Blood is the only fluid connective tissues which are involved in circulating and transporting nutrients, respiratory gases, hormones, and other essential molecules within the cells, tissues, and organs. The complete process of circulation is controlled by the circulatory system.
The human circulatory system is mainly composed of the heart, blood cells, lymph, and blood vessels. There are two types of circulatory system: Open circulatory system and closed circulatory system. The main functions of the human circulatory system are:
- Transports nutrients from their sites of absorption to different tissues and organs.
- Carries waste products from different tissues to the organs to the excretory system.
- It uniformly distributes water, H+, and other chemical substances to all over the body.
- It is also involved in transporting hormones, from their sites of production to the tissue