Red Blood Cells (Erythrocytes)

Question 1

Osmotic fragility

Answer 1

lysis of red blood cells on exposure to diff osmotic solutions is called osmotic fragility

• defined as the ease with which the red cells are ruptured when they are exposed to hypotonic solutions.
• assess the integrity of red cell membrane
• osmotic fragility test helps in the diagnosis of anemia in which the phy properties of the red cells are altered
• detects whether or not the rbcs can be easily hemolyzed
• isotonic solution - intact eg, 0.9 % nacl
• hypertonic - shrink
• hypotonic - swell and burst

when the rate of hemolysis pf red cells is inc, the osmotic fragility is said to be increased and vice versa.

normal - begins - 0.45-0.50 and completes at 0.30-0.33

conditions of diminished fragility

• iron deficiency anemia
• thalassemia
• sickle cell anemia
• obstructive jaundice
• postsplenectomy

and increased fragility

• hereditary spherocytosis
• congenital hemolytic anemia
• other conditions in which spherocytes are found in blood

Question 2

destruction of hb

Answer 2

• when rbc burst and release hb, it is almost immediately phagocytosed by the macrophages especially kuffer cells of liver and macrophages of spleen and bone marrow
• during next few hours to days, macrophages release iron from the hb and pass it back into the blood to be
• —- carried by transferrin to the bone marrow for the production of new rbc
• —– or to the liver and other tissues for storage in the form of ferritin
• porphyrin converted by macrophages into bile pigment bilirubin, which is released into the blood and later removed from the body by secretion through the liver into the bile.

Question 3

hematocrit

Answer 3

• fractional volume of blood that erythrocytes occupy. hematocrit or packed cell volume (pcv) is the amount of packed rbcs following centrifugation.
• when blood is centrifuged, the rbcs are packed together at the bottom of the tube by centrifugal force.
• it is impossible to pack all the rbc together hence about 3-4% of the plasma remains entrapped among the cells, hence only 96% of the measured hematocrit is the true hematocrit
• pcv is a reliable index of the red blood cell population.
• provides useful info about the red cell mass which is correlated with the red cell count and their hb content
• these above measurements (including pcv) are essential for determination of red cell indices that help in detecting and classifying diff anemias.

Normal value and variation

• vary depending on whether the person has anemia, on the degree of bodily activity and on the altitude at which a person resides
• normal men - 0.40
• normal women - 0.36
• dec in dec rbc count and inc in inc rbc count
• severe anemia - 0.10
• polycythaemia - 0.65

Question 4

ESR

Answer 4

the rate of sedimentation of erythrocytes is called esr.

• if a column of anticoagulated fresh blood is left to stand by itself without any disturbance, the erythrocytes begin ti settle at the bottom, leaving the Clear plasma above
• when there is an inc in fibrinogen, immunoglobulins or acute phase reactants, the erythrocytes tend to cluster together to form stacks known as rouleaux
• therefore esr is higher in some disease conditions- infections, malignancies, and chronic disease state

factors affecting esr - shape and no of red cells, size of rouleaux, plasma factors

Normal Values and variations - wintrobes and westergren
by westergren method
- men - 15 mm/hr
- women - 20 mm/hr

physiological variation

• pregnancy inc
• female more
• age: esr high in infants and new borns
• menstrual bleeding- more

pathological variation
• increase 
- tuberculosis
- acute inflammations - cellulitis
- chronic inflammations - arthritis
- malignancy
- all types of anemias except membrane abnormalities

• decreased

• polycythaemia
• sickle cell anemia
• hereditary spherocytosis
• hypofibrinogenemia