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45 Cards in this Set
- Front
- Back
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What structures does the orbit contain?
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The eyeball (or bulbous oculi) and ocular adnexa (eyelids, lacrimal apparatus, muscles, vessels, nerves)
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What are the borders of the orbit?
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Medially - frontal, presphenoid, and lacrimal bones
Ventrally - zygomatic salivary gland and pterygoid mm. Dorsal and lateral walls of the orbit - temporalis m. |
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What is the periorbita?
What is it continuous with medially and intracranially? |
The periorbita is a connective tissue sheath surrounding the eyeball and muscles, nerves, and vessels of the eye.
Medially, it is continuous with the periosteum of the orbit. Intracranially, it continues as the dura. |
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What three glandular tissues are near the eye?
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The lacrimal gland (7), zygomatic salivary gland (2), and the superficial gland of the third eyelid.
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What else is the zygomatic salivary gland known as in the dog and cat?
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The dorsal buccal gland or orbital gland.
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What is the zygomatic salivary gland located medial to?
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The zygomatic arch.
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What else is the ventral buccal salivary gland known as?
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The molar or buccal salivary gland.
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Which salivary gland is present in the cat and not in the dog?
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The ventral buccal salivary gland.
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What are the extrinsic ocular muscles? (8)
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Levator palpebrae superioris m.
Dorsal rectus m. Ventral rectus m. Lateral rectus m. Medial rectus m. Ventral oblique m. Dorsal oblique m. Retractor bulbi m. |
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All of the extrinsic ocular muscles originate from the same bony structure, but one. What is the origin in common, and what is the stand alone?
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All but ventral oblique m. originate from the apex of the orbit near the optic canal.
The ventral oblique m. originates from the rostral part of the palatine bone. |
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What embryonic structure do the extrinsic ocular muscles originate from?
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The somites.
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Which ocular muscles insert more anteriorly on the globe?
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The recti muscles insert more anteriorly.
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What are the OIAI of levator palpebrae superioris m.?
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Origin: Apex of the orbit
Insertion: On the superior palpebra Action: Elevate (raise) the superior palpebra Innervation: Oculomotor n. (CN III) |
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What are the origin, insertion, and innervation of the recti muscles of the extrinsic ocular muscles?
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Origin: On the skull near the optic foramen
Insertion: On the sclera Innervation: Lateral rectus m.: Abducens n. (CN VI) Dorsal, ventral and medial recti mm.: Oculomotor n. (CN III) |
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What are the actions of the recti muscles?
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The dorsal and ventral rectus mm. rotates the eyeball up and down. Rotates the eyeball around a horizontal axis.
The medial and lateral rectus mm. rotates the eyeball right and left around a vertical axis. |
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What are the OIAI of the retractor bulbi muscles?
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Origin is on the skull near the optic foramen.
Insertion is on the sclera, slightly caudal to the recti mm. The action is to retract the eye, move it backwards. These muscles are innervated by abducens n. |
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What nerve does the retractor bulbi mm. surround?
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The optic n.
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How do the dorsal and ventral oblique muscles tell us how to orient the eye?
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These muscles insert on the lateral aspect of the eyeball.
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What are the OIAI of the dorsal oblique m.?
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O: On the skull near the optic foramen
I: On the sclera, deep to the attachment of the dorsal rectus m. A: pulls the dorsal part of the eyeball medially I: Trochlear n. |
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What is the trochlea? What passes through a groove in it?
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The trochlea is a cartilaginous structure attached to the wall of the orbit at the level of the medial canthus of the eye
The tendon of the dorsal oblique m. passes through it to insert. |
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What is the OIAI of the ventral oblique m.?
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Origin: Rostral border of the palatine bone
Insertion: On the sclera, near the insertion of the lateral rectus m. Action: Pulls the ventral part of the eyeball medially. Innervation: CNIII |
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What nerves innervate the extrinsic ocular muscles? What is the mnemonic to explain it?
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CNIII, CNIV, CNVI
(LR+RB)6 + DO4 = all the rest 3 LR = Lateral rectus m. RB = Retractor bulbi mm. 6 = Abducens n. (CN VI) DO = Dorsal oblique m. 4 = Trochlear n. (CN IV) All the rest = Levator palpebrae superioris m., Dorsal rectus m., Ventral rectus m., Medial rectus m., Ventral oblique m. 3 = Oculomotor n. (CN III) |
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If you remove all ocular muscles, the ocular tunics will be exposed. What are they? What components of the eye do they contain?
