THE PALPEBRAL REGION. 



395 



nally, it is occasionally blended with the Pyramidalis nasi. Externally, it lies 

 on the temporal fascia. On the eyelids it is separated from the conjunctiva by 

 the Levator palpebrge, the tarsal ligaments, the tarsal plates, and the Meibomian 

 glands. 



The tendo palpebrarum (tendo oculi) is a short tendon, about two lines in length 

 and one in breadth, attached to the nasal process of the superior maxillary bone 

 in front of the lachrymal groove for the nasal duct. Crossing the lachrymal sac, 

 it divides into two parts, each division being attached to the inner extremity of the 

 corresponding tarsal plate. As the tendon crosses the lachrymal sac. a strong 

 aponeurotic lamina is given off from the posterior surface, which expands over 

 the sac, and is attached to the ridge on the lachrymal bone. This is the reflected 

 aponeurosis of the tendo palpebrarum. 



Use of Tendo oculi. Besides giving attachment to part of the Orbicularis 

 palpebrarum. and to the tarsal plates, it serves to suck the tears into the lachrymal 

 sac, by its attachment to the sac. Thus, each time the eyelids are closed, the tendo 

 oculi becomes tightened, and draws the wall of the lachrymal sac outward and 

 forward, so that a vacuum is made in the sac, and the tears are sucked along the 

 lachrymal canals into it. 



The Corrugator supercilii is a small, narrow, pyramidal muscle, placed at the 

 inner extremity of the eyebrow, be- 

 neath the Occipito-frontalis and 

 Orbicularis palpebrarum muscles. 

 It arises from the inner extremity 

 of the superciliary ridge; from 

 whence its fibres pass upward and 

 outward, to be inserted into the 

 under surface of the orbiculai'is, op- 

 posite the middle of the orbital arch. 



Relations. By its anterior sur- 

 face with the Occipito-frontalis and 

 Orbicularis palpebrarum muscles ; 

 by its posterior surface, with the 

 frontal bone and supratrochlear - 

 nerve. 



The Levator palpebrae will be 

 described with the muscles of the 

 orbital region. 



The Tensor tarsi (Homer's 

 muscle) (Fig. 270) is a small thin 

 muscle about three lines in breadth 

 and six in length, situated at the 

 inner side of the orbit, behind the 

 tendo oculi. It arises from the crest 

 and adjacent part of the orbital sur- 

 face of the lachrymal bone, and, pass- 

 ing across the 'lachrymal sac, divides into two slips, which cover the lachrymal 

 canals, and are inserted into the tarsal plates internal to the puncta lachrymalia. 

 Its fibres appear to be continuous with those of the palpebral portion of the 

 Orbicularis palpebrarum ; it is occasionally very indistinct. 



Neives. The Orbicularis palpebrarum, Corrugator supercilii, and Tensor tarsi 

 are supplied by the facial nerve. 



Actions. The Orbicularis palpebrarum is the sphincter muscle of the eyelids. 

 The palpebral portion acts involuntarily, closing the lids gently, as in sleep or in 

 blinking; the orbicular portion is subject to the will. When the entire muscle is 

 brought into action, the skin of the forehead, temple, and cheek is drawn inward 

 toward the inner angle of the orbit, and the eyelids are firmly closed as in photophobia. 

 When the skin of the forehead, temple, and cheek is thus drawn inward by the 



Orbicular 

 portion 



FIG. 270. Inner part of orbicularis palpebrarum, seen 

 from behind. (Henle.) 



