The tarsi are two comparatively thick, elongated plates of dense connective tissue

Dense connective tissue

Dense connective tissue, also called dense fibrous tissue, has fibers as its main matrix element. Dense connective tissue is mainly composed of collagen type I. Crowded between the collagen fibers are rows of fibroblasts, fiber-forming cells, that manufacture the fibers. Dense connective tissue...

, about 2.5 cm. in length; one is found in each eyelid

Eyelid

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...

, and contributes to its form and support. They directly abut the lid margins.

Superior

The superior tarsus (tarsus superior; superior tarsal plate), the larger, is of a semilunar

Semilunar

Semilunar can refer to:* Semilunar valves* An older name for the Lunate bone* In neurology, the semilunar fasciculus....

 form, about 10 mm. in breadth at the center, and gradually narrowing toward its extremities. It is adjoined by the Superior tarsal muscle

Superior tarsal muscle

The superior tarsal muscle is a smooth muscle adjoining the levator palpebrae superioris muscle that helps to raise the upper eyelid.-Structure:...

To the anterior surface of this plate the aponeurosis of the Levator palpebræ superioris is attached.

Inferior

The inferior tarsus (tarsus inferior; inferior tarsal plate), is smaller, is thin, elliptical in form, and has a vertical diameter of about 5 mm. The free or ciliary margins of these plates are thick and straight.

Relations

The attached or orbital margins are connected to the circumference of the orbit by the orbital septum

Orbital septum

The orbital septum is a membranous sheet that acts as the anterior boundary of the orbit. It extends from the orbital rims to the eyelids...

.

The lateral angles are attached to the zygomatic bone

Zygomatic bone

The zygomatic bone is a paired bone of the human skull. It articulates with the maxilla, the temporal bone, the sphenoid bone and the frontal bone. The zygomatic is homologous to the jugal bone of other tetrapods...

 by the lateral palpebral raphé

Lateral palpebral raphe

The lateral palpebral raphé is a much weaker structure than the medial palpebral ligament.It is attached to the margin of the frontosphenoidal process of the zygomatic bone, and passes medialward to the lateral commissure of the eyelids, where it divides into two slips, which are attached to the...

.

The medial angles of the two plates end at the lacrimal lake

Lacrimal lake

The lacrimal lake is the pool of tears in the lower conjunctival cul-de-sac, which drains into the opening of the tear drainage system . The volume of the lacrimal lake has been estimated to be between 7 and 10 µL....

, and are attached to the frontal process of the maxilla

Maxilla

The maxilla is a fusion of two bones along the palatal fissure that form the upper jaw. This is similar to the mandible , which is also a fusion of two halves at the mental symphysis. Sometimes The maxilla (plural: maxillae) is a fusion of two bones along the palatal fissure that form the upper...

 by the medial palpebral ligament

Medial palpebral ligament

The medial palpebral ligament , about 4 mm. in length and 2 mm. in breadth, is attached to the frontal process of the maxilla in front of the lacrimal groove....

).

The Meibomian glands are aligned vertically within the tarsi: 30 to 40 glands in the upper lid, and 20 to 30 in the lower lid.

Sulcus subtarsalis

Sulcus subtarsalis

Sulcus subtarsalis is a groove in the innersurface of eyelid near the eyelid margin and which is also parallel to it. This separates marginal Conjunctiva from tarsal conjunctiva. It provides space for lodging of foreign bodies. Arlt's line is a linear line present in the sulcus subtarsalis in...

is a groove in the innersurface of each eyelid.