Corpus: Cornea

The cornea is a transparent and coarse fibrous connective tissue membrane that lies in front of the eyeball and is formed in all domestic mammals.

Together with the sclera, the cornea forms the outer skin of the eye (tunica fibrosa bulbi). It is part of the anterior surface of the eyeball and, unlike the sclera, is transparent.

The cornea is slightly thinner at the central vertex cornea (corneal vertex) than at the peripheral limbus corneae. The inner edge of the cornea borders on the anterior chamber of the eye. It is almost circular in all animals, while the outer boundary and thus the outer surface is only round in carnivores and humans. In ungulates, it has a transverse oval or ovoid shape corresponding to the shape of the pupil. The blunt pole protrudes nasally, the pointed pole temporally. In these animal species, the edge of the cornea is more strongly overlapped by the sclera on the dorsal and ventral sides than on the nasal and temporal sides.

The basis of the cornea is formed by lamellar layered and parallel-fibre collagen fibrils, which are referred to as substantia propria corneae. They merge into the scleral fibres at the corneal limbus. The cornea has a regular layered structure from the outside inwards. A distinction is made between the following parts:

• anterior corneal epithelium (epithelium anterius corneae)
• anterior limiting membrane (lamina limitans anterior, Bowman membrane)
• Intrinsic layer of the cornea (substantia propria corneae)
• posterior limiting membrane (lamina limitans posterior, Descemet's membrane)
• posterior corneal epithelium (Epithelium posterius corneae)

The cornea is free of blood and lymph vessels with the exception of a delicate network of marginal loops at the limbus corneae, which is fed by rami ciliares from the lamina episclerais. The cornea is moisturised and nourished by diffusion - on the one hand by the tear fluid (from the outside) and on the other hand by the aqueous humour (from the inside). The cornea is richly supplied with sensitive nerves that permeate all layers in a plexus-like manner.

• Nickel R, Schummer A, Seiferle E. 2003 Textbook of the Anatomy of Domestic Animals, Volume IV: Nervous System. 4th, unchanged edition. Stuttgart: Parey in MSV Medizinverlage Stuttgart GmbH & Co. KG. ISBN: 978-3-8304-4150-2
• Liebich, HG. 2003. functional histology of domestic mammals. Textbook and colour atlas for study and practice. Fourth, completely revised and expanded edition. Stuttgart: Schattauer GmbH. ISBN: 3-7945-2311-3.