Structure/Morphology
The upper eyelid is 2–3 mm thick, comprising of skin and a delicate subcutaneous connective tissue in its anterior two thirds and a conjunctival mucosa in its posterior third. The palpebral part of orbicularis oculi muscle lies in between. Externally, it separates the eyelashes in front from the yellowish tarsal (meibomian) glands posteriorly. A loose fibrous layer of submuscular connective tissue lies deep to the muscle, which is extremely rich in its innervation (Standring, 2016).
The firm, dense fibrous tarsal plates provide support to the eyelids, with superior tarsal plate being larger than the inferior one. The tarsal plate is attached superiorly to the orbital septum and on the sides to the medial and lateral canthal ligaments. The deeper fibers of levator palpebrae superioris muscle are attached to the anterior surface of superior tarsus and helps eyelid elevation on sympathetic stimulation.
Related parts of the anatomy
Key Features/Anatomical Relations
The upper eyelid is separated from the inferior eyelid by a palpebral fissure but joins it at its extremities, thus, forming the medial and lateral canthi. A small elevation called the lacrimal papilla can be seen on the medial end of the palpebral margin of the eyelid. The papilla possesses an opening called the lacrimal punctum, which serves as the site of drainage of lacrimal fluid into the lacrimal canaliculi.
The arterial supply to the upper eyelid comes from medial and lateral palpebral branches of the ophthalmic artery. The veins correspond with the arteries. The lymph vessels eventually drain into superficial and deep parotid lymph nodes laterally and submandibular lymph nodes inferiorly and medially.
The cutaneous innervation of the eyelids comes from the ophthalmic (CN V1) and maxillary (CN V2) divisions of the trigeminal nerve. The upper eyelid is mainly innervated by supraorbital and supratrochlear branches of frontal nerve, lacrimal nerve, and infratrochlear branch of nasociliary nerve.
Function
The eyelids protect the eye from mechanical trauma and serve as a shield from excessive light. Periodic blinking helps prevent corneal dryness (and ulceration) by maintaining a homogenous distribution of tear film over the cornea.
References
Standring, S. (2016) Gray's Anatomy: The Anatomical Basis of Clinical Practice. Gray's Anatomy Series 41 edn.: Elsevier Limited.
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Upper Eyelid
The upper eyelid crease is a horizontal indentation formed by the attachment of the superficial levator aponeurosis fibers into the orbicularis oris intermuscular septa and subcutaneous tissue.
