorders
- Acute haemorrhage
Neutropenia
Neutrophil count <1.5 x 109/L (severe if < 0.5 x 109/L)
Consequences
- Medical emergency
o Bacterial and fungal infections
o Mucosal ulceration e.g. painful mouth ulcers
- Intravenous antibiotics must be given immediately e.g. tazobactam
causes of neutropenia
Monocytes
- Typically largest cell in blood
- Circulate for 1-3 days before migrating into tissues where they differentiate in macrophages or dendritic cells
- Phagocytose microorganisms and breakdown/remove cellular debris
- Antigen presenting role to lymphocytes
- Important in defence against chronic bacterial infections e.g. TB and fungal infections
Monocytosis (increase) causes:
- Bacterial infection e.g. tuberculosis
- Inflammatory conditions e.g. rheumatoid arthritis, Crohn’s Ulcerative colitis
- Carcinoma
- Myeloproliferative disorders and Leukaemias
Eosinophils
- In circulation for 3-8 hours before migrating into tissues
- Lifespan 8-12 days
- Responsible for immune response against multicellular parasites e.g. Helminths
- Mediator of allergic responses
- Granules contain array of cytotoxic proteins e.g. eosinophil cationic proteins and elastase
- Phagocytosis of antigen-antibody complexes
- Inappropriate activation
- Responsible for tissue damage and inflammation e.g. in asthma
causes of eosinophilia
lymphocytes originate in the
bone marrow