callus pad造句

The nearly smooth surface has a blotched periphery and a central tubercle on the callus pad distinguish it.
Sieve-tube members that are alive contain a polymer called callose, a carbohydrate polymer, forming the callus pad / callus, the colourless substance that covers the sieve plate.
The handle of the club runs diagonally across the base of the fingers on my left hand, from the base of the forefinger to a point atop the callus pad below my little finger.
It's difficult to find callus pad in a sentence. 用callus pad造句挺难的