What is Blood?

Blood is a fluid that consists of plasma, lifeblood cells, and platelets. It circulates throughout the body delivering oxygen and nutrients to various cells and tissues. An average adult possesses around 5-6 liters. It accounts for 7% of the human body weight, with an average density of around 1060 kg/m3, very close to pure water’s density of 1000 kg/m3. It consists of erythrocytes also called red blood cells, leukocytes, and thrombocytes (platelets). By volume, the red blood cells constitute about 45% of whole lifeblood, the plasma about 54.3%, and white cells about 0.7%.


  • Supply of oxygen to hemoglobin, which is carried in red cells.
  • Supply of nutrients such as glucose, amino acids, and fatty acids.
  • Removal of waste such as carbon dioxide, urea, and lactic acid
  • Immunological functions like Circulation of WBC, and detection of foreign material by antibodies
  • Coagulation, the response to a broken blood-vessel, the conversion of blood from a liquid to a semisolid gel to stop bleeding
  • Messenger functions, including the transport of hormones and the signaling of tissue damage
  • Regulation of core body temperature
  • Hydraulic functions.

Components Of Blood

Components Of Blood

  • Plasma: The liquid state of blood can be contributed to plasma as it makes up  ~55%. It is pale yellow in color and when separated, it consists of salts, nutrients, water, and enzymes. Plasma also contains important proteins and other components necessary for overall health. Hence, lifeblood plasma transfusions are given to patients with liver failure and life-threatening injuries.
  • RBC: RBC consists of Haemoglobin, a protein. They are produced by the bone marrow to primarily carry oxygen to the body and carbon dioxide away from it.
  • WBC: It’s responsible for fighting foreign pathogens (such as bacteria, viruses, fungi) that enter our body. They circulate throughout our body and originate from the bone marrow.
  • Platelets: Tiny disc-shaped cells help regulate blood flow when any part of the body is damaged, thereby aiding in fast recovery through clotting of blood.

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