Glands of the eye
Figure 1: Superficial anatomy of glands and ducts of the canine eye.
Source: McCracken T.O., Kainer R.A. and Carlson D. (2008) Color atlas of small animal anatomy: the essentials, : Blackwell Publishings.
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Figure 2. Superficial anatomy of glands and ducts of the feline eye.
Source: McCracken T.O., Kainer R.A. and Carlson D. (2008) Color atlas of small animal anatomy: the essentials, : Blackwell Publishings.
Lacrimal gland
- Small, flat lobular structure lying on the medial side of the orbital ligament within the periorbita
- Small ducts that cannot be seen without a microscope empty their secretion into the conjunctival sac at the dorsal fornix
- Tubuloacinar gland on the episclera in the superior temporal orbit. These glands produce approximately 60% of the serous portion of tears in dogs
Third eyelid gland
- Tubuloacinar gland on the base of the third eyelid that produces approximately 40% of the serous portion of the tears
Lacrimal gland and third eyelid gland are mixed mucoserous tubuloacinar glands which are responsible for production of the aqueous portion of the tear film.
Meibomian (tarsal) gland
- About 20 to 40 glands exist in the superior and inferior eyelid
- Synonymous with tarsal gland. The eyelid glands produce the lipid layer of the tear film which prevent evaporation of tear film
- Lipid secreting glands located within the superior and inferior eyelid that produces the outermost layer of the tear film on to the eyelid margin. The ducts exit the eyelid margin to deliver the lipid component of the tear film
Moll glands
- Modified sweat glands
Zeis glands
- Modified sebaceous glands associated with the cilia
Moll glands and Zeis glands are located within the eyelid and contribute minimally to the tear film formation.
Conjunctival goblet cells
- Conjunctival goblet cells are mucin secreting glands located within the palpebral conjunctiva. Mucin produced by these glands contribute to the innermost layer of the tear film
Figure 3. Canine nasolacrimal duct
Source:
McCracken T.O., Kainer R.A. and Carlson D. (2008) Color atlas of small
animal anatomy: the essentials, : Blackwell Publishings.
Figure 4. Feline nasolacrimal duct
Source:
McCracken T.O., Kainer R.A. and Carlson D. (2008) Color atlas of small
animal anatomy: the essentials, : Blackwell Publishings.
Nasolacrimal canaliculi
The tear film is drawn into the nasolacrimal canaliculi via a negative intracanicular pressure created by contraction of levator palpebrae supeiors and orbicularis oculi muscles. In dogs, the lacrimal sac is poorly developed and is simply a juction of the two canaliculi.
References
- Bruce H.G., Cheryl L.C. and Robert L.P. (2004) Veterinary ophthalmology essentials, 1st edn., Philadelphia: Elsevier.
- Evans H.E. and Lahunta A. (2010) Guide to the dissection of the dog, 7th edn., Missouri: Saunders Elsevier.
- Maggs D.J., Miller P.E. and Ofri R. (2013) Slatter's fundamentals of veterinary ophthalmology, 5th edn., Missouri: Elsevier.
- McCracken T.O., Kainer R.A. and Carlson D. (2008) Color atlas of small animal anatomy: the essentials, 1st edn., Iowa: Lippincott Williams & Wilkins.
