Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Neuro 2019 Exam 2 > Orbit and Eye Anatomy and Embryology > Flashcards

Orbit and Eye Anatomy and Embryology Flashcards

1
Q

General features of the orbit

A
  1. Bony cavity housing the eyeball and supporting structures.
  2. Depth of the orbit is nearly twice as long as the width.
  3. Each orbit is shaped like a quadrangular pyramid with its base facing anterolateral and its apex facing posteromedial.
  4. The contralateral medial orbital walls are oriented parallel to one another; while the contralateral lateral orbital walls are oriented perpendicular.
  5. Orbital axes (long axis through orbit) are oriented at 45° to one another.
  6. Optical axes (long axis through the globe) are parallel to the medial walls.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Bones of the orbit

A

Seven bones contribute to the bony orbit (frontal, maxilla, sphenoid, lacrimal, ethmoid, palatine, zygomatic).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

apex of the orbit

A

lesser wing of sphenoid surrounding optic canal.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

base of the orbit

A

– formed by the orbital margin and orbital opening

a. Orbital margin is formed by frontal, zygomatic, and maxilla bones.
b. Orbital margin is thickened to provide support and protection to the eyeball.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

roof of the orbit

A

a. Frontal bone and some sphenoid – separates orbit from anterior cranial fossa
b. Fossa for lacrimal gland

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Floor of the orbit

A

a. Maxilla bone – separates orbit from maxillary sinus
b. Zygomatic bone
c. Palatine bone

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Medial wall of the orbit

A

separates orbit from sphenoidal and ethmoidal air sinuses

a. Ethmoid bone
b. Lacrimal bone
c. Maxilla bone
d. The lacrimal fossa; houses the medial portion of the lacrimal system.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

lateral wall of the orbit

A

a. Zygomatic bone

b. Sphenoid – greater wing

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Foramina of the orbit

A
  1. Optic canal – optic nerve and ophthalmic artery
  2. Superior orbital fissure – CN III, IV, V1, and VI, superior ophthalmic vein
  3. Inferior orbital fissure – inferior ophthalmic vein, infraorbital a.v.n, zygomatic nn.
  4. Anterior ethmoidal foramen – anterior ethmoidal a.v.n.
  5. Posterior ethmoidal foramen – posterior ethmoidal a.v.n.
  6. Nasolacrimal canal – nasolacrimal duct
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

CLINICAL CORRELATION: Orbital Fractures

A
  1. Orbital margins are strong, fractures here likely occur at sutures between bones.
  2. Blowout fracture – fracture of orbital walls (usually inferior or medial).
    a. Damage to floor of orbit can involve maxillary sinus; intraocular fat/bleeding can spread to maxillary sinus.
    b. Often the inferior rectus muscle will get trapped in the fractured orbital floor; causing diplopia.
    c. Enophthalmos due to movement of fat into surrounding spaces of muscle entrapment.
    d. Damage to medial wall can involve sphenoidal and ethmoidal air sinuses.
    e. Damage to roof can involve anterior cranial fossa.
    f. The globe can also be damaged (detached retina; bleeding)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

CLINICAL CORRELATION: Orbital Tumors

A
  1. Malignant tumors originating in the sphenoidal and ethmoidal sinuses, middle cranial, or infratemporal fossa can erode through the thin walls of the orbit or pass directly through foramina. These tumors can compress the orbital contents.
  2. Can cause exophthalmos.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

orbital fascias and fat

A

periorbital fascia
muscular fascias of extraocular eye muscles
check ligaments
fascial sheath of eyeball (Tenon’s capule, fascia bulbi)
Orbital fat

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Periorbital fascia

A

– lines bones of orbit.

a. Continuous with periosteal dura at optic canal and superior orbital fissure.
b. Continuous with the orbital septum anteriorly.
c. Continuous with muscular fascias of extraocular eye muscles.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Check ligaments

A

a. Medial and lateral; attach to medial and lateral orbital walls.
b. Limit abduction and adduction of the eye.
c. Prevent posterior retraction of the eyeball by the rectus muscles.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Fascial sheath of eyeball

