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Anatomy of Lacrimal Apparatus

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Contents Lacrimal apparatus Main gland Accessory glands Blood supply and Nerve supply Lacrimal Passages

Puncta Canaliculi Sac Nasolacrimal duct

Tear film Functions of tear film Lacrimal pump mechanism

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Lacrimal Apparatus

The lacrimal apparatus comprises Main lacrimal gland Accessory lacrimal glands Lacrimal passages, which include :▪ Puncta▪ Canaliculi▪ Lacrimal Sac▪ Nasolacrimal Duct (NLD)

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Main Lacrimal GlandOrbital Part:

About the size and shape of a small almond Situated in the lacrimal fossa on the frontal

bone, at the outer part of the orbital plate The superior surface is convex and lies in

contact with the bone The inferior surface is concave and lies on

the levator palpebrae superioris (LPS )muscle 10-12 ducts pass downward from the gland

and open into the lateral part if the superior fornix

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Main Lacrimal Gland

Palpebral Part : It is small and consists only of 1-2

lobules It is situated in the course of the ducts of

the orbital part Posteriorly it is continuous with the

orbital part

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Accessory Lacrimal Glands Glands of Krause :

They are microscopic groups of acini that lie beneath the palpebral conjunctiva between the fornix and the edge of the tarsus

There are about 42 in the upper fornix and 6-8 in the lower fornix

The ducts of numerous acini unite to form a larger duct that open into the fornix

Glands of Wolfring : These are present near the upper border of the

superior tarsal plate and along the lower border of the inferior tarsus

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Structure : All glands are made up of serous acini and ducts, connective tissue and puncta

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Blood Supply : Main gland is supplied by lacrimal artery, a branch of ophthalmic artery

Nerve Supply: Sensory supply : Lacrimal nerve Sympathetic supply : Carotid plexus of

cervical sympathetic chain Secretomotor fibres

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Lacrimal Passages

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Lacrimal Puncta

Two small rounded or oval openings, on the upper and lower lids, about 6 and 6.5 mm respectively, temporal to the inner canthus

Each punctum is situation on a slight elevation called lacrimal papilla

Normally, puncta dip into lacus lacrimalis

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Lacrimal Canaliculi

Each canaliculus has two parts : vertical (1-2mm) and horizontal (6-8mm) which lie at right angles to each other

Horizontal canaliculi open either separately or join together and open into the lacrimal sac

Fold of mucosa at this point forms the Valve of Rosenmuller which prevents reflux of tears

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Lacrimal Sac

Lies in lacrimal fossa which is formed by lacrimal bone and frontal process of maxilla

When sac is distended, it measures 12-15mm vertically and 5-6mm horizontally

Fundus extends slightly beyond medial palpebral ligament and sac itself is surrounded by fibres of the orbicularis muscle

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Nasolacrimal Duct Extends from neck of sac to inferior meatus of

the nose It is about 15-18mm long, and lies in a bony

canal formed by maxilla and inferior turbinate Direction is downwards, backwards and

laterally Surface marking : Line joining inner canthus

to ala of nose Mucous lining forms an imperfect Valve of

Hasner at the lower end of the duct and prevents reflux from the nose

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Tear Film Structure of fluid covering the cornea

: Mucus Layer Aqueous layer Lipid or Oily Layer

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Functions of the Tear Film Keeps cornea and conjunctiva moist Provides oxygen to conjunctival

epithelium Washes away debris and noxious

irritants Prevents infection due to presence of

antibacterial substances Facilitates movement of lids over the

globe

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Elimination of tears Lacrimal Pump Mechanism

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Applied Anatomy Dry eye or Keratoconjunctivitis Sicca (KCS)

due to lacrimal gland deficiencies or obstructions

Hyperlacrimation due to tumors or cysts of the lacrimal gland, or the effect of strong parasympathomimetic drugs

Epiphora due to pump failure or obstructions Dacryocytitis due to blockage or infection In atonia of the sac tears aren’t drained

through lacrimal passages, in spite of anatomical patency, leading to epiphora

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References

Parsons’ Diseases of the Eye; 21st Edition; Editors : Ramanjit Sihota, Radhika Tandon; Elsevier

A K Khurana : Comprehensive Ophthalmology; Fifth Edition; New Age International Publishers

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Thank You