5 Haemopoiesis, the Spleen and Bone Marrow Flashcards
Where does bone marrow become more limited to in adults?
Pelvis, sternum, skull, ribs, vertebrae
What cell types can haematopoietic stem cells develop into? (4)
- Erythroid
- Megakaryocyte/Platelet/Thrombocyte
- Granulocytes
- Lymphocytes
What are 4 properties/characteristics of the HPSC (haemopoietic stem cell)?
- Has greatest power of self renewal in adult
- Can differentiate into lots of different cells
- Mobilises out of bone marrow
- Can undergo apoptosis
What are the sources of haemopoietic stem cells if needed in a clinical scenario?
- Bone marrow aspiration
- Stem cells- mobilised by GCSF- collected by leucopharesis in peripheral blood
- Umbilical cord stem cells
Name the system which removes and controls blood cells.
Reticuloendothelial system (RES)
How does the reticuloendothelial system work?
- =Network of cells and tissues- contain phagocytic cells: monocytes, macrophages, kupffer cells, microglial cells (CNS)
- Identifies and mounts appropriate immune response
- Dispose of blood cells
Kupffer cell= specialised macrophage
What are the main organs of the Reticuloendothelial system?
- Spleen
- Liver
What are the 2 types of tissue found in the spleen?
- Red Pulp: sinuses lined with endothelial macrophages and chords
- White Pulp: structure=similar to lymphoid follicle
Where does blood enter the spleen?
Splenic artery
Which tissue tissue in the spleen do each of the following preferentially pass through?:
White cells
Plasma
RBCs
State 4 functions of the spleen (in adults).
- Sequestration and phagocytosis- removal of old/abnormal red cells - macrophages
- Blood pooling - so platelets and RBCs= rapidly mobilised during bleeding
- Extramedullary haemopoiesis- pluripotent stem cells
- Immunological function- 25% T cells and 15% B cells produced in spleen
What does in mean if you can palpate the spleen below the costal margin?
Spleen=enlarged
How can you measure the sze of the spleen?
- Palpate in right iliac fossa- spleen with move towards hand on inspiration
- Feel for splenic notch
- Measure CM from costal margin in mid-clavicular line
State some possible causes of splenomegaly?
- Back pressure- portal hypertension in liver disease
- Overworking red and white pulp
- Increase in extramedullary haemopoiesis
- Infiltrated by cells- eg cancer cells (leukaemia)
- Infiltrated material eg Gaucher’s disease, sarcoidosis
What are the 3 categories of Splenomegaly?
- Massive- chronic myeloid leukaemia, malaria
- Moderate- chronic myeloid leukaemia, malaria, lymphoma, liver cirrhosis
- Mild- chronic myeloid leukaemia, malaria, lymphoma, liver cirrhosis, hepatitis, autoimmune diseases
What is Hypersplenism?
Low blood count due to pooling of blood in spleen
(Removing too many red blood cells)
What is there an increased risk of if the spleen is enlarged?
Rupture (no longer protected by ribcage)–> haematoma
What is hyposplenism?
Lack of functioning splenic tissue
What causes hyposplenism?
- Splenectomy
- Sickle cell disease
- Multiple infarcts then fibrosis
- Caeliac disease
How might hyposplenism be detected?
Howell Jolly Bodies shown on blood film
If a patient has hyposplenism, what is the patient at greater risk of?
- Overwhelming sepsis
- Especially from Encapsulated Organisms
- Pneumococcus
- Haemophilus influenzae
- Meningococcus
Name 4 functions of a Red Blood Cell.
- Oxygen delivery
- Maintain haemoglobin in ferrous (reduced) state
- Maintain osmotic equilibrium
- Generate energy
What condition can develop as a result of changes in the red blood cell membrane?
Red cell survival reduces (broken down more easily)
Can develop Haemolytic anaemia
In 5 steps, describe how the body responds if a patient becomes anaemic.
- Cells in kidney- detect reduced pO2
- Increased erythropoietin production
- (erythropoietin) Stimulates maturation of RBCs
- Increase:
- RBCs
- Haemoglobin
- O2 delievered
- Eventually- erythropoietin production falls- feedback loop
What is cytopenia?
Reduction in number of RBCs
What type of blood cell is reduced in number for each of the following conditions?:
- Anaemia
- Leucopenia
- Neutropenia
- Thrombocytopenia
- Pancytopenia
- Anaemia: RBC/Haemoglobin
- Leucopenia: Low WBC
- Neutropenia: Low neutrophil
- Thrombocytopenia: Low platelet
- Pancytopenia: All
What has occured in a patient with each of the following conditions?
- Erythrocytosis
- Leucocytosis
- Neutrophilia
- Lymphocytosis
- Thrombocytosis
Increase in circulating:
- Erythrocytosis-RBCs
- Leucocytosis-WBCs
- Neutrophilia-Neutrophils
- Lymphocytosis- Lymphocytes
- Thrombocytosis- Platelets
What is a neutrophil?
- First responder phagocyte
- Most common WBC
Circulate in bloodstream- live 1-4 days
How is neutrophil maturation controlled?
- Hormone: G-CSF
Why might G-CSF be administered clinically?(2)
- Severe neutropenia
- Sepsis after chemotherapy
What are some possible causes of neutrophilia? (increased circulating neutrophils)
- Infection
- Cancer
- Tissue damage
- Acute inflammation
- Drugs eg steroids
- Acute haemorrhage
- Myeloproliferative disease
What are possible causes of neutropenia due to increased use/removal of neutrophils?
- Immune destruction
- Sepsis
- Splenic pooling
Apart from reduced production and increased removal of neutrophils, what are the other (2) causes of neutropenia?
- Benign, ethnic neutropenia
- Cyclic neutropenia (autosomal dominant disorder)
What are some possible causes of neutropenia due to a reduced production of neutrophils?
- B12/folate deficiency
- Infiltration of bone marrow by fibrosis/malignancy
- Aplastic anaemia- empty bone marrow
- Radiation
- Drugs
- Viral infection
- Congenital disorders
Describe 2 complication of Neutropenia?
- Mucosal ulceration eg in mouth
- Neutropenic sepsis (life threatening)= medical emergency. IV antibiotics given immediately
What do monocytes develop into?
Macrophages (once migrated to tissues)
What may cause monocytosis?
- Carcinoma
- Chronic infection
- Chronic inflammatory conditions eg ulcerative collitis
What’s the lifespan of an eosinophil?
8-12 days
What is the function of eosinophils?
Mediate:
allergic response
hypersensitivity reactions
Migrate–> epithelial surfaces
What do the granules in an eosinophil contain?
Arginine, phospholipid, enzymes
Name some conditions which eosinophilia is commonly due to:
- Allergic diseases:
- Asthma
- Eczema
- Hay fever
- Drug hypersensitivity:
- Penicillin
- Parasitic infection: Round worm, flukes
Name some conditions which eosinophilia is rarely due to?
- Hodgkin lymphoma
- Acute myeloid leukaemia
What are basophils?
Least common but LARGEST blood cell
Granules contain:
- Histamine
- Heparin
- Hyaluronic acid
- Seratonin
What may cause Basophilia?
- Immediate hypersensitivity reactions
- Ulcerative collitis
- Chronic myeloid leukaemia
What types of cells do lymphocytes differentiate into?
What are some possible causes of lymphocytosis?
Reactive:
- Viral infections
- Stress related : MI/Cardiac arrest
- Post splenectomy (No where for lymphocytes to rest)
- Smoking
Lymphoproliferative (malignant):
- Lymphoma (cells spill out of infiltrated bone marrow)
- T-cell leukaemia
