2.01 - Introduction to Haematology Flashcards
What is haematopoiesis?
Production of mature blood cells from stem cells in the bone marrow:
- red blood cells
- platelets
- white blood cells
Distribution of haematopoiesis in
a) fetal
b) children
c) adults
a) liver and spleen
b) throughout the skeleton
c) axial skeleton
What cell does haematopoiesis begin from?
Multipotent haematopoietic stem cell (HPSC) - haemocytoblast.
Structure of erythrocytes.
- biconcave structure
- enucleated
Structure of haemoglobin.
Globular tetramer protein:
- 2 alpha chains
- 2 beta chains
- 4 haem groups
Deoxyhaemoglobin exists in low affinity (T) state or high affinity (R) state - when oxygen binds, it converts from T to the R state.
Lifespan of erythrocytes.
120 days
Process of erythropoiesis.
- Interstitial peritubular cells in the kidney detect hypoxia.
- Kidney produces EPO in response to hypoxia.
- Common myeloid progenitor (CMP) differentiates, releasing reticulocytes.
- Reticulocytes mature into erythrocytes (RBCs).
- Number of RBCs and Hb increases, allowing more O2 to be delivered to tissues.
How long does it take for reticulocytes to mature into erythrocytes?
2 days.
Process of thrombopoiesis.
- Liver produces TPO in response to thrombocytopenia.
- CMP cells differentiate into megakaryocytes.
- Platelets bud off from the membrane of megakaryocytes.
Process of monocytosis.
- Inflammation (acute or chronic).
- CMP cells differentiate into myeloblast.
- Myeloblast differentiates into monocyte.
- Monocyte leaves the blood circulation after 20 hours, and become tissue macrophages.
Function of
a) monocyte
b) macrophage
a) phagocytosis in the blood
b) phagocytosis in the tissue
Products of granulopoiesis.
- basophils
- neutrophils
- eosinophils
Process of granulopoiesis.
- Microbial infection triggers release of G-CSF.
- CMP cells differentiate into myeloblast.
- Myeloblast differentiates into granulocytes.
Function of:
a) neutrophils
b) eosinophils
c) basophils
a) phagocytose any foreign organisms by releasing reactive oxygen species.
b) actions against parasitic infection; raised in anaphylaxis.
c) release histamine as part of the immune response.
Process of lymphopoiesis.
Common lymphoid progenitor (CLP) cells differentiate into:
- natural killer cells
- B lymphocytes
- T lymphocytes
What organs are part of the reticuloendothelial system?
- kidney
- liver
- spleen
- lymph nodes
- bone marrow
What is the function of the spleen?
White pulp: forms antibodies and removes any bacteria or erythrocytes coated in antibodies; particularly effective against encapsulated bacteria.
Red pulp: removes old RBCs and metabolises haemoglobin.
Role of the spleen in haemorrhage.
In response to bleeding, platelets and RBCs are pooled in the spleen to minimise blood loss.
What are the encapsulated bacteria?
Some Have Pretty Nice Capsules:
Streptococcus pneumoniae
Haemophilus influenzae
Pseudomonas aeruginosa
Neisseria meningitidis
Cryptococcus
Causes of splenomegaly.
- overworking red or white pulp
- backpressure 2° to portal hypertension
- leukaemia
- infection
- accumulation of waste products of metabolism
Infective causes of splenomegaly.
- malaria
- Schistosomiasis
- HIV
- EBV
Causes of hyposplenism.
- splenectomy
- sickle cell disease
- coeliac disease
Indications for splenectomy.
- splenic rupture
- cancer
- hereditary spherocytosis
- ITP
Management of asplenic patients.
- vaccinations
- prophylactic antibiotics
- carry a card notifying medical staff of their condition