Lymphocytes

Agranulocyte 20-45% of WBCsSpherical, dark-staining

nucleusThin rim of blue staining

cytoplasmEach lymphocyte

recognizes and acts against a specific antigen

Lymphocytes

T lymphocytes can attack foreign cells directly

(17.6)

Lymphocytes B lymphocytes transform into plasma cells and

secrete antibodies

Hemostasis means prevention of blood loss and this achieved by:

1. Vascular constriction2. Formation of a platelet plug3. Formation of blood clot4. Growth of fibrous tissue into the blood clot

Hemostasis

After blood vessel has been cut, the smooth muscle wall contract; this immediately reduces the flow of blood from the ruptured vessel

Vascular Constriction

Platelets or thrombocytesFormed in the bone marrow from

megakaryocytes Do not have nuclei Function in the clotting process.Normal value – 150,000 to 300,000/cubic

millimeter.It has a half life in the blood of 8 – 12 days, its

functional process run out over several weeks

Formation of platelet plug

Formed by fragmentation from megakaryoctyes

1. Contractile protein thrombosthenin that can cause the platelet to contract

2. Endoplasmic reticulum that store Calcium ions

3. Mitochondria capable of forming ATP4. Enzymes that can synthesize prostaglandins

which involves in local tissue reactions5. Contain fibrin stabilizing factor6. Growth factors that causes vascular cells to

grow and multiply

Platelet functional characteristics

Platelet begin to swell and assume irregular forms when comes in contact with collagen fibers

They become sticky so that they adhere to collagen in the tissue

They secrete ADP and form thromboxane which activate nearby platelets

The damaged vascular wall activates increasing numbers of platelets thus forming platelet plug. (In small vessels the platelet plug is all that is necessary to stop the bleeding).

Mechanism of platelet plug

Platelet Plug Formation

1. Exposed collagen binds and activate platelets

2. Release of platelet factors

3. Attract more platelets

4. Aggregate into platelet plug

Blood coagulation take place in three steps 1. As result of rupture blood vessels, formation of

prothrombin activator (protein manufacture in the liver)

2. Conversion of prothrombin to thrombin in the presence of calcium

3. The thrombin acts as enzyme to convert fibrinogen (blood protein) into fibrin fibers that enmesh platelet, blood cells and plasma to form clot

Note: vitamin K is required by liver for formation of prothrombin

Blood coagulation in the ruptured vessel

ProthrombinProthrombin CaActivator

Thrombin

Fibrinogen Fibrinogen monomer

CaFibrin fibers

Activated fibrinStabilizing factor

Cross linked fibrin fibers

Blood Coagulation

SEM of a clot with platelet, fibrin mesh, rbc’s

The clot composed of meshwork of fibrin fibers entrapping blood cells, platelets and plasma

Overview of Hemostasis: Clot Formation & Vessel Repair

Prothrombin activator is generally formed in two ways

1. Extrinsic pathway (begins with trauma to the vascular wall)

2. Intrinsic pathway (begin with the blood)

Initiation of coagulation

Pathways for initiating clotting

Preventing blood clotting in vascular system is

1. Smoothness of the endothelial cell surface2. Layer of glycocalyx on the endothelium3. Protein bound with the endothelial

membrane thrombomodulin which binds thrombin

Prevention of blood clotting in the vascular system

The most important anticoagulant in the blood1. Fibrin fibers2. Antithrombin III or antithrombin-heparin

cofactor Both fibrin fibers and antithrombin acts as

antithrombin About 85-90% of thrombin becomes adsorbed

to the fibrin fibers The thrombin that does not adsorb combines

with antithrombin III which block the effect of thrombin

Antithrombin action of fibrin and antithrombin III

Heparin is anticoagulant, low concentration in the blood

Effectiveness of antithrombin III increases when it combines with heparin

Heparin is formed by basophilic and mast cell

Heparin

Plasma protein contain euglobulin called plasminogen when activated becomes plasmin

Plasmin resemble trypsinPlasmin digest fibrin fibers and other protein

coagulantsPlasmin caused lysis of a clot

Fibrinolysis of blood clot - plasmin

Injured tissue release activator called tissue plasminogen activator (t-PA) which convert plasminogen to plasmin

Activation of plasminogen

Dissolving the clot

Red blood cells White blood cells Platelets

1 Site of formation

formed in bone marrow, life-span: 4 months

formed in bone marrow or thymus

formed in blood marrow

2 Shape biconcave discs,no nucleus,red colour

phagocytes: irregular, lobed nucleus & granular cytoplasm

irregular shape,no nucleus,tiny pieces of cell fragments,

A comparison of RBCs, WBCs and Platelets

Red blood cells White blood cells Platelets

3 Size small in size some large & some small

tiny cell fragments

4 Number 5,000,000 /mm3 7,000 /mm3 250,000/mm3

5 Function

contain haemoglobin to carry oxygen from lungs to all parts of body

phagocytes kill pathogens & digest dead cellslymphocytes produce antibodies for killing pathogens

for blood clotting

A comparison of RBCs, WBCs and Platelets

AlbuminHelps control osmotic pressureHelps control diffusion of water

Globulin Includes antibodies (Abs)Transport proteins (lipids, iron, copper, etc.)

Fibrinogen Involved in clotting

Plasma proteins

All the albumin and fibrinogen and 50 – 80% of globulin are formed in the liver

The reminder of the globulin are formed in the lymphoid tissues

Formation of the plasma proteins

Normal values

Total protein: 4.2 - 5.6 g/dlAlbumin: 2.3 - 3.5 g/dlGlobulin: 1.9 – 2.1 g/dl

66 kDa

ALBUMIN

·Accounts for ~50% of the total plasma protein and ~ 50% of the total liver protein production

Half-life ~ 20 days

Highly polar

At pH 7.4 it is anionic with 20 negative charges per molecule

Regulation of colloidal pressure

Functions of albumin

Maintenance of the osmotic pressure of plasmaTransport of free fatty acids

ALBUMIN

GlobulinGlobulin is made up of different proteins called alpha, beta, and gamma types.

Some globulins are made by the liver, while others are made by the immune system.

Other globulins transport metals, such as iron, in the blood and help fight infection.