|"The Capillary Tree"|
Photo by Matthew Hadley
Adjective & noun. Mid-17th century.
[Latin capillaris, from capillus hair, after Old & modern French capillaire: see -ARY.]
A1 adj. Of or pertaining to hair; hairlike, especially in tenuity. M17
A2 adj. Of a tube etc.: having a hairlike bore. M17
A3 adj. Of, pertaining to, or occurring in capillaries. E19
3 capillary attraction, capillary repulsion the tendency of liquid in a
capillary tube to rise, recede, as a result of surface forces.
B1 noun. A capillary vessel; especially any of the extremely narrow
blood-vessels which form a network between the arterioles and venules. M17
B2 noun. archaic. A fern, especially of the maidenhair. M17-18
capillaceous adj. Hairlike, threadlike. E18
capillament noun. archaic. A hairlike fibre, a filament. L17-M19
capillarity noun. Capillary attraction or repulsion; the property of exerting this. M19
If you've ever wondered what the difference is between an artery, a vein and a capillary, it's really not that difficult. Basically, the arteries carry oxygenated blood from the heart at high pressure - they're big, strong, and if you ever cut one in an accident you're in trouble. They connect to capillaries, which are exceptionally small, so small that red blood cells have to travel through them in single file. It is in the capillaries that the work of the blood really takes place, the red blood cells releasing oxygen through the thin, fragile capillary walls while simultaneously collecting waste products and carbon dioxide from the surrounding tissue. Then, the veins return this deoxygenated blood to the heart at low pressure. So:
Thick-walled vessels that carry mainly oxygenated blood from the heart at high pressure.
Tiny blood vessels within tissues that facilitate the diffusion of oxygen and nutrients and the elimination of waste.
Thin vessels that carry mainly deoxygenated blood back to the heart at lower pressure.
OK, OK ... it's not quite as simple as that; the connecting vessels between the arteries and the capillaries are the arterioles, and connecting the capillaries to the veins are the venules. And, yes, there are different types of capillary, namely the continuous capillary, the fenestrated capillary, and the sinusoidal capillary. But as a very basic, broad, not-studying-biology overview of what arteries, veins and capillaries are, it'll do for now.
The etymological connection between capillary and the Latin capillus, meaning hair, is easy to understand, considering the hairlike construction and network of capillaries, and English has retained related words like capillaceous, meaning 'hair or threadlike' and capillament, meaning 'a hairlike fibre'. Obviously a capillary's similarity to hair is only superficial, but it does somewhat illustrate just how insubstantial a capillary is. Even so, a human hair is on average 100 microns (micrometres) in width, while a capillary is between 5-10 microns. As a micron is 0.001mm, it's accurate to say that capillaries are very, very, very small indeed.
Do you have any capillary facts to share?
What in your life is capillaceous?
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