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→Cutaneous Appendages
===Eyelids===
===Eyelids===
The palpebral margin is thicker than the remainder of the eyelid and cilia grow from the margin. There are various glands in the region, including '''Moll's glands''' that are modified sweat glands, associated with the cilia. '''Meibormian glands, Zeis glands''' associated with the cilia and the '''lacrimal glands''' together produce the tear film.
The palpebral margin is thicker than the remainder of the eyelid and cilia grow from the margin. There are various glands in the region, including '''Moll's glands''' that are modified sweat glands, associated with the cilia. '''Meibormian glands, Zeis glands''' associated with the cilia and the '''lacrimal glands''' together produce the tear film.
===Beak===
The beak of birds is formed from the bones of the '''maxilla''' and '''mandible''' with a horny, keratinised covering, the '''rhamphotheca'''.
Microscopically, it is similar to the skin, with a modified epidermis. The '''stratum corneum''' is very thick, containing cell bound calcium phosphate and layered crystals of '''hydroxyapatite'''.
The beak is very sensitive to heat, cold, pressure and pain due to a high number of mechanoreceptors ('''Herbst corpuscles''') being presence.
The corpuscles are recognisable histologically as papillae, originating from the dermis ending in crater-like structures at the distal tip of the beak.
==Immunology==
==Immunology==