Introduction to Hematology

• Hematology is the study of blood, blood-forming organs, and blood disorders.
• It encompasses the physiology, pathology, etiology, and treatment of these disorders.

Components of Blood

• Blood consists of plasma and formed elements (cells).
• Plasma is the liquid component, comprising water, proteins, electrolytes, clotting factors, and other substances.
• Formed elements include red blood cells (erythrocytes), white blood cells (leukocytes), and platelets (thrombocytes).

Red Blood Cells (Erythrocytes)

• Erythrocytes are responsible for oxygen transport.
• They contain hemoglobin, an iron-containing protein that binds to oxygen.
• Erythropoiesis is the process of red blood cell production, stimulated by erythropoietin (EPO) from the kidneys.
• Red blood cells are anucleated and biconcave-shaped.
• The lifespan of a red blood cell is approximately 120 days.
• Old or damaged RBCs are removed by the spleen.
• Anemia is a deficiency in red blood cells or hemoglobin.
• Polycythemia is an excess of red blood cells.

White Blood Cells (Leukocytes)

• Leukocytes are involved in immune defense.
• They are classified into granulocytes (neutrophils, eosinophils, basophils) and agranulocytes (lymphocytes, monocytes).
• Neutrophils are the most abundant type of WBC and are crucial for phagocytosis of bacteria.
• Eosinophils defend against parasites and are involved in allergic reactions.
• Basophils release histamine and heparin, contributing to inflammation.
• Lymphocytes include T cells (cellular immunity), B cells (humoral immunity), and NK cells.
• Monocytes differentiate into macrophages, which phagocytize pathogens and cellular debris.
• Leukocytosis is an increase in the number of white blood cells.
• Leukopenia is a decrease in the number of white blood cells.

Platelets (Thrombocytes)

• Thrombocytes are involved in blood clotting (hemostasis).
• They are fragments of megakaryocytes.
• Platelets adhere to damaged blood vessel walls and aggregate to form a platelet plug.
• Thrombopoietin regulates platelet production.
• Thrombocytopenia is a deficiency in platelets.
• Thrombocytosis is an excess of platelets.

Hematopoiesis

• Hematopoiesis is the formation of blood cells, primarily in the bone marrow.
• All blood cells arise from hematopoietic stem cells.
• Cytokines and growth factors regulate hematopoiesis.

Hemostasis

• Hemostasis is the process of stopping bleeding.
• It involves vasoconstriction, platelet plug formation, and blood coagulation.
• The coagulation cascade involves a series of clotting factors that activate each other, leading to fibrin formation.
• Fibrin stabilizes the platelet plug, forming a blood clot.
• Anticoagulants prevent excessive clotting.

Blood Groups

• Blood groups are determined by the presence or absence of specific antigens on red blood cells.
• The ABO blood group system includes four main types: A, B, AB, and O.
• The Rh blood group system is another important system, with Rh-positive and Rh-negative individuals.
• Blood transfusions must be compatible to avoid transfusion reactions.

Common Hematological Tests

• Complete Blood Count (CBC): provides information about the number and characteristics of blood cells.
• Peripheral Blood Smear: examination of blood cells under a microscope to assess morphology.
• Bone Marrow Aspiration and Biopsy: used to evaluate bone marrow function and diagnose hematological disorders.
• Coagulation Tests: assess the ability of blood to clot (e.g., PT, PTT, INR).
• Flow Cytometry: identifies and counts specific cell types based on surface markers.

Hematological Disorders - Anemia

• Anemia is a condition characterized by a deficiency of red blood cells or hemoglobin, resulting in reduced oxygen-carrying capacity of the blood.

Iron Deficiency Anemia

• Caused by insufficient iron to produce hemoglobin.
• Common causes include inadequate iron intake, blood loss, and malabsorption.
• Characterized by microcytic (small) and hypochromic (pale) red blood cells.

Vitamin B12 Deficiency (Pernicious Anemia)

• Caused by impaired absorption of vitamin B12, often due to lack of intrinsic factor.
• Results in macrocytic (large) and normochromic red blood cells.

Folate Deficiency Anemia

• Caused by insufficient folate intake or absorption.
• Also results in macrocytic anemia.

Aplastic Anemia

• Bone marrow failure leading to pancytopenia (deficiency of all blood cell types).
• Can be caused by drugs, toxins, infections, or autoimmune disorders.

Hemolytic Anemia

• Premature destruction of red blood cells.
• Can be caused by genetic defects, autoimmune disorders, or infections.

Sickle Cell Anemia

• A genetic disorder characterized by abnormal hemoglobin that causes red blood cells to become sickle-shaped.
• Sickle cells can block blood vessels, leading to pain and organ damage.

Thalassemia

• A group of genetic disorders characterized by reduced or absent production of globin chains.
• Results in microcytic and hypochromic anemia.

Hematological Disorders - Leukemia

• Leukemia is a group of cancers that affect the blood and bone marrow.
• Characterized by abnormal proliferation of white blood cells.

Acute Lymphoblastic Leukemia (ALL)

• Affects lymphocytes and progresses rapidly.
• Most common in children.

Acute Myeloid Leukemia (AML)

• Affects myeloid cells and progresses rapidly.
• More common in adults.

Chronic Lymphocytic Leukemia (CLL)

• Affects lymphocytes and progresses slowly.
• Most common leukemia in adults.

Chronic Myeloid Leukemia (CML)

• Affects myeloid cells and progresses slowly.
• Associated with the Philadelphia chromosome.

Hematological Disorders - Lymphoma

• Lymphoma is a cancer that affects the lymphatic system.
• Characterized by abnormal proliferation of lymphocytes.

Hodgkin Lymphoma

• Characterized by the presence of Reed-Sternberg cells.
• Often starts in a single lymph node and spreads in an orderly fashion.

Non-Hodgkin Lymphoma

• A diverse group of lymphomas that do not have Reed-Sternberg cells.
• Can arise in any lymph node or organ.

Hematological Disorders - Myeloproliferative Neoplasms (MPNs)

• MPNs are a group of disorders characterized by overproduction of one or more blood cell types in the bone marrow.

Polycythemia Vera (PV)

• Increased production of red blood cells.

Essential Thrombocythemia (ET)

• Increased production of platelets.

Primary Myelofibrosis (PMF)

• Replacement of bone marrow with fibrous tissue.

Hematological Disorders - Bleeding Disorders

Hemophilia

• Inherited bleeding disorder caused by deficiency of clotting factors (e.g., factor VIII in hemophilia A, factor IX in hemophilia B).

Von Willebrand Disease

• Most common inherited bleeding disorder, caused by deficiency or dysfunction of von Willebrand factor (vWF).

Disseminated Intravascular Coagulation (DIC)

• A life-threatening condition characterized by widespread activation of the coagulation system, leading to thrombosis and bleeding.

Thrombotic Thrombocytopenic Purpura (TTP)

• A rare blood disorder characterized by formation of blood clots in small blood vessels throughout the body.

Overview of hematology, the study of blood and its disorders. Covers blood components like plasma, red blood cells (erythrocytes), white blood cells (leukocytes), and platelets. Focuses on the function and production of red blood cells, including erythropoiesis and the role of hemoglobin.