What does "beds" mean here? "the peripheral beds within the body and lungs"

Question

What does "beds" mean here?

A ventricle is one of two large chambers in the heart that collect and expel blood received from an atrium towards the peripheral beds within the body and lungs. The atrium (an adjacent/upper heart chamber that is smaller than a ventricle) primes the pump.

Source: Ventricle (heart) - Wikipedia

I wonder if it means spaces, chambers or body cavities.

I've already googled it, but couldn't find anything.

bed

1.a piece of furniture upon which or within which a person sleeps, rests, or stays when not well.

2.the mattress and bedclothes together with the bedstead of a bed.

3.the bedstead alone.

(However, maybe it's a mistake from Wikipedia)

Answer 1

'Vascular bed' is a piece of medical jargon that compares our body's tissues to a garden bed of soil for the purposes of bloodflow. When the blood leaves the heart's chambers or the lungs' periphery, it enters smaller and smaller blood vessels in an expanding pattern for the purpose of 'saturating' the body with oxygenated blood, just like watering a bed of soil causes the dry soil to slowly absorb the water outward from the point of contact. While much of our vascular system can be thought of as a self-recycling pump made of big tubes, eventually the pathways become so fine that it's more accurate to think of it as a saturated (or unsaturated) substance. That's the bed.