I believe this question relates to human body.
The human body can be compared to a very complex process plant. As a matter of fact it is the most complicated process plant, much more complicated and sophisticated than any other plant or equipment designed or built by human beings.
The complete body system cannot be described completely even in a hundred pages. Therefore I will only indicate some of the main features of the human body.
The body system incorporates many sub-systems within itself that makes it highly self-managed and self sustaining. Not only a body is able to operate by itself, the body also has the ability to make new bodies, to grow, to maintain itself to restore from normal wear and tear, and to repair any damages by external influences.Some parts of the body like heart and kidneys work continuously for the lifetime.Body also has the capacity to monitor the environment and, based on the environmental condition, adjust its internal working to maintain its health.
The body also interacts with the external environments and other living beings to serve its objectives. The body decides the objectives as well as the means to achieve these objectives by itself. It also then uses its external organs to interact with and alter the external environment.
The whole body may be divided into different organs, each performing some specific functions within the total body. Thus each organ acts like a sub-system within the total body system. The main organs of the body are described below.
- Skin, nails and hair: Skin provides an outer covering for the body for protection. It also provides the sense of touch including feeling of temperature. It plays an important role in maintaining body temperature through mechanism of sweating. Sweat also removes some waste material from the body.
- Skeletal system: provides a rigid structure for housing the various body organs and provides rigid components for body movement and application of force.
- Muscular system: Used as to control movements of the body. Force required for all movements of the body is applied through muscular action.
- Digestive system: It accepts food from outside, digests it to extract inputs required for energy, repair and growth of the body, and remove remaining unused part of food from body.
- Respiratory system: Supplies oxygen required by the body and removal of carbon dioxide from the body.
- Circulatory system: It pumps and circulates blood throughout the body to supply oxygen, energy and other material required to different parts of the body, and to carry away waste material from the body.
- Urinary system: removal of waste material from the body. This waste material is separated from the blood (a part of circulation system) by kidneys.
- Reproductive system: It help humans to reproduce themselves.
- Endocrine system: It produces different hormones for controlling and regulating body functions.
- Nervous system including organs of senses such as eyes and ears: It enables the body to obtain information about outside environment as well as internal functioning of the body. It also includes brain for processing information and decision making.
The body can also be classified in term of external parts such as hands, legs, and so on. These external body parts interact with the environment and perform external work.