The tarsi (tarsal plates) are two comparatively thick, elongated plates of
dense connective tissue, about in length for the upper eyelid and 5 mm for the lower eyelid; one is found in each
eyelid, and contributes to its form and support. They are located directly above the lid margins. The tarsus has a lower and upper part making up the
palpebra
An eyelid is a thin fold of skin that covers and protects an eye. The levator palpebrae superioris muscle retracts the eyelid, exposing the cornea to the outside, giving vision. This can be either voluntarily or involuntarily. The human eyeli ...
e.
Superior
The ''superior tarsus'' (''tarsus superior''; superior tarsal plate), the larger, is of a
semilunar
Semilunar can refer to:
* Semilunar valves
* Semilunar ganglion, or the trigeminal ganglion
* An older name for the Lunate bone
The lunate bone (semilunar bone) is a carpal bone in the human hand. It is distinguished by its deep concavity and cr ...
form, about in breadth at the center, and gradually narrowing toward its extremities. It is adjoined by the
superior tarsal muscle.
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, is elliptical in form, and has a vertical diameter of about . 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.
The lateral angles are attached to the
zygomatic bone by the
lateral palpebral raphe.
The medial angles of the two plates end at the
lacrimal lake, and are attached to the frontal process of the
maxilla
The maxilla (plural: ''maxillae'' ) in vertebrates is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. The t ...
by the
medial palpebral ligament).
The
sulcus subtarsalis
Sulcus subtarsalis is a groove in the inner surface of eyelid near the eyelid margin and which is also parallel to it. This separates marginal conjunctiva
The conjunctiva is a thin mucous membrane that lines the inside of the eyelids and cov ...
is a groove in the inner surface of each eyelid.
Along the inner margin of the tarsus are modified sebaceous glands known as tarsal glands (or
meibomian glands
Meibomian glands (also called tarsal glands, palpebral glands, and tarsoconjunctival glands) are sebaceous glands along the rims of the eyelid inside the tarsal plate. They produce meibum, an oily substance that prevents evaporation of the eye' ...
), aligned vertically within the tarsi: 30 to 40 glands in the upper lid, and 20 to 30 in the lower lid, which secrete a lipid-rich product which helps keep the lacrimal secretions or tears from evaporating too quickly, thus keeping the eye moist.
[Martini, 2006]
Additional images
Image:Gray379.png, Left orbicularis oculi, seen from behind
Image:Gray888.png, Sagittal section of right orbital cavity
File:Slide2www.JPG, Extrinsic eye muscle. Nerves of orbita. Deep dissection.
See also
*
References
{{Authority control
Human eye anatomy