eyelid and lacrimal

Eyelids

Protective structures that cover the eye.

Lacrimal System

System responsible for tear production and drainage.

Plica Semilunaris

Crescent-shaped fold of conjunctiva near caruncle.

Caruncle

Modified skin with sebaceous glands and hairs.

Palpebral Fissure

Space between upper and lower eyelid margins.

Upper Eyelid

Larger, more mobile eyelid covering cornea.

Lower Eyelid

Covers inferior cornea, merges into cheeks.

Blink Reflex

Involuntary closure of eyelids for protection.

Tear Film

Layer of tears that lubricates the eye surface.

Eyelashes

Hair structures preventing debris from entering the eye.

Palpebral Sulcus

Furrow separating orbital and tarsal sections.

Superior Lid Crease

Fold above upper lid margin, varies by ethnicity.

Droopy Lids

Condition known as ptosis, reduces palpebral fissure.

Medial Canthus

Inner corner where eyelids meet.

Lateral Canthus

Outer corner where eyelids meet.

Anterior Margin

Outer aspect of eyelid containing eyelashes.

Posterior Margin

Inner aspect of eyelid containing glands.

Grey Line

Histological change separating eyelid margin zones.

Conjunctiva

Mucous membrane covering the eye and eyelids.

Ethnic Variations

Differences in eyelid anatomy among populations.

Observation Skills

Essential for assessing eyelid and eye health.

Tarsal Plate

Structural component providing eyelid shape and support.

Cilia

Hair-like structures arranged in 2-3 rows.

Sensitive to touch

Cilia highly responsive to tactile stimuli.

Glands in hair follicles

Sebaceous and sweat glands open into follicles.

Upper eyelid cilia count

Approximately 100 to 150 cilia present.

Lower eyelid cilia count

Approximately 50 to 75 cilia present.

Cilia growth cycle

Grows fully in months, lasts one month.

Madarosis

Abnormal loss of eyelashes.

Gland of Zeis

Modified sebaceous glands near eyelash follicles.

Gland of Moll

Modified sweat glands providing oily secretions.

Cyst of Zeis

Waxy cyst filled with oily sebum.

Cyst of Moll

Clear, fluid-filled cyst from gland blockage.

Eyelid internal structure

Includes skin, muscles, connective tissues, and conjunctiva.

External skin of eyelid

Thinnest skin in the body for mobility.

Eyelid movement

Constant movement occurs with each blink.

Lid laxity

Increases with age, affecting eyelid firmness.

Dermatochalasis

Excess skin causing eyelid droop.

Sub-cutaneous tissue

Loose connective tissue without fat.

Oedema

Swelling due to fluid accumulation.

Orbicularis oculi

Main eyelid muscle for closure.

Palpebral part

Involuntary eyelid movements during blinking.

Orbital part

Forces eyelid closure to temporal region.

Lacrimal part

Muscle behind lacrimal sac for tear drainage.

Riolan's muscle

Maintains lid margin close to globe.

Horner's muscle

Surrounds lacrimal apparatus, aids tear drainage.

Levator palpebrae superioris

Opens upper eyelid, antagonist to orbicularis oculi.

Occipito-frontalis muscle

Assists in opening the eyelid.

Muller's muscle

Smooth muscle aiding eyelid elevation.

Tarsal plate

Thick central part containing meibomian glands.

Meibomian glands

Secrete oily component of tear film.

Orbital septum

Connective tissue separating eyelid from orbital cavity.

Palpebral ligaments

Fibrous attachments connecting tarsal plates.

Ophthalmic artery

Key arterial supply to the eyelids.

Lacrimal artery

Provides blood supply to lacrimal gland.

Infra-orbital artery

Supplies lower eyelid region.

Venous drainage

Drains via forehead, temple, and ophthalmic veins.

Lymphatic drainage

Lateral aspect drains 2/3, medial aspect 1/3.

Tear film

Protects and lubricates the ocular surface.

Lacrimal apparatus

System producing and draining tears.

Tear film

Fluid layer maintaining ocular surface health.

Glycocalyx

Polysaccharide network connecting ocular surfaces.

Mucous layer

Innermost tear film layer, stabilizes and hydrates.

Aqueous layer

Middle layer, contains water, proteins, and salts.

Lipid layer

Outer layer, reduces evaporation and stabilizes film.

Tear film function

Maintains moisture, comfort, and optical clarity.

Tear film composition

Multiple constituents aiding ocular defense and hydration.

Conjunctival goblet cells

Cells producing mucins for tear film stability.

Mucins

High molecular weight glycoproteins in mucous layer.

Lysozyme

Bacteriolytic enzyme in aqueous layer for defense.

Lactoferrin

Protein binding iron, limiting bacterial growth.

Secretory IgA

Antibody providing immune defense in tears.

Buffering ions

Regulate tear film pH between 7.0-7.4.

Osmotic regulation

Maintains ion balance between tear film and cornea.

Meibomian glands

Glands producing lipids for tear film stability.

Meibum

Lipid-protein mix secreted by meibomian glands.

Tear drainage

Process removing excess tears from the eye.

Tear evaporation

Loss of tear film due to environmental exposure.

Optical surface

Smooth layer provided by lipid for clear vision.

Mucins

Network within the aqueous layer of tears.

Glycocalyx

Trans-membrane molecules in the aqueous layer.

Lacrimal Apparatus

System responsible for tear production and drainage.

Lacrimal Gland

Exocrine gland secreting tears into the fornix.

Basal Secretion Rate

≈ 2.2μl/min of tear fluid.

Lacrimal Passage

Pathway for tear drainage from eye.

Lacrimal Puncta

Small openings at eyelid margins for tear entry.

Lacrimal Canaliculi

Ducts connecting puncta to lacrimal sac.

Lacrimal Sac

Reservoir for tears before drainage to nose.

Nasolacrimal Duct

Duct connecting lacrimal sac to nasal cavity.

Lacrimal Fossa

Depression housing the lacrimal sac.

Lacrimal Fossa Dimensions

≈ 16mm high, 4-9mm wide, 2mm deep.

Accessory Glands

Small glands aiding in tear film secretion.

Krause Glands

Located in superior fornix, part of accessory glands.

Wolfring Glands

Located in middle of eyelids, part of accessory glands.

Tear Film

Layer of tears covering the ocular surface.

Tear Flow Route

Canaliculi → lacrimal sac → nasolacrimal duct.

Valve of Hasner

Prevents nasal secretions from entering nasolacrimal duct.

Eyelid Mediation

Mechanism pushing tears medially during blinking.

Tear Absorption

Process where tears are absorbed by tissues.

Tear Evaporation

Loss of tears due to ambient conditions.