THE MUSCLES OF THE HEAD AND NECK 127 



of the malar bone to be inserted into each tarsal plate 

 at the external commissure of the eyelids. 



Actions. Orbicularis palpebrarum is the muscle 

 which closes the eye suddenly, as in winking, or as a 

 protection in shutting the eye against the entrance 

 of a foreign body. The palpebral portion closes the 

 lids, as in sleep. The tendo-oculi serves to suck the 

 tears into the lacrymal sac, by its attachment to the 

 sac. (See Lacrymal Apparatus, page 398). 



Nerve Supply facial nerve. 



Corrugator Supercilii. They are two small muscles 

 found at the inner extremity of the eyebrow, beneath 

 the occipitofrontalis and orbicularis palpebrarum, with 

 which they fuse. 



Action is to draw the eyebrow downward and inward 

 and to form the vertical wrinkles of the forehead; it 

 is called the "frowning" muscle, and is the means of 

 expressing anxiety, suffering, and thought. 



Nerve Supply facial nerve. 



The Muscles of the Orbit (Orbital Region) 



Levator palpebrse superioris Rectus internus 

 Rectus superior Rectus externus 



Rectus inferior Obliquus oculi superior 



Obliquus oculi inferior 



Levator Palpebrse Superioris. This, the elevator of 

 the upper lid, is a thin, flat, and slightly triangular- 

 shaped muscle found within the orbital cavity (and 

 like the other muscles of this group cannot be seen 

 until the skull-cap has been removed and the roof of 

 the orbit opened) above the eye-ball. 



Actions. Raises the upper eyelid and is the opposite 

 in action to the palpebral portion of the orbicularis 

 palpebrarum. 



Nerve Supply. Motor oculi or third cranial nerve. 



