Blood-2 Lesson # 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 Phagocytosis 4 Chemotaxis 3 2 Mast cells Amoeboid movements Diapedesis 1 Neutrophils Bacteria From damaged tissue Inflammatory chemicals From mast cells From blood Increased permeability Blood capillary or 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 Functions 1- They phagocyte bacteria, which have been market by antibodies and complement proteins. - Their nucleus has 2 to 5 lobes. - Granules are chemically neutral. NeutrophilsBacterial 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. EosinophilsInfection 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. VasodilatorAnticoagulant 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. Functions They 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). Eosinophilic myelocyte Basophilic myelocyte Neutrophilic myelocyte Immature T-lymphocytes migrate to the thymus to complete their development. Promonocyte Pro- erythroblast Day 1 Mature Red Blood Cell Megakaryocyte Platelets Hemocytoblast Lymphoid Stem Cell Lymphoblast Myeloid Stem Cell Progenitor cell Myeloblast Monoblast

Hemocytoblast Myeloid Stem Cell Lymphoid Stem Cell Progenitor cell Myeloblast Monoblast Mega- karyocyte Proerythro- blast Lymphoblast Lymphocytes Erythrocytes Platelets Granulocyte s Monocytes Neutrophils Eosinophils Basophils B lymphocytes T lymphocytes NK 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 Production Production 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 of bone marrow Duplication of DNA several times without cytoplasmic division. Megakaryocyte Progenitor cell

Hemostasis a) Vascular Phase b) Platelet Phase c) 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 chemicals attract more platelets, which release more chemicals. Released chemicals attract 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 Fibrin polymer Fibrin polymer c) Coagulation Phase:

Damaged tissue Platelets Factor XII Extrinsic PathwayIntrinsic Pathway Ca +2 The activation cascade to factor X is longer. The activation cascade to factor X is shorter. Fibrin polymer 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.