Blood: The River of Life - Composition and Function
Welcome to this module on Blood Composition and Function, a cornerstone topic for your AIIMS preparation. Understanding blood is crucial as it's the primary transport system of the body, carrying vital substances to every cell and removing waste products. We'll delve into its intricate components and their remarkable roles.
What is Blood?
Blood is a specialized connective tissue consisting of cells suspended in a liquid matrix. It circulates throughout the body, performing a multitude of essential functions. On average, an adult human has about 4-6 liters of blood.
Composition of Blood
Blood is broadly divided into two main components: plasma and formed elements. Together, these make up the entire volume of blood.
Plasma: The Liquid Matrix
Plasma is the medium through which all blood components travel. Its composition is dynamic, reflecting the body's metabolic state and needs.
| Plasma Component | Approximate Percentage | Key Function |
|---|---|---|
| Water | 90% | Solvent for transport, temperature regulation |
| Plasma Proteins | 7-8% | Albumin (osmotic pressure), Globulins (immunity, transport), Fibrinogen (clotting) |
| Electrolytes | ~1% | Maintain pH, osmotic balance, nerve and muscle function |
| Nutrients | Trace amounts | Energy, building blocks for cells |
| Hormones | Trace amounts | Chemical messengers |
| Waste Products | Trace amounts | Transported for excretion (e.g., urea, CO2) |
Formed Elements: The Cellular Components
These are the cellular components of blood, each with specialized roles in maintaining health and defending the body.
Red Blood Cells (Erythrocytes)
White Blood Cells (Leukocytes)
White blood cells are the body's defense mechanism, playing a crucial role in the immune system. They are larger than red blood cells and have nuclei.
| Type of Leukocyte | Key Role |
|---|---|
| Neutrophils | Phagocytosis of bacteria |
| Lymphocytes | Immune response (antibody production, cell-mediated immunity) |
| Monocytes | Phagocytosis, differentiate into macrophages |
| Eosinophils | Combat parasitic infections, allergic reactions |
| Basophils | Release histamine and heparin (inflammation, clotting) |
Platelets (Thrombocytes)
Functions of Blood
Blood performs a remarkable array of functions essential for survival. These can be broadly categorized as transport, regulation, and protection.
Blood's primary role is transport. It carries oxygen from the lungs to tissues and carbon dioxide from tissues to the lungs. It transports nutrients absorbed from the digestive system to cells and waste products from cells to excretory organs like the kidneys and liver. Hormones produced by endocrine glands are also transported by blood to their target organs. Blood also distributes heat throughout the body, aiding in thermoregulation.
Text-based content
Library pages focus on text content
Regulation is another key function. Blood helps maintain homeostasis by regulating body temperature, pH balance through buffer systems, and fluid balance. It also plays a role in regulating electrolyte balance.
Protection is achieved through the immune system (white blood cells and antibodies) that defends against pathogens, and through the clotting mechanism (platelets and clotting factors) that prevents excessive blood loss from injuries.
Transport, Regulation, and Protection.
Key Takeaways for AIIMS Preparation
For your AIIMS exams, focus on the specific percentages of plasma and formed elements, the detailed composition of plasma (especially proteins), and the distinct roles of each type of white blood cell. Understanding the structure-function relationship of red blood cells (hemoglobin, biconcave shape) and platelets (clotting factors) is also critical. Be prepared for questions on hematopoiesis (blood cell formation) and blood disorders.
Remember the mnemonic 'Never Let Monkeys Eat Bananas' for the order of white blood cells by abundance: Neutrophils, Lymphocytes, Monocytes, Eosinophils, Basophils.
Albumin
Learning Resources
Provides a comprehensive overview of blood, its composition, and functions with clear diagrams.
An accessible video explaining the components of blood and their roles in the human body.
A detailed and authoritative source covering the biology, composition, and functions of blood.
An official resource from a leading hematology society, explaining blood components and their importance.
A chapter from an open-access biology textbook detailing the cellular and plasma components of blood.
A chapter from a medical textbook providing in-depth physiological information on blood.
A clear explanation from Johns Hopkins Medicine on the basics of blood and its functions.
An excellent resource for medical students, breaking down blood components and their anatomical relevance.
An engaging and informative video from CrashCourse that covers the essential functions of blood.
A high-quality video tutorial explaining blood composition and its critical functions in the body.