A

(Tenon’s capsule, fascia bulbi)

a. Thin membrane surrounding eyeball; external to sclera.
b. Continuous with the muscular fascia of the extraocular eye muscles.
c. Separates eyeball from orbital fat.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Orbital fat

A

a. Cushion
b. Lubrication
c. Protection
d. CLINICAL CORRELATION: With starvation, the eyes often become sunken-in (enophthalmos) due to loss of orbital fat.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Eyelids - function, layers

A
  1. Moveable folds of skin, muscle, and connective tissue which cover the eye.
  2. Function: protection; spread lacrimal fluid to lubricate cornea.
  3. Structure
    - -a. Skin
    - -b. Loose connective tissue
    - -c. Muscle (orbicularis oculi and levator palpebrae superioris)
    - -d. Tarsal plate
    - —–1. Dense ct for structural support of eyelid.
    - —–2. Orbital septum – fibrous membrane connecting tarsi to margins of orbit.
    - ———a. Functions to contain the orbital fat within the orbit.
    - ———b. Also helps to limit spread of infections between face and orbit.
    - —–3. Medial palpebral ligament – connect tarsi to medial wall of orbit.
    - —–4. Lateral palpebral ligament – connect tarsi to lateral wall of orbit.
    - -e. Palpebral conjunctiva
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Glands associated with eyelids

A

a. Tarsal (Meibomian) glands (sebaceous glands)
b. Glands of Zeis (smaller sebaceous glands)
c. Glands of Moll (sweat gland)
d. CLINICAL CORRELATION – Glands can become obstructed and inflamed; forming a chalazion (meibomian cyst) or a hordeoum (cyst of eyelash glands).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Muscles associated with eyelids

A

orbicularis oculi

levator palpebrae superioris (LPS)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Orbicularis oculi

A
  1. Sphincter muscle of eyelid
  2. Innervation – CN VII
  3. CLINICAL CORRELATION: CN VII impairment results in an eyelid that cannot close completely. Inferior eyelid tends to fall away from the eyeball and result in dryness and irritation of the cornea and sclera.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Levator palpebrae superioris (LPS)

A
  1. Origin – lesser wing of sphenoid
  2. Insertion – skin of superior eyelid
  3. Function – elevates superior eyelid
  4. Innervation – CN III
  5. Note: the superior tarsal portion of LPS attaches to the superior tarsal plate and is innervated sympathetically. **
  6. CLINICAL CORRELATION: Impairment of CN III can result in an inability to open the upper eyelid (or ptosis) due to loss of the LPS.
  7. CLINCAL CORRELATION: Horner’s syndrome (loss of sympathetic innervation to head) often presents with ptosis (drooping of the upper eyelid) due to loss of the superior tarsal portion of LPS.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Conjunctiva

A
  1. Palpebral conjunctiva – epithelium of internal eyelid
  2. Bulbar conjunctiva – outer epithelium of sclera
  3. Conjunctival sac – between palpebral and bulbar conjunctiva; opens at palpebral fissure.
  4. Conjunctival fornices (superior and inferior) are formed where bulbar and palpebral conjunctiva are continuous.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Lacrimal apparatus and the flow of tears

A
  1. Lacrimal gland
    - -a. Compound tubuloalveolar gland
    - -b. Located in lacrimal fossa in superolateral orbit.
    - -c. Secretes lacrimal fluid – watery, serous secretion – into conjunctival sac.
    - -d. Lacrimal fluid keeps sclera and cornea moist and contains an antibacterial agent for protection.
  2. Lacrimal cannaliculi
    - -a. Located in medial angle of eye.
    - -b. Begin at the lacrimal papilla; the lacrimal punctum is the opening.
  3. Lacrimal sac – receives fluid from lacrimal cannaliculi.
  4. Nasolacrimal duct – drains lacrimal fluid to nasal cavity.
  5. Flow of tears: lacrimal gland –> conjunctival sac –> surface of eye –> lacrimal papillae with puncta –> cannaliculae –> lacrimal sac–> nasolacrimal duct
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Eyeball

