Physiology Topics
Red blood cells homeostatic disorders include anemias, polycythemia and porphyria. Anemias may be due to insufficient red blood cells, decreased hemoglobin production or abnormal hemoglobin.
Anemias due to insufficient red blood cells may be hemorragic, hemolytic or aplastic. Hemorragic anemia may be due to acute bleeding or chronic blood loss, for example a bleeding ulcer. Hemolytic anemia is due to the premature cell rupture due to abnormalities, inherited defects, mismatch transfusions or infections like malaria. Aplastic anemia is a decrease in red blood cell formation due to radiation, cytotoxic drugs (like cancer chemotherapy) or genetic failure of the bone marrow.
Decreased production of hemoglobin may be due to iron deficiency or pernicious anemia. Iron deficiency may arise from malnutrition, inadequate absorption, loss of stores due to liver damage or a metabolic deficiency. Pernicious anemia is a vitamin B12 deficiency due to either an intrinsic factor defect or dietary deficiency.
Abnormal hemoglobin disorders include thalassemia and sickle-cell anemia. In thalassemia, there is a decreased rate of synthesis of one of the hemoglobin peptide chains (alpha or beta). Thalassemia is more common in people of Mediterranean origin. People with sickle-cell anemia have an abnormal type of hemoglobin (Hb-S) that forms long rod-like polymers when not associated to oxygen, bending the erythrocyte into a sickle shape and causing hemolysis. Sickle-cell anemia is an inhered disease in people or descendants from malaria-prone areas. The gene responsible for sickle-cell also increases the permeability of cell membranes to K+, causing leakage of this ion out of the cell. The malaria parasite cannot survive at low K+ levels, which gives an advantage to people with only one sickle-cell allele.
Polycythemia is an excess in red blood cells due to low-level CO poisoning, dehydration, erythropoietin abuse, or other (??) causes. There is a risk of heart disease or stroke due to the increased blood viscosity.
Porphyria is a buildup of porphyrin rings to toxic levels due to a inability to generate red blood cells. Symptoms include photosensitivity, skin lesion when exposed to light, degenerating gums (teeth look larger), pain made worst by alcohol or garlic, and excessive hair growth especially on hands. It is treated by red blood cells transfusions. This condition may be the source of the vampire legends.
Continue to "White Blood Cells " or take a quiz: [Q1] [Q2].
Need more practice? Answer the review questions below.
Question coming soon