Dictionary:

capillary

  (kăp'ə-lĕr'ē)

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1. Relating to or resembling a hair; fine and slender.
2. Having a very small internal diameter: a capillary tube.
3. Anatomy. Of or relating to the capillaries.
4. Physics. Of or relating to capillarity.

1. Anatomy. One of the minute blood vessels that connect arterioles and venules. These blood vessels form an intricate network throughout the body for the interchange of various substances, such as oxygen and carbon dioxide, between blood and tissue cells.
2. A tube with a very small internal diameter.

[From Latin capillāris, from capillus, hair.]

The terminal vessels uniting the arterial with the venous systems of the body. Capillaries are organized into extensive branching reticular beds to provide a maximal surface for exchange of fluids, electrolytes, and metabolites between tissues and the vascular system. The capillary bed has the largest cross-sectional area of the entire vascular system.

In a soil, the fine spaces between soil particles. Capillary action is the ascent (or descent) of a liquid in an area of small diameter, such as a soil pore, due to the combined effects of surface tension and the forces of cohesion and adhesion. see salination.

For more information on capillary, visit Britannica.com.

A thin tube, such as a blood vessel or a straw, through which fluids flow.

1. pertaining to or resembling a hair.
2. one of the minute vessels connecting arterioles and venules, the walls of which act as a membrane for interchange of various substances between the blood and tissue fluid. (See circulatory system.) The walls consist of thin endothelial cells through which dissolved substances and fluids can pass. At the arterial end, the blood pressure within the capillary is generally higher than the pressure in the surrounding tissues, and the blood fluid and some dissolved solid substances pass outward through the capillary wall. At the venous end of the capillary, the pressure within the tissues is generally higher, and waste material and fluids from the tissues pass into the capillary, to be carried away for disposal. See starling's hypothesis.

• continuous c. — a capillary with no pores or other interruptions in the endothelial walls, e.g. in muscle, lung, nervous system.
• fenestrated c's — capillaries with pores are scattered throughout the endothelial walls, e.g. in endocrine glands, intestines, kidneys.
• c. fragility — see capillary fragility.
• lymph c. — the smallest lymphatic vessel. Consists of an endothelial tube embedded in connective tissue.
• perforated c. — see fenestrated capillary (above).
• c. permeability — ability of large molecules to pass out of the capillary lumen into surrounding tissue spaces; inflammation, allergy, poisoning, burns cause increased permeability resulting in plasma leakage and edema in surrounding tissues.
• c. refill time (CRT) — the time required for mucosa (oral in horse or dog, vaginal in cow, sheep) which has been blanched by finger pressure to return to a normal pink color. Failure to return promptly is an indication of peripheral circulatory failure, due for example to dehydration or hypovolemic shock.
• sinus c's — part of the vasculature of avian skin. Occur together with standard capillaries but they are larger in diameter and may have some smooth muscle cells associated with the endothelial cells.
• sinusoidal c's — large and irregularly shaped; occur in endocrine glands, aortic and carotid bodies.

Blood flows from digestive system heart to arteries, which narrow into arterioles, and then narrow further still into capillaries. After the tissue has been perfused, capillaries widen to become venules and then widen more to become veins, which return blood to the heart.

The word capillary is used to describe any very narrow tube or channel through which a fluid can pass. See capillary action for details.

Capillaries are the smallest of a body's blood vessels, measuring 5-10 μm, which connect arterioles and venules, and are important for the interchange of oxygen, carbon dioxide, and other substances between blood and tissue cells.^[1]

Structure

The walls of capillaries are composed of only a single layer of cells, the endothelium. This layer is so thin that molecules such as oxygen, water and lipids can pass through them by diffusion and enter the tissues. Waste products such as carbon dioxide and urea can diffuse back into the blood to be carried away for removal from the body. Capillaries are so small the blood cells need to pass through it in a single file line.

Capillary permeability can be increased by the release of certain cytokines, such as in an immune response

This is right the endocrine belongs with digestive group

Immune response

In an immune response, the endothelial cells of the capillary will upregulate receptor molecules, thusit adds us the grand and toy effectby the site of infection and aiding extravasation of these cells into the tissue.

Capillary bed

The "capillary bed" is the network of capillaries supplying an organ. The more metabolically active the cells, the more capillaries it will require to supply nutrients.

The capillary bed usually carries no more than 25% of the amount of blood it could contain, although this amount can be increased through autoregulation by inducing relaxation of smooth muscle.

The capillaries do not possess this smooth muscle in their own walls, and so any change in their diameter is passive. Any signalling molecules they release (such as endothelin for constriction and nitric oxide for dilation) act on the smooth muscle cells in the walls of nearby, larger vessels, e.g. arterioles.

Types

Capillaries come in three types:

• Continuous - Continuous capillaries have a sealed endothelium and only allow small molecules, water and ions to diffuse.
• Fenestrated - Fenestrated capillaries (derived from "fenestra," the Latin word for "window") have openings that allow larger molecules to diffuse.^[2]
• Sinusoidal - Sinusoidal capillaries are special forms of fenestrated capillaries that have larger openings in the epithelium allowing red blood cells and serum proteins to enter.

See also

• Alveolar-capillary barrier
• Blood brain barrier

References

1. ^ Medical dictionary definition of blood+capillary from KMLE Medical Dictionary retrieved on 07-04-17
2. ^ Histology at BU 22401lba

External links

• Histology at BU 00903loa

Cardiovascular system
Blood  |  Heart  → Aorta → Arteries → Arterioles → Capillaries → Venules → Veins → Vena cava → Heart → Pulmonary arteries → Lungs → Pulmonary vein

This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)

Dansk (Danish)
n. - kapillærer, hårkar, hårrør
adj. - hårrørs-

Nederlands (Dutch)
haarvat, capillair, te maken hebbend met het haar

Français (French)
n. - capillaire
adj. - capillaire

Deutsch (German)
n. - Haargefäß
adj. - kapillar, haardünn

Ελληνική (Greek)
n. - τριχοειδές αγγείο

Italiano (Italian)
capillare

Português (Portuguese)
n. - capilaridade (f)

Русский (Russian)
капилляр

Español (Spanish)
n. - capilar, tubo capilar, vaso capilar
adj. - capilar

Svenska (Swedish)
n. - kapillaritet

中文（简体） (Chinese (Simplified))
毛细管, 毛状的, 毛细管的

中文（繁體） (Chinese (Traditional))
n. - 毛細管
adj. - 毛狀的, 毛細管的

한국어 (Korean)
n. - 모세관
adj. - 털 모양의, 모세관의

日本語 (Japanese)
adj. - 毛管の, 毛状の
n. - 毛管, 毛細血管

العربيه (Arabic)
‏(الاسم) شعري, رفيع كالشعر‏

עברית (Hebrew)
n. - ‮נימה, נימת-דם‬
adj. - ‮של נימת-דם בגוף, דק כשערה, של שערה‬

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