Histological Structure of Blood Cells Part II PDF

# Histological structure of blood cells part II ## Dr. AMAL ABD EL-HAFEZ ## Associate Professor of HIStopatHOLOGY ## Learning objectives By the end of this lecture, you will be able to: 1. Classify granulocytes and non-granulocytes. 2. Define leukemia. 3. Describe the structure of each granulocy...

# Histological structure of blood cells part II ## Dr. AMAL ABD EL-HAFEZ ## Associate Professor of HIStopatHOLOGY ## Learning objectives By the end of this lecture, you will be able to: 1. Classify granulocytes and non-granulocytes. 2. Define leukemia. 3. Describe the structure of each granulocyte and non-granulocyte. 4. Correlate the function of each granulocyte and non-granulocyte with their structure. 5. Describe the structure of the platelets & its function. # Leukocytes [white blood cells (WBCs)] ## A - Granular leukocytes = Polymorphnuclear leukocytes ## B - Non-granular leukocytes = Agranulocytes = mononuclear leukocytes | Cell Type | Percentage | Nucleus Description | Other Features | | -------------------- | ----------- | -------------------------------------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------- | | Neutrophil | 60-79% | 2-5 lobed | Very fine granules | | Eosinophil | 2-4% | bi-lobed | Pink granules | | Basophil | 0.5-1% | S-shaped | Dark blue granules | | Lymphocyte | 20-30% | Round | B-cells; T-cells | | Monocyte | 3-8% | Indented, oval | Largest leukocytes | # 1 - Neutrophils * Type of granular leukocytes containing segmented nuclei [2-5 lobes] & fine granules. * Size: 12-15 micrometer. * Development: In bone marrow from myeloblast. * Life span: 6 hours-4 days. * Removal: Die by apoptosis. * Count: 60-75% [or more] of circulating leukocytes. * Barr body: inactive X chromosome appears as a drumstick in female cells and not in normal males. ## Neutrophil Granules and Functions Neutrophil cytoplasm contains two types of granules: 1. **Small specific granules**: contains e.g. Collagenase & lysozyme =stain pink= Matrix breakdown & antimicrobial. 2. **Larger, azurophilic granules**: Are lysosomes e.g. myeloperoxidase= stain purple= phagocytosis. ## Functions: Kill bacteria through 2 mechanisms:- 1. **Oxidative mechanism (respiratory burst)**: depends on the generation of hydrogen peroxide via NADPH oxidative enzyme and its conversion to hypochlorous acid through myeloperoxidase. 2. **Nonoxidative mechanism** # Disorders of neutrophils * **Neutrophilia**: an increase in the neutrophil number as in acute bacterial infection e.g. tonsilitis, appendicitis. * **Neutropenia**: a decrease in the neutrophil number. It may be drug-induced, autoimmune, AIDS. * **Myeloperoxidase deficiency**: is caused by a defect in the NADPH oxidase/myeloperoxidase complex system leading to inefficient oxidative mechanism of neutrophils. Affected persons have prolonged # 2 - Eosinophils * Type of granular leukocytes containing bi-lobed nuclei& large eosinophilic granules. * Size: 12-15 micrometer. * Development: In bone marrow from myeloblast. * Count: 2-4% of leukocytes. * Granules: large, elongated, refractile specific granules stained by eosin. * Granule content: major basic protein [MBP]. ## Functions: * Killing of parasitic worms such as Schistosoma [Bilharzia]. * Participate in allergic reactions. # Disorders of Eosinophils * **Eosinophilia**: an increase in the circulating number. * Causes: 1. **Parasitic infection** e.g. bilharziasis 2. **Allergic reactions** e.g. asthma, and hay fever. # 3 - Basophils * Type of granular leukocytes containing irregular bi-lobed nuclei & large basophilic granules. * Size: 12-15 micrometer. * Development: In bone marrow from myeloblast. * Count: 0.5-1% of leukocytes. * Granules: Irregular size, specific granules, metachromatically with toulidin blue or Geimsa. * Granule contents: Histamine, Major basic protein. ## Functions: supplement the functions of mast cells in: * **immediate hypersensitivity reactions** [anaphylaxis]. * Little