HAEMATOLOGY AND BLOOD TRANSFUSION

HAEMATOLOGY ANDBLOOD 
TRANSFUSION


BLOOD DONATION 

DEFINITION OF TERMS

ØHematology is the study of morphology and physiology of blood. OR

ØIs the branch of medical science which deal with blood and blood  disorder

ØBlood refers to Specialized fluid tissue circulating through vascular channels which carries compounds to all cells and receives waste products of metabolism for transport to organs of excretion.

ØBlood plasma is the liquid components of ant-coagulated blood that normally holds the blood cell.

ØSerum blood is the liquid component of coagulated blood (without anticoagulant)

•Or is the liquid component that is neither contains  blood cells (RBC, WBC) nor clotting factors 

ØBlood transfusion: The transfer of blood together with blood components from one person (the donor) into the blood stream of another person (the recipient).

ØBlood donation is a process by which a blood donor voluntarily has blood drawn for storage in a blood bank for subsequent use in a blood transfusion.

FUNCTIONS OF BLOOD

i.Supply nutrients to cells & tissues such as amino acids, fatty acids and glucose.

ii.Supply of oxygen to & removal of CO2 from tissues & cells

iii.Remove breakdown products, taking them to excretory organs

iv.Transport surplus metabolites to storage organs

v.It has platelets which helps the blood to clot (coagulate) during bleeding.

vii.  Contain body's defenses against foreign substances & pathogenic organisms (WBC)

     

   COMPOSITION OF BLOOD

•Blood consists of;

1. Plasma

2. Blood cells; consists of

    i.Thrombocytes (Platelets)

    ii.Erythrocytes(RBC)

    iii.Leukocytes(WBC)

Plasma; aqueous solution of

•Proteins (albumin, fibrinogen, globulins) & blood

sugar

•Inorganic substances, Na, K, Ca, Mg ions, which

maintain chemico-physical properties of blood.

Bicarbonate & phosphate ions buffer extreme high

or low pH

•Final pH of blood is 7.4

BLOOD CELLS

•Blood is fluid connective tissue having cells (35

55% of blood) and extracellular fluid intravascular

(blood plasma) (45-65% of blood)

•Total amount of blood in man is 5 L (7‑8% body

weight)

•Blood cells are;

•1. Red blood cells or erythrocytes

•2. White blood cells or leukocytes

•3. Platelets or thrombocytes.

LEUKOCYTES (WBC)

vLeukocytes also known as WBC are cells of the

immune system  that are involved in protecting the body

against both infectious and foreign invaders.

vAll white blood cells are produced and derived from

bone marrow.

vAll white blood cells have nucleus which distinguishes

them from the other  cells (anucleated  (RBCs) and 

thrombocytes

CLASSIFICATION OF WBC

There are five types of WBC classified as ;

vWBC can be classified based on the presence or

absence of cytoplasmic granules, which are

1.Granular leukocytes

Non granular (Agranular )leukocytes

vGranular leukocytes are also classified based on

three types which are;

i. Neutrophilic

ii. Eosinophilic, &

iii.Basophilic granulocytes

vNon-granular leukocytes comprise of

i. Monocytes and

ii. Lymphocytes

vLeukocytes are also divided on basis of shape of

nucleus as

•1. mononuclear (leukocyte with non-lobed nucleus)

•2. polymorphonuclear (leukocyte with multi-lobed

nucleus) leukocytes

•The main functions of white blood cells is to defend the

body against foreign substances & pathogenic organisms

•The number of leukocytes in the BLOOD is often an

indicator of infection or diseases and thus the WBC

count is an important subset of the complete blood

count.  The normal white cell count usually range 

between 4 and 11 × 109/L.

•3: Human blood: Nucleus of the neutrophil (a) has not

constricted into distinct lobes. Neutrophils with

more or\less band‑form of nucleus are called band

neutrophils and are more immature than the lobed or

segmented neutrophils.. Blood platelets (b) and a small

lymphocyte (c). 

•Human blood: Blood smear showing erythrocytes,

platelets and large lymphocycte. 

