Topic 2
Act like curtains protecting the eye from injuries, excessive heat /water loss & also help spread the tear film over the cornea and conjunctiva & help in drainage of tears
Eyelids divided by horizontal sulcus into orbital & tarsal part
Upper lid covers 1/6th of cornea & lower just touches limbus
Canthi → merging laterally & medially ; medial 2mm higher
Palpebral aperture: gap between upper & lower 10-11 mm vertically and 28-30mm horizontally
Lid margin 2mm broad & punctum divides it, lacrimal= no glands & lashes . ciliary portion →lashes on one end& meibomian glands on the other
Structure
Skin: elastic and thinnest in body
Subcutaneous areolar: very loose no fat, easily distended
Striated Muscle: orbicularis =oval sheet across eyelids supplied by facial nerve (Zygomatic) closes the eyelids, upper lid also has levator palpebrae superioris raises the eyelid (oculomotor)
Submuscular areolar: loose +nerve & vessels (anaesthesia)
Fibrous: eyelid framework = tarsal plate+ peripheral septum
Tarsal plate=dense connective tissue →shape &firmness contains meibomian glands in parallel rows
Layer of non-striated : palpebral muscle of Muller arising from LPS supplied by sympathetic fibres
Conjunctiva: lines the lids is called palpebral conjunctiva
Glands
Meibomian: open in lid margin, secrete oily layer of tear film
Glands of Zeis: open into follicle of eyelashes
Glands of moll: sweat glands open into Zeis or hair follicles
Blood supply
Arcades forms superior and marginal arterial arcade
Post tarsal & pretarsal→drain ophthalmic/subcutaneous veins
Lymphatic’s → pre &post tarsal, lateral/medial half→ drain preauricular and submandibular lymph nodes