Quain's elements of anatomy / edited by Edward Albert Schäfer and George Dancer Thane.

Date:
1894
Catalogue details

Licence: Public Domain Mark

Credit: Quain's elements of anatomy / edited by Edward Albert Schäfer and George Dancer Thane. Source: Wellcome Collection.

Provider: This material has been provided by UCL Library Services. The original may be consulted at UCL (University College London)

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    CAPSXJLE OF TENON. ]1 Except when directed towards near objects, the axes of the eyes are nearly parallel ; the optic nerves, on the contrary, diverge considerably. Each nerve enters the corresponding eye about 2 to 3 mm. to the inner or nasal side of the axis of the eyeball. The eyeball consists of three concentric coats, and, of certain fluid and solid parts enclosed by them. The coats are (1) an external fibrous covering, forming the sclerotic (tunica sclera) and cornea, (2) a middle vascular, pigmented, and in part also muscular membrane, the choroid and iris (tunica uvea), and (8) an internal nervous and epithelial stratum, the retina. The enclosed refracting media, three in number, are the aqueous humour, the vitreous hody, and the lens. Around the posterior two-thirds of the eyeball there is a tunic of fascia, tunica vaginalis oculi, or capsule of Tenon, which is perforated by the tendons of the recti Fig. 12.—Horizontal section of orbit. (After Gerlach.) Magnified. and obliqui muscles, along which it sends sheaths which blend with the perimysium of the muscles (figs. 12 and 13). It is connected with the sclerotic by delicate con- nective tissue (adventiiia oculi, Lockwood), except posteriorly, at the entrance of the ciliary vessels and nerves, where it blends with the sclerotic. Anteriorly the capsule of Tenon is continued into the conjunctiva. This capsule is lined by flattened endothelial cells, and encloses a lymph-space, which separates the eyeball from the orbital fat. It is strengthened just behind the places where the recti muscles perforate it, by bands of fibrous'tissue (figs. 12 and 13,), and it is attached mi either side to the malar and lachrymal bones by elastic ligamentous structures, which also receive fibrous slips from the internal and external recti. These structures serve as check-ligaments (fig. 12) to these muscles. They are stated by Sappey to contain plain muscular fibres. Fibrous slips also pass from the sheaths of the superior and inferior rectus, and are attached to the conjunctiva palpebrarum and