Anatomy Of Eye & Adnexa Flashcards
Purpose of vision
Taking in info from surroundings
Energy from environment is converted to neural activity via conversion of photon into electrical signal in the retina
Vision of carnivores
More binocular, less peripheral
herbivore vision
Opposite of carnivores, less binocular and more peripheral vision
Bony orbit in species
Dog & cat - incomplete, finished w orbital ligament
Herbivores - complete by postorbital bar
Supraorbital fossa
Space dorsal & caudal to orbit
Houses extension of retrobulbar fat pad
Coronoid process of mandible extends into space
Pterygopalatine fossa
Bony orbital rim
Houses globe & adnexa, contains specific for foramina transmitting arteries, veins & nerves serving the globe & adnexa
Nerves that travel through pterygopalatine fossa
CN II
(Orbital fissure)
CN III, IC, V- ophthalmic, VI
Rostral alar foramen
CNV - maxillary
Eyelids
Palpebrae
Superior eyelid
Inferior eyelid
Internal - palpebral fissure
Lateral and medial canthus
Respective edges where two lids meet
Form the medial and lateral angles of the eye
Palpebrae stuctures
Levator palpebrae superior
Orbicularis oculi
Tarsal glands
Medial and lateral palpebral ligaments
Anchoring eyelids medially & laterally so they close in a horizontal line rather than a circle when the orbicularis oculi contracts
Levator palpebrae superioris
Narrow strip of muscle running longitudinally into upper lid
Contraction raises the upper lid
Innervated by CNIII
Simultaneous contraction of two muscles that ensure globe rotates upward & upper lid is raised
Muscles of eyelid
Various other small muscles
Levator anguli oculi medialis
Retractor anguli oculi lateralis
Orbital adnexa
Third eyelid
Cartilage supported by connective tissues that is anchored in medial canthus
Cartilage often t-shaped but shape varies
Can be carried across the anterior globe like a windshield wiper
Bulbar surface well-provided with lymphoid tissue
Mechanism of third eyelid movement
Held in traction by tonic contraction of the orbitalis (SM)
Contraction is under sympathetic control
Motion over the eye is passive
When eye is retracted into the orbit, 3rd lid slides over globe
Lacrimal apparatus
Flow of tears from Dorso lateral to Ventrolateral
Exit of tears from eye through medial canthus to nasal vestibule via nasolacrimal duct