- Lacrimal apparatus: structures concerned with secretion and drainage of lacrimal (tear) fluid.
Parts of the Lacrimal Apparatus
- Seven parts, in the order tears traverse them:
- Lacrimal gland
- Ducts of the gland
- Conjunctival sac
- Lacrimal puncta
- Lacrimal canaliculi
- Lacrimal sac
- Nasolacrimal duct
lacrimal apparatus, overview Lacrimal apparatus, overview.
Lacrimal Gland
- J-shaped serous gland, two parts:
- Large upper orbital part in the lacrimal fossa.
- Smaller lower palpebral part in the upper eyelid.
- The two are continuous around the lateral margin of levator palpebrae superioris.
- Orbital part is almond shaped, in the anterolateral part of the roof of the bony orbit.
- Palpebral part is one third the size of the orbital part, lying below levator palpebrae superioris and extending up to the superior conjunctival fornix.
- About 12 ducts (4 to 5 from the orbital part, 6 to 8 from the palpebral part) open into the lateral part of the superior fornix of the conjunctival sac.
- Secretes about 1 mL of lacrimal fluid per day.
- Half evaporates; the remaining half drains into the lacrimal sac.
- Functions of lacrimal fluid:
- Flushes the conjunctiva and keeps the cornea moist.
- Nourishes the cornea.
- Expresses emotion.
- Prevents infection through bactericidal lysozyme.
- Accessory lacrimal glands (of Krause): very small serous glands beneath the palpebral conjunctiva near the fornices.
- About 35 to 40 in the upper eyelid and 6 to 8 in the lower eyelid.