Anaemias 1

Why do we have to produce red blood cells?

Red blood cells transport oxygen from our lungs to our tissues, where they play a role in aerobic respiration (cellular metabolism). This provides our cells with enough energy to undergo cell division, protein synthesis and many other critical functions for our survival. But what happens when oxygen serum levels are low?
  1. Peritubular cells in the kidneys produce erythropoietin
  2. Proliferation and maturation of red blood cells occurs in the red bone marrow
  3. Reticulocytes (immature red blood cells) are released into the blood
  4. Mature red blood cells enter circulation
  5. Oxygen levels are normalised
Red blood cells have a reasonably long lifespan at approximately 120 days. When a red blood cell has reached its lifespan or is damaged for whatever reason, it migrates to the spleen. Here, two processes occur:
  1. Phagocytic cells destroy the old and defective red blood cells
  2. Haemoglobin is broken down into globin, which is reused for amino acid construction, and haem, which is further broken down into iron (reused in bone marrow) and unconjugated bilirubin (water insoluble). This unconjugated bilirubin is then conjugated (water soluble), secreted in bile and excreted in the faeces and urine.

What is anaemia?

Anaemia is the reduction of haemoglobin concentration in the blood to abnormal levels. It is caused by a reduced mass of circulating red blood cells and decreased amounts of haemoglobin in the red blood cells, which is of genetic cause. A low hematocrit (low red blood cell count) can also be due to production failure and haemolysis, i.e. the premature destruction of RBCs. The consequence is a reduction in oxygen transport.

Signs and symptoms of anaemia can be divided into three categories, based on the anaemia aspect of which they are a result:

Due to decreased Hb levels:

Pallor of the:
  • Skin
  • Conjunctivae
  • Mucous membranes
  • Nail beds
Due to decreased oxygen transport (tissue hypoxia):
  • Fatigue
  • Weakness
  • Headache
  • Dizziness
  • Fainting spells
  • Exertion dyspnea
Compensatory mechanisms to increase oxygen delivery to the tissues:
  • Tachycardia and palpitations (rapid heart rate)
  • Tachypnoea (increased breathing rate)
  • Diffuse bone pain, sternal tenderness (↑ erythropoiesis)

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