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Encyclopedia > Eyelid
Eyelid
Upper eyelid
Latin palpebra inferior, palpebra superior
Gray's subject #227 1025
Artery lacrimal, superior palpebral, inferior palpebral
Nerve upper: infratrochlear, supratrochlear, supraorbital, lacrimal
lower: infratrochlear, branches of infraorbital
MeSH Eyelids

An eyelid is a thin fold of skin that covers and protects an eye. With the exception of the prepuce and the labia minora, it has the thinnest skin of the whole body. The levator palpebrae superioris muscle retracts the eyelid to "open" the eye. This can be either voluntarily or involuntarily. The human eyelid features a row of eyelashes which serve to heighten the protection of the eye from dust and foreign debris. "Palpebral" (and "blepharo") means relating to the eyelids. Image File history File links Eyelashes. ... For other uses, see Latin (disambiguation). ... Section of an artery For other uses, see Artery (disambiguation). ... The Lacrimal Artery arises close to the optic foramen, and is one of the largest branches derived from the ophthalmic: not infrequently it is given off before the artery enters the orbit. ... The medial palpebral arteries (internal palpebral arteries) are arteries of the head. ... The medial palpebral arteries (internal palpebral arteries) are arteries of the head. ... Nerves (yellow) Nerves redirects here. ... The infratrochlear nerve is given off from the nasociliary just before it enters the anterior ethmoidal foramen. ... The supratrochlear nerve, smaller than the Supraorbital nerve, passes above the pulley of the Obliquus superior, and gives off a descending filament, to join the infratrochlear branch of the nasociliary nerve. ... The supraorbital nerve arises from the orbit by the supraorbital foramen and supplies the upper eyelid and forehead integuments. ... The Lacrimal Nerve is the smallest of the three branches of the ophthalmic. ... The infratrochlear nerve is given off from the nasociliary just before it enters the anterior ethmoidal foramen. ... After the maxillary nerve enters the infraorbital canal, the nerve is frequently called the infraorbital nerve. ... Medical Subject Headings (MeSH) is a huge controlled vocabulary (or metadata system) for the purpose of indexing journal articles and books in the life sciences. ... For other uses, see Eye (disambiguation). ... The prepuce is a retractable piece of skin which covers part of the genitals of primates and other mammals. ... The labia minora (nymphae) are two small cutaneous folds, situated between the labia majora, and extending from the clitoris obliquely downward, lateralward, and backward for about 4 cm. ... The levator palpebrae superioris muscle is a muscle in the orbit that elevates the superior (upper) eyelid. ... An eyelash or simply lash is one of the hairs that grow at the edge of the eyelid. ...

Contents

Anatomy

Layers

In the human eyelid, there are various layers; from superficial to deep, they are: skin, subcutaneous tissue, orbicularis oculi, orbital septum & tarsal plates, and palpebral conjunctiva. The meibomian glands lie within the eyelid and secrete the lipid part of the tearfilm. For other uses, see Skin (disambiguation). ... The distribution of the bloodvessels in the skin of the sole of the foot. ... The orbicularis oculi arises from the nasal part of the frontal bone, from the frontal process of the maxilla in front of the bickybicky WUT werd, and from the anterior surface and borders of a short fibrous band, the medial palpebral ligament. ... The orbital septum (palpebral ligament) is a membranous sheet in the upper eyelid, attached to the edge of the orbit, where it is continuous with the periosteum. ... The tarsi (tarsal plates) are two thin, elongated plates of dense connective tissue, about 2. ... The conjunctiva is a membrane that covers the sclera (white part of the eye) and lines the inside of the eyelids. ... The tear system. ...


