Erythrocytes (RBCs) Figure 17.3

Haemoglobin

Haemoglobin Definition: - It is the principal constitute (33% ) of RBCs - It is a red pigment which gives the blood its red colour Normal levels: - Infant at birth 20 gm/dl - Infant after one week 15.5gm/dl - Children (3-12 years) =11-14 gm/dl - Adult male 13-18 gm/dl - Adult female 11.5 -16 gm/dl

Structure: 1) Globin: 2 pairs of polypeptide chains (2  and 2 ) 2) 4 Haem: each is an iron-protoporphyrin : - 4 pyrrole rings  protoporphyrin - protoporphyrin + Fe++  haem

Structure of Hemoglobin Figure 17.4

Functions - Carriage of O2 & CO2 - Strong buffer system Reactions of Hb - Oxyhemoglobin: O2 bind with iron in ferrous state . It is called oxygenation not oxidation - Met Hb: strong oxidation by certain drugs or oxidizing agents  ferric state which can not carry O2. Dusky coluoration of skin like cyanosis

Carboxy Hb: carbon monoxide is a toxic gas and attached to Fe++ instead of O2. It has high affinity to Fe++ (210 times as O2). Carbamino Hb: normally CO2 attached to the amino group of globin part of Hb.

Types of Hb 1-Adult (HbA): 2  chain (each is consisted of 141 amino acids) and 2 chain (146 amino acids).(97.5% of adult Hb.) 2-HbA2: 2 chains and 2 delta (146 amino acids) chains which differ from -chains in the terminal 10 amino acids. 3-Fetal Hb (HbF): It is the type of Hb in the human fetus. It is usually replaced by adult Hb after birth . It contain 2 and 2 gamma (146 amino acids) chains which differ from -chains in 37 amino acids.

4-Glycosylated Hb: (3-7% of Hb) glucose is attached to terminal valine amino acid in -chain. This value increases in cases of uncontrolled diabetes mellitus. 5-HbS:: It is abnormal type of Hb due to congenital abnormality of -globin in which the amino acid No. 6 (glutamic acid ) is substituted by valine amino acid in the -chain  hemoglobin -S (sickle cell anemia).

Destruction of RBCs - The life span of RBCs is 120 days - Old RBCs are destroyed in narrow capillaries and spleen  Hb released and splits by the cells of the reticuloendothelial system into globin & haem. - Globin is used in protein metabolism - Haem losses its iron to be stored as ferritin. - The protoporphyrin part of haem  bile pigments

RBCs laboratory tests (A) RBCs count: By Haemocytometer Normally - In newly borns = 6 -8 millions/mm3 - In children = 4 – 5 million/mm3 - In adult male = 4.5 - 6.5 million/mm3 - Female = 4-5.8 million/mm3 Increase in: hypoxia & polycythaemia Decrease in: anaemia

(B) RBCs volume (Haematocrit value) (packed cell volume) It is the volume of RBCs contained in 100 ml of blood. Normally - In adult male = 47% (42-54%) - In adult female = 42% (37-47% - In children = 36-44 % - In newly borns = 50-58 %

Plasma (55% of whole blood) Buffy coat: leukocyctes and platelets (<1% of whole blood) Formed elements Erythrocytes (45% of whole blood) 1 2 Centrifuge Withdraw blood and place in tube Figure 17.1

Importance of Haematocrit value: Increases by: - increased RBCs (polycythaemia) - decreased plasma :(dehydration or hemo-concentration as after burn) Decreases by: - decreased RBCs (anaemia) - increased plasma (overhydration)

physiologically hematocrit value is increased in: venous blood than in arterial blood as RBCs volume is larger in venous blood (due to chloride shift phenomenon ) large vessels due to skimming phenomenon as RBCs prefer to pass in large vessels than in small blood vessels - newborn as he contains more RBCs due to relative ischemia during intrauterine life.

(C) Hemoglobin content By Sahli-Adam’s hemometer. Normally - in Male = 14-17 gm/100 ml blood - in Female = 12-15 gm/100 ml blood Decreased in anemia Increased in polycythymia

(D) Saline fragility test (Osmotic fragility test) - If the RBCs are put in hypotonic solution, H2O pass inside RBCs  the cells swell and rupture (hemolysed). - Normal RBCs show partial hemolysis at 0.45% NaCl and complete hemolysis at 0.35%. More fragility occurs in: - Infant RBCs, old RBCs, venous RBCs (have big size),  CO2 and acidity, Spherocytosis Less fragility occurs in sickle cell anaemia and iron deficiency anaemia.

(E) Erythrocytic sedimentation rate (ESR) It is the rate of RBCs sedimentation in a vertical blood column at end of one and two hours. RBCs sediment because: -Their density is more than plasma. -They tend to form rouleaux shapes, in which ratio of mass to surface area is increased causing sedimentation Normal value At 1st hour 2nd hour - Male 3-5 mm 7-12 mm - Female 4-7 mm 12-17 mm

Factors affecting E.S.R 1- Plasma fibrinogen and globulin  rouleaux formation by reduction –ve charges on RBCs  less repellent forces  sedementation rate 2- RBCs count. It decreases in polycythemia and increased in anemia. Increases in: Physiological: during menstruation, pregnancy & exercise. Pathological : Tissue destruction and inflammation due to increased fibrinogen and globulins as in: *- Acute and chronic infections *- Severe trauma *- Malignant tumors *- Rheumatic conditions *- Myocardial infarction (3) Anaemia ESR is important as prognostic test not diagnostic test