Blood is a connective tissue in fluid form. It is called as the 'fluid of life' because it carries oxygen from lungs to all parts of the body and carbon dioxide from all parts of the body to the lungs. It is called as the 'fluid of growth' because it carries nutritive substances from the digestive system and hormones from endocrine gland to all the tissues. It is called as the 'fluid of health' because it protects the body against the diseases and gets rid of the waste products and unwanted substances by transporting them to the excretory organs like kidneys.