Blood is important for regulation of the body’s pH, temperature, osmotic pressure, the circulation of nutrients and removal of waste, the distribution of hormones from endocrine glands, and the elimination of excess heat; it also contains components for blood clotting. Blood is made of several components, including red blood cells, white blood cells, platelets, and the plasma, which contains coagulation factors and serum.

Blood consists of two main components:  

• Plasma 
• Formed elements or corpuscles.

Plasma:  Plasma constitutes almost 55% of blood. Plasma is a pale yellowish, watery substance that surrounds blood cells and carries them around the body.Plasma is a combination or mixture of nutrients, gases, proteins, hormones, salts, and wastes.  

Functions of blood plasma  

• Plasma helps to regulate body temperature and maintains blood pressure. 
• Transportation of nutrients is one of the major functions of blood plasma. When a food is digested, it breaks down into amino acids, sugars, lipids and fatty acids. These are transported throughout the body by plasma. 
• Plasma also transports wastes like uric acids, ammonium salts etc., to kidneys, where it filters wastes from plasma and excretes it through urine. 
• Plasma also supplies required proteins for blood clot and immunity.

Formed Elements or Corpuscles  

Formed particles or corpuscles consists of  

• Erythrocytes or Red blood cells 
• Leucocytes or White blood cells

Blood is a fluid that moves through the vessels of a circulatory system. In humans, it includes plasma (the liquid portion), blood cells (which come in both red and white varieties), and cell fragments called platelets.

Basic functions of blood :  

1) Transport of nutrients, waste products, blood gases (oxygen and carbon dioxide) or signaling molecules  

2) Immune function  

3) To maintain homeostasis of water, ions or pH  

4) Distribution of heat throughout the body  

5) Blood clotting

The main components of blood are:

(i) Plasma 

(ii) Red blood cells 

(iii) White blood cells 

(iv) Platelets

Functions of blood plasma  

• Plasma helps to regulate body temperature and maintains blood pressure. 
• Transportation of nutrients is one of the major functions of blood plasma. When a food is digested, it breaks down into amino acids, sugars, lipids and fatty acids. These are transported throughout the body by plasma. 
• Plasma also transports wastes like uric acids, ammonium salts etc., to kidneys, where it filters wastes from plasma and excretes it through urine. 
• Plasma also supplies required proteins for blood clot and immunity.

Functions of Red blood cell

• Haemoglobin in RBC picks up oxygen in the lung tissues by forming a chemical compound with it. 
• This oxygen is carried to the tissues where it is used in the chemical reactions to produce energy. 
• It then combines with carbon dioxide which is produced in these reactions and returns to the lungs with the heart where the cycle starts again.

Functions of White blood cell

Broadly, WBC acts as a defence system in the body. There are several varieties of WBC performing specific functions such as, Neutrophils (65 to 70% of the total WBC) attack the invading bacteria and engulf them. Lymphocytes (25% of WBC) produces antibodies which protect the body against antigen and thus provide immunity against infection. Basophils secrete anticoagulant called heparin which prevents clot within the blood cells. Eosinophils and monocytes also assist in defence mechanism of the body by becoming active against specific antigens.

Function of platelets: 

They help the blood clotting process (or coagulation) by gathering at the site of an injury.