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Medical Laboratory Science · 300 Level
This is the complete lecture note for MLS 302 Basic Haematology, prepared for Medical Laboratory Science students at 300 Level. You can read it online below, open it in the full viewer, or download the PDF for offline study. It pairs with the course's video lectures, so you can read and watch together.
LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS
LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Course code: MLS 302 Course title: Basic Haematology Course credit load: 2 Units Series 1: Origin, Development and Functions of Blood Cells • Part 1: Origin of Blood Cells • Sub-Part 1.1: Haematopoiesis and Stem Cell Theory • Sub-Part 1.2: Sites of Blood Cell Formation across Life Stages • Part 2: Development of Red Blood Cells • Sub-Part 2.1: Stages of Erythropoiesis • Sub-Part 2.2: Regulation of Red Cell Production • Part 3: Development of White Blood Cells and Platelets • Sub-Part 3.1: Leucopoiesis (Granulocytes, Lymphocytes, Monocytes) • Sub-Part 3.2: Thrombopoiesis (Platelet Formation) • Part 4: Functions of Blood Cells • Sub-Part 4.1: Functions of Red Blood Cells • Sub-Part 4.2: Functions of White Blood Cells • Sub-Part 4.3: Functions of Platelets Introduction Blood is often described as the river of life, carrying essential nutrients, gases, and immune components throughout the body. At the heart of this vital fluid are the blood cells, each with unique origins, developmental pathways, and specialised functions. Understanding how these cells arise, mature, and operate is fundamental to the study of haematology, and it provides the foundation for interpreting both normal physiology and disease states. This Series will therefore set the stage for your journey into Basic Haematology by focusing on the very building blocks of blood. The aim of this Series is to equip you with the knowledge needed to explain the origin, trace the developmental processes, and analyse the functions of the different blood cells. By the end of the Series, you should be able to connect these concepts to broader haematological principles and practical applications. We shall commence this Series by exploring the origin of blood cells, with particular attention to haematopoiesis and the stem cell theory, as well as the sites of blood cell formation across life stages. Next, we will examine the development of red blood cells, considering the stages of erythropoiesis and the regulation of red cell production. Following that, we will move on to the
LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS development of white blood cells and platelets, highlighting leucopoiesis and thrombopoiesis. Finally, we will wrap up by analysing the functions of blood cells, including red cells, white cells, and platelets, thereby rounding off the Series with a comprehensive view of their roles in maintaining life. Series Learning Outcomes Upon completing this Series, you should be able to: • SLO 1.1 define the concept of haematopoiesis, including the stem cell theory and the major sites of blood cell formation across different life stages, • SLO 1.2 explain the stages of erythropoiesis and analyse the factors that regulate red blood cell production, • SLO 1.3 describe the processes of leucopoiesis, highlighting the developmental pathways of granulocytes, lymphocytes, and monocytes, • SLO 1.4 explain the process of thrombopoiesis, including the role of megakaryocytes in platelet formation, • SLO 1.5 evaluate the functions of red blood cells in oxygen transport and carbon dioxide removal, • SLO 1.6 analyse the functions of white blood cells in immunity and defence against pathogens, • SLO 1.7 describe the functions of platelets in haemostasis and wound repair, • SLO 1.8 compare the developmental pathways of red blood cells, white blood cells, and platelets, identifying similarities and differences, and • SLO 1.9 apply knowledge of blood cell origin, development, and functions to explain normal physiological processes and potential abnormalities. 1.1 Origin of Blood Cells 1.1.1 Haematopoiesis and stem cell theory The origin of blood cells is explained through the process of haematopoiesis, which is the continuous formation of new blood cells from precursor cells. Haematopoiesis ensures that the body maintains adequate numbers of red blood cells, white blood cells, and platelets to meet physiological demands. At the centre of this process are haematopoietic stem cells (HSCs), which are primitive cells capable of self-renewal and differentiation into all blood cell lineages. The stem cell theory proposes that all blood cells arise from a single population of HSCs, which then commit to specific developmental pathways under the influence of growth factors and cytokines.
LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Figure 1.1: Haematopoietic stem cell differentiation pathways Fill in the blank: The continuous process of blood cell formation from precursor cells is called __________. 1.1.2 Sites of blood cell formation across life stages The sites of blood cell formation vary depending on the stage of human development. In the embryonic stage, blood cells are first formed in the yolk sac. As development progresses, the foetal liver and spleen become the primary sites of haematopoiesis. After birth, the bone marrow takes over as the main site of blood cell production. In early childhood, haematopoiesis occurs in most bones, but as individuals age, it becomes restricted to the axial skeleton, including the sternum, ribs, pelvis, and vertebrae. This transition reflects the body’s adaptation to changing physiological needs.
LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Plate 1.1: Sites of haematopoiesis in embryonic, foetal, and adult stages Fill in the blank: In adults, the primary site of blood cell formation is the __________. Pilot questions 1.1 1. Which term describes the continuous formation of blood cells from precursor cells? 2. What is the defining characteristic of haematopoietic stem cells? 3. Name two organs that serve as major sites of haematopoiesis during foetal development. 4. In adults, which bones are the main sites of blood cell formation? 5. According to the stem cell theory, all blood cells originate from what type of cell? 1.2 Development of Red Blood Cells 1.2.1 Stages of erythropoiesis The development of red blood cells is known as erythropoiesis, which refers to the process by which haematopoietic stem cells differentiate into mature red blood cells. This process occurs in the bone marrow and involves several distinct stages. It begins with the proerythroblast, a large nucleated precursor cell. The proerythroblast matures into the basophilic erythroblast, which shows intense basophilic cytoplasm due to the presence of ribosomes. As maturation continues, the cell becomes a polychromatic erythroblast, where haemoglobin synthesis begins, giving the cytoplasm a mixed staining appearance. The next stage is the orthochromatic erythroblast,
LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS which has a smaller nucleus and more haemoglobin. Finally, the nucleus is extruded, forming a reticulocyte, which enters the bloodstream and matures into a fully functional erythrocyte. Figure 1.2: Stages of erythropoiesis in the bone marrow Fill in the blank: The immediate precursor of a mature red blood cell that still contains ribosomal remnants is called a __________. 1.2.2 Regulation of red cell production The regulation of erythropoiesis is controlled by several factors, the most important being erythropoietin (EPO), a hormone produced mainly by the kidneys in response to low oxygen levels in the blood. EPO stimulates the bone marrow to increase red blood cell production, ensuring adequate oxygen delivery to tissues. Other factors influencing erythropoiesis include iron, which is essential for haemoglobin synthesis, and vitamins such as vitamin B12 and folic acid, which are required for DNA synthesis during cell division. Deficiencies in these nutrients can lead to anaemia, a condition characterised by reduced red blood cell numbers or impaired function. Regulator Function Role in Red Cell Production Erythropoietin Hormone produced mainly by the kidneys. Stimulates bone marrow to increase red blood cell production in response to low oxygen levels.
LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Regulator Function Role in Red Cell Production Iron Essential mineral for haemoglobin synthesis. Enables oxygen transport by forming the core of haemoglobin molecules. Vitamin B12 Required for DNA synthesis and cell division. Supports maturation of red blood cells and prevents megaloblastic anaemia. Folic acid Necessary for DNA synthesis and nucleotide formation. Promotes proper red blood cell development and prevents folate-deficiency anaemia. Box 1.1: Key regulators of erythropoiesis Fill in the blank: The hormone produced by the kidneys that stimulates red blood cell production is called __________. Pilot questions 1.2 1. What is the term used to describe the process of red blood cell development? 2. Name the stage of erythropoiesis where haemoglobin synthesis begins. 3. Which hormone is the primary regulator of red blood cell production? 4. Identify two vitamins essential for DNA synthesis during erythropoiesis. 5. What is the name of the immature red blood cell that enters the bloodstream before becoming a mature erythrocyte? 1.3 Development of White Blood Cells and Platelets 1.3.1 Leucopoiesis (granulocytes, lymphocytes, monocytes) The development of white blood cells is called leucopoiesis, which refers to the formation and maturation of the different types of white blood cells. These include granulocytes (neutrophils, eosinophils, and basophils), lymphocytes (B cells, T cells, and natural killer cells), and monocytes. Granulocytes develop in the bone marrow from myeloid progenitor cells, and their cytoplasm becomes filled with granules that contain enzymes and mediators of immune defence. Lymphocytes, on the other hand, arise
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