Main components of Blood

• Main Components of Blood

  • Plasma
  • Red blood cells
  • White blood cells
  • platelets
• Plasma


  • Yellowish liquid in blood
  • contains mainly water, blood cells, excretory products and substances such as nutrients
  • transports blood cells around the body
  • transports excretory substances (e.g. urea, excess amino acids) to excretory organs for removal
  • Transports nutrients from small intestines to other parts of the body
  • transports hormones from endocrine glands to target organs
• Red blood cells


  • transports oxygen from the lungs to other parts of the body
  • Contains haemoglobin that can combine reversibly with oxygen
  • haemoglobin (purplish red) + oxygen = oxyhaemoglobin (bright red)
  • biconcave shape which increases the surface area to volume ratio, increasing the rate of diffusion of oxygen into and out of the cell
  • no nucleus to make more space available for more haemoglobin
  • flexible and can change into a bell-shaped structure so that they can move easily through narrow capillaries
• White blood cells


  • two types, phagocyte and lymphocyte
  • phagocytes perform the progress phagocytosis, where phagocytes engulf and destroy pathogens such as bacteria
  • lymphocytes produce antibodies that can recognise and destroy pathogen, cause pathogens to clump together for easy ingestion by phagocytes, and neutralise toxins produced by bacteria

  
• Platelets


  • cytoplasm fragments
  • contain an enzyme that catalyses the conversion of fibrinogen to fibrin threads
  • fibrin threads entangle with red blood cells to form blood clots that seals wounds
• Tissue rejection


  • the immune system may recognise a donated organ or blood as foreign tissue and cause tissue rejection