Red Blood Cells - Function And Haemolytic Aneamias

Question 1

Erythrocyte function depends on?

Answer 1

Integrity of the membrane

Haemoglobin structure and function

Cellular metabolism

Question 2

Red cell membrane

Answer 2

Biconcave in shape —> aids manoeuvrability

Lipid bilayer supported by protein cytoskeleton and contains transmembrane proteins
—> maintain integrity, shape and elasticity/deformability

Question 3

Hereditary spherocytosis

Answer 3

Caused by disruption of vertical linkages in membrane

Cells that are approximately spherical in shape —> lack cellular pallor

Result from loss of cell membrane but same amount of cytoplasm

Less flexible —> membrane had to squeeze around cyto

Question 4

Hereditary elliptocytosis

Answer 4

Disruption of horizontal linkages

Become elliptical in shape

Question 5

Cellular metabolism

Answer 5

Highly adapted
- generation of ATP to meet energy requirements
- maintenance of:
. Haemoglobin function
. Membrane integrity and deformability
. RBC volume

Question 6

G6PD

Answer 6

Glucose-6-phosphate dehydrogenase

Important enzyme in hexose mono phosphate shunt
—> shunt tightly coupled to glutathione metabolism
—> protects red cell from oxidant damage

Deficiency —> vulnerable to oxidant damage

Question 7

Glucose-6-phosphate dehydrogenase (G6PD) deficiency

Answer 7

Most prevalent enzyme disorder

X-linked inheritance —> affected individuals usually hemizygous males

Usually causes intermittent, severe intravascular haemolysis —> result of infection or exposure to an exogenous oxidant

Question 8

Inatravascular haemolysis

Answer 8

Associated with appearance of irregularly contracted cells

Irregular in outline but smaller that normal cells

Result from oxidant damage to the cell membrane and to the haemoglobin
—> haemoglobin is denatured and forms round inclusions known as Heinz bodies

Question 9

Polycythaemia

Answer 9

Too many red cells in the circulation

Hb, RBC and Hct are all increased

Question 10

Causes of polycythaemia: excessive transfusion

Answer 10

Blood doping

Question 11

Causes of polycythaemia: response to hypoxia

Answer 11

Appropriately increased erythropoietin

Question 12

Cause of polycythaemia: inappropriate erythropoietin use

Answer 12

Inappropriately administered to haematologically normal subjects

Renal or other tumour inappropriately secretes erythropoietin

Question 13

Causes of polycythaemia: abnormal function of the bone marrow - polycythaemia vera

Answer 13

Intrinsic bone marrow disorder

Myeloproliferative disorder

Can lead to ‘thick blood’ —> vascular obstructions/thrombosis

Blood can be removed to reduce viscosity

Drugs can be given to reduce bone marrow production of red cells