PLATELETS

•Platelets are the cells that circulate within our blood

and bind together when they recognize damaged blood

vessels,”

•“When you get a cut, for example, the platelets bind to

the site of the damaged vessel, thereby causing a blood

clot. There’s an evolutionary reason why they’re there.

It’s to stop us from bleeding.”

•Platelets, the smallest of our blood cells, can only be

seen under a microscope. 

•They’re literally shaped like small plates in their non

active form. A blood vessel will send out a signal when it

becomes damaged. When platelets receive that signal,

they’ll respond by traveling to the area and transforming

into their “active” formation. To make contact with the

broken blood vessel, platelets grow long tentacles and

then resemble a spider or an octopus.

•A normal platelet count ranges from 150,000 to

450,000 platelets per microliter of blood. Having more

than 450,000 platelets is a condition

called thrombocytosis; having less than 150,000 is

known as thrombocytopenia. You get your platelet

number from a routine blood test called a complete

blood count (CBC).

•The medical term for having too many platelets is

thrombocytosis, and there are two types:

•Primary or essential thrombocytosis – Abnormal cells

in the bone marrow cause an increase in platelets, but

the reason is unknown

•Secondary thrombocytosis – The same condition as

primary thrombocytosis, but may be caused by an

ongoing condition cancer, inflammation, or infection.

•When you don’t have enough platelets, it’s called

thrombocytopenia.

•Symptoms include easy bruising, and frequent bleeding

from the gums, nose.

•Your platelet count drops when something is preventing

your body from producing platelets. There are a wide

range of causes, including:

•Medications

•An inherited condition

•Certain types of cancer, such as leukemia or lymphoma

•Chemotherapy treatment for cancer

•Kidney infection or dysfunction

•Too much alcohol

Platelets are involved in the clotting (coagulation of

blood). When we bleed the platelets clump together to

form a clot.

Platelets have been observed to play a role in coagulation

like in ;

•Maintain haemostasis

•Provide platelet phospholipid (platelet factor 3), carry

coagulation factors on their surfaces.

RED BLOOD CELLS

•Red blood cells (RBC) constitute 99 % of blood cells

•They are the smallest cells in the mammalian body

•A total red blood count is approximately 5.00 x 1012 / L

•Erythrocyte    (Red blood cell) normal range adult ;

ümale 4.6 – 6.5 x 1012 per litre,

üfemale 3.9 – 5.6 x 1012 per litre and

üchildren 3.2 – 5.3 1012 per litre

•They function in the transportation of oxygen to cells

and tissues and carbon dioxide from cells and tissues to

the lungs for exchange with O2

•Normal  morphology of red  blood cell

•Normal red blood cell  have the following features:

•Shape : round , biconcave disc

•Diameter : 6.7-7.7µm (average 7.2 µm) 

•Thickness : 1.7  -2.4 µm   (average  2.1 µm)

•The life span of red blood cells has a range of 100 to

120 days

•The cytoplasm of erythrocytes is rich in hb an iron

containing molecule that can bind oxygen and is

responsible for the red color of the cells.

•Hemoglobin Is the oxygen carrying pigment of the

erythrocytes, formed by developing erythrocyte in the

bone marrow.

•Haem is attached to each polypeptide chain ,and it is

this party of the molecule which is principal responsible

for its oxygen carrying capacity.

•If the ferrous (Fe2)  ion of  haem is oxidised to the ferric

(Fe3 ) form , then the oxygen carrying capacity of the

haemoglobin is lost

•Haemoglobin pigments

•In the circulation haemoglobin normally takes the form

of oxyhaemoglobin

•Certain other forms can be produced if haemoglobin is

acted upon by other chemicals .eg Carboxyhaemoglobin,

methaemoglobin

FORMS OF HEMOGLOBIN

1. Carboxyhaemoglobin  (Hb CO)

•Carbon monoxide  has an affinity  for haemoglobin

many times greater than  that of oxygen. Therefore , even

in low concentration carbon monoxide will rapidly bind

to haemoglobin to form carboxyhaemoglobin.

• It is found in high concentration in case of carbon

monoxide poisoning, because these compound can not

carry oxygen may leads to hypoxic death. It is also found

in lower concentration in people who smock tobacco

2. Methaemoglobin 

•Methaemoglobin is formed when  the ferrous iron of

haemoglobin is oxidised to ferric form. High levels of

methaemoglobin can be found in individual who are

being treated    with sulphonamide which may cause

oxidation of haemoglobin.

