They deliver oxygen and nutrients to cells while removing carbon dioxide to be eliminated from the lungs.
There are different types of capillaries with specific functions in the body.
This article describes the structure and function of capillaries.
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It also explains the effects of capillary dysfunction and the diseases and conditions that cause them.
There are about 40 billion capillaries in the average human body.
Capillaries are extremely thin, measuring approximately 5 micrometers in diameter.
They are so small thatred blood cellsneed to flow through them single file.
Capillaries in the central nervous system are also involved in the blood-brain barrier.
This barrier limits the ability of toxins (including certain medications) to pass through into the brain.
Drugs that act on the brain need to be designed to circumvent this barrier.
While arteries deliver these to the capillaries, the capillaries are where the actual exchange takes place in cells.
When you exercise, more capillary beds are recruited to prepare for an increased need for oxygen in tissues.
The same mechanisms are involved in the regulation ofblood pressure.
Capillary Microcirculation
Capillaries regulate fluid movement between the circulatory system and tissues.
This process is determined by the balance of two forces:hydrostaticpressure andosmoticpressure.
Hydrostatic pressure pushes fluids and nutrients out of capillary walls through pores in fenestrated capillaries.
The pressure is triggered by the force of blood entering the capillary.
Osmosis is resulting from the imbalance of salt and water on the inside and outside of capillaries.
Examples include:
Associated Conditions
Capillaries are involved in several health concerns.
Some are relatively common while others are rare.
Summary
Capillaries are the smallest blood vessels in the circulatory system.
Capillaries are involved when your skin blanches or you get a rash or hives.
They can break or get inflamed, causing petechiae, rosacea, or spider veins.
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