Definition

1. Noun:

   • A very small blood vessel: A capillary is any of the tiny, thin-walled blood vessels that connect the smallest arteries (arterioles) to the smallest veins (venules). They form a network throughout the body's tissues to allow the exchange of oxygen, nutrients, and waste products between the blood and the cells.
   • A tube with a very fine bore: A capillary is also a tube with a very small internal diameter, in which liquid can be drawn upward against gravity by capillary action (the interplay of cohesion and adhesion forces).

2. Adjective:

   • Relating to or resembling a hair; very fine and slender: Describes something that is long and thin like a hair, often referring to tubes or vessels with an extremely small internal diameter.
   • Of or involving capillary action: Pertaining to the phenomenon where liquid spontaneously rises or moves in a narrow space, such as a thin tube or porous material.

Usage Examples

• Noun (Blood vessel):

  • Oxygen diffuses from the blood in the capillary into the surrounding tissue.
  • The doctor explained how nutrients are delivered to cells through the walls of capillaries.

• Noun (Tube):

  • The scientist used a glass capillary to collect a tiny sample of the liquid.
  • Water climbs up the soil's capillaries due to capillary action.

• Adjective:

  • A capillary tube is essential for this precise chemical experiment.
  • The rise of water in a thin plant root is a capillary phenomenon.

Advanced Usage

• Capillary action (or capillarity): The ability of a liquid to flow in narrow spaces without the assistance of, or even in opposition to, external forces like gravity.

  • Capillary action is what allows water to travel from the roots to the leaves of a tree.

• Capillary bed: The network of capillaries in a specific area of tissue.

  • The capillary bed in the lungs is where gas exchange occurs.

Variants and Related Words

• Capillarity (n): Another term for capillary action.
• Capillary-sized (adj): Having a diameter comparable to that of a capillary vessel; extremely small.

Synonyms

• Noun (Vessel): blood vessel, microvessel.
• Noun (Tube): fine tube, micropipette.
• Adjective: hair-like, fine, slender, thin-bore.

Related Phrases

• Capillary refill: A test to check blood circulation by pressing on a fingernail and observing how quickly color returns, indicating blood flow through capillaries.

  • The nurse checked the patient's capillary refill time.

• Capillary rise: The height to which a liquid ascends in a capillary tube.

  • The experiment measured the capillary rise of different fluids.

Adjective

1. long and slender with a very small internal diameter
   • a capillary tube
2. of or relating to hair

Noun

1. any of the minute blood vessels connecting arterioles with venules
2. a tube of small internal diameter; holds liquid by capillary action