THE MUSCLES OF THE EYELIDS 



381 



The medial palpebral ligament (tendo oculi), about 4 mm. in length and 2 mm. 

 in breadth, is attached to the frontal process of the maxilla in front of the lacrimal 

 groove. Crossing the lacrimal sac, it divides into two parts, upper and lower, 

 each attached to the medial end of the corresponding tarsus. As the ligament 

 crosses the lacrimal sac, a strong aponeurotic lamina is given off from its posterior 

 surface; this expands over the sac, and is attached to the posterior lacrimal crest. 



The lateral palpebral raphe is a much weaker structure than the medial palpebral 

 ligament. It is attached to the margin of the frontosphenoidal process of the 

 zygoma-tic bone, and passes medialward to the lateral commissure of the eyelids, 

 where it divides into two slips, w r hich are attached to the margins of the respective 

 tarsi. 



Probe in frontal sinus 



Probe in ant. eth- 

 moidal cells 



Crista galli 



Lacrimal part of 



,, Orbicularis oculi 



Probe in lacrimal sac 



f Probes from frontal 

 \sinus and ant. eth- 

 moidal cells 



Middle meatus 



Septum of nose 



Probe in nasolacrimal 

 duct 



Infraorbital nerve and artery 



FIG. 379. Left orbicularis oculi, seen from behind. 



The Corrugator 1 (Corrugator supercilii) is a small, narrow, pyramidal muscle, 

 placed at the medial end of the eyebrow, beneath the Frontalis and Orbicularis 

 oculi. It arises from the medial end of the superciliary arch; and its fibers pass 

 upward and lateralward, between the palpebral and orbital portions of the Orbicu- 

 laris oculi, and are inserted into the deep surface of the skin, above the middle of 

 the orbital arch. 



Nerves. The Orbicularis oculi and Corrugator are supplied by the facial nerve. 



Actions. The Orbicularis oculi is the sphincter muscle of the eyelids. The palpebral portion 

 acts involuntarily, closing the lids gently, as in sleep or in blinking; the orbital portion is subject 

 to the will. When the entire muscle is brought into action, the skin of the forehead, temple, 

 and cheek is drawn toward the medial angle of the orbit, and the eyelids are firmly closed, as in 

 photophobia. The skin thus drawn upon is thrown into folds, especially radiating from the 

 lateral angle of the eyelids; these folds become permanent in old age, and form the so-called 

 "crows' feet." The Levator palpebrse superioris is the direct antagonist of this muscle; it raises 

 the upper eyelid and exposes the front of the bulb of the eye. Each time the eyelids are closed 

 through the action of the Orbicularis, the medial palpebral ligament is tightened, the wall of 

 the lacrimal sac is thus drawn lateralward and forward, so that a vacuum is made in it and the 



1 The corrugator is not recognized as a separate muscle in the Basle Nomenclature. 



