BLOOD CELLS AND HEMATOPOESIS

By: Dr. Surekha Aditya Bakle

Constituents of the blood

- Blood consists of :

1- Plasma: fluid part of blood contains proteins and electrolytes.

2- Formed elements: blood cells (erythrocytes, white blood cells, platelets).

Blood is about 8% of the total body weight (5L). It is either arterial blood or venous blood.

FIG. 14.16

Plasma Proteins: 7%-9% of plasma volume.

i- Mainly albumins: account for 60% to 80% of the plasma proteins (produced by the liver).

ii- Globulins:

iiA- Alpha globulin and Beta globulin: transport lipids- and fats- dissolved vitamins.

iiB- Gamma globulins: antibodies produced by lymphocytes (immunity).

iii- Fibrinogen: essential for blood clotting (produced by the liver).

Plasma proteins

FORMED ELEMENTS OF BLOOD

Formed elements : cells and cell fragments (platelets)The cells of blood :• red blood cells

(RBC) • white blood cells

(WBCs, leukocytes).

Formed elements of the blood

• Contain the protein haemoglobin.

• Haemoglobin carries oxygen around the body.

• At the centre of the haemoglobin molecule is an iron atom (heme).

1- Red blood cells (erythrocytes)

Hemoglobin

• Most abundant cells of the blood.

• Do not have a nucleus

• Biconcave discs, 7 m diameter and 2.2 m thick.

FIG. 14.8

Note that, in muscle, myoglobin (Mb) binds oxygen. Mb consists of only 1 protein chain.

Note the 4 protein chains that make up 1 molecule of Hb.

2- Platelets

• Called also Thrombocytes.

• The smallest of the formed elements.

• They play an important role in blood clotting.

3- White blood cells WBC (Leukocytes)

• Protective cells of the body. They contain nuclei, move in amoeboid fashion and they can pass the capillary wall (diapedesis or extravasation).

• They are granular or agranular (non granular).

• Neutrophils are the most abundant type of the granular cells.

Granular Agranular

MOVEMENT OF LEUKOCYTES THROUGH EPITHELIA Protect against infection: phagocytize bacteria; produce proteins

that destroy foreign particles Diapedesis: leukocytes can squeeze between cells and leave the

circulation

Fig. 14.14

Infection

BLOOD SLIDES IN LABORATORY

NEUTROPHILS •60-70% of total leucocytes•9-12 µm in diameter•Multilobe nucleus •Female : drum stick/Barr Body• Granules :•Small spesific granules•Azurophilic granules (Lysosomes)•Tertiary granules (gelatine and cathepsins)

•Function :• Phagocytes

EOSINOPHILS4% of total leucocyte10 - 14 µm in diameterBilobed nucleusMany large spesific granules stained by eosinFunction :• Eliminate antibody-

antigen complexes• Destroy parasitic

worms

BASOPHILS <1% of total leucocyte8-10 µm in diameterS-shape nucleus (irregular lobes) Large spesific granules obscured the nucleusGranules (dark blue) contain heparin & histaminSurface receptor (Ig E receptors)Function :As initiator of inflamatory process

LYMPHOCYTES

20%-25% of total leucocyte 8-10 µm in diameterRound nucleus with slight indented, occupies most of the cellContain few azurophilic granules

MONOCYTES Largest circulating blood cells3-8% ot total leucocyte Large, acentric, kidney- shape nucleusnumerous azurophlic granulesMigrate to the connective tissue MACROPHAGES (phagocytose antigens and as APC)

PLATELETS

250.000-400.000 platelets/mm32 to 4 µm in diameterDisplay peripheral clear region (hyalomere ) and central darker region (granulomere) receptor molecules (glycocalyx) on plasmalemmaFunction : Blood clott

HEMATOPOIESIS Mature blood cells have a relatively

short life span Must be continusly replaced by stem

cells Stem cells produce in HEMATOPOIETIC

ORGAN

1- Hematopoiesis

Blood cells are formed by a process of hematopoiesis.

During embryogenesis the blood cells are formed from stem cells in the liver.

Soon after birth the stem cells migrate to the bone marrow.

Erythropoiesis is the formation of erythrocytes.

Leukopoiesis is the formation of leukocytes.

Bone marrow

Formation of blood cells

PRENATAL HEMOPOIESIS Subdivide into four phases :

Mesoblastic : begin after 2 weeks after conception at yolk sac Mesenchymal cells aggregate into blood islands

Hepatic Begins at 6 weeks until end of gestation Nucleated erythrocyte Appear of leucocyte (8th week)

Splenic Begin at second trimester until end of gestation

Myeloid Begin at the end of second trimester Hemopoiesis at bone marrow

POSTNATAL HEMOPOIESIS Hemopoiesis almost exclusively in

BONE MARROW Stem cells undergo

multiple cells divisions and differentiation

Replace the cells that leave the blood stream, die or destroy

FIG. 14.6

BONE MARROWA gelatinous, vascular connective tissue located in medulary cavity of long bones Responsible for hemopoiesisStructure :

