Anatomy of the Orbit and Eyeball

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Questions and Answers

What is the primary cause of epiphora?

Infection of the lacrimal gland

Overproduction of lacrimal fluid

Excessive evaporation of tears

Blockage of the nasolacrimal system (correct)

Which cranial nerve is responsible for parasympathetic stimulation of the lacrimal gland?

CN V (Trigeminal nerve)

CN II (Optic nerve)

CN VII (Facial nerve) (correct)

CN III (Oculomotor nerve)

What condition can result from partial blockage within the trabecular meshwork?

Cataract

Dacryoadenitis

Glaucoma (correct)

Epiphora

What is the role of the ciliary body in relation to the lens?

Production of the aqueous humor Signup and view all the answers

Which of the following correctly describes the innervation of the ciliary muscle?

Parasympathetic fibres from CN III Signup and view all the answers

Which bone contributes to the superior wall (roof) of the orbit?

Frontal bone Signup and view all the answers

What structure is affected in a condition called 'Stye'?

Eyelashes Signup and view all the answers

Which cranial nerve is responsible for eyelid elevation?

CN III (Oculomotor nerve) Signup and view all the answers

What is the primary function of the lacrimal glands?

Produce tears Signup and view all the answers

Which structure carries the optic nerve into the orbit?

Optic canal Signup and view all the answers

Which of the following nerves passes through the superior orbital fissure?

Lacrimal nerve Signup and view all the answers

Which condition results from the loss of function in the levator palpebrae superioris muscle?

Ptosis Signup and view all the answers

What is the primary role of the tarsal glands located in the eyelids?

Preventing tear evaporation Signup and view all the answers

Which cranial nerve is NOT associated with eye movement?

CN VII (Facial nerve) Signup and view all the answers

Which structure collects tears from the conjunctival sac?

Lacrimal canaliculi Signup and view all the answers

What is the purpose of the ciliary muscle in the eye?

To control the shape of the lens for near vision Signup and view all the answers

What occurs at the optic chiasma?

Nasal fibres decussate Signup and view all the answers

Which of the following best describes the function of the sphincter pupillae?

Pupillary constriction Signup and view all the answers

What is the correct action of the lateral rectus muscle?

Abduct the eye Signup and view all the answers

In which part of the eye does the central retinal artery radiate from?

Optic disc Signup and view all the answers

What is the primary characteristic of the macula lutea?

It has the highest concentration of cones Signup and view all the answers

What type of nerve supply is responsible for the action of the dilator pupillae?

Sympathetic Signup and view all the answers

Which cranial nerve controls the superior oblique muscle?

CN IV Signup and view all the answers

Which condition is characterized by asymmetry of eye movement?

Strabismus Signup and view all the answers

What is the clinical significance of the blind spot in the eye?

It is where the optic nerve exits the retina Signup and view all the answers

What is the result of infection in the lacrimal gland?

Dacryoadenitis Signup and view all the answers

Which structure is primarily responsible for the production of aqueous humor?

Ciliary body Signup and view all the answers

What condition is characterized by increased intra-ocular pressure leading to optic nerve damage?

Glaucoma Signup and view all the answers

What is the pathway of tears from the lacrimal gland to the nasal cavity?

Lacrimal gland → Puncta → Nasolacrimal ducts → Inferior nasal meatus Signup and view all the answers

Which cranial nerve is involved in the accommodation reflex by innervating the ciliary muscle?

CN III Signup and view all the answers

Which structure serves as the apex of the orbit?

Optic canal in the lesser wing of the sphenoid Signup and view all the answers

Which nerves pass through the inferior orbital fissure?

Inferior division of oculomotor nerve and Zygomatic nerve Signup and view all the answers

What happens during the process of opening the eyelids?

Contraction of the levator palpebrae superioris muscle Signup and view all the answers

Which component of the lacrimal apparatus is responsible for collecting fluid from the conjunctival sac?

Lacrimal sac Signup and view all the answers

What is the primary function of tarsal glands in the eyelids?

Prevention of tear evaporation Signup and view all the answers

Which muscle is directly responsible for drooping of the eyelid when dysfunctional?

Levator palpebrae superioris Signup and view all the answers

Which cranial nerve primarily governs the secretion of the lacrimal gland?

Cranial nerve VII Signup and view all the answers

What structure is primarily involved in the formation of the medial wall of the orbit?

Ethmoid bone Signup and view all the answers

Which condition is indicated by inflammation of the conjunctiva?

Conjunctivitis Signup and view all the answers

What characterizes the superior wall of the orbit?

Comprised of the lesser wing of the sphenoid and the orbital part of the frontal bone Signup and view all the answers

Which muscle is responsible for the accommodation of the lens for near vision?

Ciliary muscle Signup and view all the answers

Which cranial nerve controls the lateral rectus muscle responsible for abduction of the eye?

Abducent nerve (CN VI) Signup and view all the answers

What is the main function of the optic disc in the retina?

Acts as a blind spot due to lack of photoreceptors Signup and view all the answers

In which part of the eye does the central retinal artery originate?

Optic disc Signup and view all the answers

Which condition is characterized by clouding of the lens due to protein clumping?

Cataracts Signup and view all the answers

What type of vision loss is associated with retinal detachment?

Central or peripheral vision loss depending on severity Signup and view all the answers

Which intrinsic muscle of the eye is responsible for pupillary constriction?

