The brain
organ system
Organ systems are most complex and fragile starting with the atoms. The most complex organ systems is the organism. In between are the molecules, cell, tissue, organ, and organ system.
The brain is the most important organ of the nervous system. The spinal cord and the brain are the main parts of the nervous system but the spinal cord is not considered to be an organ.
kidneys
lungs
The lungs.
Kidney
YES it is an organ system?
The skeletal system is the organ system that works most closely with the muscular system.
Skin is an organ, not an organ system. It is part of the integumentary system.
skin!
The Kidneys