484 



HUMAN ANATOMY. 



Nerve-Supply. — By fibres from the rami temporales of the facial nerve. 

 Action. — To draw the auricle upward and forward. 



Fig. 



Internal palpebral ligament 

 Tensor tarsi 



500. 



Orbicularis palpebrarum 



I Upper tarsal plate 



External 

 palpebral 

 raphe 



6. Orbicularis Palpebrarum (Figs. 499, 500). 



The orbicularis palpebrarum (m. orbicularis oculi) is an elliptical sheet whose 

 fibres have their origin in the neighborhood of the inner angle of the eye and curve 

 thence, some upward and outward and some downward and outward, around the 

 rima palpebralis to terminate in the neighborhood of the external angle. The course 

 of the fibres lies partly in the substance of the upper and lower eyelids and partly over 

 the bones surrounding the margin of the orbit. In accordance with these relations, it 

 is customary to regard the muscle as consisting of two main portions, \.\\q pars palpe- 

 bralis and the /ar.$- orbitalis. 



The internal palpebral ligament (ligamentum palpebrale mediale). Where the 

 fibres of the orbicularis arise at the inner angle of the eye there is a dense band of 

 fibrous tissue which is attached at one extremity to the frontal process of the maxilla. 

 Thence it is directed outward across the outer surface of the lachrymal sac and bifur- 

 cates to be inserted into the inner border of each tarsal plate. Just before its bifur- 

 cation the ligament gives off from its posterior surface a bundle which is reflected 



inward over the lachrymal sac and 

 passes behind this to be attached to the 

 crest of the lachrymal bone. 



This ligament, which is also known 

 as the tendo oculi, may be regarded as 

 the tendon of origin of the fibres of the 

 orbicularis oculi. At the outer angle 

 of the eye there is a certain amount of 

 decussation of the fibres of the muscle 

 to form a raphe palpebralis lateralis, 

 but there is no distinct formation of a 

 fibrous band comparable to the inter- 

 nal ligament. 



Pars Palpebralis. — The palpe- 

 bral portion of the muscle arises partly 

 from the internal palpebral ligament 

 and partly from the crest of the lachrymal bone. The fibres which take origin from 

 the ligament arch outward in the upper and lower eyelids to terminate in the lateral 

 palpebral raphe, forming a thin, pale sheet in the subcutaneous tissue of the eyelid. 

 Its marginal fibres, sometimes more or less distinct from the others, form what has 

 been termed \S\& pars ciliaris or muscle of Riolan. 



The fibres which arise from the posterior lachrymal crest are usually regarded as 

 forming either a distinct muscle, which has been termed the tensor tarsi or Horner s 

 muscle, or else as a separate part of the orbicularis, the pars lacrimalis. It is 

 directed horizontally outward behind the lachrymal sac, resting upon the posterior 

 surface of the reflected bundle of the internal palpebral ligament. Towards its outer 

 end it bifurcates, sending a slip to each eyelid partly to be inserted into the tarsal 

 plates and partly to fuse with the rest of the pars palpebralis. 



Pars Orbitalis. — The orbital portion of the muscle is usually of a deeper color 

 and somewhat thicker than the palpebral, and the fibres towards its periphery tend 

 to scatter themselves among the adjacent platysma muscles and to make numerous 

 connections with these. Some bundles from the lateral and lower parts of the muscle 

 which extend downward and forward upon the cheek have been regarded as a dis- 

 tinct muscle, the malaris. 



The main muscle arises from the internal palpebral ligament, the frontal process 

 of the maxilla, and the inner portions of the upper and lower margins of the orbit. 

 The fibres arch outward to the lateral palpebral raphe, a portion of those arising from 

 the maxilla iyiserting into the integument of the eyebrow and forming what has been 

 termed the corrugator siipercilii (Fig. 499). 



Nerve-Supply. — By the rami temporales and zygomatici of the facial nerve. 



Lower tarsal 

 plate 

 ""Orbicularis 

 * palpebrarum 



Orbicularis palpebrarum has been dissected from its deeper 

 surface and reflected inward with eyelids, showing lachrymal 

 portion or tensor tarsi. 



