week 1 L1 - lacrimal system and tear film

Question 1

what is included in the lacrimal apparatus?

Answer 1

• lacrimal gland
• accessory lacrimal glands of krause and wolfring
• goblet cells
• meibomian glands
• tear film
• drainage system
• eyelid surfaces

Question 2

what are the functions of the lacrimal apparatus?

Answer 2

1. normal tear production
2. tear distribution
3. tear stablity
4. tear drainage
5. keeping optical surface patent
6. lubrication
7. protection against antimicrobials and debris
8. nutrition

Question 3

what parts of the lacrimal appartus are involved in tear distribution?

Answer 3

eyelids and tear film

Question 4

what parts of the lacrimal appartus are involved in tear stability?

Answer 4

eyelids and tear film

Question 5

what parts of the lacrimal appartus are involved in tear drainage?

Answer 5

eyelids and puncta

Question 6

Nutrition is one of the mentioned functions of the lacrimal apparatus; what does this involve?

Answer 6

Oxygen going in and carbon dioxide going out

Question 7

what is included in the drainage system?

Answer 7

• Plica semilunaris/caruncle
• puncta
• canaliculae
• lacrimal sac
• nasolacrimal duct

Question 8

what are the missing components of the lacrimal apparatus?

Answer 8

1. lacrimal gland
2. tear film
3. meibomian gland
4. goblet cells

Question 9

how thick is the tear film?

Answer 9

approximately 10 micrometres

Question 10

what is in the tear film?

Answer 10

98% water: oil, mucin, salts, metabolites, immunoglobulins, antibacterials

Question 11

what happens to the osmolarity o the tea film with increased stimulation?

Answer 11

it also increases

Question 12

describe the trilaminar structure of the tear film and their purpose

Answer 12

1. basal mucin layer = attachment
2. central aqueous phase = hydration
3. superficial oily (Lipid) layer = anti-evaporation

Question 13

name 3 functions of the tear film

Answer 13

1. blinking
2. lid opening
3. lid closure

Question 14

what does blinking do?

Answer 14

distribute tears and expels excess tears

Question 15

what does opening the lid do?

Answer 15

1. smooths out the tear film to appropriate thickness
2. creates surface conditions conducive to tear spreading

Question 16

what does lid closure do to the corneal surface?

Answer 16

wipes it clean

Question 17

what does lid closure do to the tear lake?

Answer 17

asissts in the drainage of it

Question 18

what does lid closure do with secretions?

Answer 18

it aids in expression of fresh secretions of goblet cells (mucins), glands of krause and wolfring (aqueous) and meibomian glands (oily layer)

Question 19

what is the total volume of the tear film?

Answer 19

5-9 microlitres (including th meniscus)

Question 20

what is the average rate of secretion of the tear film?

Answer 20

1.2-1.3 microlitres per minute

Question 21

what is the ph of the open eye and the closed eye respectively?

Answer 21

open eye: 7.45
closed eye: 7.25
(CO2 +lactic acid)

Question 22

what increases pH?

Answer 22

crying

Question 23

what decreases pH?

Answer 23

infection (possibly due to corneal antibacterial response, resulting in H+ release)

Question 24

Describe the lacrimal gland

Answer 24

it is continuous but in 2 portions either side of LPS: orbital (large) and palpebral (smaller)