Body area vs organ system

What is the difference between a Body Area and an Organ System

re: Body area vs organ system

In the 1995 Documentation Guidelines there are body areas and organ systems.
https://www.cms.gov/Outreach-and-Education/Medicare-Learning-Network-MLN/MLNEdWebGuide/EMDOC.html
For purposes of examination, the following body areas are recognized:
Head, including the face
Neck
Chest, including breasts and axillae
Abdomen
Genitalia, groin, buttocks
Back, including spine
Each extremity

Organ systems:
For purposes of examination, the following organ systems are recognized:
Constitutional (e.g., vital signs, general appearance)
Eyes
Ears, nose, mouth, and throat
Cardiovascular
Respiratory
Gastrointestinal
Genitourinary
Musculoskeletal
Skin
Neurologic
Psychiatric
Hematologic/lymphatic/immunologic

re: Body area vs organ system

How do you tell the difference in musculoskeletal body area vs organ system