Lacrimal Apparatus

COMPONENTS

The structures concerned with secretion and drainage of the lacrimal or tear fluid constitute the lacrimal apparatus. It is made up of the following parts:
1. Lacrimal gland and its ducts
2. Conjunctival sac.
3. Lacrimal puncta and lacrimal canaliculi.
4. Lacrimal sac.
5. Nasolacrimal duct.

Lacrimal Gland

It is a serous gland
situated chiefly in the lacrimal fossa on the anterolateral part of the roof of the bony orbit and partly on the upper eyelid.
Small accessory lacrimal glands are found in the conjunctival fornices.
The gland is ‘J' shaped, being indented by the tendon of the levator palpebrae superioris muscle.
It has:

1. An orbital part which is larger and deeper, and

2. A palpebral part smaller and superficial, lying within the eyelid

• About a dozen of its ducts pierce the conjunctiva of the upper lid and open into the conjunctival sac near the superior fornix.

• Most of the ducts of the orbital part pass through the palpebral part. Removal of the latter is functionally equivalent to removal of the entire gland.

• After removal, the conjunctiva and cornea are moistened by accessory lacrimal glands.

• The gland is supplied by the lacrimal branch of the ophthalmic artery and by the lacrimal nerve.

• The nerve has both sensory and secretomotor fibres.

• The lacrimal fluid secreted by the lacrimal gland flows into the conjunctival sac where it lubricates the front of the eye and the deep surface of the lids.

• Periodic blinking helps to spread the fluid over the eye.

• Most of the fluid evaporates.

• The rest is drained by the lacrimal canaliculi.

• When excessive, it overflows as tears.

Conjunctival Sac

The conjunctiva lining the deep surfaces of the eyelids is called palpebral conjunctiva and that lining the front of the eyeball is bulbar conjunctiva.

The potential space between the palpebral and bulbar parts is the conjunctival sac.
The lines along which the palpebral conjunctiva of the upper and lower eyelids is reflected on to the eyeball are called the superior and inferior conjunctival fornices.

The palpebral conjunctiva is thick, opaque, highly vascular, and adherent to the tarsal plate.
The bulbar conjunctiva covers the sclera. It is thin, transparent, and loosely attached to the eyeball. Over the cornea, it is represented by the anterior epithelium of the cornea. 

Lacrimal Puncta and Canaliculi

Each lacrimal canaliculus begins at the lacrimal punctum, and is 10 mm long.
It has a vertical part which is 2 mm long and a horizontal part which is, 8 mm long.

There is a dilated ampulla at the bend. Both canaliculi open close to each other in the lateral wall of the lacrimal sac behind the medial palpebral ligament. 

Lacrimal Sac

It is membranous sac 2 mm long and 5 mm wide,
situated in the lacrimal groove behind the medial palpebral ligament.

Its upper end is blind.
The lower end is continuous with the nasolacrimal duct.
The sac is related anteriorly to the medial palpebral ligament and to the orbicularis oculi. Medially, the lacrimal groove separates it from the nose.
Laterally, it is related to the lacrimal fascia and the lacrimal part of the orbicularis oculi. 

Nasolacrimal Duct

It is a membranous passage 18 mm long.
It begins at the lower end of the lacrimal sac, runs downwards, backwards and laterally, and opens into the inferior meatus of the nose. A fold of mucous membrane called the valve of Hasner forms an imperfect valve at the lower end of the duct. 

Clinical Anatomy

Inflammation of the lacrimal sac is called dacro cystitis.
The ducts of lacrimal gland open through its palpebral part into the conjunctival sac, Because of this arrangement, the removal of palpebral part necessitates the removal of the orbital part as well
Excessive secretion of lacrimal fluid, i.e. tears is mostly due to emotional reasons. The tears not only flow on the cheeks but also flow out through nasolacrimal duct and the nasal cavity, due to stimulation of pterygopalatine ganglion.
Excessive secretion of the lacrimal fluid overflowing on the cheeks is called epiphora.
Epiphora may result due to obstruction in the lacrimal fluid pathway, either at the level of punctum or canaliculi or nasolacrimal duct. 

Watch lectures on YouTube:

Lacrimal Apparatus | Components, Features, Structure with its Blood & Nerve supply