Lecture 6: Tear Film & Lacrimal System

Complete set of 207 single-concept practice flashcards covering the tear film and lacrimal system from OPT 8123 Lecture 6.

What is the title of OPT 8123 Lecture 6?

Tear Film & Lacrimal System.

What is the thickness of the tear film?

$$4\text{--}8\,\mu\text{m}$$

What is the outermost tear film layer?

Lipid layer.

What is the middle tear film layer?

Aqueous layer.

What is the innermost tear film layer?

Mucin layer.

Do tear film layers always remain separate?

No; the aqueous and mucin layers can intermix.

What is the mucoaqueous layer?

The intermixed aqueous and mucin portions of the tear film.

What tear film function provides an optically smooth surface?

Providing a smooth refractive surface.

How does the tear film support ocular surface moisture?

It maintains ocular surface moisture.

How does the tear film support corneal oxygenation?

It supplies oxygen to the cornea.

How does the tear film support corneal hydration?

It maintains corneal hydration.

What does the tear film do to surface debris?

It traps and clears debris.

What protective function does the tear film perform against pathogens?

It helps prevent infection.

How does the tear film contribute to healing?

It regulates wound repair.

How thick is the lipid layer of the tear film?

$$50\text{--}100\,\text{nm}$$

What substance makes up the tear film lipid layer?

Meibum.

What is meibum composed of?

Lipids and proteins.

What class of lipid includes cholesterol in meibum?

Nonpolar lipids.

What class of lipid includes fatty acids in meibum?

Nonpolar lipids.

What class of lipid includes waxy esters in meibum?

Nonpolar lipids.

Which polar lipids are named in meibum?

Phospholipids.

Which glands produce the lipid layer?

Meibomian glands.

How does the lipid layer affect tear evaporation?

It reduces tear evaporation.

What kind of barrier does the lipid layer form?

A hydrophobic barrier.

How does the lipid layer contribute to comfort?

It maintains ocular surface lubrication.

Which tear film layer is thickest?

Aqueous layer.

What percentage of total tear thickness is the aqueous layer?

Approximately $90\%$

Which salts-containing layer is the middle tear film layer?

Aqueous layer.

Which nutrient named in the aqueous layer is a sugar?

Glucose.

What catalytic proteins are found in the aqueous layer?

Enzymes.

What macromolecules besides enzymes occur in the aqueous layer?

Proteins.

What protective substances are found in the aqueous layer?

Antibacterial substances.

What is the primary source of the aqueous layer?

Main lacrimal gland.

What is an additional source of the aqueous layer?

Accessory lacrimal glands.

What is the aqueous layer's debris-related function?

Clear debris.

What is the aqueous layer's surface-related function?

Maintain ocular surface health.

What two components compose the mucin layer?

Mucins and mucus.

What are mucins chemically?

Glycoproteins.

What is mucus composed of?

Mucins, proteins, electrolytes, and water.

Which immune proteins are also found in the mucin layer?

Immunoglobulins.

Which nitrogenous waste substance is also found in the mucin layer?

Urea.

Which sugar is also found in the mucin layer?

Glucose.

Which cells produce the mucin layer?

Goblet cells.

How does the mucin layer help attach tears to the eye?

It adheres the aqueous layer to the ocular surface.

What surface structure does the mucin layer bind to?

Glycocalyx.

What does the mucin layer trap?

Debris and microbes.

Which cells produce the glycocalyx?

Corneal epithelial cells.

What molecules does the glycocalyx contain?

Glycoproteins.

How does the glycocalyx affect friction?

It reduces friction.

What is the glycocalyx's role in tear retention?

Tear adherence.

What protective role does the glycocalyx perform?

Immune defense.

What signaling role does the glycocalyx perform?

Cell communication.

What surface structures are labeled beneath the mucoaqueous layer in the tear film diagram?

Glycocalyx and corneal epithelium.

What is the overall lacrimal system divided into?

