Science Desk: Behind every heartbeat, every breath, and every movement, an invisible network is hard at work—carrying oxygen, defending against disease, and keeping the body in balance. Unit 3 introduces us to the lifelines of human survival: body fluids, blood, and the lymphatic system. Together, they form a complex transport and defense network, ensuring that the body runs like a well-oiled machine.
Download UNIT 3 – Blood and Body Fluids — The Lifelines of Human Survival Notes
Get simplified revision notes for this unit:
⬇️
Download Unit 3 Notes PDF
Body Fluids: The Hidden Medium of Life
While often overlooked, body fluids play a central role in sustaining life. They serve as the medium through which nutrients, hormones, and gases are delivered to cells while waste products are removed.
Intracellular fluid (ICF): Found within cells, it makes up nearly two-thirds of the body’s fluid. It is vital for chemical reactions and maintaining cell structure.
Extracellular fluid (ECF): Located outside cells, this includes plasma, interstitial fluid, and lymph. ECF acts as the bridge between cells and the circulatory system.
Without these fluids, the exchange of materials that keeps cells alive would come to a standstill.
Blood: The River of Life
Blood is far more than a red liquid—it is a specialized connective tissue composed of plasma and cellular elements.
Composition of Blood
Plasma: The fluid component, consisting mostly of water, transports nutrients, hormones, and waste.
Red blood cells (RBCs): Rich in hemoglobin, they carry oxygen from the lungs to tissues.
White blood cells (WBCs): The body’s defense force, fighting infections and foreign invaders.
Platelets: Small cell fragments essential for clotting.
Functions of Blood
Transport of gases, nutrients, and hormones.
Regulation of body temperature and pH.
Defense against pathogens.
Healing through clot formation.
Hemopoiesis: The Birth of Blood Cells
All blood cells arise through hemopoiesis, the process of blood cell formation. It takes place primarily in the bone marrow. Stem cells differentiate into various lineages, giving rise to RBCs, WBCs, and platelets.
Formation of Hemoglobin
Hemoglobin, the oxygen-carrying pigment of RBCs, is synthesized from iron, globin proteins, and heme groups. Its efficiency makes it one of nature’s most remarkable molecules, enabling humans to thrive in diverse environments.
Anemia: When Blood Falls Short
Anemia arises when the body lacks healthy red blood cells or hemoglobin. This leads to fatigue, weakness, and pale skin due to reduced oxygen transport. Causes range from iron deficiency to genetic conditions like sickle-cell anemia.
Coagulation: Stopping the Flow
Every cut or injury could be life-threatening if not for the body’s coagulation mechanism. The process unfolds in a cascade: platelets aggregate, clotting factors activate, and fibrin threads form a mesh that seals the wound. This tightly regulated sequence prevents excessive blood loss while avoiding dangerous clots.
Blood Grouping and Rh Factor
Blood compatibility is a matter of life and death in transfusions.
ABO system: Classifies blood into A, B, AB, or O, based on antigens present on RBC surfaces.
Rh factor: Determines whether blood is Rh-positive or Rh-negative.
A mismatch in transfusion can trigger severe immune reactions. Hence, blood typing is crucial before any transfusion procedure.
Significance of Transfusion
Blood transfusion saves countless lives in surgeries, trauma, and chronic diseases. However, it must be handled with precision to avoid complications like hemolytic reactions.
Disorders of Blood
Blood is not immune to disease. Disorders include:
Leukemia: Cancer of WBCs, leading to uncontrolled cell growth.
Hemophilia: A genetic disorder where clotting factors are absent, causing prolonged bleeding.
Thalassemia: A hereditary defect in hemoglobin production.
These conditions highlight the delicate balance blood maintains to keep us alive.
Reticuloendothelial System: The Body’s Cleanup Crew
Also known as the mononuclear phagocyte system, the reticuloendothelial system (RES) consists of specialized cells like macrophages. Its job is to remove worn-out blood cells, engulf pathogens, and recycle components like iron from hemoglobin. This silent system ensures that blood remains pure and effective.
The Lymphatic System: Silent Protector
Beyond blood, another vital fluid circulates through the body—lymph. Though less discussed, the lymphatic system is equally crucial in maintaining health.
Lymphatic Organs and Tissues
The system is supported by lymph nodes, spleen, thymus, and tonsils. These organs filter harmful substances and serve as training grounds for immune cells.
Lymphatic Vessels and Circulation
Lymphatic vessels collect excess interstitial fluid and return it to the bloodstream. Along the way, lymph passes through lymph nodes, where immune cells stand guard against infections.
Functions of the Lymphatic System
Maintains fluid balance by draining excess tissue fluid.
Absorbs and transports fats from the digestive system.
Plays a central role in immunity, producing and housing lymphocytes.