Illustration from Anatomy &amp; Physiology, Connexions Web site. <a rel="nofollow" class="external free" href="http://cnx.org/contents/14fb4ad7-39a1-4eee-ab6e-3ef2482e3e22@6.27:189">http://cnx.org/contents/14fb4ad7-39a1-4eee-ab6e-3ef2482e3e22@6.27:189</a>, Jun 19, 2013.
OpenStax College
CC BY 3.0
Anatomy &amp; Physiology, Connexions Web site. <a rel="nofollow" class="external free" href="http://cnx.org/contents/14fb4ad7-39a1-4eee-ab6e-3ef2482e3e22@6.27:189">http://cnx.org/contents/14fb4ad7-39a1-4eee-ab6e-3ef2482e3e22@6.27:189</a>, Jun 19, 2013.