In anatomy, the dorsum is the upper side of animals that typically run, fly, swim or crawl in a horizontal position, and the back side of animals (like humans) that walk upright. In vertebrates the dorsum contains the backbone. The term dorsal refers to anatomical structures that are either situated toward or grow off that side of an animal. The opposite side of the animal is described with the terms ventrum and ventral.
The term "dorsum" is used for the upper surface of the body of nudibranch sea slugs.
Dorsal (posterior) means the back or toward the back of the body; behind. For example, the heart is posterior to the breastbone.  Due to its embryological orientation on the posterior during development, the top-side of the foot is referred to as the "Dorsum of the foot".
- "Essentials of Human Anatomy and Physiology", Elaine N. Marieb, Tenth Edition