THE VASCULAR TUNIC. 



H57 



the veins, which begin between the meshes of the choriocapillaris, the two systems 

 being separate. 



The nerves of the choroid arise from the long and short ciliary nerves during 

 their course on the inner surface of the sclera. They form a plexus within the 

 lamina suprachorioidea, which contains groups of ganglion cells, and sends numerous 

 nonmedullated fibres chiefly to the muscular coats of the arteries. A few ganglion 

 cells are found along the blood-vessels. The choroid contains no sensory nerve-fibres. 



FIG. 1213. 



Choroidal stromr 

 Pigmented cells. 



Clear cells 

 Blood-vessels 



.Choroidal 

 stroma 



Clear cells 



Sections of ciliary processes ; A, from anterior ; B, from posterior part ; two epithelial layers, pigmented and clear, 

 of pars ciliaris retinae cover choroidal stroma. X 80. 



The Ciliary Body. The ciliary body (corpus ciliare), the middle portion of 

 the vascular tunic, extends from the ora serrata to the sclero-corneal junction. 

 Sections through the eyeball in a meridional direction (F;g. 1214) show that it has 

 a triangular form. The outer side is in apposition to the sclera, the inner is covered 

 by the pigmented extension of the retina, and the short anterior side, at right angles 

 to the outer, extends inward from the pectinate ligament toward the lens. 



The ciliary body presents three subdivisions ; the ciliary ring, the ciliary pro- 

 cesses and the ciliary muscle. 



FIG. 1214. 



Cornea Canal of Schlemm 



J 



Pectinate ligament 



Ciliary muscle (radial fibres) 

 clera 



Meridional fibres 



Ciliary processes Circular fibres Choroid Pars ciliaris retinas 



Meridional section of ciliary region, showing ciliary body with its muscle and processes. X 40. 



The ciliary ring, or orbicuhts ciliaris, consists of a smooth band of tissue, 4 

 mm in width, in advance of the ora serrata. It differs in structure from the choroid 

 in the absence of the choriocapillaris, its vessels running in a longitudinal direction 

 and returning the blood from the iris and ciliary body to the venae vorticosae. On 

 its inner surface, delicate meridionally placed folds make their appearance, by the 

 union of which the ciliary processes are formed. 



The ciliary processes constitute the remainder of the inner portion of the 

 ciliary body. They form an annular series of folds, between 68 and 80 in number, 

 which surround the lens and act as points of attachment to its suspensory ligament. 



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