1. King Saud University Riyadh Saudi Arabia
Dr. Gihan Gawish
Assistant Professor
Dr Gihan Gawish

2. Erythrocytes
Dr Gihan Gawish

3. Dr Gihan Gawish

4. Structure of Erythrocytes (RBCs)
Biconcave discs, a nucleate, essentially no organelles
Filled with hemoglobin (Hb), a protein that functions in gas transport
Contain the plasma membrane protein spectrin and other proteins that:
Give erythrocytes their flexibility
Allow them to change shape as necessary
Dr Gihan Gawish

5. Structure of Erythrocytes (RBCs)
Dr Gihan Gawish

6. Erythrocytes (RBCs)
Erythrocytes are an example of the complementarity of structure and function
Structural characteristics contribute to its gas transport function
Biconcave shape has a huge surface area relative to volume
Erythrocytes are more than 97% hemoglobin
ATP is generated an aerobically, so the erythrocytes do not consume the oxygen they transport
Dr Gihan Gawish

7. Erythrocyte Function
RBCs are dedicated to respiratory gas transport Hb reversibly binds with oxygen and most oxygen in the blood is bound to Hb
Hb is composed of the protein globin, made up of two alpha and two beta chains, each bound to a heme group
Each heme group bears an atom of iron, which can bind to one oxygen molecule
Each Hb molecule can transport four molecules
of oxygen
Dr Gihan Gawish

8. Hemoglobin
A heme group consists of an iron (Fe) ion (charged atom) held in a heterocyclic ring, known as a porphyrin.
Dr Gihan Gawish

9. Erythrocyte sedimentation rate (ESR)
It is the rate at which red blood cells precipitate in a period of 1 hour.
It's a common hematology test which is a non-specific measure of inflammation.
To perform the test, anticoagulated blood is placed in an upright tube, known as a Westergren tube and the rate at which the red blood cells fall is measured and reported in mm/h.
Dr Gihan Gawish

10. (ESR)
The ESR is governed by the balance between pro-sedimentation factors, mainly fibrinogen, and those factors resisting sedimentation, namely the negative charge of the erythrocytes (zeta potential).
When an inflammatory process is present, the high proportion of fibrinogen in the blood causes red blood cells to stick to each other.
Dr Gihan Gawish

11. (ESR) The red cells form stacks called 'rouleaux' which settle faster.
Rouleaux formation can also occur in association with some lymphoproliferative disorders in which one or more immunoglobulins are secreted in high amounts.
Rouleaux formation can, however, be a normal physiological finding in horses, cats and pigs.
Dr Gihan Gawish

12. (ESR) The ESR is increased by any cause or focus of inflammation.
The ESR is decreased in sickle cell anemia, polycythemia, and congestive heart failure.
The basal ESR is slightly higher in females.
Dr Gihan Gawish

13. Blood Group
The ABO blood group system is the most important blood type system (or blood group system) in human blood transfusion.
blood type is a classification of blood based on the presence or absence of inherited antigenic substances on the surface of (RBCs).
These antigens may be proteins, carbohydrates, glycoproteins, or glycolipids, depending on the blood group system
Dr Gihan Gawish

14. ABO Group
The associated anti-A antibodies and anti-B antibodies are usually IgM antibodies, which are usually produced in the first years of life
Blood types are inherited and represent contributions from both parents.
Dr Gihan Gawish

15. Blood Group
Many pregnant women carry a fetus with a different blood type from their own
the mother can form antibodies against fetal RBCs.
Sometimes these maternal antibodies are IgG, a small immunoglobulin, which can cross the placenta and cause hemolysis of fetal RBCs, which in turn can lead to hemolytic disease of the newborn, an illness of low fetal blood counts which ranges from mild to severe
Dr Gihan Gawish

16. Rhesus blood group system
The Rhesus system is the second most significant blood group system in human blood transfusion.
The most significant Rhesus antigen is the RhD antigen because it is the most immunogenic of the five main rhesus antigens.
It is common for RhD negative individuals not to have any anti-RhD IgG or IgM antibodies, because anti-RhD antibodies are not usually produced by sensitization against environmental substances.
However, RhD negative individuals can produce IgG anti-RhD antibodies following a sensitizing event: possibly a fetomaternal transfusion of blood from a fetus in pregnancy or occasionally a blood transfusion with RhD positive RBCs.
Dr Gihan Gawish

17. Serology
Antibody Screen is a test that is always performed on patients who may require red blood cell transfusion, and this test will detect most clinically significant red cell antibodies.
Dr Gihan Gawish

18. ABO Crossmatching O A B AB
Dr Gihan Gawish

19. Structure of Hemoglobin
Dr Gihan Gawish

20. Hemoglobin (Hb) Oxyhemoglobin – Hb bound to oxygen
Oxygen loading takes place in the lungs
Deoxyhemoglobin – Hb after oxygen diffuses into tissues (reduced Hb).
Carbaminohemoglobin – Hb bound to carbon dioxide
It binds to globin’s amino acids
Carbon dioxide loading takes place in the tissues
Dr Gihan Gawish

