lacrimal gland and tears

Question 1

what is the tubuloracinar?

Answer 1

a gland with branching tubles that end with secretory alveoli

Question 2

what two glands do tear film production

Answer 2

the lacrimal gland and the accessory glands

Question 3

give three accesory gland examples

Answer 3

Glands of wolfrin, meibomian gland and the gland of moll

Question 4

what are the two cell types in the lacrimal gland?

Answer 4

secretory and myoepithelial

Question 5

what do myoepithelial cells do?

Answer 5

surround each acinus and produce contractile forces to push tears down the duct

Question 6

Give the 7 main functions of the tear film

Answer 6

-maintains a smooth refracting surface over the cornea
-transports metabolic products to and from the epithelial cells of the cornea

Question 7

what gland produces most of the tear fluid

Answer 7

lacrimal gland
lacrimal produces 90% and accessory produces 10%

Question 8

what is the resting level of tear fluid?

Answer 8

1.5ml/day this can increase over 100x when the lacrimal gland is stimulated

Question 9

what does the lipid layer of the tear flim do?

Answer 9

-inhibits tear evaporation
-protects aqueous layer from polar lipid contamination
-acts as hydrophobic barrier at meibomian gland orifices to prevent outflow of tears

Question 10

draw out the layers of the tear film

Answer 10

check ss in optom ss folder file

Question 11

what are the functions of the mucous layer of the tear film?

Answer 11

-to allow tears to wet the epithelium
-to maintain the stability of the tear film when blinking

Question 12

Where from is the mucous layer of the tear film produced?

Answer 12

mainly by goblet cells in the conjunctiva but some is produced by the main lacrimal gland

Question 13

Give the sequence of the lacrimal drainage system

Answer 13

1. Lacrimal puncta
2. lacrimal canaliculi
3. lacrimal sac
4. nasolacrimal duct
5. nasal cavity

Question 14

Give the route of lacrimal fluid within the orbit

Answer 14

1. lacrimal gland
2. conjunctival sac
3. lacrimal lake
4. lacrimal puncta where it then drains out

Question 15

What part of the brains control tears?

Answer 15

-the hypothalamus as it influences the lacrimal cells by being involved in controlling emotions

Question 16

What is the sympathetic nervous system?

Answer 16

Activates fight or flight response. Involved in production of adrenaline and control of the cardiovascular system

Question 17

What is the parasympathetic nervous system

Answer 17

Rest and digest - slows heart rate and increases intestinal and gland activity and relaxes sphincter muscles in the gut

Question 18

What is the trigeminal ganglion?

Answer 18

Sensory ganglion of the trigeminal nerve and is responsible for sensation in the face

Question 19

What are the steps that cause humans to blinkin terms of tear film?

Answer 19

-tear film evaporates causing hypertonicity (high salt)
-hypertonicity draws water from epithelial cells
-epithelial cells draw water from the stroma
-the hypertonicity causes a slight sting that causes the blink to restore isotonicity

Question 20

Give the steps to show how the drainage system is driven by pressure gradients throughout the stages of blinking

Answer 20

1. Before blinking, the system is open
2. Canaliculi are filled with fluid and there’s no pressure gradient in the system
3. Closing phase
4. Puncta meet and close
5. Canaliculi and sac are compressed
6. Horners muscle contracts during a blink squeezing the lacrimal sac
7. Pressure increases so fluid moves into the duct
8. Reopening
9. Sac and Canaliculi re-expand causing negative pressure in the sac
10. Puncta reopen and fluid flows into the Puncta and Canaliculi

Question 21

What happens in the schirmers tear flow test?

Answer 21

-paper tabs are inserted into the lower lids and then removed after 5 minutes
-less than 10mm wetting is abnormal

Question 22

What three things has the schirmers test been used to show?

Answer 22

-topical proparacaine hydrochloride anaesthesia reduces mean tear flow rate by 40%
-no statistically significant difference in tear production between men and women
-tear production doesn’t drop significantly with age

Question 23

What is the tear breakup time?

Answer 23

The number of seconds that elapse between the last blink and the appearance of the first dry spot in the tear film

Question 24

What are the issues with measuring tear breakup time in practise?

Answer 24

-uneven mixing of fluorescein
-unknown fluorescein concentration
-lag time between the appearance if a dry spot and it’s discovery by the observer

Question 25

What are the advantages of the rose bengal stain

Answer 25

-stains dry epithelium while cells are still in situ
-stains corneal filaments bright pink
-stains lipid contaminated mucous strands

Question 26

What are the symptoms, signs and causes of dry eyes?

Answer 26

Symptoms: mild burning and grittiness caused by corneal drying, blurred vision in extreme cases
Signs: reduced tear meniscus on lower eyelid, dullness of the cornea, fluorescein and rose bengal staining of inferior cornea and conjunctiva, reduced wetting if schirmer’s test
Causes: abnormalities in any of the tear film layers e.g. lack of lipid layer, shrograns disease

Question 27

Give the symptoms and causes of watery eyes

Answer 27

-symptoms: excess production of fluid from the lacrimal gland
-causes: reflex watering due to inflammatory conditions like foreign body, iritis, acute glaucoma, injury

Question 28

Give an example of a lacrimal gland disorder
What are the symptoms signs and causes?

Answer 28

Dacryoadenitis

Symptoms: swelling and tenderness of the lateral aspect if the upper eyelid
Signs: inflammation of the lacrimal gland
Causes: acute infections and chronic infections such as mumps