Lacrimal Apparatus

00:01 And now we can move one to the last topic of our discussion, the lacrimal and the nasolacrimal apparatus of the orbit.

00:08 The lacrimal apparatus is involved in the production of tear fluid.

00:13 Tears are essential to the normal functioning of the eye.

00:17 They lubricate the anterior surface of the eye to minimise friction and protect it by washing away any debris microbial or otherwise.

00:26 This protective tear fluid sometimes also called the tear film is composed of three layers.

00:32 The outermost lipid layer is derived from the hydrophobic sebaceous secretions of the meibomian glands.

00:39 And again, this prevents tear film evaporation.

00:43 The metal isotonic aqueous layer is secreted by the lacrimal gland and is composed mainly of water, electrolytes, antimicrobial proteins and IGA.

00:54 The aqueous layer supplies and hydrates the avascular cornea with oxygen and nutrients and helps to dispose of waste products.

01:04 And the innermost hydrophilic mucus layer is secreted by goblet cells of the conjunctiva and this layer helps to evenly distribute the tear film across the globe of the eye.

01:15 Disruption in any of the layers of the tear film can cause dry eye disease.

01:21 However, by far the largest component of the tear film is the middle aqueous layer, and again this is secreted mainly by the lacrimal gland.

01:30 The lacrimal gland is a tubular aster gland that consists of orbital and palpebral parts.

01:38 Now once the tear film is produced, it must be drained away to make room for the new tear fluid that is constantly being produced.

01:47 Although tears do not evaporate to some extent, the majority of the tear film is drained via the nasal lacrimal drainage system.

01:56 Once tears have been secreted into the superior fornix and make their way across the interior globe by collecting the lacrimal lake located at the medial canthus of the orbit.

02:08 Once their tears drained into the lacrimal puncta, which are connected to the lacrimal ducts.

02:15 The lacrimal ducts then unite to form a common duct which is connected to the lacrimal sac and the nasal lacrimal duct.

02:23 From the lacrimal sac tears flow down the nasal lacrimal duct which opens up anteriorly into the inferior nasal meatus and are then subsequently has slowed and this is the end.