BLOOD II

1. BLOOD II dr. NindyaAryanty, M.Med.Ed

2. White Blood Cells (WBCs) • WBCs have nuclei and other organelles, and lack hemoglobin • 5000 to 10,000 WBCs/mm3. Circulating WBCs represent only a small fraction of the total WBC population • Divided into 2 groups based on their appearance after staining: (1) granular leukocytes, or granulocytes (with abundant stained granules - secretory vesicles and lysosomes)—the neutrophils, eosinophils, and basophils; and (2) agranular leukocytes, or agranulocytes(also contain vesicles and lysosomes; but they are just smaller and difficult to see with the light microscope)—the monocytes and lymphocytes.

3. WBC Circulation and Movement • WBCs circulate for only a short time of their life span. • White blood cells migrate through the loose and dense connective tissues of the body, using the bloodstream to travel from one organ to another and for rapid transportation to areas of infection or injury. • WBCs can detect the chemical signs of damage to surrounding tissues. When problems are detected, these cells leave the bloodstream and enter the damaged area.

5. WBC Circulation and Movement • Circulating WBCs have four characteristics: a. All Can Migrate Out of the Bloodstream • When WBCs in the bloodstream are activated, they contact and adhere to the vessel walls in a process called margination. • After further interaction with endothelial cells, the activated WBCs squeeze between adjacent endothelial cells and enter the surrounding tissue. This process is called emigration, ordiapedesis

7. WBC Circulation and Movement b. All Are Capable of Amoeboid Movement. • Amoeboid movement is a gliding motion made possible by the flow of cytoplasm into slender cellular processes extended in the direction of movement. • The mechanism is not fully understood, but it involves the continuous rearrangement of bonds between actinfilaments in the cytoskeleton, and it requires calcium ions and ATP. • This mobility allows WBCs to move through the endothelial lining and into peripheral tissues.

8. WBC Circulation and Movement c. All Are Attracted to Specific Chemical Stimuli. • This characteristic,called positive chemotaxis,guidesWBCs to invading pathogens, damaged tissues, and other active WBCs. d. Neutrophils, Eosinophils, and Monocytes Are Capable of Phagocytosis • These cells may engulf pathogens, cell debris, or other materials. Neutrophils and eosinophilscalled microphages, to distinguish them from the larger macrophages in connective tissues. • Macrophages are monocytesthat have moved out of the bloodstream and have become actively phagocytic

10. Types of WBCs-Neutrophils (1) Neutrophils • 50 to 70 % of the circulating WBCs are neutrophils the most numerous of WBCs. • The granules of these WBCs are chemically neutral and thus are difficult to stain with either acidic or basic (alkaline) dyes. • Their cytoplasm is packed with pale granules containing lysosomal enzymes and bactericidal (bacteria-killing) compounds. • A mature neutrophil has a very dense, segmented nucleus with two to five lobes = polymorphonuclear

11. Types of WBCs-Neutrophils • Neutrophils are highly mobile, and are generally the first of the WBCs to arrive at the site of an injury. • attacking and digesting bacteria that have been • “marked” with antibodies or with complement proteins—plasmaproteins involved in tissue defenses. • Upon encountering a bacterium, a neutrophil quickly engulfs it, and the metabolic rate of the neutrophil increases dramatically. • This respiratory burst accompanies the production of highly reactive, destructive chemical agents, including hydrogen peroxide and superoxide anions, which can kill bacteria. • Meanwhile, the vesicle containing the engulfed pathogen fuses with lysosomes that contain digestive enzymes and small peptides called defensins. Defensins kill a variety of pathogens, including bacteria, fungi, and enveloped viruses, by combining to form large channels in their plasma membranes. The digestive enzymes then break down the bacterial remains.

12. Types of WBCs-Neutrophils • While actively engaged in attacking bacteria, a neutrophil releases prostaglandins and leukotrienes. • The prostaglandins increase capillary permeability in the affected region, contributing to local inflammation and restricting the spread of injury and infection. • Leukotrienes are hormones that attract other phagocytes and help coordinate the immune response. • Most neutrophils have a short life span, surviving in the bloodstream for only about 10 hours. When actively engulfing debris or pathogens, they may last 30 minutes or less. A neutrophil dies after engulfing one to two dozen bacteria, but its breakdown releases chemicals that attract other neutrophilsto the site. • A mixture of dead neutrophils, cellular debris, and other waste products form the pusassociated with infected wounds.