21. Production of Erythrocytes
Hematopoiesis – blood cell formation
Hematopoiesis occurs in the red bone marrow of the:
Axial skeleton and girdles
Epiphyses of the humerus and femur
Hemocytoblasts give rise to all formed elements
Dr Gihan Gawish

22. Production of Erythrocytes Erythropoiesis
A hemocytoblast is transformed into a proerythroblast
Proerythroblasts develop into early erythroblasts
Dr Gihan Gawish

23. Production of Erythrocytes: Erythropoiesis
The developmental pathway consists of three phases
1 – ribosome synthesis in early erythroblasts
2 – Hb accumulation in late erythroblasts and norm oblasts
3 – ejection of the nucleus from normoblasts and formation of reticulocytes
Reticulocytes then become mature erythrocytes 1-2% of RBC in health people
Dr Gihan Gawish

24. Production of Erythrocytes: Erythropoiesis
Dr Gihan Gawish

25. Regulation and Requirements for Erythropoiesis
Circulating erythrocytes – the number remains constant and reflects a balance between RBC production and destruction
Too few RBCs leads to tissue hypoxia
Too many RBCs causes undesirable blood viscosity
Erythropoiesis is hormonally controlled and depends on adequate supplies of iron, amino acids, and B vitamins
Dr Gihan Gawish

26. Hormonal Control of Erythropoiesis
Erythropoietin (EPO) release by the kidneys is triggered by:
Hypoxia due to decreased RBCs or hemoglobin content
Decreased oxygen availability
Increased tissue demand for oxygen
Enhanced erythropoiesis increases the: RBC count in circulating blood
Oxygen carrying ability of the blood
Dr Gihan Gawish

27. Erythropoietin Mechanism
Homeostasis: Normal blood oxygen levels
Increases O2-carrying ability of blood
Reduces O2 levels in blood
Erythropoietin stimulates red bone marrow
Enhanced Erythropoiesis increases RBC count
Dr Gihan Gawish
Kidney (and liver to a smaller
extent) releases erythropoietin

28. Dietary Requirements of Erythropoiesis
Erythropoiesis requires:
Proteins, lipids, and carbohydrates
Iron, vitamin B12, and folic acid
The body stores iron in Hb (65%), the liver, spleen, and bone marrow
Intracellular iron is stored in protein-iron complexes such as ferritin and hemosiderin
Circulating iron is loosely bound to the transport protein transferrin
Dr Gihan Gawish

29. Fate and Destruction of Erythrocytes
The life span of an erythrocyte is 100–120
days
Old RBCs become rigid and fragile, and their Hb begins to degenerate
Dying RBCs are engulfed by macrophages
Heme and globin are separated and the iron is salvaged for reuse
Dr Gihan Gawish

30. Fate and Destruction of Erythrocytes
Heme is degraded to a green pigment biliverdin
Biliverdin is converted to a yellow pigment called bilirubin
The bilirubin is picked up by the liver and secreted into the intestines as bile
Dr Gihan Gawish

31. Fate and Destruction of Erythrocytes
The intestines metabolize it into urobilinogen and stercobilinogen
These degraded pigments leave the body
in feces and urine, in a pigment called stercobilin and urobilin
Dr Gihan Gawish

32. Fate and Destruction of Erythrocytes
Globin is metabolized into amino acids and is released into the circulation
Hb released into the blood is captured by
haptoglobin and phagocytized
Dr Gihan Gawish

33. Low O2 levels in blood stimulate kidneys to produce erythropoietin.
Erythropoietin levels rise in blood.
Erythropoietin and necessary raw materials in blood promote erythropoiesis in red bone marrow.
New erythrocytes enter bloodstream; function about 120 days.
5. Aged and damaged red blood cells are engulfed by macrophages of liver, spleen, and bone marrow; the hemoglobin is broken down.
Dr Gihan Gawish

34. Erythrocyte Disorders
Anemia – blood has abnormally low oxygen-carrying capacity
It is a symptom rather than a disease itself
Blood oxygen levels cannot support normal metabolism
Signs/symptoms include fatigue, paleness, shortness of breath, and chills
Dr Gihan Gawish

35. Platelets
Platelets are fragments of megakaryocytes with a blue-staining outer region and a purple granular center
Their granules contain serotonin, Ca2+, enzymes, ADP, and platelet-derived growth factor (PDGF)
Platelets function in the clotting mechanism by forming a temporary plug that helps seal breaks in blood vessels
Platelets not involved in clotting are kept inactive
Dr Gihan Gawish

36. Genesis of Platelets The stem cell for platelets is the hemocytoblast
The sequential developmental pathway is as shown
Stem cell
Developmental pathway
Hemocytoblast Megakaryoblast Promegakaryocyte Megakaryocyte Platelets
Dr Gihan Gawish