Digestive System - to convert food particles into simpler micromolecules that can be absorbed into the bloodstream and used by the body.
Circulatory System - to deliver oxygenated blood to the various cells and organ systems in our body so they can undergo cellular respiration.
Nervous system - to coordinate the body's response to changes in its internal and external environment.
Excretory System - it get rid of the body wastes, including excess water and salts.
Respiratory System - to provide the body with a fresh supply of oxygen for cellular respiration and remove the waste product carbon dioxide.
Endocrine System - to control growth, development, metabolism and reproduction through the production and secretion of hormones.
Skeletal System - to provide structure and support to the human body
Muscular System - works with the skeletal and nervous system to produce movement, also help to circulate blood through the human body.
NOTE: Immune system isn't included. It wasn't considered as one of the body systems. But it was asked by the teacher, immune system's function is to remove infectious diseases and other pathogens from the human body.