Blood

Blood Composition

  • Blood is a fluid connective tissue that circulates throughout the body via the cardiovascular system.
  • It consists of red blood cells, white blood cells, platelets, and plasma.

Red Blood Cells

  • Red Blood Cells (RBCs), also known as erythrocytes, play a vital role in carrying oxygen from the lungs to the cells in the body.
  • They contain a protein called haemoglobin which binds to oxygen and gives RBCs their typical red colour.
  • RBCs are biconcave disc-shaped which increases their surface area for oxygen absorption and makes it easier for them to travel through tiny blood vessels.
  • Red blood cells lack a nucleus to allow more room for haemoglobin and have a lifespan of about 120 days.

White Blood Cells

  • White Blood Cells (WBCs), also known as leukocytes, are key players in the immune system, helping the body to fight infection.
  • They are larger than RBCs but are fewer in number.
  • WBCs are formed in the bone marrow and are able to move in and out of blood vessels to reach affected tissues.
  • They function by either phagocytosis (engulfing harmful particles) or by producing antibodies to combat specific pathogens.

Platelets

  • Platelets are fragments of cells that help in the clotting process when a blood vessel is injured to prevent the loss of blood.
  • They aggregate at the site of injury, stick to the lining of the damaged vessel, and form a plug to stop blood leakage.
  • They also release chemicals to promote the formation of fibrin, a protein that meshes together to form a solid clot.

Plasma

  • Plasma is the yellow liquid component of blood in which blood cells and platelets are suspended.
  • It carries nutrients, hormones, and waste products across different parts of the body.
  • Important substances transported by plasma include dissolved glucose, amino acids, mineral ions, hormones, carbon dioxide, and urea.
  • Plasma also helps control the body’s pH and fluid balance.

Functions of Blood

  • Blood plays vital roles in transportation, regulation, and protection.
  • It transports oxygen and nutrients to cells, removes waste products from cells, transports hormones, and helps maintain body temperature.
  • Its regulatory functions include maintaining body pH and balancing fluid volume.
  • The protective function of blood includes preventing blood loss through clotting and combating infections with WBCs and antibodies.