Accessory Structures of the

The conjunctiva lines the space between the inner surface of the eyelids and the anterior surface of the eye lateral to the cornea

The conjunctiva is a thin, transparent mucous membrane that extends from the corneoscleral limbus located on the lateral margin of the cornea across the sclera (bulbar conjunctiva) and covers the internal surface of the eyelids (palpebral conjunctiva). It consists of a stratified columnar epithelium containing numerous goblet cells and rests on a lamina propria composed of loose connective tissue. The goblet cell secretion is a component of the tears that bathe the eye.

The primary function of the eyelids is to protect the eye

The skin of the eyelids is loose and elastic to accommodate their movement. Within each eyelid is a flexible support, the tarsal plate, consisting of dense fibrous and elastic tissue. Its lower free margin extends to the lid margin, and its superior border serves for the attachment of smooth muscle fibers of the superior tarsal muscle (of Mtiller). The undersurface of the tarsal plate is covered by the conjunctiva (Fig. 23.16). The orbicularis oculi muscle, a facial expression muscle, forms a thin oval sheet of circularly oriented skeletal muscle fibers overlying the tarsal plate. In addition, the connective tissue of the eyelid contains tendon fibers of the levator palpebrae superioris muscle, which open the eyelid (see Fig. 23.16)

In addition to eccrine sweat glands, which discharge their secretions directly onto the skin, the eyelid contains four other major types of glands (see Fig. 23.16):

• Tarsal glands (Meibomian glands), long sebaceous glands embedded in the tarsal plates that appear as vertical yellow streaks in the tissue deep to the conjunctiva. About 25 tarsal glands are present in the upper eyelid, and 20 are present in the lower eyelid. The sebaceous se-

orbital 1 palpebral j lacrimal gland accessory lacrimal gland (of Krause)

Lacrimal And Tarsal Glands

epidermis palpebral conjunctiva aprocrine glands of eyelids (of Moll)

sebaceous glands of eyelashes (of Zeis)

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