The location and direction of movement in AU113, sharp lip puller (indicated by the arrow).

<p>The lips are in the neutral position. AU113 is very difficult to code from photographs unless there is a very strong action, or it is combined with AU12, lip corner puller.</p

The facial muscles of the horse.

<p>NB. Levator labii superioris a.n. represents the levator labii superioris alaeque nasi, which is often also called the levator nasolabialis. Synonyms for the levator annuli oris fascialis muscle include the dilator nares muscle and the caninus muscle. The frontoscutularis has a frontal and a temporal arm.</p

AU10, upper lip raiser (+ 16 + 17 + 25 + 27 + AD1 [AD1 seen in part B only]).

<p>Part A shows appearance changes 1, 2, 3, 4, and 7; part B shows appearance changes 2, 4, 5, 6, and 7.</p

Direction and area of AUH13, nostril lift.

<p>The picture on the left shows the neutral face, the picture on the right shows the face with a mild action of AUH13 applied. The arrow illustrates the location and direction of movement.</p

The general neutral ear position of a horse, although there is some individual variation.

<p>The general neutral ear position of a horse, although there is some individual variation.</p

AU12, lip corner puller, without AU113, sharp lip puller, (A) and AU12 with AU113 (B).

<p>Note the difference in the shape at the corner of the mouth. AU12 produces a curvature at the mouth corner; however, when AU113 is applied with AU12 the mouth has an angular appearance at the top corner, with corresponding wrinkles in the skin surrounding the mouth. See <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0131738#pone.0131738.s024" target="_blank">S15 Video</a> for a demonstration of these actions acting simultaneously.</p

The starting ear position (A) and then with EAD103, ear flattener, and EAD104, ear rotator, applied (B).

<p>An example of how the ears can almost disappear in a frontal view of a strong action.</p

AD160, lower lip relax, seen from a distance and a close up view.

<p>Note that from a distance, although subtle, AD160 can be identified by the visible pink flesh from the inside of the lower lip.</p

An example of the wrinkles seen with AU122, upper lip curl.

<p>These wrinkles are also characteristic of AU10, upper lip raiser, however in AU10 there is no puckering or eversion of the lip.</p

A guide to anatomical direction.

<p>A guide to anatomical direction.</p