Innervation

In humans, the sensory nerve supply to the upper eyelids is from the infratrochlear, supratrochlear, supraorbital and the lacrimal nerves from the ophthalmic branch (V1) of the trigeminal nerve (CN V). The skin of the lower eyelid is supplied by branches of the infratrochlear at the medial angle, the rest is supplied by branches of the infraorbital nerve of the maxillary branch (V2) of the trigeminal nerve. The infratrochlear nerve is given off from the nasociliary just before it enters the anterior ethmoidal foramen. ... The supratrochlear nerve is a branch of the frontal nerve, which itself comes from the ophthalmic division of the trigeminal (or fifth) cranial nerve. ... Supraorbital can refer to: Supraorbital artery Supraorbital foramen Supraorbital gland Supraorbital nerve Supraorbital ridge Supraorbital vein Category: ... The Lacrimal Nerve is the smallest of the three branches of the ophthalmic. ... The trigeminal nerve is the fifth (V) cranial nerve, and carries sensory information from most of the face, as well as motor supply to the muscles of mastication (the muscles enabling chewing), tensor tympani (in the middle ear), and other muscles in the floor of the mouth, such as the... The infratrochlear nerve is given off from the nasociliary just before it enters the anterior ethmoidal foramen. ... After the maxillary nerve enters the infraorbital canal, the nerve is frequently called the infraorbital nerve. ...


Blood supply

In humans, the eyelids are supplied by two arches on each upper and lower lid. The arches are formed by anastamoses of the lateral palpebral arteries and medial palpebral arteries, branching off from the lacrimal artery and ophthalmic artery, respectively. The lateral palpebral arteries are small arteries which supply the eyelid. ... The medial palpebral arteries (internal palpebral arteries), two in number, superior and inferior, arise from the ophthalmic, opposite the pulley of the Obliquus superior; they leave the orbit to encircle the eyelids near their free margins, forming a superior and an inferior arch, which lie between the Orbicularis oculi and... The Lacrimal Artery arises close to the optic foramen, and is one of the largest branches derived from the ophthalmic: not infrequently it is given off before the artery enters the orbit. ... The opthalmic artery is a branch of the internal carotid artery which supplies branches to supply the eye and other structures in the orbit: Central retinal artery Supraorbital artery Supratrochlear artery Lacrimal artery Dorsal nasal artery Short posterior ciliary arteries Long posterior ciliary arteries Posterior ethmoidal artery Anterior ethmoidal artery...


Usage

Blinking eye
Blinking eye

When an eye becomes dry, "blinking" – closing the eyelid and opening it again rapidly – can help to spread moisture across the surface of the eye and ease the discomfort. Blinking also serves the purpose of helping to remove irritants which have landed in the eye. When a person chooses to blink one eye as a signal to another in a social setting, it is known as "winking." Image File history File links Animated gif of a blinking eye/moving eyelid. ... Example of a blinking eye (slow-motion) Blinking is the rapid closing and opening of the eyelid. ... A man winking his right eye The wink is an intentional facial expression made by closing one eye; it is distinguished from the blink by the fact that the other eye remains open. ...


Most animals with eyelids have a reflex to close the eyes when a threat comes too near. This is done involuntarily to protect the eye from contact with the threat. It is often strong enough to overcome any voluntary resistance. For other uses, see Reflexive (disambiguation). ...


Eyelids also serve the purpose of helping the animal to control the amount of light entering the eye (control of the iris is autonomic). Without eyelids, many animals would be helpless to block visual sensory overload under very bright light. Many animals also use eyelids to block light from reaching the eyes during sleeping cycles. In anatomy, the iris (plural irises or irides) is the most visible part of the eye of vertebrates, including humans. ...


Types

In humans, each eye has an upper and lower eyelid which operate as a pair, however, it is primarily the upper eyelid that moves across the exposed surface of the eye during blinking. Lower eyelids in most animals move vertically.


Many terrestrial vertebrates have an eyelid known as a nictitating membrane, or haw. This eyelid is closer to the eye than the outer lids and is usually transparent. The purpose of the nictitating membrane is to add protection to the eye from debris and irritation, and in land animals it also serves as a barrier while swimming. Camels, crocodiles, cats, birds, and polar bears are among animals that have this membrane. The nictitating membrane sweeps across the eye diagonally or horizontally. In humans, the plica semilunaris (or semilunar fold) is thought to be the vestigial remnant of the nictitating membrane. This article does not cite any references or sources. ... Many species of land animals have a nictitating membrane, which can move across the eyeball to give the sensitive eye structures additional protection in particular circumstances. ... A vestigial organ is an organ whose original function has been lost during evolution. ...