•Methaemoglobin  is an inert pigment and does  not

carry oxygen

•Methaemoglobin can also occur as a result of an

inherited abnormality  of the haemoglobin molecule

•The iron ion may be either in the Fe2+ or in the

Fe3+ state, but ferrihemoglobin (methemoglobin) (Fe3+)

cannot bind oxygen.

•In binding, oxygen temporarily and reversibly oxidizes

(Fe2+) to (Fe3+) while oxygen temporarily turns into the

superoxide ion, thus iron must exist in the +2 oxidation

state to bind oxygen. If superoxide ion associated to

Fe3+ is protonated, the hemoglobin iron will remain

oxidized and incapable of binding oxygen. In such cases,

the enzyme methemoglobin reductase will be able to

eventually reactivate methemoglobin by reducing the

iron center.

vErythropoiesis

•Is the development process by which new erythrocytes

are produced. Through this process erythrocytes are

continuously produced in the bone marrow, at a rate of

about 2 million per second in a healthy adult

•During the early stages of life, erythrocytes are

produced first by the yolk sac and then by the developing

spleen during the third month of gestation, until the bone

marrow is formed in the seventh month and takes over

erythrocyte production exclusively.

REGULATION OF ERYTHROPOIESIS

•Thinking logically you might suspect that because the

primary function of erythrocytes is to transport O2 in the

blood, the primary  stimulus  for erythrocyte production

is low O2 levels. You would be correct, but low O2

levels do not stimulate erythropoiesis directly on the

bone marrow.

•Instead, it stimulates the kidneys to secrete

the hormone erythropoietin into the blood, and

this hormone in a domino effect stimulates the bone

marrow to produce erythrocytes

•Erythropoietin acts on derivatives of

undifferentiated cells that have already been committed

to becoming red blood cells (RBC’s), stimulating the

proliferation and maturation of these cells into mature

RBCs.

•This increase in erythropoietin activity elevates the

number of circulating RBCs, thereby raising the O2

carrying capacity of the blood and restoring the delivery

of O2 to the body tissue to normal.

•Once the O2 level in the tissues of the kidneys is

brought back to normal, erythropoietin secretion is

turned down until it is needed again. This is an example

of a negative feedback mechanism.

Erythrocyte properties

•Red blood cells or erythrocytes contain haemoglobin

(Hb)

•Hb gives the red colour of blood

•On centrifugation erythrocytes are heavier and settle to

the bottom to form a packed cell pellet, white blood cells

form a layer (buffy coat) on top of the red blood cell

pack, platelets are settled on top of the white blood cells

•Erythrocytes are circular biconcave discs in most

mammals

•Mammalian erythrocytes have no nuclei (anucleate).

•RBC life span 120 days only, short because of the lack

of nuclei

•RBC has Hb;

 (1) globin, a protein and

(2) iron containing heme pigment

•Blood volume is 6–8 % of body weight, % of blood

volume occupied by RBC is called hematocrit or packed

cell volume (PCV)

•PCV depends on number & size of cells and plasma

volume

FUNCTIONS OF RBC

vPrimary function of erythrocytes is to carry Hb, Hb

carries oxygen by being oxidized to O2―Hb (oxy

haemoglobin) then transports O2 to cells, Hb has high

affinity for O2

vHemoglobin is involved in the transport of other gases,

it carries some of the body's respiratory carbon

dioxide as carbaminohemoglobin, in which CO2 is

bound to the globin protein

Common disorders of red blood cell

•The following is the abnormal morphology of the red

blood cell

1. Anisocytosis is the variation of the size of the red

blood cell (microcytic , macrocytic)

• microcytic means the cell is smaller  than normal  

• macrocytic is larger than normal  cell.

2. Polychromasia is the variation of colour in stained

red blood cells

•Hypochromasia is the low colour stained to red blood

cells (large central pallor)

3. Poikilocytosis is the variation of red blood cells in

shape

•Sickle cells is the red blood cells with a sickle shaped

shape.