This document provides information on the differential leukocyte count and components of blood. It describes the types of white blood cells, including their characteristics, functions, and roles in immunity and healing. The key white blood cell types are neutrophils, eosinophils, basophils, monocytes, lymphocytes, and platelets. It also summarizes the process of hemostasis, blood coagulation, and factors involved in clotting and bleeding disorders.

2. DIFFERENTIAL LEUCOCYTE COUNT
TOTAL LEUCOCYTE COUNT
4000 – 11000 per cubic mm of blood

5. Neutrophils
• Neutrophils are also known as polymorphonuclear
leukocytes because the nucleus is multilobed( 1 to 6 lobes
are present)
• Small, fine granules present. Granules appear purple in
colour since it takes both stains equally.
• Diameter is 10-14 microns
• Amoeboid or phagocytic in nature
• Functions are
• Along with monocytes, neutrophils provide the first line
of defence against invading microorganisms
• Neutrophils move by diapedesis towards the site of
infection by means of chemotaxis[attraction by
chemicals released from infected area]
• At the site of infection neutrophils get adhered to
infected tissues and destroy them by phagocytosis.

6. PHAGOCYTOSIS

7. Eosinophil
 Eosinophils have coarse or larger granules in the cytoplasm,
stain pink or red with eosin
 Nucleus is bilobed and spectacle shaped. Rarely trilobed
also
 Diameter 10-14 microns
 Functions
• Eosinophils are weak phagocytes.
• Eosinophils, act against parasitic infections
• Along with mast cells and basophils, they participate in
allergic reactions like asthma.
• They are responsible for detoxification, disintegration
and removal of foreign substances.

8. Basophils
• Basophils also have coarse granules in the cytoplasm and stain
purple blue
• Nucleus is bilobed
• Diameter is 8-10 microns
• Functions are
• They play an important role in healing processes
• They help initiate the inflammatory process at sites of
injury.
• Both mast cells and basophils liberate heparin, histamine,
bradykinin, serotonin.
• The mast cells and basophils play an important role in
some types of allergic reactions [hypersensitivity reaction ]

9. MONOCYTES
• They are the largest of the white blood cells with
diameter of 14-16 microns
• The cytoplasm is clear without granules
• The nucleus is round, oval, horse shoe shaped, bean
shaped or kidney shaped.
• The nucleus is placed either in the centre or pushed to
one side and a large amount of cytoplasm is seen
• Functions:
• They function mainly as phagocytic (engulfing) cells.
They are important in the long-term clean up of
debris in an area of injury.
• They are precursors of tissue macrophages.
• They act by secreting certain substances like
interleukin, colony stimulating factors, platelet
activating factors etc.

10. LYMPHOCYTES
• have large single nuclei that occupy almost whole of
the cells.
• Nucleus is oval or round shaped .
• A rim of cytoplasm may or may not be present.
I. Depending upon the function, lymphocytes are
classified in to two categories;
i. T lymphocytes concerned with cellular
immunity
ii. B lymphocytes concerned with humoral
immunity
II. Depending on the size, the lymphocytes are
divided in to two types;
i. Large lymphocytes are younger cells with a
diameter 10-12 microns
ii. Small lymphocytes are older cells with a
diameter of 7-10 microns

12. PLATELETS (THROMBOCYTES)
• are minute discs 1 to 4 micrometres in diameter.
• The normal concentration of
platelets in the blood is
between 150,000 and 300,000
per microliter
• They do not have nuclei and
cannot reproduce.
• The platelet membrane
contains large amounts of
phospholipids that activate
multiple stages in the blood-
clotting process
• On its surface is a coat of
glycoproteins
• It has a half-life in the blood of
8 to 12 days

13. HEMOSTASIS
• Means prevention of
blood loss or simply
Stoppage of bleeding.
• Whenever a vessel is
severed or ruptured,
haemostasis is achieved
by a series of reactions.
It occurs in three stages:
1. Vascular constriction
2. Formation of a
platelet plug
3. Formation of a
blood clot as a result
of blood coagulation

14. VASOCONSTRICTION
• Immediately after injury, blood vessels constricts and
decreases the loss of blood from the damaged portion
• When the blood vessel is cut, endothelium get
damaged and collagen is exposed.
• The platelets get adhered to this collagen and
activates platelets
• Activated platelets secrete serotonin and other
vasoconstrictor substances
• The adherence of platelets to collagen is accelerated
by von Willebrand factor.