A

Organ of vision; composed of 3 tunics; lens; vitreous and aqueous chambers.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

External Fibrous tunic

A
  1. Sclera
    a. Tough, opaque fibrous layer covering posterior 5/6 of globe.
    b. Provides structural support for eye and provides for muscle attachment.
  2. Cornea
    a. Avascular, dehydrated, transparent layer covering anterior 1/6 of globe.
    b. Provides most of eye’s refractile capabilities.
    c. Numerous pain receptors located within cornea
    d. CLINICAL CORRELATION: Corneal neovascularization = blood vessels grow into corneal stroma secondary to hypoxia.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Middle vascular tunic (uvea)

A

includes choroid, ciliary body, iris

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

Choroid

A

a. Highly vascularized, loose connective tissue; located deep to sclera.
b. Provides vascular supply to fibrous layers and outermost layers of retina.
c. Contains melanocytes which produce melanin to absorb photons of light.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

Iris

A

a. Central aperture forms pupil; controls the amount of light entering the pupil.
b. Muscles
1. Sphincter pupillae
a. Reduces diameter of pupil (miosis) to decrease light entering eye.
b. Parasympathetic innervation (CN III).
2. Dilator pupillae
a. Increases diameter of pupil (mydriasis) to increase light entering eye.
b. Sympathetic innervation.

29
Q

Ciliary body

A

a. Ciliary processes
1. Finger-like extensions from ciliary body.
2. Secrete aqueous humor into posterior chamber.
3. Suspensory ligaments (zonule fibers) extend from ciliary processes to len.

b. Ciliary muscle
1. Parasympathetic innervation (CN III)
2. Accommodation
- -a. Control of lens thickness via suspensory ligaments.
- -b. When looking at distant objects, the ciliary muscle is relaxed and there is tension on the suspensory ligaments of the lens. The ciliary processes pull on the lens and cause it to be stretched and thinned.
- -c. When focusing on near objects, the ciliary muscle contracts. The ciliary muscle pulls the ciliary body medially and anteriorly and reduces tension on suspensory ligaments. Less tension on the suspensory ligaments means that the lens becomes rounded and thicker.
- -d. No stimulation – lens is thin and flat to focus distant.
- -e. Parasympathetic stimulation (CN III) – lens round to focus near.

30
Q

Inner neural tunic

A

(retina)
1. Visual receptor portion of retina.

  1. Contains the rods/cones which respond to photons of light.
  2. Contains the ganglion cells which will form the optic nerve.
  3. Ora serrata – the anterior termination of retina.
  4. Optic disc (blind spot) – located on the posterior pole of globe. Represents site of entry of optic nerve (CN II) and the central retinal artery and vein. No photoreceptive cells.
  5. Macula lutea is a yellow-pigmented zone located about 2.5 mm lateral to optic disk.
  6. Fovea centralis – oval depression located in the central of the macula. Site of greatest visual acuity due to density of cone cells.
  7. Blood supply of retina
    a. Central retinal artery supplies neural portion of retina (except rods/cones).
    b. Choroid vessels supplies pigmented epithelium and rod/cone layer
  8. CLINICAL CORRELATION: Retinal detachment occurs when the pigmented epithelium separates from the underlying rods and cones layer. Detachment can cause blindness if not corrected immediately due to loss of metabolic support and blood supply to rods and cones.
31
Q

Lens

A
  1. Transparent, refractile, flexible, biconvex disk located posterior to iris.
  2. Function: Refraction and accommodation
  3. CLINCIAL CORRELATION: Presbyopia refers to a hardening (loss of elasticity) of the lens; inability to accommodate and focus on near objects.
  4. CLINICAL CORRELATION: Cataracts develop when the proteins of the lens aggregate; producing an opaque lens.
32
Q

Eye Chambers

A

Aqueous chambers

Vitreous bodies

33
Q

Aqueous chambers

A

a. Anterior chamber is located between cornea and iris.

b. Posterior chamber is located between iris and lens.

