Lecture 4 - RBC

Question 1

What happens in the Bone marrow

Answer 1

primary haematopoiesis

Question 2

What are the two types of marrow

Answer 2

Red marrow - active
Yellow marrow - inactive

Question 3

What are the types of lymphoid tissue

Answer 3

Primary - bone marrow and thymus
Secondary - activation, spleen, lymph nodes, tonsils & adenoids, gut associated

Question 4

Describe the spleen in RBC production

Answer 4

Filters circulating blood (checking for blood borne pathogens - particularly capsulated)

Question 5

describe the kidney in RBC production

Answer 5

Produces Epo for RBC (growth factor)

Question 6

Describe the liver in RBC production

Answer 6

foetal, thrombopoietin for platelet production - coagulation factors

Question 7

Describe blood pathology

Answer 7

Maintains cells - identify and predicts disease - study disease, quantitative studies

Question 8

Describe platelets

Answer 8

anucleate, slightly granular,
fragmentation of megakaryocytes in BM,
maintain blood vessels by initiating repairs
Involved in haemostasis

Question 9

Describe erythrocytes

Answer 9

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)

Question 10

Describe the life cycle of RBC

Answer 10

EPO released from kidney (low O2 tension) -> produced in bone marrow -> circulates through body -> pass through sinusoids of MPS -> trapped & phagocytes

Question 11

Describe reticulocytes

Answer 11

Immature RBCs released from BM - contain residual RNA and organelles (1-2% of peripheral), mature over 1-2 days - specialised stains to visualise

Question 12

Describe polychromatic cells

Answer 12

Immature
Purple on blood film
Same as retic but seen on routine stain

Question 13

Describe RBC membrane

Answer 13

Biconcave confers deformability
elasticity - lipids
tensile strength - cholesterol
protection from microbial & mechanical damage - carbohydrate
structural integrity - transmembrane and skeletal integrity

Question 14

Describe anaemia

Answer 14

Low Hb - reduce O2 carrying capacity

Question 15

describe anaemia classification by size and colour

Answer 15

Size (MCV) & colour (MCH)
Small pale, underfilled, microcytic
Large and red (macrocytic)
normal and red (normocytic, normochromic)

Question 16

describe anaemia classification by aetiology

Answer 16

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)

Question 17

Describe Sickle Cell Anaemia

Answer 17

Point mutation in chromosome 11 (polymerises when deoxygenated) - decreased oxygen-carrying capacity & occlude vessels

Question 18

Describe SCA pathology

Answer 18

HbS polymers break through membrane - Ca2+ influx cross links mem. proteins and activates ion channels -> efflux of K+ & H2O

Question 19

What triggers SCA

Answer 19

Triggered by acidosis, hypoxia, dehydration, infection etc.

Question 20

What does SCA lead to

Answer 20

Occlusion of vessels -> infarction
Aplastic crisis -> transfusion

Question 21

Describe Hereditary Spherocytosis (HS)

Answer 21

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)

Question 22

What does HS lead to

Answer 22

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)

Question 23

Describe G6PD (glucose-6-phosphate dehydrogenase deficiency)

Answer 23

involved in production of reduced glutathione & NADPH - protects against oxidative damage (X-linked recessive)
Advantage against malaria - oxidative stress

Question 24

Describe G6PD morphology

Answer 24

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