(RBC)
Learning Objectives
At the end of the session you must be able to :
Describe the morphology and function of RBC
Describe the sites of erythropoiesis
Describe Stages of Differentiation of Red Blood Cells
Enumerate the factors regulating
erythropoiesis
Q.1. Which dietary component is needed for the synthesis of DNA and influences the production of RBCs?
a. Calcium b. Iron
c. Vitamin A d. Folic acid e. Vitamin D
MCQ
MCQ
Q.2. 1 gm of haemoglobin can combine with?
a. 13.4 ml of oxygen
b. 1.34 ml of oxygen
c. 20 ml of oxygen
d. 2 ml of oxygen
Q.3. The hormone erythropoietin stimulates red blood cell production in the red bone marrow. Where in the body is erythropoietin produced?
a) Spleen b) Kidney c) Liver
d) Thyroid
MCQ
Red Blood Cell = Erythrocyte
Red blood cells (RBC) constitute 99 % of cellular component of blood.
Lacks a nucleus, and contains
hemoglobin—a red, iron-rich protein that binds oxygen.
Function in the transportation of oxygen to
cells and tissues and carbon dioxide from
cells and tissues to the lungs for exchange
with O2
Hematocrit?
Adult males: 42%-54%
Adult women: 38%-46%
RBC Morphology
RBC is a flexible ,
biconcave disc like cell.
Diameter – 7.2 μm (6.9-7.4)
Thickness – 2.5 μm at
periphery & 1 μm at centre
The average volume of
the RBC is 90 – 95 μm3 .
RBC Morphology
Cross section of capillary with red blood cells
Human red blood cells (4,000× magnification).
RBC Morphology
Advantages of biconcave shape –
Flexible capillaries minimum diameter – 3.5 μm.
RBC a “bag” that can be deformed into almost any shape.
Greater surface area
Can withstand changes of osmotic pressure
Allow easy exchange of O2, CO2 & rapid diffusion of other substances.
Spectrin
a contractile protein
maintains shape and flexibility of RBC
Normal counts
Counts are measured as the number of red cells per cubic millimeters (mm3) of blood.
At birth – 6-7 millions/mm3
Adult males – 5-6 millions/mm3
Adult females – 4.5-5.5 millions/mm3
Persons living at high altitudes have greater numbers of RBCs
Heamoglobin conc. of RBC
The whole blood of men contains an average of 15 g of Hb / 100 ml of blood
for women, it contains an average of 14 g / 100 ml
1 gram of hemoglobin can combine with 1.34 ml of oxygen.
Therefore, in a normal man a maximum of about 20 ml of oxygen can be carried in hemoglobin in each 100 ml of blood,
In a normal woman 19 ml of oxygen can be carried.
MCV MCH
MCHC
Erythropoiesis
Erythropoiesis (from Greek 'erythro'
meaning "red" and 'poiesis' meaning "to make") is the process which produces
red blood cells (erythrocytes).
Sites of Erythropoiesis
During intrauterine life
Mesoblastic stage/Intravascular stage (3rd week to 3 months)
Yolk sac (nucleated RBC)
Hepatic stage (after 3 months)
Liver and spleen
Myeloid stage (20th week – till birth)
Bone marrow
Sites of Erythropoiesis
In children
Bone marrow of all bones (till 5 years of age)
Marrow of only long bones (till 20 years of age
In adults (after 20yrs)
Proximal portions of the humeri, femur and tibiae,
Skull
Vertebrae
Ribs
Sternum
pelvis
Membranous bones
Sites of Erythropoiesis
Stages of Erythropoiesis
The blood cells begin their lives in the bone marrow from a single type of cell called the pluripotential hematopoietic stem cell (PHSC).
Hematopoietic stem cells (HSCs) are bone marrow cells that are capable of producing all types of
blood cells.
They differentiate into one or another type of
committed stem cells (progenitor cells). These in turn form the various differentiated types of blood cells.
