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Information about Capillary

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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

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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

References

External links

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Cardiovascular system
Blood  |  Heart → Aorta → Arteries → Arterioles → Capillaries → Venules → Veins → Vena cava → Heart → Pulmonary arteries → Lungs → Pulmonary vein
Capillary action, capillarity, capillary motion, or wicking is the ability of a substance to draw another substance into it. The standard reference is to a tube in plants but can be seen readily with porous paper.
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The blood vessels are part of the cardiovascular system and function to transport blood throughout the body. The most important types, arteries and veins, carry blood away from or towards the heart, respectively.
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1 micrometre =
SI units
010−6 m 010−3 mm
US customary / Imperial units
010−6 ft 010−6 in
A micrometre (American spelling: micrometer; symbol µm
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An arteriole is a small diameter blood vessel that extends and branches out from an artery and leads to capillaries.

Arterioles have thin muscular walls (usually only one to two layers of smooth muscle) and are the primary site of vascular resistance[1].
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A venule is a small blood vessel that allows deoxygenated blood to return from the capillary beds to the larger blood vessels called veins.
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2, −1
(neutral oxide)
Electronegativity 3.44 (Pauling scale)
Ionization energies
(more) 1st: 1313.9 kJmol−1
2nd: 3388.3 kJmol−1
3rd: 5300.5 kJmol−1

Atomic radius 60 pm
Atomic radius (calc.
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Carbon dioxide is a chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom. It is a gas at standard temperature and pressure and exists in Earth's atmosphere in this state.
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Blood is a specialized biological fluid consisting of red blood cells (also called RBCs or erythrocytes), white blood cells (also called leukocytes) and platelets (also called thrombocytes) suspended in a complex fluid medium known as blood plasma.
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endothelium is the thin layer of cells that line the interior surface of blood vessels, forming an interface between circulating blood in the lumen and the rest of the vessel wall. Endothelial cells line the entire circulatory system, from the heart to the smallest capillary.
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molecule is defined as a sufficiently stable electrically neutral group of at least two atoms in a definite arrangement held together by strong chemical bonds.[1][2] In organic chemistry and biochemistry, the term molecule
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2, −1
(neutral oxide)
Electronegativity 3.44 (Pauling scale)
Ionization energies
(more) 1st: 1313.9 kJmol−1
2nd: 3388.3 kJmol−1
3rd: 5300.5 kJmol−1

Atomic radius 60 pm
Atomic radius (calc.
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Water is a common chemical substance that is essential to all known forms of life.[1] In typical usage, water refers only to its liquid form or state, but the substance also has a solid state, ice, and a gaseous state, water vapor.
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Lipids can be broadly defined as any fat-soluble (hydrophobic), naturally-occurring molecules. The term is more-specifically used to refer to fatty-acids and their derivatives (including tri-, di-, and monoglycerides and phospholipids) as well as other fat-soluble sterol-containing
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This article is about the physical mechanism of diffusion. For alternative meanings, see diffusion (disambiguation).


Diffusion is the net movement of particles from an area of high concentration to an area of low concentration.
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Carbon dioxide is a chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom. It is a gas at standard temperature and pressure and exists in Earth's atmosphere in this state.
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Urea is an organic compound with the chemical formula (NH2)2CO.

Urea is also known as carbamide, especially in the recommended International Nonproprietary Names (rINN) in use in Europe.
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Blood is a specialized biological fluid consisting of red blood cells (also called RBCs or erythrocytes), white blood cells (also called leukocytes) and platelets (also called thrombocytes) suspended in a complex fluid medium known as blood plasma.
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Permeability, permeable and semipermeable have several meanings:
  • Permeability (electromagnetism), is the degree of magnetization of a material in response to a magnetic field

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Cytokines are a group of proteins and peptides that are used in organisms as signaling compounds. These chemical signals are similar to hormones and neurotransmitters and are used to allow one cell to communicate with another.
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immune system is a collection of mechanisms within an organism that protects against disease by identifying and killing pathogens and tumor cells. It detects a wide variety of agents, from viruses to parasitic worms, and needs to distinguish them from the organism's own healthy
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immune system is a collection of mechanisms within an organism that protects against disease by identifying and killing pathogens and tumor cells. It detects a wide variety of agents, from viruses to parasitic worms, and needs to distinguish them from the organism's own healthy
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endothelium is the thin layer of cells that line the interior surface of blood vessels, forming an interface between circulating blood in the lumen and the rest of the vessel wall. Endothelial cells line the entire circulatory system, from the heart to the smallest capillary.
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For other uses, see Receptor.


In biochemistry, a receptor is a protein on the cell membrane or within the cytoplasm or cell nucleus that binds to a specific molecule (a ligand), such as a neurotransmitter, hormone, or other substance, and initiates
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An infection is the detrimental colonization of a host organism by a foreign species. In an infection, the infecting organism seeks to utilize the host's resources to multiply (usually at the expense of the host).
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MeSH C21.866.371

Extravasation refers to the leakage of a fluid out of its container. In the case of inflammation, it refers to the movement of white blood cells from the capillaries to the tissues surrounding it.
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organ (Latin: organum, "instrument, tool") is a group of tissues that perform a specific function or group of functions. Usually there is a main tissue and sporadic tissues. The main tissue is the one that is unique for the specific organ.
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Metabolism is the complete set of chemical reactions that occur in living cells. These processes are the basis of life, allowing cells to grow and reproduce, maintain their structures, and respond to their environments. Metabolism is usually divided into two categories.
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Autoregulation is a specific form of homeostasis used to describe the tendency of the body to keep blood flow constant when blood pressure varies.[1].

While most systems of the body show some degree of autoregulation, it is most clearly observed in the kidney, the
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Smooth muscle is a type of non-striated muscle, found within the "walls" of hollow organs and elsewhere like the bladder and abdominal cavity, the uterus, male and female reproductive tracts, the gastrointestinal tract, the respiratory tract, the vasculature, the skin and the
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