13. Types of WBCs-Eosinophils • Eosinophils= acidophils granules stain darkly with eosin, a red dye. The granules also stain with other acid dyes. • Represent 2–4 % of the circulating WBCs • Similar in size to neutrophils. • Typically bilobed (two-lobed) nucleus • Eosinophilsattack objects that are coated with antibodies. • Although they will engulf antibody-marked bacteria, protozoa, or cellular debris, their primary mode of attack is the exocytosis of toxic compounds, including nitric oxide and cytotoxic enzymes. • This is particularly effective against multicellular parasites, such as flukes or parasitic roundworms, that are too big to engulf. • The number of circulating eosinophilsincreases dramatically during a parasitic infection. • Eosinophilsincrease in number during allergic reactions as well. • Eosinophilsare also attracted to sites of injury, where they release enzymes that reduce inflammation produced by mast cells and neutrophils. This will control the spread of inflammation to adjacent tissues.

14. Types of WBCs- Basophils • Basophils have numerous granules that stain darkly with basic dyes. In a standard blood smear, the inclusions are deep purple or blue • Basophilsare smaller than neutrophils or eosinophils. They are also relatively rare, accounting for < 1% of the circulating WBC population. • Basophils migrate to injury sites and cross the capillary endothelium to accumulate in the damaged tissues, where they discharge their granules into the interstitial fluids. • The granules contain histamine (which dilates blood vessels), and heparin(a compound that prevents blood clotting). • Stimulated basophils release these chemicals into the interstitial fluids to enhance the local inflammation initiated by mast cells. • Although the same compounds are released by mast cells in damaged connective tissues, mast cells and basophils are distinct populations with separate origins. • Other chemicals released by stimulated basophilsattract eosinophils and other basophils to the area.

15. Types of WBCs-Monocytes • The nucleus of a monocyte is usually kidney-shaped or horseshoe-shaped, and the cytoplasm is bluegray and has a foamy appearance. It nearly twice the diameter of a typical RBC • The cytoplasm’s color and appearance are due to very fine azurophilic granules (azur- blue; -philic loving), which are lysosomes. • An individual monocyte is transported in the bloodstream, remaining in circulation for only about 24 hours before entering peripheral tissues to become a tissue macrophage. • Some become fixed (tissue) macrophages, which means they reside in a particular tissue; examples are alveolar macrophages in the lungs or macrophages in the spleen. Others become wandering macrophages, which roam the tissues and gather at sites of infection or inflammation. • Macrophages are aggressive phagocytes, often attempting to en gulf items as large as or larger than themselves. • While phagocytically active, they release chemicals that attract and stimulate neutrophils, monocytes, and other phagocytic cells. • Active macrophages also secrete substances that draw fibroblasts into the region. The fibroblasts then begin producing scar tissue, which will wall off the injured area.

16. Types of WBCs- Lymphocytes • Lymphocytes are slightly larger than RBCs • Typically have a large, round nucleus surrounded by a thin halo of cytoplasm • Account for 20–30% of the circulating WBC population. • Lymphocytes continuously migrate from the bloodstream, through peripheral tissues, and back to the bloodstream. • Circulating lymphocytes represent only a small fraction of all lymphocytes. At any moment, most of lymphocytes are in other connective tissues and in organs of the lymphatic system.

17. Types of WBCs- Lymphocytes • The circulating blood contains three functional classes of lymphocytes: • T cells are responsible for cell-mediated immunity, a specific defense mechanism against invading foreign cells, and for the coordination of the immune response. T cells either enter peripheral tissues and attack foreign cells directly, or they control the activities of other lymphocytes. • B cells are responsible for humoral immunity, a specific defense mechanism that involves the production of antibodies. These antibodies are distributed by blood, lymph, and interstitial fluid and are capable of attacking foreign antigens throughout the body. Activated B cells differentiate into plasma cells, which are specialized to synthesize and secrete antibodies. Whereas the T cells responsible for cellular immunity must migrate to their targets, the antibodies produced by plasma cells in one location can destroy antigens almost anywhere in the body. • Natural killer (NK) cells are responsible for immune surveillance the detection and subsequent destruction of abnormal cells. NK cells, sometimes known as large granular lymphocytes, are important in preventing cancer.