Sphincter pupillae Signup and view all the answers

Which extrinsic eye muscle is responsible for moving the eye downward and outward?

Superior oblique Signup and view all the answers

What is the action of the medial rectus muscle?

Adducts the eye Signup and view all the answers

Which statement correctly describes the pathway of visual information from the retina to the brain?

Axons from the optic tract enter the midbrain before going to the visual cortex Signup and view all the answers

Study Notes

Orbit, Eyeball and Lacrimal Apparatus

Learning Outcomes:
- Identify the bones composing the orbit and their boundaries.
- Describe anatomical features of eyelids, conjunctiva, and lacrimal gland, explaining the significance of maintaining corneal integrity.
- Identify and describe contents of superior and inferior orbital fissures.
- Detail extraocular muscles of the eyeball.
- Explain the roles of cranial nerves III, IV, and VI, including their testing and lesions.
- Describe the structure of the eyeball and the retina.

Bones of the Orbit

Bones: Frontal, Sphenoid, Lacrimal, Ethmoid, Maxilla, Zygomatic.

Orbit - Boundaries

Superior Wall (Roof): Orbital part of the frontal bone, lesser wing of the sphenoid.
Inferior Wall (Floor): Zygomatic process of the maxilla, zygomatic bone.
Medial Wall: Frontal process of the maxilla, lacrimal, ethmoid, and frontal bones.
Lateral Wall: Zygomatic bone, frontal process of the zygomatic bone, zygomatic process of the frontal bone.
Apex: Optic canal in the lesser wing of the sphenoid.

Fissures and Foramina

Sphenoid Bone: Surrounds vital structures entering and exiting the orbit.
Details of specific fissures and foramina and contents are included in the images.

Superior Orbital Fissure

Contents: Frontal nerve, inferior and superior divisions of oculomotor nerve, nasociliary nerve, abducens nerve, lacrimal nerve, superior ophthalmic vein, superior ophthalmic vein, trochlear nerve.

Inferior Orbital Fissure

Contents: Zygomatic nerve, orbital branch of pterygopalatine ganglion, inferior division of inferior ophthalmic vein, infraorbital vessels (artery and vein), infraorbital nerve.

Optic Canal

Contents: Optic nerve, ophthalmic artery.

Infraorbital Foramen

Contents: Infraorbital nerve and vessels.

Eyeball (Surface Anatomy)

Details: Diagram showing the location of the eyebrow, eyelids (eyelashes and commissures), the palpebral fissure, and associated structures like the caruncle, lacrimal gland, conjunctival sac, and lacrimal lake.

Eyeball (Innervation, Blood Supply)

Details: Diagrams indicating the flow of blood/vascular supply, sensory/motor nerve supply

Lacrimal Apparatus

Components: Lacrimal glands, lacrimal canaliculi, lacrimal sac, nasolacrimal duct.
Function: Gland produces tears, which drain through the system into the nose.
Clinical Conditions: Epiphora, dacryoadenitis.

Ciliary Body

Function: Lens shape and aqueous humour production.
Innervation: Parasympathetic fibers.

Retina

Layers: Two layers — pigment and neural layers — attached at the optic nerve and ora serrata.
Optic Disc (OD): Site of optic nerve exit, lacking photoreceptors (blind spot).
Macula Lutea: Area of highest visual acuity, containing fovea centralis (highest concentration of cones).

Optic Nerve

Function: Carries visual impulses from the retina to the brain.
Structure: Covered in meninges, central retinal artery and vein within the meninges.

Clinical Aspects:

Mention of retinal detachment, diabetic retinopathy, hyphema (blood in the anterior chamber), cataracts, glaucoma (increased intraocular pressure damaging the optic nerve), cavernous sinus thrombosis, strabismus (eye muscle weakness causing misalignment)

Extraocular Muscles

Function: Move the eye.
Types: 4 rectus (superior, inferior, medial, lateral) and 2 oblique (superior, inferior).
Nerve Supply: Cranial nerves III, IV, and VI.

Intrinsic Muscles

Location: Within the eyeball.
Function: Control lens shape and pupil size.
Innervation: Autonomic nerve fibers (parasympathetic/sympathetic)
Types: Ciliary muscle(accomodation), sphincter pupillae (pupil constriction), dilator pupillae (pupil dilation).

Motor Nerve Supply

Abducens (CN VI): Lateral Rectus.
Trochlear (CN IV): Superior Oblique.
Oculomotor (CN III): Superior rectus, inferior rectus, medial rectus, inferior oblique.

Axis of Eye

Describes the axis of the eyeball and its relationship to the orbit.

Action of Muscles

Explains the actions of each eye muscle from a central gaze position.

Clinical Examination of the Eye

Techniques to isolate the action of each eye muscle

Strabismus

Cause: Poor vision, eye physically stuck.post-trauma.
Types: Esotropia (eyes turn inward), exotropia (eyes turn outward), hypertropia (eyes turn up or down)

Pupillary Light Reflex

Pathway: Light source > optic nerve > oculomotor nerve > pupillary constriction.

SDL (Specific Disease List)

Mentions Horner's syndrome, cavernous sinus thrombosis, and cataracts.

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Description

This quiz tests your knowledge on the anatomy of the orbit, including its bones and boundaries, as well as the extraocular muscles and cranial nerves involved. You'll describe essential features such as the eyelids, conjunctiva, lacrimal gland, and the structure of the eyeball and retina. Perfect for students studying anatomy or ophthalmology.