-- card: 8001 from stack: in -- bmap block id: 8738 -- flags: 0000 -- background id: 2278 -- name: Eyelids -- part 1 (button) -- low flags: 00 -- high flags: 2000 -- rect: left=314 top=324 right=336 bottom=326 -- title width / last selected line: 0 -- icon id / first selected line: 0 / 0 -- text alignment: 1 -- font id: 0 -- text size: 12 -- style flags: 0 -- line height: 16 -- part name: 1 ----- HyperTalk script ----- on mouseUp visual iris close go to card id 17155 end mouseUp -- part 2 (button) -- low flags: 00 -- high flags: 2000 -- rect: left=330 top=324 right=336 bottom=342 -- title width / last selected line: 0 -- icon id / first selected line: 0 / 0 -- text alignment: 1 -- font id: 0 -- text size: 12 -- style flags: 0 -- line height: 16 -- part name: 1 ----- HyperTalk script ----- on mouseUp visual iris close go to card id 21276 end mouseUp -- part 3 (button) -- low flags: 00 -- high flags: 2000 -- rect: left=344 top=324 right=336 bottom=356 -- title width / last selected line: 0 -- icon id / first selected line: 0 / 0 -- text alignment: 1 -- font id: 0 -- text size: 12 -- style flags: 0 -- line height: 16 -- part name: 1 ----- HyperTalk script ----- on mouseUp visual iris close go to card id 21768 end mouseUp -- part contents for background part 1 ----- text ----- X. Eyelids (palpebrae): A. Features: 1. Upper lid is larger. 2. Tarsal portion: Near margin, smooth close fit. 3. Orbital portion: Loose skin between tarsal and forehead or cheek. 4. Cilia: Eyelashes, 100-150 on upper, 50-75 on lower. 5. Pores of meibomian gland are inner to cilia. 6. Palpebral fissure: Opening between margins. 7. Canthus: Angle between eyelids, medial and lateral. 8. Lacrimal caruncle: In medial canthus, pinkish to white skin, may have hairs and glands. 9. Plica semilunaris or semilunar fold: Fold of conjunctival tissue, allows eye movement without stretching conjunctiva. 10. Lacrimal lake: Point of tear accumulation. (See diagram 1) B. Layers of the eyelid: Anterior to posterior. 1. Skin: a. Stratified squamous epithelium, sloughs off outer layers. b. Cornified, keratinized, toughened by proteins. c. Thin compared to rest of body. d. Ends at pores of meibomian glands. 2. Connective tissue: a. Areolar, loose, allows swelling in case of pathology or injury. 3. Muscles: a. Obicularis oculi: 1. Striated, closes eyelids. 2. Transverse band. 3. Connected at medial canthus to maxillary and frontal bones. 4. Temporal ends of fibers interdigitate at raphae. 5. Innervated by (VII) facial nerve. 6. Subcomponents: a. Muscle of Riolan:(pars ciliaris), at lid margin, separated from main band by lash follicles, its function is to keep margin near globe. b. Horner's muscle: (pars lacrimatis), at medial canthus, continuous with obicularis and Riolan's, goes to lacrimal bone and surrounds caniculi. Pulls tears from eye into caniculi. b. Levator palpebrae: 1. Striated, opens eyelid, if it fails ptosis results. 2. Origin: Annulus of Zinn and sphenoid bone. 3. Transverses apex of orbit over SR, tendons pierce septum and insert into skin of upper lid. 4. Innervated by (III) oculomotor nerve. 5. Gives rise to unstriated Muller's muscle of the eyelid, attached to tarsal plate, sympathetic innervation. 6. Levator and SR are attached to upper fornix. 4. Tarsal plates: a. Fibrous connective tissue. b. Tough, flexible, shape retaining. c. Hold eyelid against the globe. 5. Conjunctiva: a. Mucous membrane. b. Types: 1. Palpebral: Lines eyelids. 2. Bulbar: Covers globe to limbus. a. Both meet at fornix or cul-de-sacs. c. Meets skin at muco-cutaneous junction posterior to pores of the meibomian glands. d. Bulbar conjunctival epithelium is continuous with the corneal epithelium at the limbus. e. Layers of the conjunctiva: 1. Stratified columnar epithelium: Two layers thick at tarsal plate, 10-15 layers thick at limbus, not keratinized, has goblet cells. 2. Conjunctival stroma: Connective tissue with blood vessels which dilate with irritation, has lymphatic channels and lymphatic tissue, especially at fornix. 