Anatomy of the Orbit and Eye Movement
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Questions and Answers

What is the primary function of the eyelids?

  • To regulate the amount of light entering the eye
  • To facilitate venous drainage of the eyeball
  • To lubricate the eye with tears
  • To protect the eye from aggressions (correct)

    • Which of the following veins drains into the cavernous sinus?

  • Angular vein
  • Inframbital vein
  • Superior ophthalmic vein (correct)
  • Pterygoid plexus

    • What is the name of the syndrome characterized by palpebral ptosis, miosis, and lack of sweating?

  • Triángulo de la muerte
  • Palpebral syndrome
  • Papilledema
  • Horner's syndrome (correct)

    • What is the type of muscle fiber attached to the superior tarsus?

    <p>Smooth muscle fibers</p> Signup and view all the answers

    What is the primary function of the lacrimal system?

    <p>To lubricate the eye with tears</p> Signup and view all the answers

    What is the name of the vein that forms from the angular vein of the face and the supraorbital vein?

    <p>Superior ophthalmic vein</p> Signup and view all the answers

    What is the function of the tarsal glands?

    <p>To form the fluid that seals the lids while we sleep</p> Signup and view all the answers

    What is the type of nervous system that innervates the smooth muscle fibers attached to the superior tarsus?

    <p>Sympathetic nervous system</p> Signup and view all the answers

    What is the name of the structure that separates the eyelids from the orbital cavity?

    <p>Orbital septum</p> Signup and view all the answers

    What is the primary function of the superior and inferior tarsus?

    <p>To support the eyelids</p> Signup and view all the answers

    What is the function of the sympathetic nervous system in relation to the eye?

    <p>Enhances vasomotor activity</p> Signup and view all the answers

    Where do tears accumulate before being drained?

    <p>Lacrimal caruncle</p> Signup and view all the answers

    What is the function of the puncta on the eyelids?

    <p>To drain tears</p> Signup and view all the answers

    Where does the nasolacrimal duct open?

    <p>Inferior nasal meatus</p> Signup and view all the answers

    What happens to the tears that flow down from the lacrimal sac?

    <p>They enter the nasal cavity</p> Signup and view all the answers

    What is the effect of blinking on the lacrimal sac?

    <p>It compresses the sac, increasing tear flow</p> Signup and view all the answers

    What is the function of the lacrimal canaliculi?

    <p>To drain tears into the lacrimal sac</p> Signup and view all the answers

    What is the final destination of tears that are drained from the eye?

    <p>The oral cavity</p> Signup and view all the answers

    What is the gland that is pierced by the tendon of the Levator palpebrae superioris?

    <p>Lacrimal gland</p> Signup and view all the answers

    What is the path taken by tears after they are drained from the eye?

    <p>Lacrimal sac → nasolacrimal duct → nasal cavity → oral cavity</p> Signup and view all the answers

    From which part of the brain does the retina derive?

    <p>Diencephalon</p> Signup and view all the answers

    What is the origin of the lens?

    <p>Ectodermal</p> Signup and view all the answers

    What is the relationship between the optic vesicle and the lens placode?

    <p>The optic vesicle curves around and encloses the lens placode</p> Signup and view all the answers

    What happens to the ectodermal cells as they form the lens placode?

    <p>They change from polygonal to cuboid</p> Signup and view all the answers

    What is the resulting structure formed by the optic vesicle as it curves and becomes concave?

    <p>Optic cup</p> Signup and view all the answers

    What is the source of layers 2-10 of the retina?

    <p>Internal layer of the optic cup</p> Signup and view all the answers

    What is the result of trauma to the retina?

    <p>Appearance of the intraretinal space</p> Signup and view all the answers

    What happens to the choroid fissure during the development of the optic nerve?

    <p>It closes and the artery becomes embedded within the optic nerve</p> Signup and view all the answers

    What is the function of the hyaloid artery during development?

    <p>Provides blood supply to the lens</p> Signup and view all the answers

    What forms the retinal layer in the eye?

    <p>Inner layer of the stalk</p> Signup and view all the answers

    What is the result of the transformation of the optic stalk into the optic nerve?

    <p>Growth of the axons of the ganglion cells</p> Signup and view all the answers

    What is the space surrounding the optic nerve?

    <p>Subarachnoid space</p> Signup and view all the answers

    What happens to the distal part of the hyaloid artery in the adult?

    <p>It disappears</p> Signup and view all the answers

    What would cause an increase in intracranial pressure?

    <p>Edema of brain parenchyma</p> Signup and view all the answers

    What type of muscle derives from paraxial mesoderm?

    <p>Striated muscle</p> Signup and view all the answers

    What is the level of origin of the nerves that migrate with the somitomeres?

