Haematology Flashcards
(40 cards)
Define Haemopoiesis
Production of blood cells in the bone marrow
Describe the Reticuloendothelial System (RES)
RES= network in blood and tissues which part of the immune system containing phagocytic cells
Cells of the RES can identify and mount an appropriate immune response to foreign antigens
Main organs= spleen and liver
All blood passes through the spleen so damaged/ old RBCs can be disposed of
Definition of Neutrophil
first responder phagocyte, commonest white cell, essential part of innate immune system
once mature- circulate in bloodstream then invade tissue (1-4 days)
controlled by the hormone G-CSF
Describe the function of the hormone G-CSF
- increase production of neutrophils
- decrease time to release mature cells from bone marrow
- enhances chemotaxis
- enhances phagocytosis & killing of pathogens
Define causes & consequences of Neutropenia
Causes of neutropenia:
- B12/ folate deficiency
- Infiltration of bone marrow by malignancy or fibrosis
- Aplastic anaemia
- Radiation- mature cells killed
- Drugs- chemo, antibiotics
- Viral infection
- Congenital disorders
Consequences of neutropenia:
- Severe life threatening bacterial &/ infection
- Mucosal ulceration
Definition of monocytes
respond to inflammation & antigenic stimuli
migrate to tissues- become macrophages
lysosomes contain lysozyme, complement, interleukins, CSF
phagocytosis, pinocytosis
Causes of monocytosis
- Chronic inflammatory conditions- RA, Crohn’s
- Chronic infection- TB
- Carcinoma
- Myeloproliferative disorders/ leukaemias: CMML; aCML; JMML
Define Eosinophils
responsible for dealing with some parasites
mediator of allergic response
migrate to epithelial suraces
phagocytosis of antigen- antibody comple
mediate hypersensitivity reactions- eg to drugs, asthma, skin inflammation
Causes of Eosinophilia
- Allergic diseases: asthma, eczema, hayfever
- Drug hypersensitivity
- Hodgkin lymphoma
- Acute lymphoblastic leukaemia, acute myeloid leukaemia
Define basophils
least common but largest
active in allergic reactions & inflammatory conditions
dense granules contain histamine, heparin, hyaluronic acid, serotonin
Causes of Basophilia
Reactive: immediate hypersensitivity reactions, UC, RA
Myeloproliferative: CMC, MPN (ET/ PRV/ MF), systemic mastocytosis
Define lymphocytes
originate in bone marrow
B cells (humoral immunity)- antibody (immunoglobulin) forming cells
T cells (cellular immunity)- CD4+ helper cells, CD8+ cells
Natural killer cells (cell mediated cytotoxicity)
Causes of lymphocytosis
Reactive: viral infections, bacterial infections, stress relted, post splenectomy, smoking
Lymphoproliferative (ie malignant): chronic lymphocytic leukaemia (B cells), T or NK cell leukaemia, lymphoma
Describe the appearance and the function (4) of the spleen
• Red pulp- sinuses lined by endothelial macrophages and cords
• White pulp- similar structure to lymphoid follicles
• Blood enters via the splenic artery and white cells and plasma preferentially pass through the white pulp and red cells pass through the red pulp
• Functions:
1. Sequestration and phagocytosis
Old/abnormal RBCs removed by macrophages
2. Blood pooling
Platelets & RBC rapidly mobilised during bleeding
3. Extramedullary Haemopoiesis
4. Immunological function
25% of T cells and 15% of B cells present in the spleen
Define hyposplenism and (3) causes
= lack of functioning splenic tissue causes: - Splenectomy - Sickle cell disease - Coeliac disease Blood film reveal Howell Jolly Bodies
What is the problem If a patient has a lack of functioning spleen tissue?
- Prone to infections by encapsulated bacteria: (-) Neisseria Meningitidis, (+) Streptococcus pneumoniae, (-) Haemophilus influenzae
- Spleen contains splenic macrophages, T cells and B cells
- Polysaccharide capsule (sugar) decreases pathogen recognition and adherence by phagocytes
- Lack of antibody production
Define splenomegaly and (4) causes
= enlargement of the spleen; typically associated with an increased workload
causes:
- Haemolytic anaemia: increased number of defective RBS removed from circulation
- Portal hypertension: increases back pressure
- Infiltration by leuaemias and lymphomas
What are the clinical signs of splenomegaly
• To be able to palpate the spleen below the costal margin
MASSIVE- chronic myeloid leukaemia, myelofibrosis, malaria, schistosomiasis
MODERATE- as above + lymphoma, leukaemia, cirrhosis
MILD- as above + infections, infiltrative disorders, autoimmune diseases
Define hypersplenism
= low blood count can occur due to pooling of blood in the enlarged spleen
risk of rupture if enlarged and no longer protected by the rib cage- can haemorrhage or outgrow blood supply (infarction)
Describe the process of erythropoiesis
- Patient becomes anaemic- reduced pO2 detected in interstitial peritubular cells in kidney
- Increased production of erythropoietin by the kidney
- This stimulates maturation and release of RBCs from marrow
- Total red cells + haemoglobin rises
- More O2 delivered
- -ive feedback loop- erythropoietin production falls
Explain the concepts of a normal range and be able to assess whether a lab test is likely to be normal or abnormal
Range of assays performed in BC will vary slightly from trust to trust including ranges for results
Explain the significance of the reticulocyte count
Useful test in evaluating different kinds of anaemia
Explain the meaning and possible clinical significance of the terms that are frequently used to describe abnormalities in a blood count or film
increase= -osis or -ilia
decrease= -enia
Display an understanding of how a FBC is analysed
- WBC count
- RBC count
- [Haemoglobin]
- Haematocrit= fraction of whole blood volume that consists of RBCs (average red cell count [mean cell volume] x no .of red cells per litre)
- Mean cell (/ corpuscular) volume= average volume of red cells measured in femtolitres ( determine whether anaemia is microcytic or macrocytic)
- Mean cell haemoglobin= [haemoglobin] in a given volume/ no of red cells in same volume
- Platelet count
- Reticulocytes
- Differential WBC counts
- Blood film/ peripheral blood smear= drop of blood thinly dispersed to obtain monolayer of cells- air dried and fixed in methanol before staining = high/ low counts, blood parasites, abnormalities
