Ocular Adnexa
Orbit
Figure 1: Lateral view of skull.
Source: Evans H.E. and Lahunta A. (2010) Guide to the dissection of the dog, 7th edn., Missouri: Saunders Elsevier.
Orbital fascia
Figure 2: Schematic transection of orbital fasciae and orbital structures at the level of the eyeball.
Source: Dyce K.M., Sack W.O. and Wensing C.J.G. (2010) Textbook of veterinary anatomy, 4th edn., Missouri: Saunders Elsevier.
Click HERE to test yourself!!!
Superficial muscular fascia
Deep muscular fascia
Eyelids (Palpebrae)
Figure 3: Sectioned eyelid viewed obliquely from behind.
Source: Dyce K.M., Sack W.O. and Wensing C.J.G. (2010) Textbook of veterinary anatomy, 4th edn., Missouri: Saunders Elsevier.
Click HERE to test yourself!!!
Third Eyelid
Figure 4: The eye and ocular adnexal structures.
Source: McCracken T.O., Kainer R.A. and Carlson D. (2008) Color atlas of small animal anatomy: the essentials, 1st edn., Iowa: Lippincott Williams & Wilkins.
Orbit
Figure 1: Lateral view of skull.
Source: Evans H.E. and Lahunta A. (2010) Guide to the dissection of the dog, 7th edn., Missouri: Saunders Elsevier.
- Cavity housing eyeball and its adnexa among orbital fat
- Frontal, lacrimal, maxillary, presphenoid, palatine and zygomatic bones of skull
- Periorbita
- Fibrous sheath of connective tissue and smooth muscle
- Surrounds eyeball, its muscles, vessels and nerves
Orbital fascia
Source: Dyce K.M., Sack W.O. and Wensing C.J.G. (2010) Textbook of veterinary anatomy, 4th edn., Missouri: Saunders Elsevier.
Click HERE to test yourself!!!
Superficial muscular fascia
- Lies within priorbita
- Abundant adipose tissue
- Envelops levator palpebrae superioris and lacrimal gland
Deep muscular fascia
- Fibrous sleeve
- Extends from eyelids and limbus
- Surrounds eyeball, ocular muscles and optic nerve
- Vagina Bulbi
- Surrounds eyeball
- Narrow episcleral space between eyeball and vagina bulbi à movement of eyeball against retrobulbar fat
Eyelids (Palpebrae)
Source: Dyce K.M., Sack W.O. and Wensing C.J.G. (2010) Textbook of veterinary anatomy, 4th edn., Missouri: Saunders Elsevier.
Click HERE to test yourself!!!
- Arise from bony margins of orbit
- Moisten cornea by distributing tears or lacrimal fluid
- Blinking for protection against trauma
- Eyelashes (cilia)
- Protects eye from particles
- Small ciliary and sebaceous glands
- Levator palprbrae superioris elevates upper eyelid
- Orbicularis oculi closes eye
- 3 smooth muscle sheets
- Maintain normal eye protrusion and retracted eyelid position
- Tarsus
- Thickened fibrous edge formed by orbital septum of periorbita
- Tarsal ‘Meibomian’ glands
- Secrete lipid
- Palpebral conjunctiva
- Mucous membrane with goblet cells
- Continues as bulbar conjunctiva on sclera and anterior epithelium on cornea
- Conjunctival sac & fornix
- Space between lids and eyeball
- Fun fact: This is a hiding place for grass seeds
- Highly vascular
Third Eyelid
Source: McCracken T.O., Kainer R.A. and Carlson D. (2008) Color atlas of small animal anatomy: the essentials, 1st edn., Iowa: Lippincott Williams & Wilkins.
- Nictitating membrane
- Conjunctiva fold
- Dorsoventral orientation between lacrimal caruncle and eyeball
- Supported by a T-bar of cartilage
- Kept retracted by smooth muscle (m. orbitalis) and sympathetic nervous system
- Gland of third eyelid
- Eye protection and tear distribution
- Tears enter eye on bulbar surface
References
- Dyce K.M., Sack W.O. and Wensing C.J.G. (2010) Textbook of veterinary anatomy, 4th edn., Missouri: Saunders Elsevier.
- Evans H.E. and Lahunta A. (2010) Guide to the dissection of the dog, 7th edn., Missouri: Saunders 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.
