A piece of skin which covers the eye.
Movable fold of skin over the eye.
Two folds of skin that protect the surface of each eye. The upper and lower eyelids close quickly as a reflex action to shield the eye against harsh light and foreign objects. They also secrete an oily component of tears. Their constant blinking action moves tears over the surface of the eyes to keep them moist and clean. The eyelashes along the edge of each eyelid are actually three to four rows of hairs that help sift out dust and other materials before they reach the eye. The eyelid itself is held in position by ligaments attached to the eye socket of the skull. The eyelids can also close tightly and push the eyeball back into the socket to prevent injury.
The protective covering of the eye. Each eye has two eyelids consisting of skin, muscle, and connective tissue. Each eyelid is lined with membrane (conjunctiva) and fringed with eyelashes. Stimulation of the pain receptors in the cornea causes the eyelids to close in a reflex action.
One of two movable protective folds that cover the anterior surface of the eyeball when closed. They are separated by the palpebral fissure. The upper (palpebra superior) is the larger and more movable. It is raised by contraction of the levator palpebrae superioris muscle. Angles formed at the inner and outer ends of the lids are known as the canthi. The cilia, or eyelashes, arise from the edges of the eyelids. The posterior surface is lined by the conjunctiva, a mucous membrane.
An eyelid is a fold of tissue located at the upper or lower edge of an eye socket (orbit). Ligaments connected to the bony edges of the socket hold the eyelids in place. These lids consist of thin plates of fibrous tissue known as tarsal plates, which are covered by muscles and a thin layer of skin. The inner layer is coated by an extension of the conjunctiva (the transparent membrane that covers the white part of the eye). Each eyelid has a row of eyelashes along its edge. Just behind the eyelashes are the openings of ducts that lead from the meibomian glands, responsible for secreting the oily fluid in tears.
The eyelids function as protective shutters, quickly closing as a reflex action whenever anything approaches the eye. Additionally, they play a role in spreading the tear film evenly across the cornea, which is the clear front dome of the eyeball.
Eyelid disorders encompass a chalazion, which is a swelling of a meibomian gland, blepharitis, an inflammation of the eyelid’s edge, and a stye, a small abscess at the base of one of the lashes.
Specific disorders can impact the shape and alignment of the eyelids. These conditions comprise entropion, where the eyelid margin turns inward, ectropion, where the eyelid margin turns outward, and ptosis, which causes the eyelid to droop downward, potentially covering part or all of the eye.
Myokymia, which refers to the twitching of the eyelid, is a common occurrence often caused by fatigue. On the other hand, blepharospasm, a prolonged contraction of the eyelid, is typically associated with conditions like photophobia (abnormal sensitivity of the eyes to sunlight) or the presence of a foreign body. Moreover, the skin of the eyelid is a frequent location for the occurrence of basal cell carcinoma.
The two movable flaps, one above and one below, that shield the front part of the eye.