Secretory and drainage systems.

Which glands are included in the lacrimal system?

Main and accessory lacrimal glands.

What ocular surface fluid is included in the lacrimal system?

Tear film.

What openings are included in the lacrimal system?

Puncta.

What small tear-drainage tubes are included in the lacrimal system?

Canaliculi.

What tear-collecting structure is included in the lacrimal system?

Lacrimal sac.

What duct is included in the lacrimal system?

Nasolacrimal duct (NLD).

What is the function of the lacrimal secretory system?

Produce the tear film.

Which aqueous-producing structures belong to the lacrimal secretory system?

Main and accessory lacrimal glands.

Which lipid-producing structures belong to the lacrimal secretory system?

Meibomian glands.

Which mucin-producing cells belong to the lacrimal secretory system?

Conjunctival goblet cells.

In what bony depression is the main lacrimal gland located?

Fossa for the lacrimal gland.

In which bone is the lacrimal gland fossa located?

Frontal bone.

In which region of the frontal bone is the lacrimal gland fossa?

Temporal portion.

Where is the lacrimal gland relative to the superior temporal orbital margin?

Posterior to it.

How is the lacrimal gland fixed to the orbit?

By connective tissue attaching it to orbital periosteum.

What eyelid examination maneuver can sometimes reveal the lacrimal gland?

Upper lid eversion.

What condition may make the lacrimal gland visible on upper lid eversion?

Lacrimal gland prolapse.

What are the approximate dimensions of the lacrimal gland?

$$25 \times 20\,\text{mm}$$

How is the lacrimal gland classified histologically?

Tubuloacinar exocrine gland.

What type of secretion does the lacrimal gland produce?

Serous secretion.

What secretion mechanism is used by the lacrimal gland?

Merocrine secretion.

What is the principal fluid component of lacrimal gland secretion?

Water.

What ions-containing component is present in lacrimal gland secretion?

Electrolytes.

What enzyme is named as an antibacterial agent in lacrimal gland secretions?

Lysozyme.

What iron-binding antibacterial protein is named in lacrimal gland secretions?

Lactoferrin.

What immune proteins are named in lacrimal gland secretions?

Immunoglobulins.

What are the three main lacrimal gland cell types?

1. Acinar

2. Ductal

3. Myoepithelial cells

What is the function of lacrimal acinar cells?

Secretory epithelial cells.

What is the shape of lacrimal acinar cells?

Pyramidal.

What is an acinus in the lacrimal gland?

An arrangement of secretory acinar cells around a central lumen.

What epithelium forms the lacrimal gland ducts?

A single layer of cuboidal epithelial cells.

What is the function of lacrimal myoepithelial cells?

Contraction.

What does the histology diagram label as the central space of an acinus?

Central lumen.

What secretory cell structures are labeled in the lacrimal gland histology diagram?

Secretory granules.

What layer is labeled surrounding the glandular epithelium in the histology diagram?

Basal lamina.

What two duct segments are labeled in the lacrimal gland acinus diagram?

1. Intercalated duct

2. Striated duct

What structural unit is labeled as a cluster of acini in the lacrimal gland diagram?

Lobule.

What ducts are labeled in the lobule diagram?

1. Intralobular duct

2. Excretory duct

What structure divides the main lacrimal gland into two portions?

Levator aponeurosis.

What are the two portions of the main lacrimal gland?

Orbital and palpebral portions.

How do the orbital and palpebral portions compare histologically?

They are histologically identical.

Which portion of the lacrimal gland is larger?

Orbital portion.

What borders the superior edge of the orbital lacrimal gland portion?

Periorbita of the lacrimal fossa.

What borders the inferior edge of the orbital lacrimal gland portion?

Levator aponeurosis.

What borders the lateral edge of the orbital lacrimal gland portion?

Lateral rectus muscle.

What borders the medial edge of the orbital lacrimal gland portion?

Levator muscle.