Lacrimal Gland & Tears Flashcards
What is the function of lacrimal apparatus?
Production and drainage of tear film
Describe the components of the tear film produced by the Lacrimal gland
Aqueous component of tears
Water fluid containing electrolytes, proteins and enzymes
Describe the components if the tear film produced by the accessory glands
1. Meibomian glands
2. Goblet cells
3. Wolfring and Krause glands
- Meibomian glands- oily substance called meibum
- Goblet cells- mucins
- Wolfring and Krause glands- additional aqueous fluid
What is the definition of a tubuloacinar gland and how does it function (context of lacrimal gland)
Contains both tubular and acinar structures
Tubular- tubules involved in transporting tears produced by gland
Acinar- small sac-like structures that produce and store secretions (tears)
What is the meaning of serous
Producing, or resembling serum (having a thin watery consistency)
Functions of tear film
- Maintains smooth refracting surface over cornea
- Lubricates eyelids
- Transports metabolic products to and from corneal epithelial cells
- Prevents desiccation of corneal epithelium
- Bactericidal properties
- Provides pathway for WBCs in case of injury
Where is the tear fluid produced
Lacrimal glands- 90%
Accessory glands- 10%
What is the resting volume of tears
1microliter/min
1.5 ml/day
*can increase to over 100x during stimulation
What is the pH of tears
pH 7.5
What is the rate of turnover of tears
16% per min
Guve the three layers of the tear film
Lipid layer
Aqueous & mucus
Mucous layer
Function of lipid layer
- inhibits tear evaporation
- acts as a hydrophobic barrier to prevent outflow of tears at the Meibomian gland
What makes 60% and 40% of the tear film
Aqueous phase 60%
Mucinous phase 40%
Function of aqueous layer
Provides moisture, lubrication and nutrients
