Superior tarsus

At a glance

English

Superior tarsus

Latin (TA2)

Tarsus superior

System

Connective tissue

Region

Head

Side

Paired, left and right

About the superior tarsus

The superior tarsus is the stiffening plate of the upper eyelid. Though sometimes called the tarsal cartilage, it is made of dense fibrous tissue rather than true cartilage. It is shaped like a half-moon: about 10 mm high in the middle and tapering towards each end, roughly twice the height of the plate in the lower lid. Its curve matches the front of the eyeball, which it keeps the lid pressed against.

Its lower border, the free or ciliary margin, is straight and thick and runs just above the edge of the lid where the lashes emerge. Its upper border, the attached or orbital margin, is convex and is joined to the orbital rim by the orbital septum. At the medial end the two tarsi meet near the lacrimal lake and are held by the medial palpebral ligament against the maxilla's frontal process; at the lateral end the lateral palpebral raphe and ligament anchor them on the zygomatic bone.

Two lifting muscles act on the plate. The aponeurosis of levator palpebrae superioris spreads down in front of it and attaches to its anterior surface, with slips continuing to the skin to form the upper lid crease. The superior tarsal muscle (Müller's muscle), a sheet of smooth muscle, lies behind the aponeurosis and joins the upper edge of the plate. Behind the tarsus is the conjunctiva, tightly adherent to it; a shallow groove on its inner surface near the margin, the subtarsal sulcus, is where small particles lodge and why doctors evert the lid to look for them.

Within the plate lie the tarsal (meibomian) glands, long sebaceous glands placed side by side whose oil keeps the tear film from evaporating. Their blockage gives a chalazion. Loss of sympathetic supply to the superior tarsal muscle causes the mild drooping of the lid seen in Horner syndrome; damage to the levator causes more severe ptosis.

Function and supply

Begins at

Medially the medial palpebral ligament ties its end to the maxilla (frontal process); laterally the lateral palpebral ligament ties it to the zygomatic bone.

Ends at

Its upper margin joins the orbital rim through the orbital septum and receives the superior tarsal muscle; its front surface receives the levator aponeurosis.

Function

Gives the upper eyelid its form and rigidity, transmits the pull of the levator and superior tarsal muscles when the lid is raised, and houses the tarsal glands.

Nerve supply

Sensation from the upper lid travels in branches of the ophthalmic nerve, chiefly the supraorbital, supratrochlear and lacrimal nerves.

Blood supply

From the superior palpebral arterial arcades, fed by the medial palpebral branches of the ophthalmic artery and the lateral palpebral branches of the lacrimal artery.