Where blood comes from

Every cell traces back to one stem cell

All blood cells are born in the bone marrow from a single haematopoietic stem cell that commits down one of two roads:

Myeloid → red cells, platelets, and front-line immune cells.
Lymphoid → the lymphocytes (B, T, NK) — your specific, learned immunity.

Why a coach cares: it’s a production line. Starve it — low protein, iron, B12, thyroid — and you see it downstream as fewer or poorer cells.

Build a red cell and you need raw materials: protein, iron, B12, folate, B6, copper and a thyroid signal. Miss one and the line stalls.