Composition and Function of the Blood in Humans

Composition and Function of the Blood in Humans




Living cells require nutrients, oxygen (O2), and other essential substances for their survival and proper functioning. Similarly, they need to expel waste and harmful substances continuously to maintain tissue health. To facilitate these exchanges, efficient mechanisms for substance transport to and from cells are essential. Different animal groups have evolved various methods for this purpose.


1. Transport Mechanisms in Simple Organisms:

  • Simple organisms like sponges and coelenterates circulate water from their surroundings through their body cavities. This facilitates the exchange of substances with the cells. 
  • Water circulation aids in nutrient delivery and waste removal, ensuring the cells' survival and functioning.


2. Transport Mechanisms in Complex Organisms:

  •  More complex organisms employ specialized fluids within their bodies for substance transport. 
  • Blood, the primary body fluid in higher organisms, including humans, serves as a crucial medium for substance transportation. 
  • Lymph, another body fluid, complements blood in transporting certain substances.


3. Composition and Properties of Blood and Lymph:

  •  Blood is a complex fluid comprising various components, including red blood cells (RBCs), white blood cells (WBCs), platelets, plasma, and dissolved substances like nutrients, gases, and hormones. 
  • Lymph, or tissue fluid, consists of interstitial fluid that collects in the lymphatic vessels. It plays a vital role in immune function and nutrient transport.


4. Circulation Mechanism of Blood:

  • The circulatory system, comprising the heart, blood vessels, and blood, facilitates the circulation of blood throughout the body. 
  • Blood vessels, including arteries, veins, and capillaries, form a network for transporting blood to various tissues and organs. 
  • The heart pumps blood through the circulatory system, ensuring the continuous flow of oxygen, nutrients, and other vital substances to cells while removing waste and carbon dioxide.


Composition and Function of the Blood in Humans


  • Blood is a vital fluid found in humans that plays a crucial role in maintaining health and sustaining life. Comprising a complex mixture of cellular and liquid components, blood serves multiple functions essential for the body's survival. 
  • Blood consists of several key components. 
  • Blood is a unique type of connective tissue that plays a vital role in the human body.  
  • It comprises two main components: plasma and formed elements. 
  • Red Blood Cells (RBCs): These cells, also known as erythrocytes, are responsible for transporting oxygen from the lungs to various tissues and organs throughout the body. They contain hemoglobin, a protein that binds with oxygen. 
  • White Blood Cells (WBCs): Also called leukocytes, WBCs are essential components of the immune system. They defend the body against infections and foreign invaders by identifying and destroying pathogens, such as bacteria and viruses. 
  • Platelets: These small cell fragments play a crucial role in blood clotting and wound healing. When a blood vessel is damaged, platelets adhere to the site to form a plug, preventing excessive bleeding. 
  • Plasma: Plasma is the liquid component of blood, constituting approximately 55% of its volume. It contains water, electrolytes, proteins (such as albumin, globulins, and fibrinogen), hormones, nutrients, and waste products. 
  • This remarkable tissue serves a multitude of vital functions, including oxygen transport, nutrient delivery, waste removal, immune defense, and clot formation.


Functions of Blood:

  • Oxygen Transport: RBCs transport oxygen from the lungs to tissues and organs, where it is utilized for cellular respiration, the process that produces energy (ATP) for cellular activities. 
  • Nutrient Transport: Blood carries nutrients, such as glucose, amino acids, fatty acids, vitamins, and minerals, absorbed from the digestive system to cells throughout the body, providing them with the necessary energy and building blocks for growth and repair. 
  • Waste Removal: Blood transports waste products, including carbon dioxide, urea, and other metabolic by-products, from cells to organs like the lungs, liver, and kidneys for elimination from the body. 
  • Immune Response: WBCs play a crucial role in the body's immune defense by identifying and neutralizing pathogens, such as bacteria, viruses, and fungi, as well as removing dead or damaged cells. 
  • Blood Clotting: Platelets and clotting factors in the blood work together to form blood clots, preventing excessive bleeding when blood vessels are damaged. This process, known as hemostasis, is essential for wound healing and preventing blood loss.