LACRIMAL APPARATUS

LACRIMAL APPARATUS

Consists of secretory & excretory systems.
Secretory system consists of:

Lacrimal gland & its duct
Accessory lacrimal glands (Gland of Krause, Glands of Wolfring)

Excretory system consists of:

Lacrimal puncta
Lacrimal canaliculi
Lacrimal sac
Nasolacrimal duct

TEAR

Major function of lacrimal apparatus is to secrete & drain tear.
Tear film consists of 3 layers:

1. Mucous / mucin layer (innermost)

Secreted by conjunctival goblet cells, crypts of Henle, glands of Manz.

2. Aqueous layer (intermediate):

This forms the bulk of the tear.
It is secreted by main lacrimal & accessory lacrimal glands.

3. Lipid layer (outermost):

Secreted by the Meibomion, Zeis & Moll glands.

CAUSES OF TEAR DEFICIENCY (Dry Eye)

1. Aqueous deficiency (Keratoconjunctivitis sicca):

Congenital alacrimia
Sjogren’s syndrome
Riley Da syndrome

2. Mucin deficiency:

Xeropthalmia
conjunctival scarring (Stevens- Johnson syndrome, Trachoma)

3. Lipid deficiency:

Congenital anhydrotic ectodermal dysplasia along with absence of meibomian gland
Chroniv blepheritis

4. Chronic eyelid function:

Bell’s palsy
Exposure keratitis
Pterygium

LACRIMAL PUMP

Eyelids & the orbicularis muscle create a physiological pump which pumps the tears into the two puncta.
Then finally drain it into the inferior meatus through nasolacrimal duct.
Eyelids are opposed against the globe, this creates a capillary action for tears.
Orbicularis muscle contraction & relaxation creates a anegative pressure in the lacrimal sac which sucks in the ear.

Exam Important