

THE ACCESSORY ORGANS OF THE EYE 



1021 





In the fetus, the lens is nearly spherical, and has a slightly reddish tint; it is soft and breaks 

 down readily on the slightest pressure. A small branch from the arteria centralis retina; runs 

 forward, as already mentioned, through the vitreous body to the posterior part of the capsule 

 of the lens, where its branches radiate and form a plexiform network, which covers the posterior 

 surface of the capsule, and they are continuous around the margin of the capsule with the vessels 

 of the pupillary membrane, and with those of the iris. In the adult, the lens is colorless, trans- 

 parent, firm in texture, and devoid of vessels. In old age it becomes flattened on both surfaces, 

 slightly opaque, of an amber tint, and increased in density (Fig. 886). 



Vessels and Nerves. The arteries of the bulb of the eye are the long, short, and anterior 

 ciliary arteries, and the arteria centralis retinae. They have already been described (see p. 571). 



The ciliary veins are seen on the outer surface of the choroid, and are named, from their arrange- 

 ment, the venoe vorticosce; they converge to four or five equidistant trunks which pierce the 

 sclera midway between the sclero-corneal junction and the porus opticus. Another set of veins 

 accompanies the anterior ciliary arteries. All of these veins open into the ophthalmic veins. 



The ciliary nerves are derived from the nasociliary nerve and from the ciliary ganglion. 



The Accessory Organs of the Eye (Organa Oculi Accessoria). 



The accessory organs of the eye include the ocular muscles, the fasciae, the eye- 

 brows, the eyelids, the conjunctiva, and the lacrimal apparatus. 



The Ocular Muscles (musculi oculi}. The ocular muscles are the: 

 Levator palpebrse superioris. Rectus medialis. 



Rectus superior. Rectus lateralis. 



Rectus inferior. Obliquus superior. 



Obliquus inferior. 



Tendon of Obliquus superior 

 Orbital plate of frontal bone 

 Levator palpebrce superioris , 

 Rectus superior 



[ Orbicularis oculi 

 Superior tarsus 

 Upper eyelid 



inferior 

 Roof of maxillary sinus & ^ Orbicularis oculi 



Obliquus inferior 

 FIG. 888. Sagittal section of right orbital cavity. 



The Levator palpebrae superioris (Fig. 888) is thin, flat, and triangular in shape. 

 It arises from the under surface of the small wing of the sphenoid, above and in 

 front of the optic foramen, from which it is separated by the origin of the Rectus 

 superior. At its origin, it is narrow and tendinous, but soon becomes broad arid 

 fleshy, and ends anteriorly in a wide aponeurosis which splits into three lamellae. 

 The superficial lamella blends with the upper part of the orbital septum, and is pro- 

 longed forward above the superior tarsus to the palpebral part of the Orbicularis 

 oculi, and to the deep surface of the skin of the upper eyelid. The middle lamella, 

 largely made up of non-striped muscular fibers, is inserted into the upper margin 

 of the superior tarsus, while the deepest lamella blends with an expansion from 

 the sheath of the Rectus superior and with it is attached to the superior fornix 

 of the conjunctiva. 





