Early anatomists often named muscles based upon their resemblance to common shapes. Some muscles named in this fashion include the deltoid, trapezius, orbicularis, and teres.

deltoid (delt, G: "triangle"; oid, G: "like")
trapezius (trapez, G: "table")
serratus (serrat, L: "a saw" or "saw toothed")
teres (tere, L: "round")
orbicularis (orbi, L: circle; cul, L: "little")
latissimus (lat, L: "broad" or "wide"; simus, L: "a likeness")

What would the following muscles look like and where would they be found: latissimus dorsi, orbicularis oculi, orbicularis oris?

9. Type of Action Produced By the Muscle:

The name of many muscles also includes that type of movement (action) which they bring about. Following are some terms that describe movements at joints brought about by muscle contraction. Each of these actions assumes that the body is in the anatomical position.

flexion (flex, L: "to bend") decreases the angle at a joint
extension (ex, L: "out"; ten, L: "stretch") increases the angle at a joint
adduction (ad, L: "to" or "toward"; duct, L: "lead") pulls the limb toward the midline
abduction (ab, L: "away" or "from"; duct, L: "lead") pulls the limb away from the midline
pronation (pron, L: "bent forward") turning the palm downward
supination (supin, L: "lying on the back") turning the palm upward

Muscles that pull an appendage inward are often termed flexors (e.g. flexor carpi radialis, flexor carpi ulnaris) while muscles that bring about extension are termed extensors (e.g. extensor digitorum, extensor carpi radialis).