1. At what point during a pregnancy does this organ or system begin to develop, function, and become fully developed? 2. Are there specific substances that are harmful to this organ system's...

Organs: Arms, legs, nose, mouth, kidneys, intestine, heart,liver

Extracted text: 1. At what point during a pregnancy does this organ or system begin to develop, function, and become fully developed? 2. Are there specific substances that are harmful to this organ system's development? How do these substances reach the fetus? 3. What nutrients are required for the organ system's development?