palpebralen

Palpebralen refers to the eyelids, the paired movable folds that protect the anterior surface of the eye. Each lid comprises skin, subcutaneous tissue, the orbicularis oculi muscle at the lid margin, a supportive tarsal plate, and the palpebral conjunctiva that lines the inner surface. The upper and lower palpebrae define the palpebral fissure, the opening between lids.

The lid margin includes eyelashes and the glandular structures that contribute to the tear film. The tarsal plates contain the Meibomian glands, which secrete lipids to stabilize the tear film. Other glands along the lid margin include sebaceous glands (often referred to as Zeis glands) and sweat glands (Moll). Movement is produced primarily by the levator palpebrae superioris, elevating the upper lid, aided by the superior tarsal (Müller) muscle; the orbicularis oculi muscle assists in lid closure.

Functionally, the palpebralen protect the eye from mechanical injury and foreign bodies, help distribute the tear film during blinking, and aid tear drainage. Proper eyelid function is important for maintaining ocular surface health and comfort, and for protecting the cornea during sleep and wakefulness.

Development and clinical relevance: eyelids develop from surface ectoderm with supporting mesenchyme and typically separate before birth after a brief transient fusion. Common conditions affecting the palpebralen include blepharitis (inflammation of the eyelid margins), chalazion or styes (gland or follicle infections), and ptosis or entropion/ectropion, which can alter lid position and function. In many mammals, an additional protective structure called the nictitating membrane may also be present. Related topics include the palpebral fissure and blepharoplasty.