Blood-2 Lesson # 4 (Chapter 19) Objective s: 1- To describe the types of white blood cells and their major functions. 2- To describe the platelets and their functions. 4- To discuss the reaction sequences responsible of blood clotting.
Dec 23, 2015
Blood-2Lesson # 4 (Chapter 19)
Objectives:
1- To describe the types of white blood cells and their major functions.2- To describe the platelets and their functions.4- To discuss the reaction sequences responsible of blood clotting.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Splinter
Phagocytosis4
Chemotaxis3
2
Mast cells
Amoeboid movements
Diapedesis1
Neutrophils
Bacteria
Fromdamaged
tissue
Inflammatorychemicals
Frommastcells
Fromblood
Increasedpermeability
Blood capillaryor venule
WBC Circulation and Movement
Circulating WBCs have four characteristics:
1- Diapedesis or migration: They can migrate out the bloodstream.
2- Amoeboid movements: They move through the endothelium and into peripheral tissues
3- Positive chemotaxis: They are attracted by specific chemicals.
4- Phagocytosis: They have the ability to engulf pathogens, cell debris, and other materials.
General Functions of WBCs or Leukocytes
Functions
1- They protect the body against bacteria, virus, parasites, and cancerous cells.
2- They remove foreign substances such as toxins, and waste
3- They destroy dead, abnormal and worn out cells.
4- They participate in the inflammatory and immune response.
They are complete cells with nucleus and organelles.
1- Granulocytes
2- Agranulocytes
They contains granules, which contain lysosomal enzymes and bactericidal compounds.
They have few or any granules.
Neutrophils Eosinophils Basophils
Monocytes Lymphocytes
Types of White Blood Cells
1- Neutrophils
Functions1- They phagocyte bacteria, which have been market by antibodies and complement proteins.
- Their nucleus has 2 to 5 lobes.
- Granules are chemically neutral.
Neutrophils Bacterial infection
- They form 50% to 70% of the circulating white blood cells (WBC). Normal value: 7,000 to 8,000/mm. 3
Granulocytes
(Neutrophilia)
2- Eosinophils
-They form 2% to 4% of circulating WBC.
- They have bilobulated nucleus.
- Granules are chemically acid (red).
Functions
1- They defend the body against parasites worms and flukes.
Eosinophils Infection by parasites and allergy
Granulocytes
2- They phagocyte bacteria, protozoa and cellular debris.
(Eosinophilia)
-They form less than 1% of circulating WBC.
- Granules are chemically basic (purple to blue).
Function
- Granules contain histamine and heparin.
Vasodilator Anticoagulant
They accumulate in damaged tissues and release chemicals that enhance inflammation.
3- Basophils
Granulocytes
- They are the largest leukocytes.
- They are spherical with a nucleus that is oval or kidney bean shaped.
Functions
2- They release chemicals that attract other WBCs to the injury site.
3- They defend the body against bacteria and viruses.
4- They help activate the lymphocytes.
Agranulocytes
4- Monocytes
1- They stay in the blood for only 24 hours and then they move into the peripheral tissues, where they become macrophages, which are very active and aggressive phagocytes.
- They form 20% to 30% of the circulating WBCs.
- They have large nucleus and do not have granules.
FunctionsThey play a crucial role in the specific immunity.
T cells: (cell-mediated immunity): They destroy virus infected cell, and they coordinate the immune response.
B cells: (humoral immunity): They produce the plasma cells, which produce the antibodies.
NK cells: They detect abnormal or cancerous cells and target them for destruction ( Immune surveillance).
5- Lymphocytes
Agranulocytes
WBC Production (leucopoiesis).
Eosinophilicmyelocyte
Basophilicmyelocyte
Neutrophilicmyelocyte
Immature T-lymphocytes migrate to the thymus to complete their development.
PromonocytePro- erythroblast
Day 1
Mature Red Blood Cell
Megakaryocyte
Platelets
Hemocytoblast
LymphoidStem Cell
Lymphoblast
Myeloid Stem Cell
Progenitor cell
Myeloblast
Monoblast
Hemocytoblast
Myeloid Stem Cell
Lymphoid Stem Cell
Progenitor cell
Myeloblast MonoblastMega-karyocyte
Proerythro-blast
Lymphoblast
Lymphocytes
Erythrocytes Platelets Granulocytes
Monocytes
NeutrophilsEosinophilsBasophils
B lymphocytesT lymphocytesNK lymphocytes
Blood Cell Production
6- Platelets
- They are fragments of megakaryocytes.
- There are only 1/3 of them in the blood stream. The rest of them are in the spleen and other vascular organs.
Functions- They transport enzymes and other chemicals that help to initiate and regulate blood clotting.
- They form a temporary plug in the ruptured blood vessel wall.
- They contract to reduce the size of the hole in the vessel wall.
Megakaryocyte
Platelets
Platelet ProductionProduction of platelets is called thrombopoiesis and takes place in the bone marrow.
Megakaryocytes are gigantic cells (150 mm), visible to the naked eye, with a huge multilobular nucleus and multiple sets of chromosomes.
Platelets
Bloodflow
Proplatelets Endothelium
Sinusoid ofbone marrow
Duplication of DNA several times without cytoplasmic division.
Megakaryocyte
Progenitor cell
Hemostasisa) Vascular Phase
b) Platelet Phasec) Coagulation Phase
It is the most immediate protection against blood loss.
It is produced by:
-Pain receptors (some directly innervate blood vessels to constrict).
- Smooth muscle injury.
- Platelets release serotonin (vasoconstrictor).
It is the prompt constriction of a broken vessel.
a) Vascular Phase:
It provides time for other two clotting pathways.
b) Platelet Phase
Platelets do not adhere to the because the endothelium smooth, and coated with prostacyclin, a platelet repellant.
Broken vessel exposes collagen.
Upon contact with collagen, platelet emit pseudopods that stick to damaged vessel and other platelets - pseudopods contract and draw walls of vessel together forming a platelet plug.
Platelets degranulate releasing a variety of substances that attract more platelets, promote platelet aggregation and produce vasoconstriction.
STIMULUS
Clotting occurs as platelets adhere to site
and release chemicals.
Clotting proceeds; newly forming clot grows.
Break or tear in blood vessel wall.
Released chemicalsattract more platelets, which release more chemicals.
Released chemicalsattract more platelets, which release more chemicals.
Feedback cycle initiated
Feedback cycle ends after clot seals break.
Positive feedback
mechanism
It is the last but the most effective defense against bleeding.
The final goal of coagulation is to transform the fibrinogen (a soluble protein) into fibrin, a sticky protein that adheres to the blood vessels and form a net where blood cells are trapped
Fibrinogen FibrinFibrin
polymer
Prothrombin Thrombin
Fibrinpolymer
c) Coagulation Phase:
Prothrombin Thrombin
Damaged tissue
Platelets
Tissue Factor (factor III)
Factor XII
Extrinsic Pathway Intrinsic Pathway
Ca+2 Ca+2
Inactive Factor X
Prothrombinase
Active Factor X
The activation cascade to factor X is longer.
The activation cascade to factor X is shorter.
Fibrinogen Fibrin
Fibrinpolymer
The Two Mechanisms of Coagulation
The Common Pathway
It is initiated by release of tissue factor (factor III) from damaged tissue.
The activation cascade to factor X is shorter.
Extrinsic Pathway
Intrinsic Pathway
It is initiated by platelets releasing factor XII.
The activation cascade to factor X is longer
Calcium is required for either pathway.In most cases of bleeding, both the extrinsic and intrinsic mechanism work simultaneously.