This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Ophthalmology
Meibomian glands secrete which component of sweat? 
Select and explain. 
A. Water (aqueous), B. Mucin, C. Protein, D. Lipid
D: Lipid
Answer: D: Lipid 
Explanation: Ans. is 'd' i.e., Lipid The major function of lacrimal apparatus is to secrete and drain the tear. Tear film consists of 3 layers :- Mucous or mucin layer (innermost):- Secreted by conjunctival goblet cells, crypts of Henle, glands of Manz. Aqueous layer (intermediate) :- This forms the bulk of the tear. It is secreted by main lacrimal and accessory lacrimal glands. Lipid layer (outermost) :- Secreted by the Meibomion Zeis, and Moll glands.