Vitreous humor
The vitreous body or vitreous humor is a transparent, avascular gel that occupies ~80% of the globe and helps to maintain the position of the retina and the shape of the globe.
Gross anatomy
Situated within the globe between the lens and the optic cup, its anterior surface is indented by the hyaloid fossa, creating a concavity for the lens. The more gel-like consistency of the peripheral cortex transitions to a liquid zone near the center. This cortex is particularly dense at the base of the vitreous, located at the ciliary body. The vitreous is traversed by Cloquet’s canal.
Attachments
- ciliary body: the strongest attachment of the vitreous occurs at the pars plana of the ciliary body adjacent to the ora serrata
- lens: the vitreous thickens in to an array of radially-aligned zonular fibers to form the suspensory ligament of the lens
- optic disc: a peripapillary attachment adheres the vitreous to the edge of the optic disc
Relations
- anteriorly: ciliary body, zonule, lens
- posteriorly: retina
Histology
The vitreous consists of 99% water and is filled with hyaluronan, a glycosaminoglycan arranged in long chains. The cortex derives its structure from a loose network of type II collagen fibrils and fibers, which are interspersed with cells similar to mononuclear phagocytes called hyalocytes.
Development
The primitive vitreous body begins as a network of cytoplasmic processes left behind after separation of the lens rudiment and optic vesicle during formation of the optic cup. The cells are therefore derived partly from each of the lens and retina. These cytoplasmic processes condense around the ciliary body, forming the basis of the suspensory ligament of the lens.
The liquid part of the vitreous is absent at birth and only first appears at around age four, gradually increasing throughout life to compose up to 50% of the vitreous by age 70 years.
Related pathology
Shrinking of the vitreous in old age can lead to traction on the retina at its peripapillary attachment, leading to macular holes or even retinal detachment.
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Assoziationen und Differentialdiagnosen zu Glaskörper:
