Haematological System Overview

Haematological System

• Includes blood, blood vessels, and blood-forming organs
• Haematologists diagnose and treat blood conditions, and work in laboratories

Haematopoiesis

• Blood cell formation from pluripotent hematopoietic stem cells (HSCs) in bone marrow
• Produces red blood cells (RBCs), white blood cells (WBCs), and platelets

Blood Functions

• Delivers oxygen and nutrients to tissues
• Removes waste products like carbon dioxide
• Regulates body temperature
• Maintains pH balance
• Regulates fluid balance
• Provides defense against infections

Acellular Component of Blood

• Plasma (55% of blood volume)
• Composed of 90% water and 10% proteins, electrolytes, hormones, and waste products

Cellular Components of Blood

• Red blood cells (RBCs) or erythrocytes (45% of blood volume)
• Contain hemoglobin (Hb) for oxygen transport
• Produced in the bone marrow via erythropoiesis
• Lifespan of 120 days
• White blood cells (WBCs) or leukocytes (less than 1% of blood volume)
• Responsible for immune response
• Platelets or thrombocytes (less than 1% of blood volume)
• Anucleate cells that support blood clotting

Types of Haematopoiesis

• Erythropoiesis: RBC synthesis
• Myelopoiesis: WBC synthesis
• Thrombopoiesis or megakaryopoiesis: platelet synthesis

Regulation of Haematopoiesis

• Hematopoietic Growth Factors (e.g., erythropoietin, thrombopoietin), and cytokines stimulate cell proliferation and differentiation
• Produced by stromal cells and organs like kidneys and liver
• Growth factors bind to cell receptors, activating transcription factors in the nucleus, modulating gene expression

Erythropoiesis

• Takes place in bone marrow
• Regulated by erythropoietin (EPO), a renal hormone
• Hypoxia induces EPO production
• EPO stimulates RBC production
• Requires iron (for Hb), vitamin B12 and folate (for DNA synthesis), copper, and pyridoxine (vitamin B6)
• B12 or folate deficiency can lead to megaloblastic anemia
• Stimulated by thyroid hormones

Haemolysis

• Breakdown of RBCs
• Usually takes place after 120 days
• Removed by macrophages of the reticuloendothelial (RE) system
• Haemolytic anemia occurs when RBC destruction is not compensated by erythropoiesis
• Can be extravascularly or intravascularly-mediated
• Intravascular haemolysis is almost always pathological

Explore the fundamentals of the haematological system, including blood components, their functions, and the process of haematopoiesis. This quiz covers the roles of blood in oxygen delivery, waste removal, and immune defense, as well as the acellular and cellular components of blood.