Capillary
The smallest blood vessels, where exchange of oxygen, nutrients, and waste occurs between blood and tissues. Capillaries connect arteries to veins.
Used in the Books
This term appears in 4 chapters:
"... huge ears - radiators to dump excess heat). Resource delivery: Cells need nutrients delivered through the bloodstream (a surface area problem - capillary walls have area, blood flow is distributed). But the organism's total nutrient demand is volume-based."
"...te = 4.2 mL/second - Pressure differential: -15 to -30 atmospheres (negative pressure at leaves vs. positive at roots) - Vessel diameter: 0.02-0.5mm (capillary-sized tubes) - Driving force: Evaporation at leaves creates suction, not pumping at roots - Distribution: Single 2-foot-diameter trunk → 2,000+ branc..."
"The models rely on three key assumptions. First, networks are space-filling, meaning they reach all tissues. Second, terminal units - capillaries and smallest vessels - are size-invariant. They're the same size in mice and elephants, which is empirically true."
"...tructure. The mammalian circulatory system exemplifies this: the aorta branches into major arteries, which branch into arterioles, which branch into capillaries - each level smaller and more numerous than the previous. This branching is approximately self-similar (arterioles look like scaled-down arteries) an..."
Biological Context
Capillary walls are just one cell thick, allowing diffusion. The human body contains about 40 billion capillaries with a total length of roughly 100,000 km. No cell is more than a few cells away from a capillary. Capillary density varies by tissue metabolic needs.
Business Application
Organizational capillaries: the fine-grained distribution networks that reach every part of the organization. Like biological capillaries, they're where actual exchange and delivery happens—the last mile of any distribution system.