    <p>III, IV and VI CN</p> Signup and view all the answers

    Where can the somitomeres be found during the 6th week?

    <p>Around the lens placode</p> Signup and view all the answers

    How many striate muscles arise from the myotomes of the somitomeres?

    <p>7</p> Signup and view all the answers

    What is the point of insertion for all the striate muscles except for the levator palpebrae?

    <p>The sclera of the eyeball</p> Signup and view all the answers

    What is the name of the ring structure through which the superior oblique muscle tendon passes?

    <p>Trochlea</p> Signup and view all the answers

    Which muscle has a tendon that pierces the orbital septum and inserts into the skin of the superior eyelid?

    <p>Levator palpebrae superioris</p> Signup and view all the answers

    What type of muscle fibers attach to the superior tarsus?

    <p>Smooth muscle fibers</p> Signup and view all the answers

    Which cranial nerve innervates the extrinsic eye muscles?

    <p>Trochlear nerve (IV CN) and Abducens nerve (VI CN)</p> Signup and view all the answers

    What is the function of the superior tarsal muscles?

    <p>To elevate the eyelid</p> Signup and view all the answers

    Where do the rectus muscles originate from?

    <p>A common tendinous ring</p> Signup and view all the answers

    What type of innervation do intrinsic muscles of the eye receive?

    <p>Autonomic innervation</p> Signup and view all the answers

    What is the function of the constrictor muscle of the pupil?

    <p>To decrease pupil diameter</p> Signup and view all the answers

    What nerve carries visceral efferents to the intrinsic muscles of the eye?

    <p>Oculomotor nerve (III CN)</p> Signup and view all the answers

    What is the function of the ciliary muscle?

    <p>To accommodate the eye</p> Signup and view all the answers

    Which muscle receives sympathetic innervation?

    <p>Dilator muscle of the pupil</p> Signup and view all the answers

    What is the function of the extrinsic muscles of the eye?

    <p>To move the eyeball</p> Signup and view all the answers

    Which layer of the eye is continuous with the optic nerve?

    <p>Neural layer</p> Signup and view all the answers

    What is the name of the thin layer of fat that surrounds the eyeball?

    <p>Orbital fat</p> Signup and view all the answers

    What is the function of the tarsal plates in the eyelids?

    <p>To provide consistency to the eyelids</p> Signup and view all the answers

    What is the name of the fascia that surrounds the eyeball?

    <p>Tenon's capsule</p> Signup and view all the answers

    What is the primary origin of the 7 striate muscles that move the eye?

    <p>Somitomeres</p> Signup and view all the answers

    Which muscle tendon passes through a ring structure called the trochlea?

    <p>Superior oblique muscle</p> Signup and view all the answers

    Where do the majority of the striate muscles take insertion in the eyeball?

    <p>Laterally, around the ora serrata</p> Signup and view all the answers

    Which muscle does not insert into the sclera of the eyeball?

    <p>Levator palpebrae muscle</p> Signup and view all the answers

    What is the origin of the inferior oblique muscle?

    <p>Medial aspect of the orbit</p> Signup and view all the answers

    Study Notes

    Extrinsic Muscles of the Eye

    • Extrinsic muscles are striated muscles surrounding the eyeball, responsible for its movement.
    • Seven key muscles include superior, inferior, medial, and lateral rectus muscles, superior and inferior oblique muscles, and levator palpebrae.
    • Innervated by cranial nerves III (oculomotor), IV (trochlear), and VI (abducens).

    Blood Supply to the Eye

    • The eye is primarily supplied by branches of the ophthalmic artery, derived from the internal carotid artery.
    • The central artery of the retina provides essential supply to layers 2-10 of the retina.
    • Superior and inferior ophthalmic veins drain venous blood from the eye, eventually merging with the cavernous sinus.

    Development of the Eyeball

    • The eyeball originates from the optic vesicle, which forms as an evagination of the diencephalon.
    • The lens develops from the lens placode, an ectodermal thickening under CNS influence.

    Structure of the Eye

    • The eye is supported by a periosteum lining called periorbita, which thickens anteriorly to form the orbital septum.
    • Bulbar fascia (Tenon’s capsule) is a thin connective tissue surrounding the eyeball.
    • Check ligaments (lateral and medial) limit eye movement by attaching to the orbital bones.

    Neural Anatomy

    • Retina is the innermost layer of the eye and part of the central nervous system.
    • The optic nerve is formed from the optic stalk and is surrounded by the dura mater and arachnoid meninges, transmitting intracranial pressure changes.

