Why are some proteins and fatty acids considered essential

Because fatty acids are also known as lipids and lipids are used for long term energy, and proteins are also used for energy. I think that this makes them essential because they are able to keep a healthy amount of energy in their system and without them they would not be able to do so. 

Answersuicide;

Answeralong with the tissue lining,the blood,tissue,and unfertilized egg leave the uterus,going through the vagina on the way out of the body,(menstrual period);