34
Q

Aqueous humor

A
  1. Produced in posterior chamber by ciliary processes of ciliary body.
  2. Flows from posterior chamber to anterior chamber via pupil.
  3. Drains to venous system via the scleral venous sinus (Canal of Schlemm) at the iridocorneal angle. The scleral venous sinus is covered by a trabecular meshwork (endothelial lined spaces) which helps drain aqueous humor.
  4. Scleral venous sinus drains to vorticose and anterior ciliary veins.
  5. CLINICAL CORRELATION: Glaucoma is a condition caused by excess aqueous humor in the anterior and posterior chambers. Most often due to decreased outflow of aqueous humor (failure to drain due to blockage of scleral venous sinus) or from increased production of aqueous humor. Glaucoma results in increased intraocular pressure; can cause blindness if left untreated.
35
Q

Vitreous body

A

a. Between lens and posterior surface of eye.

b. Filled with vitreous humor – a transparent, refractile jelly-like substance.

36
Q

Exophthalmos

A

a. Protrusion of eyeball from orbit.

b. Seen in certain diseases such as hyperthyroidism, orbital tumors.

37
Q

Enophthalmos

A

a. Retraction of eyeball into orbit.

b. Seen in certain disorders such as starvation.

38
Q

Embryologic structures contributing to the eyeball

A
  1. Neural Ectoderm (Optic Vesicles)
    a. Derived from evaginations of the forebrain neuroectoderm
    b. Meninges carried along with developing eye.
    c. Optic vesicles invaginate on themselves to form a double-walled optic cup.
    d. Optic cup retains connection to forebrain at optic stalk.
    e. Choroid fissure forms on ventral surface of optic cup – carries hyaloid vessels
    f. Forms retina, optic nerve
  2. Surface Ectoderm
    a. Lens placode → lens vesicle.
    b. Forms the lens.
  3. Mesenchyme –fibrous (sclera, cornea) and vascular (choroid, iris, ciliary body) layers
39
Q

Embryology of retina and optic nerve

A
  1. Outer layer of optic cup – pigmented layer of retina
  2. Inner layer of optic cup – all neural layers of retina
  3. Nerve fibers from retina migrate through the choroid fissure to form CN II.
  4. 7th week – choroid fissure closes.
  5. CLINICAL CORRELATION: Congenital retinal detachment occurs when the inner and outer layer of optic cup fail to fuse; separation of pigmented and neural layers of retina (will result in blindness if not reattached).
40
Q

Embryology of choroid

A

Choroid is derived from vascular layer of mesenchyme surrounding optic cup.

41
Q

Embryology of iris and ciliary body

A
  1. Outer portion is derived from vascular mesenchyme surrounding optic cup.
  2. Inner portion is derived from the optic cup (NO neural elements)
  3. Most infants are born with blue/gray eyes due to lack of melanocytes in anterior portion of iris. Melanocytes migrate into the anterior iris in the first 6-10 months.
  4. The iridopupillary membrane is a vascular structure which originally separates the anterior and posterior aqueous chambers; degenerates around week 15.
  5. CLINICAL CORRELATION: Iridopupillary membrane degenerates after week 15. Failure of the membrane to degenerate leads to congenital atresia of the pupil.
  6. CLINICAL CORRELATION: Coloboma results from a failure of the choroid fissure to fuse during the 7th week of development (may also involve retina).
42
Q

embryology of sclera and cornea

A

Sclera and cornea are derived from fibrous layer of mesenchyme surrounding optic cup.

