Orbit Anatomy and Ocular Motor Physiology - Vocabulary Flashcards

A comprehensive set of vocabulary flashcards covering orbital anatomy, extraocular muscles, connective tissues, and ocular motor physiology from the lecture notes.

Optic foramen

Opening at the apex of the orbit that serves as the entrance to the optic canal; transmits the optic nerve and ophthalmic artery.

Optic canal

Large sphenoidal opening through which the optic nerve and ophthalmic artery pass.

Frontal bone

Bone that forms the superior rim of the orbit.

Zygomatic bone

Bone contributing to the inferior and lateral orbital rim.

Maxillary bone

Bone contributing to the inferior and medial parts of the orbital rim.

Supraorbital notch

Notch (or foramen) near the center of the superior orbital margin; transmits supraorbital vessels and nerve.

Infraorbital foramen

Opening in maxillary bone below orbital rim through which infraorbital artery and nerve pass

Lateral orbital tubercle (Whitnall’s tubercle)

Whitnall’s tubercle on the frontal process of the zygomatic bone; attachment site for lateral levator tendon and ligaments.

Lacrimal tubercle

Medial-lower marginal process; attachment site for ligaments; continuous with anterior lacrimal crest on maxillary bone.

Sphenoid

Bone that closes the orbit at the back; has lesser and greater wings extending laterally.

Lesser wing

Upper, smaller wing of the sphenoid.

Greater wing

Lower, larger wing of the sphenoid.

Optic canal

Opening to transmit the optic nerves; entrances are the optic foramina.

Sella turcica

Saddle-shaped superior surface of the sphenoid; contains the pituitary fossa.

Superior orbital fissure

Large gap between greater and lesser wings; separates the orbital ceiling from the lateral wall.

Pterygoid process

Process extending from the sphenoid; articulates with the palatine bone.

Palatine bone

Bone contributing the smallest amount to the orbital structure.

Ethmoid bone

Bone filling the gap between maxillary and sphenoid; contains ethmoidal foramina; orbital plate is lamina papyracea.

Lacrimal bone

Smallest bone on the medial wall of the orbit; between the nasal process of the maxilla and the ethmoid.

Nasolacrimal fossa

Depression where the lacrimal sac lies at the lacrimal–maxillary junction.

Lacrimal crests

Anterior lacrimal crest on the maxillary bone; posterior lacrimal crest on the lacrimal bone.

Nasolacrimal canal

Tunnel from the lacrimal fossa to the nasal cavity.

Lacrimal fossa

Shallow depression in the orbital plate of the frontal bone marking the lacrimal gland.

Trochlear fossa

Small depression in the frontal bone at the trochlea site.

Trochlea

U-shaped pulley for the tension of the superior oblique; located on the medial wall just behind the orbital rim.

Inferior orbital fissure

Posterior gap between the lateral wall and the orbital floor.

Infraorbital groove

Groove in the orbital floor that becomes the infraorbital canal.

Infraorbital suture

Line above the infraorbital canal where maxillary bone foci meet; a common blowout fracture site.

Ethmoidal foramina

Openings in the medial wall of the orbit for ethmoidal arteries and nerves.

Comminution fracture

Breakage of one or more bones forming the margin.

Blowout fracture

Rupture of orbital plates, most commonly the orbital floor (maxillary bone).</

Exophthalmos

Abnormal protrusion of the eye (proptosis).

Enophthalmos

Abnormal recession of the eye within the orbit.

Orbital cellulitis

Infection of orbital tissues (not the eye itself); often associated with ethmoidal sinuses; lamina papyracea involvement.

Lamina papyracea

Orbital plate of the ethmoid bone; medial wall; very thin, separates orbit from ethmoidal sinuses.

Periosteum

Dense connective tissue that tightly adheres to bone.

Periorbita

Periosteal lining of the orbit; continuous with the external periosteum at the orbital margin.

Episclera

Thin layer with small vessels covering the sclera, except the cornea.

Tenon’s capsule

Outer layer that envelops the episclera and the extraocular muscles.

Check ligaments

Bands of connective tissue between Tenon’s capsule and periorbita; medially and laterally prominent for the recti; less so for inferior rectus and levator.

Suspensory ligament (Whitnall’s ligament)

A sling of connective tissue spanning the orbit; helps support the globe.

Superior transverse ligament (Whitnall’s ligament)

Ligament attached to the orbital ceiling; allows the levator to pass through.

Septum orbitale (orbital septum)

Sheet of connective tissue from the orbital margin that extends into the eyelids.

Chondrocytes

Specialized cells found in cartilage.

Cartilage

Connective tissue with a collagen-proteoglycan matrix.

Osteoblasts

Bone-forming cells that lay down new bone matrix.

Osteocytes

Mature bone cells embedded in the bone matrix.

Dermal bones

Orbital bones formed intramembranously (direct bone formation, without cartilage preformation); typically mesodermal in origin.

Osteoclasts

Bone-resorbing cells involved in remodeling.

