In biology, an organ is a functional unit that is separate from the surrounding tissue.
It is a collection of tissues forming a unit with structure and performs a certain function. It is not only present in humans and animals but also in plants and single-cell organisms.
Organ has a parenchyma, the main tissue and a stroma, the sporadic tissues. In the heart organ, the myocardium is the parenchyma and the nerves, blood and connective tissues are the stroma.
These are very important organs that an organism cannot live well and long without them. There are 5 critical organs in a human body
When different organs perform similar function, their cooperation forms an organ system. It is also called body or biological system. And here are the 11 major organ systems in mammals and its function.
1. Cardiovascular system- pumping and directing blood flow throughout the body
2. Digestive system- digesting food
3. Endocrine system- communicating using body hormones
4. Excretory system- maintaining fluid and electrolyte balance; excreting urine
5. Immune system- defending the body against harmful agents
6. Integumentary system- protecting body from damage like abrasion and water loss
7. Muscular system- allowing movement with muscles
8. Nervous system- collecting, transferring and processing information
9. Reproductive system- producing offspring
10. Respiratory system- breathing
11. Skeletal system- providing support and protection