Dorsum (biology)

Overview
In anatomy, the dorsum is the upper side of animals that typically run, fly or swim 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.

In humans, the top of the foot and the top of the penis (in the erect position, while standing) are considered dorsal. The top of the foot is called the dorsum. It contains small extensor muscles and extensor tendons from the leg. It is supplied by the deep peroneal nerve.

Examples of anatomical terms that include "dorsal" are the dorsal fin of fish, dorsal root ganglion, dorsal root, dorsal nerve, dorsum sellae, dorsal arch, dorsalis pedis artery, dorsal ramus, dorsal scales of snakes, dorsal respiratory group, dorsal venous arch, and dorsiflexion among others.

In lepidoptera, the dorsum also refers to the trailing edge of the wing (the leading edge is called the costa).

Human Neuroanatomy
In human neuroanatomy, once you reach the forebrain, dorsal is equivalent to superior and ventral is equivalent to inferior.

Nerve rootlets stemming from the spinal cord (CNS) form dorsal (sensory) and ventral (motor) roots before these unite to form the spinal nerve (PNS).