Capillaries · Whole body
Capillaries
Capillaries are the tiniest blood vessels, connecting the smallest arteries to the smallest veins. Their walls are so thin that oxygen, nutrients and waste pass through them into and out of tissues.
What it is
Capillaries are microscopic blood vessels, only one cell thick, forming vast networks throughout every tissue.
Where it runs
Everywhere in the body, in dense networks within tissues and organs.
What it does
Allow oxygen, nutrients and waste products to move between the blood and the body's cells — the whole point of the circulation.
When things go wrong
Common problems affecting the capillaries
- Damage in conditions like diabetes (affecting eyes, kidneys and nerves)
- Fragility causing easy bruising
Education and reference only. This explains the anatomy in plain terms and is not a diagnosis. Sudden severe chest, back or abdominal pain, sudden breathlessness, or stroke symptoms (FAST) are emergencies — call 999.
Did you know?
An interesting fact
If all the body's capillaries were laid end to end, they would stretch for tens of thousands of miles — enough to circle the Earth several times.
Answers
Capillaries: frequently asked questions
What do capillaries do?
Capillaries are the tiny vessels where oxygen, nutrients and waste pass between the blood and the body's cells — the actual exchange that circulation exists for.
Sources
Where this is drawn from
- NHS — Blood and the circulatory system
- Gray's Anatomy for Students
- British Heart Foundation — how the heart works
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