43
Q

embryology of aqueous and vitreous chambers of eye

A
  1. The eye chambers form in areas of cell death within eyeball.
  2. Vitreous humor is likely derived from neural crest cells.
44
Q

embryology of the lens

A
  1. Derived from lens vesicle

2. CLINICAL CORRELATION: Congenital aphakia – agenesis of lens placode.

45
Q

embryology of extrinsic eye muscles

A

Extrinsic eye muscles form from mesoderm of myotomes

46
Q

Arterial Supply to Orbit and Eyeball

A

Ophthalmic artery

  1. Arises from internal carotid artery.
  2. Enters orbit via optic canal.
  3. Branches
    a. Central retinal artery
  4. Pierces optic sheath and runs within optic nerve.
  5. Supplies retina (except rods/cones and pigmented epithelium layers).
    b. Short posterior ciliary – pierce sclera near optic nerve to supply choroid.
    c. Long posterior ciliary – pierce sclera anteriorly to supply ciliary body/iris.
    d. Anterior ciliary arteries – arise from muscular branches; to ciliary body and iris.
    e. Lacrimal – to larimal gland and lateral portions of eyelids.
    f. Supraorbital – to forehead and scalp.
    g. Posterior ethmoidal a.
    h. Anterior ethmoidal a.
    i. Medial palpebral a. – medial eyelids.
    j. Supratrochlear – to forehead and scalp
    k. Dorsal nasal – supplies dorsal surface of nose.
47
Q

Venous Drainage of ORbit and Eyeball

A

A. Central retinal vein – usually drains directly to cavernous sinus.
B. Vorticose veins drain the choroid, ciliary body, and iris.
C. Superior and inferior ophthalmic veins – exit orbit via superior and inferior orbital fissures (respectively). Drain to cavernous sinus and pterygoid venous plexus (respectively).
D. CLINICAL CORRELATION – Thrombophlebitis of the cavernous sinus may send a clot to the central retinal vein; may lead to vision loss.

48
Q

clinical correlation re: intracranial pressure

A

Increased intracranial pressure can affect the eye due to the fact that the meninges and CSF continue along the optic nerve. Thus, the optic nerve, central retinal artery, and central retinal vein can be compressed and occluded.

a. Occlusion of the central retinal vein can cause papilledema (retinal edema).
b. Compression of the optic nerve can cause blindness.
c. Retinal artery occlusion can also cause blindness due to loss of blood supply to retina.

49
Q

Movements of the eye

A

A. Adduction – movement of the pupil towards midline (toward nose)
B. Abduction – movement of pupil laterally (toward ear)
C. Elevation – movement of pupil superiorly.
D. Depression – movement of pupil inferiorly
E. Extortion – superior pole of eyeball rotated laterally.
F. Intortion – superior pole of eyeball rotated medially.

50
Q

Medial rectus

A
  1. Origin – common tendinous ring
  2. Insertion – medial surface of eyeball
  3. Function – adducts eye
  4. Innervation – CN III
  5. Testing integrity – eye held in abducted position; loss of adduction.
51
Q

Lateral rectus

A
  1. Origin – common tendinous ring.
  2. Insertion – lateral surface of the eyeball
  3. Function – abducts eye.
  4. Innervation – CN VI
  5. Testing integrity – eye held in adducted position; loss of abduction
52
Q

Superior rectus

A
  1. Origin – common tendinous ring
  2. Insertion – superior surface of eyeball
  3. Function – elevates, adducts; intorsion
  4. Innervation – CN III
  5. Testing integrity – weakness of elevation; loss of elevation when eye is fully abducted.
53
Q

Inferior rectus

A
  1. Origin – common tendinous ring
  2. Insertion – inferior surface of eyeball
  3. Function – depresses, adducts; extorsion
  4. Innervation – CN III
  5. Testing integrity – weakness of depression; loss of depression when eye is fully abducted.
54
Q

Inferior oblique

A
  1. Origin – anterior portion of floor of orbit
  2. Insertion – inferior surface of eyeball, posterior to the equator (vertical axis)
  3. Function – elevates, abducts; extorsion.
  4. Innervation – CN III
  5. Testing integrity – weakness of elevation; loss of elevation when eye is fully adducted.
55
Q

Superior oblique

A
  1. Origin – common tendinous ring
  2. Insertion – superior surface of eyeball, posterior to the equator (vertical axis)
  3. This muscle passes through a trochea and changes its direction to attach to the eyeball.
  4. Function – depresses, abducts; intorsion.
  5. Innervation – CN IV
  6. Testing integrity – weakness of depression; loss of depression when eye is fully adducted.
56
Q