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The fibrous tunic contains the cornea, sclera, and limbus. This is the tough outer coat.
The vascular tunic, or uvea, includes the choroid, ciliary body, and iris. This is the pigmented and vascular layer. The nervous tunic consists of the retina. This is the internal surface of the eye. |
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What is the function of the retina?
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The light and visions are transformed by the rods and cones of the retina and transmitted by the optic nerve to the brain.
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What is the ciliary ring?
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The ocular components that attach to the lens: the suspensory ligaments.
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What is the cornea?
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The transparent anterior 1/6 of the eye.
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What is the sclera?
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The posterior 5/6 of the eye continuous with the cornea. This tough fibrous layer is composed of collagen and elastic fibers.
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What is the limbus?
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AKA the corneoscleral junction. The junction between the cornea and sclera.
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What is the function of the choroid?
What is present in the middle layer of the choroid in cats and dogs? |
It supplies the retina with nutrients.
The tapetum lucidum is present in the choroid in cats and dogs and is their "eye shine" in reduced illumination. |
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What is the function of the tapetum lucidum?
Where is it located? |
It is a reflective surface in the choroid that reflects light back to the photoreceptors to enhance dark-adapted vision.
The tapetum lucidum is located in the dorsal half of the fundus (or back) of the eye, in the choroid. |
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What is the ciliary body? What is it a continuation of, and what does it continue as?
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The ciliary body is a ring of loose CT made of elastic fibers, blood vessels, smooth muscle and melanocytes.
It's a continuation of the choroid and gives rise to the ciliary processes. |
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What are the ciliary processes?
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Extensions of the ciliary body that produce aqueous humor
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How are the ciliary bodies and processes attached to the lens capsule?
What is the function of these attachments? |
Lens fibers, or zonule fibers, or suspensory ligaments.
The lens fibers anchor the lens in place. |
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What is the iris?
What is it an extension of? |
The iris is the colored externsion of the choroid that covers the lens except at the pupil.
It lies between the anterior and posterior chambers of the eye. |
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What are the iris colors and pupils characteristics of dog and cat eyes?
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Dog - brown, golden yellow or blue irises with round pupils.
Cat - blue, green, or golden irises with constricted slits or dilated round pupils. |
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What are the muscles of the iris?
What are their actions and innervations? |
The sphincter pupillae muscle and dilator pupillae muscle.
Sphincter pupillae muscle - concentric ring within the iris around the pupil. Acts to constrict the pupil and is innervated by parasympathetic fibers of CNIII. Dilator pupillae muscle are the radially oriented fibers along the caudal border of the iris innerveratd by the sympathetic nerves (carried with CNIII) that dilate the pupil. |
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What is the pars optica retinae?
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A covering of the fundus of the eye, is a part of the visual retina. Composed of 10 layers - contains the rods and cones.
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What are the parts of the non-visual retina?
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2 layers, the pars ciliaris retinae and pars iridica retinae.
The pars ciliaris retinae covers the ciliary body and processes. The pars iridicae retinae covers the posterior aspect of the iris. |
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What is the junction of the visual and non-visual retinae called? Where is it located?
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This is called the ora serrata and is located just caudal to the ciliary body.
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What is the function of the lens?
What is it composed of? |
To focus light rays on the retina.
Composed of epithelial cells and their secretory products. |
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What makes up the anterior compartment of the eye?
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Compartment located between the cornea and lens. Filled with aqueous humor.
Has an anterior and posterior chamber. Anterior chamber bounded by cornea and iris, contains the filtration angle. Posterior chamber bounded by the iris and lens. |
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What is the function of the aqueous humor? What produces it?
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The aqueous humor is produced by the ciliary body and processes and functions to nourish and provide oxygen to the lens and cornea.
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What is the flow pattern of the aqueous humor?
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It flows from the posterior chamber of the anterior compartment into the anterior chamber by passing through the pupil between the iris and lens.
It exits the anterior chamber at the filtration (iridocorneal) angle (between the iris and cornea), through a trabecular meshwork near the limbus, then to the venous scleral sinus which leads directly into the venous system. |
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What is the canal of Schlemm?
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The venous scleral sinus that the aqueous humor drains from the filtration angle into.
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What is in the posterior compartment of the eyeball?
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It contains vitreous body: transparent refractile gel, 99% water, electrolytes, collagen fibers and hyaluronic acid.
The vitreous body adheres to the retina over its entire surface. |
