Conjunctiva, lacrimal apparatus

The conjunctiva (tunica conjunctiva) is a thin transparent membrane. It covers the posterior surfaces of the upper and lower eyelids (tunica conjunctiva palpebrarum). It passes to the bulb, where it covers the sclera and reaches the edge of the cornea (tunica conjunctiva bulbi). The conjunctival epithelium changes to the anterior corneal epithelium. There is a deep slit - fornix conjunctivae superior et inferior. The conjunctiva also has lymphatic tissues and lymph nodes mediating the immune function.

Conjunctival epithelium

It is composed of multilayered cylindrical epithelium. It contains goblet cells, which produce conjunctival mucus. There are also glandulae mucinosae and accessory lacrimal glands – glandulae lacrimales accessoriae – located at the fornix.

Anatomy

Eye conjunctiva 1. limbus corneae (corneal edge) 2. tunica conjunctiva bulbi 3. fornix conjunctivae inferior 4. tunica conjunctiva palpebrarum 5. limbus palpebrae anterior 6. plica semilunaris conjunctivae 7. caruncula lacrimalis

• Tunica conjunctiva bulbi (bulbar conjunctiva) – connects to the corneal epithelium and covers the sclera in front. The mucous connective tissue gradually disappears towards the cornea.
• Tunica conjunctiva palpebrarum (palpebral conjunctiva) – continues to the back of the eyelid. It is immovably connected to the tarsal plate.
• Fornix conjunctivae superior (upper conjunctival vault) – when the eyelid is opened, it folds into mucous folds, thus allowing the eyelid to move. It contains the ducts of the lacrimal glands, which moisten the cornea. On the lateral side of the eye, it passes into the inferior conjunctival fornix.
• Fornix conjunctivae inferior (lower arch of the conjunctiva) – its arching allows eyelid movement.
• Lacus lacrimalis (tear pool) – located in the medial corner of the eye, at the junction of the two arches of the fornix. The conjunctiva is arched here into a small pink bump – the caruncula lacrimalis.
• Plica semilunaris cunjunctiva – crescent-shaped reserve conjunctival lash, located at the inner corner of the eye.
• Saccus conjunctivalis – a slit covered by conjunctiva and located between the back of the eyelids and the eyeball.

Vessels and nerves of the conjunctiva

Vessels

The anterior ciliary arteries supply the bulbar conjunctiva. The vessels for the palpebral conjunctiva (lid conjunctiva) come from the palpebral arches.

Nerves

Innervation is mediated by the 1st and 2nd branches of the trigeminal nerve.

Lacrimal apparatus

The basis for the lacrimal apparatus (apparatus lacrimalis) is the lacrimal gland, which produces tears, or lacrimae. These travel through the ductuli excretorii. They are dispersed in the fornix conjuctivae superior over the surface of the cornea, eyelid and bulbar conjunctiva. The tears then flow through the rivus lacrimalis into the lacrimal lake (lacus lacrimalis). They are then drained by the lacrimal ducts into the nasal passage.

Anatomy

lacrimal apparatus

Lacrimal gland (tear gland)

Tubuloalveolar gland composed of lobules.

• Ductuli excretorii – emerge from the lacrimal gland.
• Pars orbitalis – The upper and larger part of the gland. It is located behind the orbital septum.
• Pars palpebralis – is the lower and smaller part.
• Rivus lacrimalis – The capillary gap between the anterior surface of the cornea and the eyelids. Tears flow here to the inner corner of the eye.
• Lacus lacrimalis (tear lake) – a depression from which tears flow into the tear ducts.
• Punctum lacrimale – small openings at the tops of the papillae lacrimales (=elevations at the medial edge of the eyelid). They function as the entrance to the canaliculus lacrimalis.
• Canaliculi lacrimales (tear ducts) – thin ducts (superior and inferior). Leading tears to the lacrimal sac.

Saccus lacrimalis (tear sac)

A tubular sac in the inner edge of the fossa sacci lacrimalis. Here it fuses with the periosteum, which allows the sac to be permanently open. It is surrounded anteriorly and posteriorly by the superficial and deep parts of the medial palpebral ligament. Caudally, the lacrimal sac changes into the ductus nasolacrimalis, or tear duct. The duct passes through the canalis nasolacrimalis and ends under the inferior nasal concha (meatus nasi inferior), where its mouth is covered by a mucous fold – plica lacrimalis (valvula Hesneri).

Vessels and nerves of the lacrimal apparatus

The lacrimal gland arteries arise from the lacrimal artery. The lacrimal ducts are supplied by arteries from the medial side of the eyelid. The lacrimal sac and the nasolacrimal duct have arteries from the medial wall of the orbit and the medial wall of the nasal cavity.

The sympathetic lacrimal plexus runs along the lacrimal artery. The parasympathetic visceromotor fibers come from the superior salivatory nucleus of the facial nerve.

References

Related articles

• Eye (histology)
• Lacrimal bone
• Eyelids
• Orbit

Used literature

• ČIHÁK, Radomír. Anatomie 3. - edition. Grada, 1997. 655 pp. ISBN 9788071691402.

• PETROVICKÝ, Pavel. Anatomie s topografií a klinickými aplikacemi : Neuroanatomie, smyslová ústrojí a kůže. III. svazek. - edition. Osveta, 2002. 542 pp. ISBN 9788080630485.