Blood

Components of Blood

Red Blood Cells

  • Red Blood Cells, or erythrocytes, are created in the bone marrow and have a lifespan of about 120 days.
  • They contain a protein called haemoglobin which has a high affinity for oxygen, allowing it to be transported around the body.
  • They have a biconcave shape to increase the surface area to volume ratio in order to enhance the process of gas exchange.

White Blood Cells

  • White Blood Cells, or leucocytes, play a major role in the body’s immune system, detecting and attacking foreign pathogens.
  • There are various types of white blood cells, including lymphocytes which produce antibodies and memory cells, and phagocytes which engulf and digest pathogens.

Platelets

  • Platelets are small fragments of cells that play a crucial role in clotting the blood, helping to prevent excessive bleeding when an injury occurs.
  • They accumulate at the site of a wound, adhering to the damaged blood vessel and forming a plug, a process known as haemostasis.

Plasma

  • Plasma is the liquid portion of blood, making up around 55% of its volume.
  • It is a yellowish fluid that transports soluble products of digestion, waste products, hormones, antibodies and heat around the body.

Blood Groups

  • There are four main blood types: A, B, AB and O. These are determined by the type of antigens found on the surface of the red blood cells.
  • Each blood group has corresponding antibodies in the plasma that will react with the ‘foreign’ antigens, hence it is critical to match the blood types during blood transfusions.

Blood Vessels

Arteries

  • Arteries carry oxygenated blood from the heart to the various parts of the body.
  • Artery walls are thick and muscular to withstand the high pressure of blood being pumped from the heart.

Veins

  • Veins carry deoxygenated blood from the various parts of the body back to the heart.
  • Vein walls are thinner, and they contain valves to prevent the backflow of blood, as the blood in veins is under low pressure.

Capillaries

  • Capillaries, the smallest of the blood vessels, connect arterioles and venules, ensuring oxygen, nutrients, and waste products can be exchanged between the body’s cells and the bloodstream.
  • They have very thin, permeable walls to facilitate the exchange of substances.

Overall, blood is vital for maintaining homeostasis and supplying your cells with essential nutrients. Its different components have specialised roles that ensure your body can respond to changes and combat diseases.