English to Italian Medical Medical (general) Improved modalities for the treatment of degenerative diseases of the retina

Si tratta del brevetto Improved modalities for the treatment of degenerative diseases of the retina.
Nel lungo background of the invention trovo queste frasi:
Additionally, the retinal pigment epithelium is one of the most important cell types in the eye, as it is crucial to the support of the photoreceptor function.
It performs several complex tasks, including phagocytosis of shed outer segments of rods and cones, vitamin A metabolism, synthesis of mucoploysacharides involved in the metabolite exchange in the subretinal space, transport of metabolites, regulation of angiogenesis, absorption of light, enhancement of resolution of images, and the regulation of many other functions in the retina through secreted proteins such as proteases and protease inhibitors.

segmenti esterni e poi non capisco cosa intendano per shed...
Grazie.