RBCs and Haemoglobin Flashcards
Briefly outline the function of normal Hb (2)
Binds reversibly with O2, picking it up in the lungs and releasing it in other tissues.
The oxygen dissociation curve for Hb can be left or right shifted. Explain how this relates to oxygen affinity of Hb and how the level of 2,3-DPG affects the oxygen dissociation curve (4)
Left shift- increased affinity and low level of 2,3-DPG. Right shift- decreased affinity and high level of 2,3-DPG.
Name the predominant Hb in adult red cells (½) HbA
2 alpha & 2 beta globin chains (2). Each globin chain has a haem group, which consists of 4 porphyrin rings containing a single atom of iron (2)
Outline the functions of red blood cells including the role of normal Hb (3½)
RBCs in arterial blood carry O2 from the lungs to the tissues and they carry CO2 when they return in venous blood to be expired in the lungs. Haemoglobin binds reversibly with O2, picking it up in the lungs and releasing it in other tissues.
Outline the main functions of red blood cells (2)
RBCs in arterial blood carry O2 from the lungs to the tissues and they carry CO2 when they return in venous blood which is expired in the lungs.
70-year-old male smoker with general malaise, dysuria, pain in his right flank and a recent difficulty in passing urine. Temperature was 38.5°C and BP 170/100 mm. Hg. Bilateral pitting ankle oedema and haemoglobin = 20g/dl.
Give one possible explanation for a haemoglobin level of 20g/dl [1]
The presence of an erythropoietin-secreting neoplasm (most probably a renal cell carcinoma). Polycythaemia (as a result of cigarette-induced chronic lung disease or any cause)
Name the organ responsible for haptoglobin synthesis (½) & State the function of haptoglobin (1) (CPATH)
Liver. Avidly binds free haemoglobin, preventing renal loss (salvages iron) & renal tubular damage
State the direction in which haptoglobin will change with: (2x½ = 1)
Haemolysis
Inflammation
Haemolysis - decrease
Inflammation - increase
Alcoholic patient with malaria & massive increase in unconjugated bilirubin & severe haemoglobinuria.
State whether haptoglobin will be increased, decreased or unchanged in this patient (½)
Decreased
Name the haemopoietic growth factor that stimulates erythropoiesis/ hormone involved in RBC production (1)
Erythropoietin
Describe the role of Erythropoietin (EPO) in haematopoiesis. Include its site of synthesis and the control of its production (5)
EPO regulates erythropoiesis (½). Produced in peritubular interstitial cells of kidney (1)
Main stimulus for production is low oxygen tension in kidney tissue (1)
Can be caused by anaemia, low atmospheric O2, defective cardiac or pulmonary function, and poor renal perfusion (½ each)
List three (3) causes of endogenous erythropoietin elevation (1½)
Anaemia, Cardiorespiratory disease with hypoxia, Tumours (rarely), Low atmospheric 02, High affinity Hb
Outline the structure of a reticulocyte and briefly describe its morphological features on a blood film (2) (NB)
Reticulocyte is a newly formed RBC at the stage where it has lost its nucleus but still has some residual RNA.
Stains blue-grey on the blood film. If many reticulocytes are present, the term polychromasia is used.
Describe how RCC assists in determining the cause of anaemia (4) (Super NB)
Indication of bone marrow response to anaemia.
Normally, a reduction in Hb will cause an increase in erythropoietin synthesis which drives the bone marrow to produce more red cells. The result is increased release of reticulocytes from the bone marrow and an increase in the RCC.
If the RCC is low or inappropriately normal, it indicates that the bone marrow is unable to respond (e.g. marrow infiltration, aplasia) or the synthesis of erythropoietin is impaired.
If the RCC is increased, it indicates that the anaemia may be caused by bleeding or haemolysis.
List three (3) causes of a raised RCC [1½] (NB)
Haemorrhage, Haemolysis, Response to treatment of anaemia
