BIOL 2420 Lecture Notes - Lecture 4: Hereditary Spherocytosis, Fetal Hemoglobin, Bilirubin
26 Apr 2018
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Unit 3 – Lecture 4
RBCs Live About 4 Months
- red blood cells live for about 120 +/- 20 days
- increasing fragile older red blood cells may rupture as they try to squeeze through narrow
capillaries
o they also could be ingested by scavenging macrophages as they pass through the spleen
- many components of the destroyed cells are recycled
o amino acids from the globin chains are incorporated into new proteins
o some iron from the heme groups is reused to make new heme groups
- the spleen and liver convert remnants of the heme groups to a colored pigment (bilirubin)
o bilirubin is carried by plasma albumin to the liver
▪ in the liver bilirubin is incorporated into a secretion called bile
o bile is secreted into the digestive tract
o bilirubin metabolites leave the body in the feces
- small amounts of other bilirubin metabolites are filtered from the blood in the kidneys – they
contribute to the yellow color of urine
- bilirubin levels in the blood can become elevated
o jaundice: the increased levels of bilirubin cause skin and whites of eyes to take on a
yellow color
o accumulation of bilirubin can occur for several reasons
▪ newborns – fetal hemoglobin is being broken down and replaced with adult
hemoglobin are particularly susceptible to bilirubin toxicity
• they are monitored in the first few weeks of life for bilirubin toxicity
▪ liver disease – the liver is unable to process or excrete bilirubin
RBC Disorders Decrease Oxygen Transport
- hemoglobin plays a critical role in oxygen transport
o red blood cell count and hemoglobin context of the body are important
o anemia: a condition occurring when hemoglobin content is too low
▪ the blood cannot transport enough oxygen to the tissues
▪ people with this condition are usually tired and weak (especially during exercise)
Table 16.3 – causes of anemia
Accelerated Red Blood Cell Loss
Blood loss: cells are normal in size and hemoglobin content but low in number
Hemolytic anemias: cells rupture at an abnormally high rate
Hereditary
Membrane defects (example: hereditary spherocytosis)
Enzyme defects
Abnormal hemoglobin (example: sickle cell anemia)
Acquired
Parasitic infections (example: malaria)
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