lungs
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.
The lungs.
The Kidneys
skin!
the skull because it protects the brain
organ system
The small intestine is where most of the absorption of nutritients occurs.
The most important organ in the reproductive system is typically considered to be the gonads, which are the testes in males and the ovaries in females. These organs produce sex hormones and gametes (sperm in males, eggs in females) that are essential for reproduction.
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.
All of it except the appendix. But you have to take care it
The most important organ of our respiratory system is the Lungs. The lungs are the organs that extract or absorb oxygen from the air we breathe and fills our blood with life giving oxygen.
Most people call this an organ system.