Stages of Erythropoiesis
Committed stem cell that produces erythrocytes is called Colony-forming unit–erythrocyte, CFU-E
PHSC Pluripotent Hemopoietic stem cell BFU-E Burst Forming Unit Erythrocyte CFU-E Colony Forming Unit Erythrocyte
PROERYTHROBLAST
BASOPHILIC ERYTHROBLAST
POLYCHROMATOPHILIC ERYTHROBLAST ORTHOCHROMATIC ERYTHROBLAST
RETICULOCYTE ERYTHROCYTE ERYTHROCYTE
E R Y T H R O P O I E S I S GM CSF erythro
IL-1,IL-6,IL-3
GM CSF erythro
PHSC Pluripotent Hemopoietic stem cell BFU-E Burst Forming Unit Erythrocyte CFU-E Colony Forming Unit Erythrocyte
PROERYTHROBLAST EARLY NORMOBLAST
INTERMEDIATE NORMOBLAST LATE NORMOBLAST
RETICULOCYTE ERYTHROCYTE ERYTHROCYTE
E R Y T H R O P O I E S I S GM CSF erythro
IL-1,IL-6,IL-3
GM CSF erythro
ERYTHROPOIESIS
15-20µm- basophilic cytoplasm, nucleus with nucleoli.
14-17 µm-mitosis, basophilic
cytoplasm, nucleoli disappears.
10-15µm- ’POLYCHROMASIA’
Hb appears, nucleus condenses.
7-10µm- PYKNOTIC Nucleus.
Extrusion, Hb is maximum.
7.3µm- Reticulum of basophilic material in the cytoplasm.
7.2µm- Mature red cell with Hb.
CELLS/FEATURES SIZE CYTOPLASM NUCLEUS HAEMOGLOB IN
PROERYTHROBLAST 15‐20
μm BASOPHILIC LARGE WITH RETICULAR FORMATION
ABSENT
EARLY 12‐
16μm BASOPHILIC LARGE,NUCLEOLI
DISAPPEARED. ABSENT
INTERMEDIATE 10‐
14μm
POLYCHROM
ATIC CONDENSED APPEARS
LATE 8‐
10μm
ACIDOPHILI C
SMALL
PYKNOTIC INCREASES
RETICULOCYTE 7‐
7.5μm
RETICULUM
LIKE ABSENT INCREASES
Factors Affecting Erythropoiesis
Erythropoietin (EPO): major humoral regulator of erythropoiesis
Interleukins:
IL3, IL6 & IL1
Iron
Vitamin B12 (Cyanocobalamine) + Folic Acid + Vitamin C(Ascorbic Acid)
Intrinsic factor for absorption of B12
Erythropoietin
The principal stimulus for red blood cell is a circulating hormone called erythropoietin.
Glycoprotein MW-34000.
90% formed in endothelial cells of the
peritubular capillaries of the renal tubules.
10% formed in liver, hepatic cells & Kupffer cells.
Stimuli for production of erythropoeitin
hypoxia,
high altitude,
anemia,
chronic lung or heart diseases,
catecholamines,
prostaglandins &
androgens.
Formed in hours, RBC’s take 2-3 days to appear in peripheral blood.
Erythropoietin
Erythropoietin
erythropoietin causes the cells to pass more rapidly through the different erythroblastic stages than they normally do
The rapid production of cells continues as long as the person remains in a low O2 state or until enough RBCs have been produced to carry adequate
amounts of O2 to the tissues.
Vitamin B12, Folic Acid and Intrinsic Factor
important for final maturation of the RBCs are two vitamins, vitamin B12 and folic acid - essential for the synthesis of DNA,
Larger than normal red cells called macrocytes – irregular and oval - their fragility causes them to have a short life.
The parietal cells of the gastric glands secrete a glycoprotein called intrinsic factor, which
combines with vitamin B12 in food and makes the B12 available for absorption by the gut
