Once the three primary germ layers have formed and the embryo has undergone and transverse folding, the process of , or organ development, can begin. The upper and lower limbs attain their adult shapes, and the rudimentary forms of most organ systems have developed by week of development.

Vaccines are weakened forms of disease causing microorganisms, which are given to patients to prevent disease. after the vaccine is administered, the immune system responds by creating a(n) to recognize the a.) antibody, antibiotic b.) antigen, antibody c.)antibiotic, antibody d.)antibody, antigen