Craniofacial dysostosis

Disorder with abnormal ossification of facial bones during development.

Endochondral bone

Bone formed from a cartilage model that is later ossified (e.g., sphenoid and ethmoid).

Lateral palpebral ligament

Connective tissue supporting the lateral aspect of the eyelids.

Levator aponeurosis

Insertion tendon of the levator palpebrae superioris in the upper eyelid.

Medial wall

Orbital wall bounded by the sphenoid, maxillary, ethmoid, and lacrimal bones.

Lateral wall

Orbital wall bounded by the zygomatic and sphenoid bones.

Ceiling

Orbital roof formed by the frontal and sphenoid bones.

Floor

Orbital floor formed by the maxillary, palatine, and zygomatic bones.

Levator (levator palpebrae superioris)

Muscle that elevates the upper eyelid.

Superior rectus

Elevates the eye; also adducts and intorts; origin from the common tendinous ring and optic nerve sheath; insertion about 7.4 mm from limbus; innervation by CN III ( superior division).

Lateral rectus

Abducts the eye; origin from the common tendinous ring and greater wing of sphenoid; insertion about 6.9 mm from the cornea; innervation by CN VI; lacrimal artery/nerve run along its superior border.

Medial rectus

Adducts the eye; origin from the common tendinous ring and optic nerve sheath; insertion about 5.5 mm from the cornea; innervation by CN III (inferior division).

Inferior rectus

Depresses the eye; adducts slightly; innervation by CN III (inferior division); insertion about 6.7 mm from limbus.

Superior oblique

Anatomical origin at the lesser wing; functional origin at the trochlea; innervation by CN IV; actions include intorsion, abduction, and depression.

Inferior oblique

Originates on the maxillary bone below the nasolacrimal fossa; inserts on the posterior-lateral globe; primarily extorts; secondarily abducts and elevates.

Abducens nerve

CN VI; Innervates the lateral rectus; enters the muscle on its medial surface; relation to lacrimal artery/nerve along its superior border.

Perimysium

Connective tissue sheath around a bundle of muscle fibers.

Epimysium

Connective tissue sheath around an entire muscle.

Sarcolemma

The cell membrane of a muscle fiber.

T-tubules

Membrane-lined tunnels that bring extracellular space close to the cytoplasm in muscle fibers.

Sarcoplasmic reticulum

Membrane-bound organelle that stores and releases calcium for muscle contraction.

Myofibrils

Bundles of contractile proteins within a muscle fiber.

Actin

+Thin filament; major component of myofibrils.

Myosin

Thick filament; motor protein in muscle contraction.

Fast-twitch

Muscle fibers with rapid, forceful contractions; fatigue quickly.

Slow-twitch

Muscle fibers with slower, sustained contractions; resistant to fatigue.

Motor end plate

Specialized motor nerve terminal ending that forms a synapse with a muscle fiber.

En grappe endings

Cluster of nerve terminals from a single motor neuron innervating a muscle fiber.

Tonic fibers

Muscle fibers that contract in a slow, graded fashion.

Motor unit

A motor neuron plus all the muscle fibers it innervates.

Acetylcholine

Neurotransmitter used by motor nerves to activate muscle fibers.

Membrane channels

Ion channels that regulate sodium movement across the sarcolemma.

Ratchet model

Mechanism of actin–myosin interaction where a ratcheting action produces contraction.

EOM motor units

Extraocular muscle motor units typically comprising 5–17 muscle fibers per nerve.

Thick fibers

Fast-twitch muscle fibers rich in myosin.

Thin fibers

Slow-twitch muscle fibers with sustained, graded contractions and multiple synapses.

Myasthenia gravis

Autoimmune disease with antibodies against acetylcholine receptors; causes ptosis, diplopia, and orbital movement abnormalities.

Ptosis

Drooping of the upper eyelid.

Diplopia

Double vision.

Blepharospasm

Chronic spasm of the orbicularis oculi muscles.

Muscle spindles

Sensory receptors that report muscle length.

Golgi tendon organs

Sensory receptors that report muscle tension.

Intrafusal

Small muscle fibers within a muscle spindle.

Extrafusal

Muscle fibers outside the muscle spindle proper.

Oculocardiac reflex

Reflex where stretch of extraocular muscles slows or stops the heartbeat.

Common tendon of Zinn

Origin of the four rectus muscles; oval ring of connective tissue continuous with periorbita, anterior to the optic foramen.

Muscle cone

Cone-shaped group of muscles traveling from the common tendon ring to their insertions.

Insertion spiral of Tillaux

Imaginary line connecting rectus insertions that spirals outward clockwise from MR to SR.

Physiological insertion

Point where muscle contraction force acts, typically offset from the anatomical insertion.

Hering diagram

Plot of the trajectories the visual axis would follow if each extraocular muscle contracted in isolation.

Brown’s syndrome

Inability to elevate the adducted eye; may be due to abnormal tendon sheath around the superior oblique.