Vascular compartmentExtensive network of

sinusoids , arteries and veins form the

Hemopoietic compartmentIslands of

hematopoietic cells Hemopoietic cells in

various stage of maturation

HEMOPOIETIC GROWTH FACTORS TABLE 10-6 GARTNER COLOUR TEXT HISTOLOGY

Regulated the hemopoiesis Produce by spesific cells Acts on specific stem cells, progenitor

cells, and precursor cells The route to deliver growth factor :

Via blood streamSecrete near the hemopoietic cellsDirect cell-cell contact

Induced rapid mitosis or and differentiation

Most ot them are glycoproteins

HEMATOPOIESIS

FIG. 14.3

ERYTHROPOIESIS Formation of red blood cells Generates 2.5 x 10 11 erythrocytes /day By two types of unipotential progenitor

cellBFU-ECFU-E

Regulate by : erythropoietin

A- Erythropoiesis

This process takes 3 days. 2 days in bone marrow and circulate in the blood in the 3rd day.

Life span of a blood cell is 120 days after which it is removed by the phagocytic cells of spleen, liver and bone marrow.

Erythropoieis = the process of formation of erythrocytes (RBCs). This process occurs in the bone marrow (myeloid tissue).

Bone marrow/myeloid tissue is the red tissue inside bones.

PROERYTHROBLAST

.

NORMOBLAST

.

RETICULOCYTE

ERYTHROCYTE Biconcave-shape diskWithout nuclei and organellesHave soluble enzymes Filled with Hemoglobin (Hb)Average life span of erythrocyte : 120 days

B- LeukopoiesisLeukopoieis = the process of formation of leukocytes (WBCs).

This process occurs in lymphoid tissue (lymph nodes, tonsils, spleen and thymus.)

GRANULOCYTOPOIESIS Formation of the granulocytes

(neuthrophil, eosinophil, and basophilCFU-Eo : eosinophil lineageCFU-Ba : Basophil lineageCFU-GM

CFH-G : Neutrophil line CFU-M : monocyte line

Influence by G-CSF, GM-CSF

GRANULOCYTOPOIESIS

EOSINOPHYL STAB

NEUTROPHYL STAB

BASOPHIL (BONE MARROW)

MONOCYTOPOIESISCFU-GM

CFU-G

PROMONOCYTE

PLATELET FORMATION CFU-Meg, gives rise the Megakaryoblast Megakaryoblast differentiate

Megakaryocytes (single lobulated nucleus)

Megakaryocytes protrude clusters of proplatelets platelets

MEGAKARYOCYTE

LYMPHOPOIESIS CFU-Ly divides form the CFU-LyB and

CFU-LyT CFU-LyB migrate to “bursa-equivalent

location”, divided B lymphocytes CFU-LyT undergo mitosis migrate to the

Thymus T lymphocytes

LYMPHOBLAST

Red blood cells antigens and blood types (ABO system)

Every antigen type is coupled with antibodies secreted by the lymphocytes act against the other antigens.

There are certain molecules on the surface of RBCs. These molecules are called antigens (agglutinogens).

As a part of our body defense system (immune system) some WBCs (lymphocytes) secret proteins called antibodies (agglutinins).

Antibodies can bind to antigens

Destroy RBCs

A blood group has A antigen which is shown as IA and antibodies for B.

Blood group B has B antigen which is shown as IB and antibodies for A.

O has no antigen and is shown as ii. It has antibodies for A and B.

A person with A may hve got gene A from each parent (IA IA ) or A from One parent and O gene from the other (IA i).

A person with group B is (IBIB) or (IBi).

A person with O group has got O gene from each parent (ii).

A person with AB blood group has got A gene from one parent and B gene from the other (IAIB).

GentotypingHere the normal genetic roles of inheritance applies:

Note that A and B aredominants and O is alwaysrecessive.

Genotyping of the blood groups

A O B O

A O A B BO OO

Transfusion reactions

Blood from a donor is usually checked by recipient serum.

A accepts A and O, but makes clot with B.

B accepts B and O, but clots with A.

AB accepts A, B and O and called universal recipient.

O can be given to A, B and AB and called universal donor.

O accepts only from O and clots with A and B because it has antibodies against them.

anti A anti B anti D-

If the donor is A and the recipient is B then agglutination will occur.

Blood typing Rhesus factor

Another group of antigens found on RBCs surface is called Rh factor. People who have this antigen on their RBCs are Rh positive (Rh+). People without Rh antigen are Rh negative (Rh-).

The Rh factor is very important when Rh- mother gives birth to Rh+ babies.

Rh- Mother

Rh+ Baby

RBC

RBC

1st pregnancy

No mixing of blood

Delivery

Bloods mixes

Anti-Rh+

Rh- Mother

Rh+ Baby

RBC

RBC

2nd pregnancy

Mother has antibodiesAgainst baby RBCs

Next pregnancy Anti-Rh+

LEARNING TASKS Expain the composition of the blood! Explain the structure of formed elements of blood! How to differentiate the blood cells from a blood-

smear? Explain the classification and function of leucocyte ! Explain the maturation of lymphocyte! What blood cell would be in abundance during an

active parasitic infection? Explain your answer! Eplain the structure and function of platelets! What blood cell in bone marrow is the earliest

recognizable stage of the red blood cell line? Describe the structure of erythrocyte if lack of this

nutrient: vitamin B12 and iron during the erythrocytopoiesis

THANK YOU