Q.

The structure of which of the following consists of a layer of single cell thickness
 a) Blood capillary          b) Artery             c) Venule          d) Arteriole 

AA
BB
CC
DD

A.

(a) Capillaries were discovered by Marcello Malpighi in 1661. These are very thin-walled, because tunica externa and tunica media are absent. Capillary wall is formed by only tunica interna or endothelium. These connect arterioles to venules and specialized for exchanging substances with interstitial fluid. According to local tissue requirements, these can be constricted or dilated.

 



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