The primary (main) action of the<unk>  is intorsion (internal rotation), the secondary action is depression (primarily in the adducted position) and the tertiary action is abduction (lateral rotation). The extraocular muscles rotate the eyeball around vertical, horizontal and antero-posterior axes. Extraocular muscles other than the medial rectus and lateral rectus have more than one action due to the angle they make with the optical axis of the eye while inserting into the eyeball. The<unk>  and inferior<unk>  muscles make an angle of 51 degrees with the optical axis. The depressing action of<unk><unk>  (making the eye look down towards the mouth) is most effective when the eye is in an adducted position. This is because as the eye is abducted (looks laterally), the contribution made by<unk><unk>  to depression of the eye decreases, as the inferior rectus muscle causes this movement more directly and powerfully. The main muscle for abduction is the lateral rectus, so although<unk><unk>  contributes to a downwards and lateral eye movement, testing this motion would not be specific enough as inferior and lateral recti muscles would also be tested. Therefore, during neurological examinations, the<unk><unk>  is tested by having the patient look inwards and downwards, testing only the depressing action of the muscle. This is a source of confusion on the subject as although clinical testing asks the patient to adduct and depress the eye, anatomically the muscle depresses and abducts it. The great importance of intorsion and extorsion produced by the two<unk>  muscles can only be understood when it is considered with regards to the other muscle actions present. The two<unk> s prevent the eye from rotating about its long axis (retina to pupil) when the<unk>  and inferior rectus muscles contract. This is because the orbit does not face directly forwards- the centre-line of the orbit is a little over 20 degrees out from the mid-line. But because the eyes do face forwards, when acting alone, as well as making the eye look up,<unk>  rectus causes it to rotate slightly about the long axis, so the top of the eye moves medially (intorsion). Similarly, in addition to making the eye look down, inferior rectus would cause the eye to rotate about the long axis so the top of the eye moves slightly laterally (extorsion), if acting alone. Clearly this is undesirable as our vision would rotate when we looked up and down. For this reason, these two rectus muscles work in conjunction with the two<unk> s. When acting alone,<unk><unk>  causes intorsion, inferior<unk> , extorsion. Hence, when inferior rectus contracts so we look down,<unk><unk>  also contracts to prevent extorsion of the eye, and when<unk>  rectus contracts so we look up, inferior<unk>  contracts to prevent intorsion, thus the undesired rotatory actions of the inferior and<unk>  recti about the long axis of the eye are cancelled out. This keeps our vision horizontally level, irrespective of eye position in the orbit.
Superior oblique muscle
Inferior oblique muscle
Morcellator
Latissimus dorsi muscle
Subscapularis muscle
Levator ani
Levator palpebrae superioris muscle
Iris sphincter muscle