Lacrimal Apparatus: Anatomy, Parts & Function

Lacrimal Apparatus

1. Lacrimal Apparatus Components,
2. Lacrimal Apparatus Blood supply,
3. Lacrimal Apparatus Nerve supply, and
4. Lacrimal Apparatus Applied anatomy

1. Lacrimal Apparatus Components: Lacrimal gland with ducts, conjunctiva! sac, lacrimal caruncle, lacrimal punctate, lacrimal canaliculus, lacrimal sac and nasolacrimal duct.

Lacrimal gland: Table 2.6 shows different parts of the lacrimal gland.

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• Functions of lacrimal fluid (tears):
  
  Maintains Transparency of cornea.Expresses emotion, Acts as bactericidal, Renders nourishment to the cornea, and Keeps the orbital Surface of the conjunctiva moist.
• Conjunctiva
  
  Gross features: It is a transparent membrane covering the sclera and lining the inner surface of the eyelid.
  Conjunctiva! sac: It is a potential space between two eyelids and the cornea/sclera in the closed position of eyelids. It consists of
  Orbital part which is in contact with the sclera and cornea.
  Palpebral part: It is highly vascular and adherent to the tarsal plate. It lines the eyelid.
  Nerve supply
  Ophthalmic division of trigeminal nerve.
  Maxillary division of trigeminal nerve.
  Blood supply: Palpebral branch of the ophthalmic artery.
• Puncta with lacrimal canaliculi: Each lacrimal canaliculus begins with punctum.
  Length of canaliculus:10 mm. It has
  L Vertical part-2 mm
  Horizontal part-8 mm
  It is lined by stratified squamous non-keratinized epithelium. It opens in the
  lateral wall of the lacrimal sac behind the medial palpebral ligament.
• Lacrimal sac: It is a membranous sac, that continues with the nasolacrimal duct.
  It is a blind pouch. Superiorly, it measures 12 x 5 mm.
  It continues inferiorly with the nasolacrimal duct.
• Relations of lacrimal sac
  Anterior
  Medial palpebral ligament.
  Orbicularis oculi muscle.
  Medially: Lacrimal groove.
• Laterally: Lacrimal fascia and lacrimal part of orbicularis oculi.
• Nasolacrimal duct: It is a membranous passage of 18 mm long.
  It runs from the lower end of the lacrimal sac and opens in the inferior meatus of the nose.
  The lower end of the duct is guarded by the valve of Hasner.
  It prevents the backward flow of fluid.

2. Lacrimal Apparatus Blood supply

Arterial supply: Lacrimal artery, a branch of the ophthalmic artery.
Venous drainage: The lacrimal vein drains into an ophthalmic vein.

Lacrimal Apparatus Nerve supply!

Sensory: The sensations are carried by a lacrimal branch of the ophthalmic division of the trigeminal nerve.

Lacrimal Apparatus Sympathetic: It is vasomotor in function (Fig. 2.14).
Preganglionic fibers arise from the spinal cord (Tl-TS segments) and goes to the superior cervical sympathetic ganglion.
Postganglionic fibers are the plexus around the internal carotid artery and around the ophthalmic artery.

The parasympathetic nerve is secretomotor in function. It is carried by the facial nerve➔ pterygopalatine ganglion➔ maxillary nerve (VII- pterygopalatine ganglion-V2).
Preganglionic fibers arising from the lacrimatory nucleus present in the pons, pass via the facial nerve, and greater petrosal nerve and join with the deep petrosal nerve to form the nerve to the pterygoid canal.

The fibers are relayed in the pterygopalatine ganglion.

Postganglionic fibers pass through the maxillary nerve (zygomaticotemporal)­ lacrimal nerve-lacrimal gland.

The parasympathetic nerve is secretomotor in function.

It is carried by facial nerve➔ pterygopalatine ganglion➔ maxillary nerve (VII- pterygopalatine ganglion-V2).

Preganglionic fibers arising from the lacrimatory nucleus present in the pons, pass via the facial nerve, and greater petrosal nerve and join with the deep petrosal nerve to form the nerve to the pterygoid canal.

The fibers are relayed in the pterygopalatine ganglion.

1. Facial nerve
2. Greater petrosal nerve
3. Nerve of pterygoid canal carotid artery
4. Zygomatico- Levator temporal palpebrae nerve superioris

Secretomotor fibers of lacrimal gland uperDeepficialJ lacrimalglandPart of Postganglionic fibers pass through maxillary nerve (zygomaticotemporal)­
lacrimal nerve-lacrimal gland.

Lacrimal Apparatus Applied anatomy

• Dacryoadenitis (dacry-tear) is the inflammation of the lacrimal gland.
• Dacryocystitis is inflammation of the lacrimal sac and presents with pain, edema, and redness.
• Dacryocystectomy is the removal of the lacrimal sac.
• Removal of the palpebral part is equal to the removal of the entire gland because the ducts of the orbital part pass through the palpebral part.
• Epiphora (Epiphora-sudden burst)-the overflow of tears.