Lecture 4 - RBC Flashcards
What happens in the Bone marrow
primary haematopoiesis
What are the two types of marrow
Red marrow - active
Yellow marrow - inactive
What are the types of lymphoid tissue
Primary - bone marrow and thymus
Secondary - activation, spleen, lymph nodes, tonsils & adenoids, gut associated
Describe the spleen in RBC production
Filters circulating blood (checking for blood borne pathogens - particularly capsulated)
describe the kidney in RBC production
Produces Epo for RBC (growth factor)
Describe the liver in RBC production
foetal, thrombopoietin for platelet production - coagulation factors
Describe blood pathology
Maintains cells - identify and predicts disease - study disease, quantitative studies
Describe platelets
anucleate, slightly granular,
fragmentation of megakaryocytes in BM,
maintain blood vessels by initiating repairs
Involved in haemostasis
Describe erythrocytes
Flexible biconcave discs - normal mean cell vol., central pallor
Cytoplasm contains - conc. haemoglobin solution and enzymes
Haemoglobin - delivers O2 to tissue and returns CO2 to lungs (tetramer)
Describe the life cycle of RBC
EPO released from kidney (low O2 tension) -> produced in bone marrow -> circulates through body -> pass through sinusoids of MPS -> trapped & phagocytes
Describe reticulocytes
Immature RBCs released from BM - contain residual RNA and organelles (1-2% of peripheral), mature over 1-2 days - specialised stains to visualise
Describe polychromatic cells
Immature
Purple on blood film
Same as retic but seen on routine stain
Describe RBC membrane
Biconcave confers deformability
elasticity - lipids
tensile strength - cholesterol
protection from microbial & mechanical damage - carbohydrate
structural integrity - transmembrane and skeletal integrity
Describe anaemia
Low Hb - reduce O2 carrying capacity
describe anaemia classification by size and colour
Size (MCV) & colour (MCH)
Small pale, underfilled, microcytic
Large and red (macrocytic)
normal and red (normocytic, normochromic)
describe anaemia classification by aetiology
Reduced production - nutritional deficiency, globin gene defects, renal disease, Bone marrow disease
Increased destruction (haemolysis) - inherited, blood loss (haemoglobinopathies - SC, mem. defects, enzymopathies - G6PD deficiency)
Describe Sickle Cell Anaemia
Point mutation in chromosome 11 (polymerises when deoxygenated) - decreased oxygen-carrying capacity & occlude vessels
Describe SCA pathology
HbS polymers break through membrane - Ca2+ influx cross links mem. proteins and activates ion channels -> efflux of K+ & H2O
What triggers SCA
Triggered by acidosis, hypoxia, dehydration, infection etc.
What does SCA lead to
Occlusion of vessels -> infarction
Aplastic crisis -> transfusion
Describe Hereditary Spherocytosis (HS)
Spectrin - 2 polypeptide chains form heterodimer, bonds to actin & ankyrin (deformability and durability) - mutations decrease mem. skeletal components (akryn 3 band or spectrin 4.2 band)
What does HS lead to
Spherical and less deformable - sequestered in spleen and destroyed
Reduced RBC lifespan, variable severity, blood film shows spherocytes & polychromasia, hyperbilirubinemia + osmotic fragility - reticulocytosis (more immune cells - decreased tun over)
Describe G6PD (glucose-6-phosphate dehydrogenase deficiency)
involved in production of reduced glutathione & NADPH - protects against oxidative damage (X-linked recessive)
Advantage against malaria - oxidative stress
Describe G6PD morphology
Severe haemolytic crisis - sphered & retracted (precipitated haemoglobin) - splenic macrophages pluck out precipitated Hb (bite cells) -> reduced lifespan and variable severity - special staining - heinz bodies, oxidised, denatured & aggregated Hb