    Intrinsic Muscles of the Eye

    • Include ciliary muscle and muscles controlling pupil diameter (constrictor and dilator).
    • Innervated autonomically; ciliary muscle contraction alters lens curvature, affecting focus.

    Actions of Extraocular Muscles

    • Lateral and medial rectus muscles move the eye horizontally.
    • Superior and inferior rectus muscles control vertical eye movements.
    • Oblique muscles provide rotation; superior oblique passes through trochlea.

    Clinical Considerations

    • Intracranial pressure changes can be assessed via the eye’s fundus.
    • Conditions like papilledema indicate increased pressure due to brain edema, hemorrhage, or tumors.

    Eyelids and Lacrimal System

    • Eyelids are composed of skin, connective tissue, and glands to protect and moisten the eye.
    • Tear drainage involves puncta connecting to lacrimal sac, leading to the nasolacrimal duct.

    Sympathetic Innervation Effects

    • Horner's syndrome results in ptosis (lid droop) and miosis (constricted pupil) due to disrupted sympathetic tone.

    Key Structures in Eye Anatomy

    • Each extraocular muscle inserts into the sclera, except levator palpebrae, which elevates the eyelid.
    • Retinal layers include a pigmented epithelium (outer) and sensory layers (inner), essential for vision.

    General Functionality

    • Eye movements are complex, organized by coordinated activation of various muscle groups.
    • The visual system is sensitive to changes in blood supply and neural health, reflecting the importance of these anatomical structures.### Eye Muscles and Their Functions
    • Levator Palpebrae Superioris: Unique muscle that elevates the eyelid; not attached to the sclera.
    • Origin of Rectus Muscles: All four rectus muscles originate from a common tendinous ring, a thickening of the periorbita around the optic canal and superior orbital fissure.
    • Insertions: Rectus and oblique muscles insert into the sclera. Rectus muscles pull the eyeball backward, while oblique muscles can slightly pull it forward.
    • Tendon of Levator Palpebrae: Pierces the orbital septum, innervating the skin of the superior eyelid and some fibers attaching to the superior tarsus.
    • Function: Muscle fibers work collectively to elevate the eyelid. Additional smooth muscle fibers, known as superior tarsal muscles, assist in this process and are controlled by the autonomic nervous system.
    • Sympathetic Activation: Elevated eyelid indicates readiness, while parasympathetic tone leads to lid closure when tired.

    Innervation of Eye Muscles

    • Cranial Nerve Innervation: Extrinsic eye muscles are innervated by cranial nerves III (Oculomotor), IV (Trochlear), and VI (Abducens).
    • Abducens Nerve: Travels within the cavernous sinus.

    Blood Supply and Structure of Orbit

    • Orbit Composition: Contains the eyeball, extrinsic eye muscles, lacrimal gland, and a thin layer of protective fat.
    • Layers of the Eye:
      • Innermost Layer: Retina, continuous with the optic nerve; contains axons of the optic nerve.
      • Vascular Layer: Includes the choroid (posterior 4/5) and the iris (anterior 1/5).
      • Fibrous Layer: Forms the cornea (anteriorly) and sclera (posteriorly), continuous with the meninges surrounding the optic nerve.
    • Periorbita: Periosteum lining the orbit, thickened to form the orbital septum, connecting to the tarsus for eyelid structure.
    • Bulbar Fascia (Tenon’s Capsule): Thin connective tissue layer surrounding the eyeball, stopping at the cornea.

    Intrinsic Muscles of the Eye

    • Muscles: Include ciliary muscle, constrictor muscle of the pupil, and dilator muscle of the pupil; these are involuntary and receive autonomic innervation.
    • Parasympathetic Actions: Contracts the ciliary muscle for accommodation (lens curvature) and constricts the pupil.
    • Sympathetic Actions: Contracts dilator muscle to increase pupil diameter; no sympathetic innervation to the ciliary muscle is necessary.

    Blood Supply to the Eye

    • Origin: Blood supplied by branches of the ophthalmic artery from the internal carotid artery.
    • Central Artery of the Retina: Vital for supplying layers 2-10 of the retina; arises where cranial nerves III, IV, and VI emerge.

    Development and Muscle Insertion

    • Somitomeres: Seven striated muscles arise from myotomes of somitomeres.
    • Insertion Points: Six muscles (superior, inferior, medial, lateral rectus, superior and inferior oblique) insert into the sclera; levator palpebrae elevates the eyelid.
    • Ora Serrata: Denotes the proximal third of the eye, differentiating the colloid from the ciliary bodies where muscle insertions are predominant.

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    Description

    Test your knowledge of the orbit's structure and the extrinsic muscles that control eye movement. Learn about the lacrimal gland, fat layer, and nervous system components that support vision.

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