The body is not a collection of separate departments
Medicine often names systems separately because it makes the body easier to study.

• Cardiovascular.

• Digestive.

• Nervous.

• Endocrine.

• Immune.

• Renal.

• Musculoskeletal.

 

But biology itself does not respect those neat boundaries.
The nervous system influences digestion.
The endocrine system influences metabolism, reproduction, sleep, repair and immune activity.
The microbiome communicates with the immune system, nervous system and metabolism.
Sleep alters hormonal signalling, brain clearance, appetite regulation, immune function and tissue repair.
The liver influences hormone metabolism.
The kidneys influence cardiovascular regulation.
Muscle communicates chemically with other tissues through signalling molecules released during movement.
Everything talks to everything.
Systems exist within systems — and between systems.
This is why 16×1 does not interpret biological domains as isolated islands.
The relationships matter.
A disturbance beginning in one area can remain local for years.
But if enough connected domains begin moving in the same negative direction, the problem becomes something larger.
It becomes systemic ageing.