15. FORMATION OF PLATELET PLUG
• The platelets get adhered to the collagen of
ruptured blood vessel and secrete ADP and
Thromboxane A2
• These two substances attract more and more
platelets which aggregate together
• This leads to the formation of a loose temporary
platelet plug, which closes the injured part of the
vessel and prevents further blood loss
• The platelet aggregation is accelerated by platelet
activating factor or PAF

16. Blood Coagulation

17.  Coagulation is the process in which blood loses its fluidity
and becomes a jelly like mass few minutes after it is shed
out or collected in a container.
 It occurs through a series of reactions due to activation of a
group of substances called clotting factors.
 Proenzymes must be activated in to enzymes which is
carried out by enzyme cascade reactions.
 Enzyme cascade refers to process that occurs through a
series of steps, each step initiating the next, until final step
is reached.
 The clotting factors are;

19. THE CLOTTING MECHANISM
STEP I
STEP II
STEP III

20. Three essential steps:
1. Formation of prothrombin activator: In
response to rupture of the vessel or damage
to the blood itself, prothrombin activator is
formed by a complex cascade of chemical
reactions occurs in the blood involving blood
coagulation factors .
2. Conversion of prothrombin into thrombin: It is
catalysed by the prothrombin activator
3. Conversion of fibrinogen to fibrin: The
thrombin acts as an enzyme to convert
fibrinogen into fibrin fibers that enmesh
platelets, blood cells, and plasma to form the
clot.

21. STAGE 1: FORMATION OF PROTHROMBIN
ACTIVATOR:
Prothrombin activator is generally considered to be
formed in two ways,
(1) by the extrinsic pathway that begins with trauma
to the vascular wall and surrounding tissues and
initiated by clotting factors released in damaged
vessels (tissue factor or thromboplastin) and
perivascular tissues - 15 seconds
(2) by the intrinsic pathway that begins in the blood
itself. uses only clotting factors found inside the
blood itself (plasma, platelets) 3- 6 seconds

22. INTRINSIC PATHWAY

23. INTRINSIC PATHWAY
 In this, the formation of prothrombin activator is initiated by
platelets within the blood itself
 Sequence of events in intrinsic pathway:
 During the injury, the blood vessel is ruptured. The
endothelium is damaged and collagen beneath the
endothelium is exposed.
 When platelets comes in contact with collagen of
damaged blood vessel, it gets activated and release
phospholipids.
 Now factor XII comes in contact with collagen, and is
converted to its activated form XIIa in the presence of
kallikrein and high molecular weight kinogen.
 The activated factor XIIa converts factor XI in to activated
XIa in the presence of kinogen
 The activated factor XIa converts factor IX in the presence
of factor IV(calcium) to its activated form IXa.

24.  Activated factor IXa activates factor X in the presence of
factor VIII and calcium to activated factor Xa
 Now the activated factor Xa reacts with platelet
phospholipid and factor V to form prothrombin
activator. This need the presence of calcium ions.
 Factor V is also activated by positive feedback effect of
thrombin.

25. EXTRINSIC PATHWAY

26. EXTRINSIC PATHWAY
 In this, the formation of prothrombin activator is initiated
by the tissue thromboplastin which is formed from the
injured tissues
 Sequence of events in extrinsic pathway are as follows:
i. The damaged tissues release factor III i.e. tissue
thromboplastin. The tissue thromboplastin contains
proteins, phospholipids and glycoprotein, which act
as proteolytic enzymes.
ii. The glycoprotein and phospholipid components of
thromboplastin converts factor X in to activated
factor Xa, in the presence of factor VII
iii. The activated Xa reacts with factor V and phospholipid
component of tissue thromboplastin to form
prothrombin activator. This reaction requires the
presence of calcium ions

27. STAGE 2: CONVERSION OF PROTHROMBIN IN TO THROMBIN
i. Prothrombin activator that is formed in the intrinsic
and extrinsic pathways convert prothrombin in to
thrombin in the presence of calcium ions.
ii. Once formed, thrombin initiates the formation of
more thrombin molecules. The initially formed
thrombin activates factor V. Factor V in turn
accelerates formation of both extrinsic and intrinsic
prothrombin activator which converts prothrombin
to thrombin

28. STAGE 3: CONVERSION OF FIBRINOGEN IN TO FIBRIN
 The final stage of blood clotting involves the conversion of
fibrinogen in to fibrin by thrombin
 Sequence of events are
i. Thrombin convert fibrinogen in to activated
fibrinogen called fibrin monomer
ii. Fibrin monomer polymerizes with other monomer
molecules and form loosely arranged strands of fibrin
iii. Later these loose strands are modified in to dense
and tight fibrin threads by fibrin stabilizing factor i.e.
factor XIII in the presence of calcium ions. All the
tight fibrin threads are aggregated to form a
meshwork of stable clot.

