The eyelids are thin, cell phone folds the cover the eyeball anteriorly. Castle offer defense from extreme light or injury, and also maintain lubrication through distributing tears end the surface ar of the eyeball.
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The eyelids are break-up into upper and also lower portions, which fulfill at the medial and also lateral canthi the the eye. The opening between the two eyelids is called the palpebral aperture or opening.
In this article, us shall look in ~ the anatomy that the eyelids – your layers, vasculature and innervation.
Fig 1 – The upper and lower eyelid.
Layers that the Eyelid
The eyelid is composed of 5 main layers (superficial come deep):Skin and subcutaneous tissueOrbicularis oculiTarsal platesLevator apparatusConjunctiva
Skin and Subcutaneous Tissue
The skin and subcutaneous tissue form the most superficial layer of the eyelid.
The great of skin is among the thinnest in the person body. In the subcutaneous layer, over there is loose connective tissue but no subcutaneous fat – and also subsequently, the eyelids are conveniently distended by oedema or blood.
The eyelashes space attached right here with your accompanying modified sweat glands – the ciliary glands of Moll. Over there are also sebaceous glands situated in this layer, known as the glands that Zeis.
The orbicularis oculi muscle has three distinctive parts – palpebral, lacrimal and also orbital.Attachments – Originates native the medial orbital margin, the medial palpebral ligament, and the lacrimal bone. It climate inserts right into the skin roughly the margin that the orbit, and also the superior and also inferior tarsal plates.Actions:Palpebral component – tenderness closes the eyelids.Lacrimal part – associated in the drainage of tears.Orbital component – tightly close the door the eyelids.
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Fig 2 – Sagittal ar of the orbit, demonstrating the class of the eyelid.
The tarsal plates are located deep to the palpebral region of the orbicularis oculi muscle. There room two plates; the premium tarsus (upper eyelid) and inferior tarsus (lower eyelid).
They plot to type the scaffolding the the eyelid, and are written of dense connective tissue. The premium tarsus likewise acts as the attachment site of the levator palpebrae superioris.
In the tarsal bowl lie the Meibomian glands (also recognized as tarsal glands). These are a specialised kind of sebaceous gland that secretes one oily problem onto the eye to sluggish the evaporation that the eye’s tear film. The oily substance additionally prevents the eyelids from sticking together when closed.
Clinical Relevance: Styes and also Chalazion
A stye (or hordeolum) is an infection the a hair follicle or Meibomian glands around the eyelash. If influence the hair follicles, they are described as external, and if they impact the Meibomian glands they room classified as internal.
Usually they room self-limiting, return they deserve to sometimes be drained by removing the hair native the affected follicle.
A chalazion is a painless granuloma the the Meibomian glands. It deserve to be identified from a stye by the absence of pain in a chalazion, whereas styes are generally painful.
The levator palpebrae superioris and also superior tarsal muscle both act to open the eyelid. They are only present in the top eyelid.
|Levator Palpebrae Superioris||Superior Tarsal Muscle|
|Attachments||Originates indigenous the lesser wing of sphenoid, and also inserts right into the upper eyelid and the exceptional tarsal plate.|
|Originates from the underside that levator palpebrae superioris and also inserts right into the exceptional tarsal plate.|
|Action||Opens the eyelid.||Assists the levator palpebrae superioris in opened the eyelid.|
|Innervation||Superior branch of the oculomotor nerve (CN III).||Sympathetic fibres indigenous the superior cervical ganglion.|
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Fig 3 – attachments of the levator palpebrae superiors to the premium tarsal plate.
The palpebral conjunctiva develops the deepest great of the eyelid.
It is a thin mucous membrane, which is reflected onto the sclera of the eyeball (bulbar conjunctiva).
The eyelid has actually a rich arterial it is provided from numerous vessels:Ophthalmic artery – lacrimal, medial palpebral, supraorbital, dorsal nasal and also supratrochlear arteries.Facial artery – angular branch.Superficial temporal artery – transverse face artery branch.
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Venous drainage is listed by a wealthy network approximately the eyelid. Medially, blood drains via the medial palpebral vein right into the angular and ophthalmic veins. Laterally, blood drains right into the superficial temporal vein native the lateral palpebral vein.