Heamatology No (2).pdf

Heamoglobin Mohammed Elshiekh Associate Professor Session No (2) Faculty Of Medicine Dept. Of Physiology Objectives : Definition Concentration Structure Function Reaction Normal & Abnormal types RBCs destruction jaundice The...

Heamoglobin Mohammed Elshiekh Associate Professor Session No (2) Faculty Of Medicine Dept. Of Physiology Objectives : Definition Concentration Structure Function Reaction Normal & Abnormal types RBCs destruction jaundice The red pigment found in the RBCs M.W is about 65000 Concentration: - 14-18g/dl in males - 12-16g/dl in females - 14-20g/dl in neonates Structure  consists of 2 parts:  Haem  Globin(4 chains)  Each subunit consists of heme +a polypeptide chain  {Hb =4 heme +4 polypeptide chains}  Each heme is synthesized from glycine and succinyle-CoA  It has a porphyrin ring containing iron in the reduced state Oxy & deoxyhaemoglobin Types of Normal Heamoglobin  Hb A: 2  and 2  chains, forms 98% of the Hb in adults  HbA2: 2  and 2  forms 2% of Hb in adults  Hb F:2  and 2 is Hb of the fetus Hb F has a much higher affinity for O2 than Hb A   CHAIN 141  CHAIN 146  CHAIN 146 BIRTH 6 A Red Blood Cell Turnover Figure 19.5  Reactions of hemoglobin Haemoglobin +O2 OxyHb[pink] Haemoglobin-O2 deoxyHb[blue] HB+glucose Glcosylated Hb[Hb A1c] Hb A1c is important in the follow up of diabetic patients  Abnormal variants of heamoglobin The abnormality is in the globin part 1. Haemoglobin S  glutamic acid in position 6 of the  chain is replaced by Valine  This change makes the Hb less soluble and precipitates easily, especially when exposed to low O2 tension  When the Hb precipitates in the red cell assume a sickle shape  The sickle cells live shorter  The effect on the patient depends on whether one or two  chains are affected: One chain: sickle cell trait [mild]  Two chains: sickle cell anaemia[sever]  Hb S is common in Africa  In Sudan HB S is mainly seen in the west 2.Thalasaemia:  A whole chain is missing either  or  chain   thalassaemia when one or 2  chains missing   thalassaemia when one or 2  chains missing  Thalassaemaia is common in the Mediterranean area Red cells breakdown RBC live for 120 days and destroyed Main sites for destruction: Spleen, liver, bone marrow The cells break down and the heamoglobin is discharged The membrane is taken by phagocytes Erythrocyte membrane Fate of heamoglobin Split into heam and globin Globin degraded to amino acids that will be reused for synthesis of new proteins The heam:  Iron taken by transferrin and reused again in synthesis of new Hb,…. porphyrin is converted to biliverdin Biliverdin is converted to bilirubin Bilirubin is a yellow pigment not soluble in water Excretion of bilirubin:  bilirubin is excreted by the liver after becoming soluble by conjugation:  Bilirubin + glucuronic acid conjugated bilirubin Conjugated bilirubin enters the small intestine in the bile BLOOD LIVER In the intestine :  Bilirubin urobilinogen (stercobilinogen)  Most of urobilinogen is reabsorbed in the terminal ileum  The rest is excreted with faeces  The excreted stercobilinogen gives the stool its normal colour The absorbed urobilinogen It is water soluble  carried to the liver and excreted again through the bile Can be filtered by the kidney and some excreted in urine Enterohepatic circulation Jaundice  Normal bilirubin level: