Different structure in an organism are specialized to perform different tasks in the organism depending on their makeup. A few examples are:
Heart, veins, arteries are structures forming the cardiovascular system and function is to facilitate transport nutrients and oxygen carried by blood all over the body.
Bones, joints, ligaments and cartilage are structures of the skeletal system and their function is support and protection of the body.
Mouth, esophagus. stomach, large and small intestines are structures of the digestive system and their function is to break down food and absorb nutrients.