6. Glands: a. Goblet cells: Unicellular, produce mucous. b. Meibomian glands: Tarsal glands. 1. In tarsal plate. 2. Long multi-branched acini. 3. 25 in upper lid, 20 in lower lid. 4. Secrete oil (sebum): Outer layer of tear film. c. Zeis: Sebaceous, usually two per hair follicle. d. Moll: Sweat glands near hair follicles, less than one per follicle. e. Krause: Conjunctival. 1. Accessory lacrimal glands. 2. Subconjunctival. 3. 42 in upper fornix, 6-8 in lower fornix. f. Wolfring: 1. Accessory lacrimal glands. 2. Middle of lids at border of tarsal plate. 3. Upper lid has 2-5, lower has 2. C. Blood supply to eyelids: 1. Sources: Ophthalmic artery to medial palpebral artery, lacrimal artery to lateral palpebral artery, both supply their respective arcades. a. Peripheral arcade: Upper lid, middle height, between obicularis and levator. b. Marginal arcade: Upper lid, nearer to lash follicles in middle of lid thickness. c. Lower lid arcade: Near lash follicles. d. Arcades branch to rest of eyelid and anastomose. D. Sensory innervation: (See diagram 2) E. Lacrimal system: 1. Functions: a. Form a perfect optical surface on the cornea. b. Lubricate. c. Prevent infection through antibacterial substances (lysozymes). d. Moisten corneal and conjunctival surfaces. e. Supply oxygen to cornea. f. Remove sloughed off epithelial cells, dust and debris. 2. Components: a. Lacrimal gland: 1. Located in lateral upper orbit, small fossa in frontal bone (not in lacrimal fossa). 2. Regions: a. Large, orbital, superior. b. Small, palpebral, inferior: Divided by aponeurosis of levator. 3. Ducted to upper fornix by 10-12 ducts. 4. Flow is temporal to nasal, superior to inferior with each blink. 5. Secretes aqueous solution of salts and organic materials. b. Accessory lacrimal glands: 1. Glands of Krause. 2. Glands of Wolfring. 3. Lacrimal drainage system: a. Components: 1. Puncta: One in upper lid and one in lower lid, openings for flow into canaliculae. 2. Canaliculae: Passage from puncta to lacrimal sac, 2 mm. up and 8 mm. nasal, 90 bend called ampulla, slightly dilated here, walls are elastic and surrounded by Muller's muscle (behind sac). 3. Lacrimal sac: In lacrimal fossa (part of lacrimal and maxillary bones), anterior to septum orbitale, outside orbit 10-15 mm. long. 4. Nasolacrimal duct: Valved duct, most important is valve of Hasner at entrance to inferior meatus (lower end). 5. Inferior meatus in nose: b. Innervation of lacrimal gland: 1. Sensory: Trigeminal (V) nerve via lacrimal nerve. 2. Reflex secretion: Facial (VII) nerve, parasympathetic (dirt, sad, happy). 3. Blood vessels in lacrimal glands dilate with sympathetic innervation. (See diagram 3) 4. Tear film: a. Layers: 1. Inner: a. Mucous: Mucin, MPS and glycoproteins. b. Secreted by goblet cells in fornix. c. Wetting agent for epithelial cells and other layers of tear film. 2. Middle: 90% of film thickness (liquid layer). a. Lacrimal fluid: Aqueous layer, tear layer. b. Secreted by lacrimal gland, Krause and Wolfring, c. Composition: 1. Ions: Sodium, potassium, chloride. 2. Glucose. 3. Urea. 4. Proteins: Albumin, globulin, lysozyme. d. Quantity: 1.2 microliters per minute (µl/min.) production, 50µl equals one drop. 3. Outer layer: a. Oil: Sebum, sebaceous, lipid. These are cholesteroles, lecithin, and fatty acids. b. Main producers are the meibomian glands, secondary are the Zeis. c. Functions: 1. Prevent tear evaporation. 2. Prevents tears from overflowing onto lids. b. Blink: 1. Spreads tear layers evenly. 2. Breakup time (BUT) should be greater than 10 seconds. c. Tear elimination sequence: 1. Close lids: a. Eyelid margins move nasally forcing tears toward lacrimal lake. b. Puncta are aligned with lacrimal lake. c. Canaliculae are compressed by Horner's muscle. 2. Open lids: a. Canaliculae open creating a negative pressure. b. Tears are sucked into canaliculae. 3. Close lids: a. Tears in canaliculae are squeezed into lacrimal sac, puncta close somewhat acting as a valve to prevent backup or retrograde. b. Further passage is passive, with valves preventing any backup.