role in reaction to parasites # Disorders of Basophils * **Basophilia**: an increase in the basophil count. * Causes: 1. **Allergic reactions** e.g hay fever, asthma, urticaria 2. **Viral infections** e.g. smallpox and chickenpox 3. **Parasitic infections** # Lymphocytes * Type of non-granular leukocytes having spherical shape, dark round nuclei, condensed chromatin, thin rim of light blue cytoplasm. * Size: 6-8 micrometer [may reach 18 micrometer]. * Count: 20-30% of leukocytes. * Staining: Immunohistochemistry. * Life span: few days to many years. ## B-lymphocytes: * Give antibody-producing plasma cells =Humoral immunity. ## T-lymphocytes: * Control the activity of other leukocytes (T-helper cells and suppressor cells), * Killing of virus-infected cells, and cancer cells [cytotoxic cells]. # Lymphocytosis * An increase in the lymphocyte count as in infectious mononucleosis, a viral infection caused by Epstein-Barr virus. # Monocytes * Type of non-granular leukocytes having oval, indented or horseshoe shaped nuclei and blue-gray [frosted glass] cytoplasm. * Size: 12-20 micrometer [largest WBC]. * Count: 3-8% of leukocytes. * EM: Golgi, RER, Lysosomes, Mitochondria, Pseudopodia at the cell surface. ## Functions: * Give mononuclear-phagocyte system cells in tissues [e.g. macrophages]; * Phagocytosis and digestion of parasites, viruses, cancer cells and senescent [dying] cells. # Disorders of monocytes * **Monocytosis**: 1. **Chronic bacterial infection** e.g. syphilis, leprosy. 2. **Bacterial endocarditis** 3. **Typhoid fever** 4. **Malignancy** e.g. Hodgkin lymphoma * **Monocytopenia**: hairy cell leukemia, Bone marrow failure. # Clinical hint # Leukemia 1. **Leukemias** are malignant neoplasms of leukocyte precursors. 2. They occur in lymphoid tissue (lymphocytic leukemias) and in bone marrow (myeloid and monocytic leukemias). 3. In these diseases, there is release of large numbers of immature forms of blood cells into the blood. 4. **Diagnosis**: bone marrow aspiration & Immunohistochemistry diagnose various types of leukemia. 5. **Treatment**: chemo/radiotherapy & bone marrow transplantation # Platelets (thrombocytes) * Non-nucleated, biconvex disc-like cell fragments. * Size: 1.5-3.5 micrometer. * Development: from the fragmentation of megakaryocytes. * Count: from 200,000 to 400,000 per microliter of blood. * Life span: 10 days. ## Each platelet has: * **Hyalomere**: a peripheral light blue zone. * **Granulomere**: a central zone containing granules: * **Alpha**: Growth factors, Clotting factors. * **Dense**: Serotonin, ATP, ADP, Calcium. * **Lysosomes**. # Platelet Function: Formation of blood clots. ## Steps: 1. **Primary aggregation**: platelet plug is formed. 2. **Secondary aggregation**: increasing the size of the platelet plug. 3. **Blood coagulation**: polymerization of fibrin. 4. **Clot retraction**: platelet actin+ myosin+ ATP. 5. **Clot removal**: enzyme plasmin [from plasma plasminogen]+ Enzymes of platelet -granules. # Disorders of platelets * **Thrombocytopenia**: a decrease in platelet count. 1. Bone marrow failure. 2. Increase platelet destruction e.g. autoimmune, viral infections, radiation, chemotherapy. * **Thrombocytosis**: overproduction of platelets. * **Thrombasthenia**: defective function of normally numbered platelets. # Complete blood count (CBC) * It is a valuable clinical investigation used to screen and diagnose many medical conditions such as acute and chronic infections and anemias. * The measured parameters in CBC include: 1. Number of RBCs, WBCs, platelets. 2. Hemoglobin and Hematocrit. 3. Other blood indices such as mean corpuscular hemoglobin (MCH), and Mean corpuscular hemoglobin concentration (MCHC). # Recommended Reference, Website * **Wheater's Functional Histology: A Text and Colour Atlas, 6th Edition** * **ISBN-13:** 978-0702047473 * **ISBN-10:** 0702047473 * **The histology tutor:** http://www2.yvcc.edu/histology zoomer/HistologyTutorials/histology_tutorials.htm