Eye TO 2

Palpebrae (Eyelids) and Associated Structures

• Definition and General Function

  • The palpebrae, commonly known as the eyelids, serve as a protective covering for the eye.

  • Blinking Mechanism: The action of blinking performs two primary tasks:

    • Lubrication: It spreads moisture across the eye surface to prevent desiccation.

    • Cleaning: It wipes off dust, dirt, or foreign debris from the surface of the eye.

  • Protection: The eyelids can close to provide a physical barrier against injury or excessive light.

• Anatomical Components of the Palpebrae

  • Orbicularis oculi: The eyelid contains fibers of the orbicularis oculi muscle, which is responsible for closing the eye.

  • Levator palpebrae superioris: The tendon of this muscle is present to facilitate the elevation (opening) of the upper eyelid.

  • Tarsal Glands: Specialized glands located within the eyelid that contribute to the oily component of the tear film.

  • Eyelashes: Hair structures extending from the border of the eyelids that assist in filtering debris.

The Conjunctiva

• Morphology and Classification

  • The conjunctiva is defined as a mucous membrane.

• Distribution and Localization

  • Palpebral Region: It lines the inner surface of the eyelids.

  • Ocular Region: It folds back over the anterior surface of the eyeball.

  • Exceptions: The conjunctiva covers the visible anterior eyeball with the specific exception of the cornea. The cornea remains uncovered by this membrane to maintain its clarity for light transmission.

The Lacrimal Apparatus

• Overview and Physiological Purpose

  • The lacrimal apparatus is the physiologic system responsible for the production, distribution, and drainage of tears.

• Major Anatomical Components and Pathway

  • Lacrimal Gland: Located superior and lateral to the eyeball, this gland is responsible for the production of tears.

  • Superior and Inferior Canaliculi: Small channels that collect tears from the surface of the eye after they have moved across the conjunctiva.

  • Lacrimal Sac: A reservoir that receives tears from the canaliculi.

  • Nasolacrimal Duct: The final drainage tube that conducts tears from the lacrimal sac into the nasal cavity (nose).

Anatomical Summary

• Sagittal View Structures

  • Based on the sagittal section of the eye, the relationship between the following structures is established:

    • Tendon of levator palpebrae superioris.

    • Fibers of orbicularis oculi.

    • Tarsal glands.

    • Eyelashes.

    • Cornea.

    • Conjunctiva.

• Lacrimal System Flow

  • The flow of fluid follows this specific sequence: Lacrimal gland $\rightarrow$ Eye surface $\rightarrow$ Superior/Inferior canaliculi $\rightarrow$ Lacrimal sac $\rightarrow$ Nasolacrimal duct.