It has been suggested that eyelids evolved as a way to remove debris from the eyes. Given that fish have a constant stream of water flowing over their eyes, it is not surprising that they do not have eyelids or need specialized membranes to perform this function.


Double eyelid

A double eyelid is a type of eyelid where a crease exists. In contrast, a single eyelid has no crease. There is a wide variation in the location of the crease, particularly in the Asian double eyelid. Further discussion and pictures of the variations in Asian double eyelids can be found [http://www.MirandaPlasticSurgery.com/asian_eyelids.html half the eyelid and the desired appearance.[1]


Indication of Personality Type

The research of notable professor Sydney Hessel has seemed to indicate a correlation in the shape of an individual's eyelid and personality type. Professor Hessel is looking into collaborating with Gary E. Schwartz, Ph.D. of The G.O.D. Experiments fame from the University of Arizona.


See also

Disorders

Eyelid affected by Stye.
Eyelid affected by Stye.

Image File history File linksMetadata Download high resolution version (984x723, 139 KB) Summary Description de: Gerstenkorn nach ca. ... Image File history File linksMetadata Download high resolution version (984x723, 139 KB) Summary Description de: Gerstenkorn nach ca. ... A stye (IPA: ) or hordeolum () is an infection of the sebaceous glands at the base of the eyelashes. ... A blepharospasm (from blepharo (eyelid) and spasm (uncontrolled muscle contraction)) is any abnormal tic or twitch of the eyelid. ... A chalazion, also known as a Meibomian gland lipogranuloma, is a cyst in the eyelid that is caused by inflammation of the meibomian gland, usually on the upper eyelid. ... Dermatochalasis is defined as excess of skin in the upper eyelid. ... Ectropion is a condition of loose eyelids. ... Entropion is a medical condition in which the eyelids fold inward. ... Hay-Wells Syndrome (HWS), also known as the ankyloblepharon-ectodermal dysplasia-clefting (AEC) syndrome, is one of at least 150 known types of ectodermal dysplasia. ... In ophthalmology, ptosis is an abnormally low position (drooping) of the upper eyelid which may grow more or less severe during the day. ... A stye (IPA: ) or hordeolum () is an infection of the sebaceous glands at the base of the eyelashes. ...

Surgeries

Asian blepharoplasty is a type of plastic surgery where the skin around the eyes is reshaped. ... Blepharoplasty is a cosmetic plastic surgical procedure intended to reshape the upper eyelid or lower eyelid by the removal and/or repositioning of excess tissue as well as by reinforcement of surrounding muscles and tendons. ... Epicanthoplasty is a type of eye surgery to reduce appearance of epicanthal folds. ...

Additional images

References

External links

  • Eyelid Anatomy at drmeronk.com

  Results from FactBites:
 
Eyelid disorders (1518 words)
Eyelids are susceptible to the same skin tumors as the skin over the rest of the body, including noncancerous tumors and cancerous tumors (basal cell carcinoma, squamous cell carcinoma, malignant melanoma, and sebaceous gland carcinoma).
A chalazion is caused by a blockage in the outflow duct of a meibomian gland.
Eyelid edema is most often caused by allergic reactions, for example, allergies to eye makeup, eyedrops or other drugs, or plant allergens such as pollen.
Richmond Eye Associates, Eye Health and Disorders - Eyelid Problems (1954 words)
Eyelid malpositions (in-turning and out-turning) and drooping eyelids (ptosis) are discussed as well.
It is important to distinguish infection involving only the eyelid from infection extending from behind the eye, or the orbit (orbital cellulitis), which is usually more severe and causes eye protrusion and double vision.
Eyelid cellulitis is treated with oral antibiotics, and sometimes with IV antibiotics in more severe cases.
  More results at FactBites »

 
 

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