29. ANTICOAGULANTS
• Dicoumarol and coumadin block the activity of vitamin K,
which is necessary for synthesis of many of the clotting
factors by the liver.
• Heparin activates a plasma protein called antithrombin III,
which, in turn, inactivates thrombin and several of the other
clotting factors.
• Because calcium is an important clotting cofactor, calcium
chelators such as EDTA, oxalate, and citrate are used to
prevent stored blood from clotting.
• Various thrombolytic agents like tissue plasminogen
activator (tPA) are also available that promote dissolution of
the fibrin clot after it is formed. These agents promote the
formation of plasmin from plasminogen that enzymatically
attacks the clot, turning it into soluble peptides.

30. BLEEDING DISORDERS
HEMOPHILIA
• Sex linked inherited blood disorder
• Cause is lack of prothrombin activator due to deficiency of
clotting factors either factor VIII, IX, or XI .
• Based on it, classified into three types;
1. Hemophilia A or classic hemophilia due to deficiency of
factor VIII
2. Hemophilia B or Christmas disease due to deficiency of
factor IX
3. Hemophilia C due to deficiency of factor XI
• Characterized by prolonged clotting time; so even a mild trauma
like tooth extraction or bruising due to falls may result in excess
bleeding which can lead to death
• Males are affected ;females are carriers

31. PURPURA
Disorders characterized by prolonged bleeding time
Result in spontaneous bleeding under the skin from ruptured
capillaries
Thus causes appearance of small tiny haemorrhagic spots called
purpuric spot.
Classified into different types ;
1. Thrombocytopenic purpura (due to deficiency of platelets),
2. Thrombasthenic purpura (due to structural or functional
abnormality of platelets)
3. Idiopathic thrombocytopenic purpura.

32. Bleeding time
• The time interval from oozing of blood after a cut or
injury till arrest of bleeding
• Determined by duke’s method using bloating paper or
filter paper
• Normal duration is 3-6 minutes
• It is prolonged in purpura
TESTS FOR CLOTTING
Clotting time
• The time interval from oozing of blood after a cut or
injury till the formation of clot
• Determined by capillary tube method
• Normal duration is 3-8 minutes
• It is prolonged in hemophilia

33. Prothrombin Time / PTT
• The time taken by blood to clot after adding tissue
thromboplastin to it.
• It indicates the total quantity of prothrombin present in the
blood
• Normal duration is about 12 seconds
• It is normal in haemophilia. It is prolonged in deficiency or
prothrombin and other clotting factors like I,V,VII & X

34. EDEMA
• Swelling caused by excessive accumulation of fluid in tissues.
• Types of edema:
1. Intracellular edema
• is the accumulation of fluid inside the cell.
• It occurs due to malnutrition, poor metabolism or
inflammation of tissues.
2. Extracellular edema
• is the accumulation of fluid outside the cell.
• It occurs because of abnormal leakage of fluid from
capillaries in to interstitial space and obstruction of
lymphatics.
• It occurs in conditions like heart failure, renal disease,
decreased amount of plasma proteins, lymphatic
obstruction, increased endothelial permeability.

35.  Extracellular oedema can be of two types: Pitting and non-
pitting oedema
 Pitting edema
• In this type of edema, when the edemated area is pressed
with the finger, the displacement of fluid occurs producing a
depression or pit. The pit is disappeared after removal of
finger when the fluid flows back to the area.
• It occurs when the interstitial fluid volume increases. When
the volume increases, the semisolid nature of interstitial fluid
becomes more fluid type and flow freely in to tissue spaces.
 Non pitting edema
• In this type of edema, edemated area is hard and a pit is not
formed by pressing.
• Edema develops due to either swelling of the cells or clotting
of interstitial fluid in the presence of fibrinogen.