biological human body systems

what is a biological system? how to improve our biological systems? what each biological system consists of?

1.  biological systems
    - The Circulatory System - heart, blood
    - The Lymphatic System - 
    - The Respiratory System - lungs
    - The Integumentary System - skin, sweat glands, hair, nails
    - The Endocrine System - 
    - The Digestive System - mouth, stomach
    - The Urinary (Excretory) System - kidneys, ureters, bladder, urethra
    - The Musculoskeletal System - skeleton, muscles
    - The Nervous System - 
        - Sensory systems - eyes, ears, nose
    - The Immune System - 
    - The Reproductive System -