CN III- Oculomotor nerve

A
  1. GSE; GVE-P
  2. Superior division – levator palpebrae superioris and superior rectus.
  3. Inferior division – medial rectus, inferior rectus, and inferior oblique muscles.
  4. Inferior division also carries preganglionic parasympathetic fibers to the ciliary ganglia.
  5. CLINICAL CORRELATION – Oculomotor nerve palsy.
    a. Ptosis or complete closure of eye (loss of levator palpebrae superioris)
    b. Diplopia
    c. Eye will be abducted and depressed (down and out)
    d. Dilation of pupil (due to loss of sphincter pupillae muscle)
    e. Loss of accommodation (due to loss of ciliary muscle)
57
Q

CN IV – Trochlear nerve

A
  1. GSE
  2. Superior oblique muscle
  3. CLINICAL CORRELATION – Trochlear nerve palsy
    a. Diplopia
    b. Eye will be slightly elevated and adducted.
    c. Loss of depression when eye fully adducted.
58
Q

CN VI – Abducens nerve

A
  1. GSE
  2. Lateral rectus muscle
  3. CLINICAL CORRELATION – Abducent nerve palsy.
    a. Diplopia
    b. Loss of eye abduction.
59
Q

Nerves of orbit – Sensory

A

A. CN II – Optic Nerve

  1. SSA – vision
  2. The optic nerve is covered in meninges (dura, arachnoid, and pia).
  3. Optic nerve fibers are axons of the ganglion cell layer of the retina which pass through the optic disc and then exit via the lamina cribrosa of sclera posterior.
60
Q

CN V1 – Trigeminal nerve; ophthalmic division

A
  1. GSA
  2. Branches
    a. Nasociliary
  3. Sensory root to the ciliary ganglia
  4. Short ciliary nerves – arise from ciliary ganglia on lateral side of optic n; carry postganglionic sympathetic, parasympathetic, and sensory fibers.
  5. Long ciliary nerves – arise from nasociliary nerve on medial side of optic n; carry postganglionic sympathetic fibers, sensory fibers.
  6. Posterior ethmoidal nn. – to ethmoidal air cells, dura.
  7. Anterior ethmoidal nn. – to ethmoidal air cells, nasal cavity, dura; terminates as external nasal nerve.
  8. Infratrochlear n. – exits orbit at medial angle; sensory to skin at root of nose, eyelids, palpebral conjunctiva, lacrimal sac.

b. Frontal
1. Supratrochlear nerve
2. Supraorbital nerve

c. Lacrimal
1. Sensory to lacrimal gland; lateral portion of superior eyelid.
2. Carries postganglionic parasympathetic and sympathetic fibers to lac

61
Q

Ciliary ganglion

A

. Located between the lateral rectus muscle and optic nerve.

  1. Contains postganglionic parasympathetic cell bodies.
  2. Receives three roots:
    a. Sensory root from nasociliary nerve
    b. Parasympathetic motor root from oculomotor nerve
    c. Sympathetic motor root from the internal carotid plexus
62
Q

Parasympathetics to the eye

A

B. Parasympathetics (sphincter pupillae and ciliary muscles)

  1. Preganglionic cells are located in the Edinger-Westphal nucleus.
  2. Preganglionic fibers travel with the oculomotor nerve.
  3. Postganglionic cells are located in the ciliary ganglion.
  4. Postganglionic fibers then distribute via the short ciliary nn to the sphincter pupillae muscle and ciliary muscle.
63
Q

Sympathetics to the eye

A

(dilator pupillae and superior tarsal muscle)

  1. Preganglionic cells are located in the upper thoracic spinal levels (T1-T2).
  2. Preganglionic fibers enter the sympathetic chain and ascend.
  3. Postganglionic cells are located in the superior cervical sympathetic ganglion.
  4. Postganglionic fibers travel with the internal carotid plexus.
  5. Internal carotid plexus gives a sympathetic motor root to the ciliary ganglion.
  6. