Structures concerned with secretion + drainage of lacrimal (tear) fluid: lacrimal gland + ducts, conjunctival sac, lacrimal puncta + canaliculi, lacrimal sac, nasolacrimal duct.

Lacrimal Gland

• Serous, J-shaped (almond-shaped); in lacrimal fossa, anterolateral roof of bony orbit; smaller part in upper eyelid
• Indented by tendon of levator palpebrae superioris → 2 continuous parts:
  • Orbital part — larger, deeper, in lacrimal fossa
  • Palpebral part — smaller (~1/3 of orbital), in upper eyelid below LPS; extends to superior conjunctival fornix
• ~12 ducts (4–5 orbital + 6–8 palpebral) → lateral superior conjunctival fornix; orbital ducts pass through palpebral part → surgical removal of palpebral part = functionally equivalent to removing entire gland

Blood supply: Lacrimal branch of ophthalmic artery Venous drainage: Ophthalmic veins

Nerve Supply of Lacrimal Gland

Parasympathetic (secretomotor): Lacrimatory nucleus (pons) → nervus intermedius → geniculate ganglion → greater petrosal nerve → nerve of pterygoid canal → pterygopalatine ganglion (relay) → maxillary nerve → zygomatic nerve → zygomaticotemporal nerve → lacrimal nerve → lacrimal gland

Sympathetic (vasomotor): T1 → superior cervical ganglion → internal carotid plexus → deep petrosal nerve → joins greater petrosal to form nerve of pterygoid canal → pterygopalatine ganglion (no relay) → zygomatic → zygomaticotemporal → lacrimal nerve → lacrimal gland

Sensory: Lacrimal nerve (ophthalmic V1)

Functions of Lacrimal Fluid

• ~1 mL/day secreted; ~half evaporates; rest drains into sac
• Moistens + nourishes cornea (avascular); flushes conjunctiva; expresses emotion; antibacterial (lysozyme)

Puncta and Canaliculi

• Puncta — small openings on medial lid margins on lacrimal papilla facing lacus lacrimalis
• Canaliculi — 2 (superior + inferior); ~10 mm each; short vertical part (~2 mm) + longer horizontal part (~8 mm) with dilated ampulla at bend; converge into lateral wall of lacrimal sac, behind medial palpebral ligament

Lacrimal Sac

• ~12 mm long, 5 mm wide; in lacrimal groove behind medial palpebral ligament; enclosed in lacrimal fascia
• Upper end = blind (closed); lower end = continuous with nasolacrimal duct
• Parts: fundus → body → neck (continues as nasolacrimal duct)

Relations:

Surgical operations on sac performed anterior to orbital cavity (orbital septum passes behind sac to posterior lacrimal crest)

Nasolacrimal Duct

• ~18 mm; lacrimal sac neck → anterior part of inferior meatus of nose
• Lodged in bony canal (maxilla + lacrimal bone + inferior nasal concha)
• Lower opening: incomplete mucosal fold = lacrimal fold (valve of Hasner) — prevents air from entering eye during nose-blowing; imperfect one-way valve

Drainage (Lacrimal Pump Mechanism)

1. Blinking
2. Capillary action of fluid film
3. Lacrimal part of orbicularis oculi contracts → tracts lacrimal fascia → distends sac → draws tears through canaliculi (“lacrimal pump”)

Development

• Eyelids: folds of skin adhering at edges in 3rd month → conjunctival sac
• Nasolacrimal duct: solid ectodermal cord along nasolacrimal groove (fusion of maxillary + lateral nasal processes) → submerges → canalises 3rd month; upper end widens → lacrimal sac → secondarily connects with conjunctival sac via canaliculi

Applied Anatomy

• Epiphora (overflow of tears) — excessive secretion OR obstruction anywhere in drainage pathway OR ectropion (lower lid eversion in old age/facial nerve palsy → punctum carried away from eye surface)
• Dacryocystitis — inflammation of lacrimal sac, often from nasolacrimal duct obstruction → stasis + infection
• Bell’s palsy — lacrimal pump failure (orbicularis oculi paralysis) → tears overflow; + risk of corneal drying → artificial tears needed

The lacrimal apparatus comprises the structures concerned with the secretion and drainage of lacrimal (tear) fluid. It consists of: the lacrimal gland and its ducts, the conjunctival sac, the lacrimal puncta and canaliculi, the lacrimal sac, and the nasolacrimal duct.

Lacrimal Gland

The lacrimal gland is a serous, J-shaped (almond-shaped) gland situated chiefly in the lacrimal fossa on the anterolateral part of the roof of the bony orbit, with a smaller part lying in the upper eyelid. Small accessory lacrimal glands are present in the conjunctival fornices.

The gland is indented by the tendon of the levator palpebrae superioris and has two continuous parts:

• Orbital part — larger and deeper, situated in the lacrimal fossa.
• Palpebral part — smaller (about one-third the size of the orbital part) and superficial, lying within the upper eyelid below the levator palpebrae superioris, extending up to the superior conjunctival fornix.

Ducts: About 12 ducts (4–5 from the orbital part, 6–8 from the palpebral part) open into the lateral part of the superior conjunctival fornix. Ducts of the orbital part pass through the palpebral part before opening; therefore, surgical removal of the palpebral part is functionally equivalent to removal of the entire gland — the conjunctiva and cornea are thereafter moistened only by accessory lacrimal glands.

Arterial supply: Lacrimal branch of the ophthalmic artery.

Venous drainage: Ophthalmic veins.

Nerve Supply of the Lacrimal Gland

The lacrimal gland receives parasympathetic (secretomotor), sympathetic, and sensory innervation.

Parasympathetic (secretomotor) pathway:

• Preganglionic fibres arise from the lacrimatory nucleus in the pons.
• They pass through the nervus intermedius → geniculate ganglion → greater petrosal nerve → nerve of the pterygoid canal → pterygopalatine ganglion (relay).
• Postganglionic fibres pass through the maxillary nerve → zygomatic nerve → zygomaticotemporal nerve → lacrimal nerve → lacrimal gland.

Sympathetic (vasomotor) pathway:

• Fibres originate from the T1 spinal segment, synapse in the superior cervical sympathetic ganglion, and travel via the sympathetic plexus around the internal carotid artery → deep petrosal nerve → join the pterygopalatine ganglion (pass through without relay) → zygomatic nerve → zygomaticotemporal nerve → lacrimal nerve → lacrimal gland.

Sensory supply: Lacrimal nerve, a branch of the ophthalmic division of the trigeminal nerve.

Functions of Lacrimal Fluid

About 1 mL of lacrimal fluid is secreted per day; roughly half evaporates and the remainder drains into the lacrimal sac. Functions include:

• Flushes the conjunctiva and keeps the cornea moist.
• Provides nourishment to the cornea (which is avascular).
• Serves to express emotion — shedding of tears during grief or sorrow.
• Prevents infection, as it contains the bactericidal enzyme lysozyme.

Conjunctival Sac, Puncta, and Canaliculi

The conjunctival sac is the potential space between the palpebral and bulbar conjunctiva, into which lacrimal fluid is secreted and where it lubricates the front of the eye and deep surface of the lids. Periodic blinking spreads the fluid over the eye.

Lacrimal puncta are small openings on the medial part of each lid margin, situated on a small conical projection called the lacrimal papilla, which faces toward the lacus lacrimalis.

Lacrimal canaliculi — there are two, superior and inferior, one in each eyelid:

• Each canaliculus is about 10 mm long, beginning at the lacrimal punctum.
• Each has a short vertical part (about 2 mm) and a longer horizontal part (about 8 mm), with a dilated ampulla at the bend.
• The superior canaliculus runs upward then bends downward and medially; the inferior canaliculus runs downward then bends upward and medially — both converge toward the lacrimal sac, opening into its lateral wall close together (sometimes via a common dilated stem), behind the medial palpebral ligament.

Lacrimal Sac

The lacrimal sac is a membranous sac, approximately 12 mm long and 5 mm wide (up to about 15 mm by 5–6 mm when distended), situated in the lacrimal groove behind the medial palpebral ligament, enclosed within the lacrimal fascia. Its upper end is blind (closed); its lower end is continuous with the nasolacrimal duct. It is divisible into three parts from above downward: fundus, body, and neck — the narrow neck continues as the nasolacrimal duct.

Relations of the lacrimal sac:

• Anteriorly: Medial palpebral ligament (and the orbicularis oculi).
• Posteriorly: Lacrimal part of the orbicularis oculi, which arises from the posterior lacrimal crest of the lacrimal bone and from the lacrimal fascia, forming a sheath around the sac.
• Laterally: Lacrimal fascia (derived from orbital periosteum) and a minute venous plexus.
• Medially: Lacrimal groove, separating the sac from the nasal cavity, and a minute arterial plexus.

Surgical operations on the lacrimal sac are performed anterior to (outside) the orbital cavity proper, because the orbital septum passes behind the lacrimal sac to attach to the posterior lacrimal crest.

Nasolacrimal Duct

The nasolacrimal duct is a membranous canal about 18 mm long, extending from the neck of the lacrimal sac to the anterior part of the inferior meatus of the nose. It is lodged within a bony canal formed by the maxilla, lacrimal bone, and inferior nasal concha. Its lower opening bears an incomplete mucosal fold called the lacrimal fold (valve of Hasner), which helps prevent air from being blown into the eye (e.g., during nose-blowing) and acts as an imperfect one-way valve.

Drainage of Tears (Lacrimal Pump Mechanism)

Drainage of tears from the conjunctival sac occurs through:

1. Blinking movements of the eyelids.
2. Capillary action of the fluid film.
3. Contraction of the lacrimal part of orbicularis oculi, which exerts traction on the lacrimal fascia, distending the lacrimal sac and drawing tears in through the canaliculi (the “lacrimal pump”).

Development

The eyelids develop as folds of skin above and below the cornea, adhering along their edges during the third month of intrauterine life; the space between the folds and the cornea becomes the conjunctival sac. The nasolacrimal duct develops from a solid ectodermal cord that forms along the nasolacrimal groove, at the line of fusion of the maxillary and lateral nasal processes. This cord becomes submerged beneath the surface ectoderm and canalises during the third month to form the nasolacrimal duct. The upper end of this duct widens to form the lacrimal sac, which secondarily connects with the conjunctival sac via the lacrimal canaliculi.

Clinical Correlation

Epiphora is the overflow of tears onto the cheeks. It may result from:

• Excessive secretion of tears (hyperlacrimation), e.g., after spicy food or emotional outbursts.
• Obstruction anywhere along the lacrimal drainage pathway — at the punctum, canaliculi, lacrimal sac, or nasolacrimal duct.
• Eversion of the lower eyelid (ectropion), carrying the lacrimal papilla and punctum away from the eye surface, seen in old age due to skin laxity or loss of orbicularis oculi tone (e.g., in facial nerve palsy).

Dacryocystitis is inflammation of the lacrimal sac, often secondary to obstruction of the nasolacrimal duct, leading to stasis and infection of tears within the sac.

Bell’s Palsy and the Lacrimal Gland: When the lacrimal gland fails to adequately distribute or drain tear fluid — as can occur in Bell’s palsy due to loss of the lacrimal pump (paralysis of the lacrimal part of orbicularis oculi) — artificial tears may be instilled at regular intervals to prevent corneal drying and desiccation.

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