The human body is a complex structure made up of various systems that work together to maintain life. It consists of organs, tissues, and cells, all performing specific functions. Major systems include the circulatory system, respiratory system, and nervous system, each playing a crucial role in overall health and functionality. The body is composed primarily of water, proteins, fats, and carbohydrates. It has a skeletal system that provides support and protection for vital organs, while muscles enable movement. The immune system helps defend against diseases, ensuring the body remains healthy and functional throughout life.