Haemopoiesis, The Spleen And Bone Marrow ILOs Flashcards
What is haemopoiesis?
Formation of blood cells from bone marrow
Bone marrow distribution in infants
All throughout the skeleton
Bone marrow distribution in Adults
Limited
Pelvis, skull, ribs, sternum and vertebrae
Haemopoiesis in the embryo
IN vasculature of the yolk sac to start
Then in the foetal liver between weeks 5-8
Haemopoiesis starts off with Haematopoietic stem cells:
They differentiate into 2 cell types:
Common Myeloid Progenitor Cells
Common Lymphoid Progenitor Cells
Common Myeloid Progenitor cells differentiate into 3 Types of cell:
Megakaryocytes
Erthryocytes
Myeloblasts
Myeoblasts differentiate into:
Granulocytes: Neutrophils, Eosinophils and Basophils
AND
Monocytes
Common Lymphoid Progenitor cell differentiations into 2 different lymphocytes
T-Lymphocytes
B-Lymphocytes
T-Lymphocyte development
In foetal liver and Thymus
B-Lymphocyte development
Foetal liver and Bone Marrow
Erythropoiesis
Formation of red cells
Protein Secreted by the KIDNEY to stimulate erythropoiesis
Erythropoietin
Thrombopoiesis
The formation of Thrombocytes (Platelets)
Thrombopoietin function
Protein that simulates formation of Megakaryocytes therefore stimulates THROMBOPOIESIS
What is a THROMBOCYTE?
Important in blood clotting
Membrane bound cytoplasm that has budded off from a Megakaryocyte
Granulopoiesis
Formation of Granulocytes (Neutrophils, Eosinophils and Basophils) from Myeloblast cells which originate from Common Myeloid Progenitor Cells
Monocytopoiesis
Production of monocytes from Myeoblasts which originate from Common Myeloid Progenitor Cells
Monocytes differentiate into either MACROPHAGES OR DENTRITIC CELLS
Macrophage function
Phagocytose foreign substances in the body
DENTRITIC Cells
Antigen presenting cells
Present the antigens of pathogens they have engulfed to Lymphocytes
Erythrocyte function
Transport Oxygen from lungs to tissues by carrying haemoglobin
Transport CO2 form the tissues back to the lungs
Erythrocyte Structure
No nucleus
Bioconcave
No mitochondria
Lipid bilayer contains proteins that maintain the structure of the cell so that it remains bioconcave and flexible
Hereditary Spherocytosis
A gene mutation of at least one of the proteins that is responsible in maintaining phospholipid bilayer of the erythrocyte and therefore its bioconcave shape
Spleen function
A filter of the blood
Spleen general structures
Splenic Artery (Brings BLood To Spleen)
Red Pulp = Sinusoids containing Macrophages RED Cells Pass through it
White Pulp = Plasma and white cells pass through it
Splenic vein
Splenic artery linked to splenic vein by a portal system
BLood Pooling in the SPleen
RED Cells and platelets accumulate in the spleen so they can be quickly mobilised during bleeeding
WHite pulp importance
Lots of antibodies synthesised here
Removes antibody covered bacteria and RBCs
Red Pulp Importance
Macrophages engulf and destroy old RBCs here
Extramedullary Haemopoiesis
When haemopoiesis occurs not in the bone marrow
E.g: Spleen and Liver
Can cause Splenomegaly
What is Splenomegaly?
Enlarged Spleen
Splenomegaly is caused by
-Extra-medullary Haemopoiesis
-Hypertension of hepatic portal vein from liver disease (blood can’t leave spleen)
-Overwork of spleen (causes increase in pulp size)
-Expanding as infiltrated by cells (Blood cancers/Leukeamia)
-Expanding as infiltrated by materials (Sarcoidosis)
Dangers of Splenomegaly
Spleen no longer fully protected by rib cage, risk of rupture
Need to avoid contact sports
Hyposplenism is
Lack of functioning splenic tissue
Hyposplenism caused by
Splenectomy
Sickle cell disease ( Red cells not bioconcave, get stuck in spleen)
Gastrointestinal diseases (ulcerative colitis, Crohns Disease and coeliac disease)
Autoimmune disorders (Rhuematioid Arthiritis and Hashimotos Disease)
Hyposplenism = BIG RISK OF
SEPSIS
Encapsulated bacteria very hard for immune system to combat without maximum splenic function
Indication of Hyposplenism
Presence of Howell Jolly Bodies in Blood Film
Normally are removed
Normal Range
Includes 95% of population
Values outside range not always abnormal
Results may be in normal range but it may be a significant change within the normal (this is abnormal)
Normal range changes with age, sex and comorbidities
Significance of reticulocyte count
Indication of production of erythrocytes and therefore activity of the bone marrow
Haematocrit (HcT)
Proportion of blood that is made up of red blood cells
Haemoglobin Concentration
A Parameter for accessing Full Blood Counts
Red Cell Count (RCC)
Number of Red Cells in a given vol of blood
Mean Cell Volume (MCV)
Helps determine cause of anaemia
Red Cell Distribution Width (RDW)
Variation in size or red blood cells
Helps determine the stage of anaemia
So if anaemia has just started there will be a wide range of sizes
If its been happening a long time, all cells would be small so RDW is low since they are all similar
Mean Cell Haemoglobin (MCH)
Average amount of haemglobin in a RBC
Used to asses
Microcytic
Small MCV (Mean Cell Volume)
Macrocytic
High MCV (Mean Cell Volume)
Anisocytosis
Increased variation non red cell size (RDW Red Cell Distribution Width)
Hypochromic
Low Mean CEll Haemoglobin
Hyperchromic
High Mean Cell Haemoglobin (MCH)
Dimorphism
2 distinct populations of red cells
Polychromatic
Reticulocytes
Megakaryocyte function
Produce Thrombocytes
Eosinophils FUnction
MEdiator of allergic responses
Immune response to parasites
In appropriate activation of eosinophils
Causes inflammation (asthma) and tissue damage
Basophils
Active in allergies and inflammatory conditions
Lymphocytes
B Cells make antibodies
T Cells (Produce T cell receptors to recognise antigens)
Natural Killer Cells
