Answer:
The question you've asked is not clear, you haven't specified which organ system are you talking about. No worries, I've noted down key functions of 11 organ systems of the human body, you can pick any of them that you want.
Some of the main functions of the 11 organ systems include the following:
Skeletal system:
shape/support for the body
protect some organs (brain, heart, lungs, spinal cord, etc.)
mineral storage (e.g., Ca and P)
site for muscle connections
site for blood cell formation
Muscular system:
movement
since there are three types of muscle—cardiac, smooth, and skeletal—there are specific functions for all of these
Cardiovascular system:
pump blood throughout the body
the blood will transport nutrients, oxygen, waste, and hormones
the blood also functions as a part of the immune system and allows the white blood cells/antibodies to gain access to infected/wounded areas
Excretory system:
produce and store urine in the kidneys and bladder
release urine through the urethra
Digestive system:
digest food into nutrients that can be absorbed
absorb nutrients
make certain vitamins (e.g., Vitamin K is made by bacteria in the large intestine)
Reproductive system:
the main function here is to produce offspring
another function—in line with the endocrine system— is to make hormones (e.g., testosterone and estrogen, which affect male and female characteristics)
Endocrine system:
hormone production
these hormones act throughout the body performing multiple jobs (e.g., blood sugar levels [insulin/glucagon], growth [growth hormone], male characteristics like facial hair [testosterone]
Integumentary system:
this is the skin
protection from some pathogens (unless you get a cut)
sensations at the skin level (texture, heat, pressure, pain)
Nervous system:
made of the central (brain and spinal cord) and peripheral nervous systems
this system transmits signals from one part of the body to another and this includes your senses
Respiratory system:
this mainly includes your lungs and trachea
the main function is the exchange of gases (oxygen and carbon dioxide)
Immune system:
the main function is to defend the body against pathogens
this is done with the help of the cardiovascular system which has white blood cells and antibodies in the blood