The lulav, whose central pillar is referred to as its backbone/spine (shidrah) resembles the backbone of the human The leaves of the myrtle branch (hadas) resemble the eyes of the human The leaves of the willow branch (aravah) resemble the lips of human The etrog resembles the heart (lev) of the human Midrash - VaYikra Rabbah 30:14
Explanations by Rabbi David Baum
Every morning in Judaism, we wake up and say prayers thanking God for the little things that make a big difference – parts of our bodies that allow to live in this world. On Sukkot, we shake the lulav every morning to help remind us even more of the importance of our bodies and how we can better 'walk' in this world – with the confidence of a straight spine; with more open eyes; with a mouth ready to speak words of praise and goodness; and a heart that is open and ready for healing.
Lulav/Palm – The Backbone/Spine …