20. The Differential Count and Changesin WBC Profiles • A variety of conditions, including infection, inflammation, and allergic reactions, cause characteristic changes in circulating populations of WBCs. • A values reported indicate the number of each type of cell in a sample of 100 WBCs : The differential count of the WBC population • Leukopenia >< Leukocytosis • The endings–penia: indicate low numbers • The ending -osis: indicate high numbers

21. WBC Production • Two stem cell: Myeloid stem cell & Lymphatic stem cell • Myeloid stem cell division creates progenitor cells, which give rise to all the formed elements except lymphocytes. • One type of progenitor cell produces daughter cells that mature into RBCs; • A second type produces cells that manufacture platelets. • A third type produces Neutrophils, eosinophils, basophils, and monocytes

22. Granulocytes (basophils, eosinophils, and neutrophils) complete their development in the red bone marrow. • Monocytesbegin their differentiation in the red bone marrow, enter the bloodstream, and complete development when they become free macrophages in peripheral tissues. • Some lymphocytes are derived from lymphoid stem cells that remain in red bone marrow; these lymphocytes differentiate into either B cells or natural killer cells. • Many of the lymphoid stem cells responsible for the production of lymphocytes migrate from the red bone marrow to peripheral lymphatic tissues, includingthe thymus, spleen, and lymph nodesproduceslymphocytes • Lymphoid stem cells migrating to the thymus  mature into T cells.

24. Regulation of WBC Production • Factors that regulate lymphocyte maturation remain incompletely understood. • Until adulthood, hormones produced by the thymus promote the differentiation and maintenance of T cell populations. • In adults, the production of B and T lymphocytes is regulated primarily by exposure to antigens (foreign proteins, cells, or toxins). When antigens appear, lymphocyte production escalates. • Several hormones are involved in the regulation of other WBC populations. The targets of these hormones, called colonystimulating factors (CSFs)

25. Four CSFs: • M-CSFstimulates the production of monocytes. • G-CSF stimulates the production of granulocytes (neutrophils, eosinophils, and basophils). • GM-CSF stimulates the production of both granulocytes and monocytes. • Multi-CSF accelerates the production of granulocytes, monocytes, platelets, and RBCs.

26. Chemical communication between lymphocytes and other WBCs assists the coordination of the immune response. • Active macrophages release chemicals that make lymphocytes more sensitive to antigens and that accelerate the development of specific immunity. In turn, active lymphocytes release multi-CSF and GM-CSF, reinforcing nonspecific defenses

27. Platelet • Platelets appear as spindle-shaped cell fragments. • Platelets are continuously replaced. Each platelet circulates for 9–12 days before being removed by phagocytes, mainly in the spleen. • Each microliter of circulating blood contains 150,000–500,000 platelets. • About one-third of the platelets in the body at any moment are in the spleen and other vascular organs, rather than in the bloodstream. These reserves are mobilized during a circulatory crisis, such as severe bleeding. • Thrombocytopenia: 80,000/µL or less • Thrombocytosis:can exceed 1,000,000/µL. Thrombocytosis usually results from accelerated platelet formation in response to infection, inflammation, or cancer.

28. Platelet Functions • Releasing Chemicals Important to the Clotting Process. By releasing enzymes and other factors at the appropriate times, platelets help initiate and control the clotting process 2. Forming a Temporary Patch in the Walls of Damaged Blood Vessels. Platelets clump together at an injury site, forming a platelet plug, which can slow blood loss while clotting occurs. • Reducing the Size of a Break in the Vessel Wall. Platelets contain filaments of actin and myosin. After a blood clot has formed, platelet filaments contract to shrink the clot and reduce the size of the break in the vessel wall.

30. Platelet Production = Thrombocytopoiesis • Occurs in the red bone marrow. • Normal red bone marrow contains megakaryocytes • During their development and growth, megakaryocytes manufacture structural proteins, enzymes, and membranes. They then begin shedding cytoplasm in small membrane-enclosed packets. • These packets are the platelets that enter the bloodstream. • A mature megakaryocyte gradually loses all of its cytoplasm, producing about 4000 platelets before the nucleus is engulfed by phagocytes and broken down for recycling. • The rate of megakaryocyte activity and platelet formation is influenced by • thrombopoietin(TPO), or thrombocytestimulating factor,(produced in the kidneys) that accelerates platelet formation and stimulates the production of megakaryocytes; • interleukin-6 (IL-6), a hormone that stimulates platelet formation; and • multi-CSF, which stimulates platelet production by promoting the formation and growth of megakaryocytes.