The Shank bone reminds us of the Passover Sacrifice of the lamb and the mighty hand of God Who took us out of Egypt.
The egg reminds us of the Chagiga Sacrifice. An egg is also a food of mourning and it reminds of the destruction of the Holy Temple.
The Haroset, a mixture of dates, nuts, apples, reminds us of the hard slavery and the making of the bricks.
The parsley (bitter herb) reminds of the back-breaking work of the Jewish people.
The horseradish (chazeret) reminds us of the bitter slavery of the Jews.
The Lettuce (maror) reminds us of the bitter slavery of the Jewish people.