Question

Smallest blood vessels in the body is
a) Vein
b) Artery
c) Capillary
d) None of the above

Answer 1

They are the minute blood vessels that form networks throughout the bodily tissues which are responsible for the transport of various substances.

Complete answer:
Capillaries are the smallest of blood vessels from 5 to 10 micrometers in diameter. They are one cell thick and help in the exchange of materials between blood and tissues. Capillaries connect to arterioles on one end and venules on the other end and supply blood to various tissues and organs of the body.

Additional information:
1. Capillaries are very tiny blood vessels, The width of these capillaries is so small that it becomes difficult for even a single red blood cell to pass through them.
2. Substances that exit include water, oxygen, and glucose while the substances which enter are water, carbon dioxide, uric acid, lactic acid, and creatinine.
3. From the heart through the arteries the blood continues to flow. These arteries will later get branched and narrower and form arterioles which further get branched and form capillaries. These capillaries are responsible for the exchange of nutrients and waste products.
4. The capillaries then join and widen to become venules, which in turn widen and converge to become veins, which then return the blood to the heart through the venae cavae.
5. The capillaries are of two types: true capillaries (it branch from arterioles and provide an exchange between tissues and the capillary blood) and lymphatic capillaries (larger in diameter than blood capillaries and have closed ends).

So, the correct answer is 'Capillary'.

Note: There are three types of blood capillaries: continuous capillaries (smaller molecules with uninterrupted lining), fenestrated capillaries (pores in endothelial linings), and sinusoidal (open-pore capillary with discontinuous endothelial lining). The capillaries were first observed in 1661 by Marcello Malpighiwhen he was observing the various organs of the body.