The skin is thin but, typical of all skin, has fine hairs and sweat glands. The loose subcutaneous tissue, with collagen and elastin fibers, contains small quantities of fat and some granules of yellow or brown-colored material.
The layers of structure of the eyelid, from front to back are:
- Subcutaneous tissue
- Orbicularis oculi muscle
- Layer of fatty tissue
- Tarsal Plate and tendon of Levator palpabrae superioris
- Meibomian glands
- Eyelashes and glands of Moll at the margins
The orbicularis oculi muscle is formed from a flat sheet of circular fibers. It is described by anatomists in three portions, though they function together: orbital, palpebral and lacrimal. The orbital portion is attached at the medial orbit to frontal and maxillary processes and to the medial palpebral ligament of the tarsal plate; the fibers encircle the orbit, blending superiorly with occipitofrontalis and corrugator. The thin palpebral portion is attached to the medial aspect of the orbit, to the medial palpebral ligament, and passes to form a circle of fibers anterior to the orbital fascia, anterior to the tarsal plate within the eyelids, and merges with the lateral margin of the eye; upper and lower fibers interlace in a commissure as the lateral palpebral raphe. A distinct portion of ciliary bundle of Riolan muscle fibers are located behind the eyelashes.
A layer of fatty tissue, the palpebral fascia of variable thickness, lies between the muscle and the tarsal plate and levator tendon attached to it. In this lie blood vessels and some strands of smooth muscle, the superior tarsal muscle of Müller.