▁Phys i ological ▁responses ▁▁ ▁Sex ual ▁ar ous al ▁causes ▁various ▁physical ▁responses , ▁most ▁significantly ▁in ▁the ▁sex ▁org ans ▁( gen ital ▁org ans ). ▁Sex ual ▁ar ous al ▁for ▁a ▁man ▁is ▁usually ▁indicated ▁by ▁the ▁sw elling ▁and ▁ere ction ▁of ▁the ▁pen is ▁when ▁blood ▁fills ▁the ▁cor pus ▁ca vern os um . ▁This ▁is ▁usually ▁the ▁most ▁prominent ▁and ▁reliable ▁sign ▁of ▁sexual ▁ar ous al ▁in ▁males . ▁In ▁a ▁woman , ▁sexual ▁ar ous al ▁leads ▁to ▁increased ▁blood ▁flow ▁to ▁the ▁cl itor is ▁and ▁vul va , ▁as ▁well ▁as ▁v ag inal ▁trans ud ation ▁- ▁the ▁se eping ▁of ▁mo ist ure ▁through ▁the ▁v ag inal ▁walls ▁which ▁serves ▁as ▁lub ric ation . ▁ ▁Male ▁ ▁It ▁is ▁normal ▁to ▁correlate ▁the ▁ere ction ▁of ▁the ▁pen is ▁with ▁male ▁sexual ▁ar ous al . ▁Phys ical ▁or ▁psych ological ▁stim ulation , ▁or ▁both , ▁leads ▁to ▁vas od ilation ▁and ▁the ▁increased ▁blood ▁flow ▁eng org es ▁the ▁three ▁sp ong y ▁areas ▁that ▁run ▁along ▁the ▁length ▁of ▁the ▁pen is ▁( the ▁two ▁corpor a ▁ca vern osa ▁and ▁the ▁cor pus ▁sp ong ios um ). ▁The ▁pen is ▁grows ▁en larg ed ▁and ▁firm , ▁the ▁skin ▁of ▁the ▁sc rot um ▁is ▁pulled ▁t ighter , ▁and ▁the ▁test es ▁are ▁pulled ▁up ▁against ▁the ▁body . ▁However , ▁the ▁relationship ▁between ▁ere ction ▁and ▁ar ous al ▁is