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eyelids
Monday 9 November 2020
The eyelids are composed of four layers: skin and subcutaneous tissue including its adnexa, striated muscle, tarsus with the meibomian glands, and the palpebral conjunctiva.
In spite of being a small organ, the eyelids contain numerous histological elements that can be the origin of benign and malignant lesions.
The eyelids are composed of four layers: Skin and subcutaneous tissue, striated muscle (orbicularis oculi), tarsus, and conjunctiva.[1]
The eyelid skin is the thinnest in the body and lacks subcutaneous fat, but otherwise contains all other skin structures. The skin epithelium is keratinized stratified squamous epithelium. Melanocytes are spread in the basal layer of the epithelium. The dermis contains fibrous tissue, blood vessels, lymphatic vessels, and nerves.
The eyelids are rich in glandular tissue: The eccrine glands – the sweat glands of the eyelid skin and the accessory lacrimal gland of Krause and Wolfring; the apocrine gland of Moll; and the sebaceous glands – the meibomian glands and the glands of Zeiss.
The entire orbital entrance is covered by the orbicularis oculi – a striated muscle that is composed of pretarsal and preseptal parts and the orbital part that is located over the external orbital bones.
The tarsi are firm plates composed of dense connective tissue, and the meibomian glands are embedded in the connective tissue of the tarsal plates.
The posterior eyelid surface is lined by the palpebral conjunctiva that is composed of epithelium and subepithelial stroma – the substantia propria.
The epithelium of the tarsal conjunctiva is mostly cuboidal and contains goblet cells. Melanocytes are scattered in the basal layer of the epithelium.
The stroma is composed of fibrovascular connective tissue.
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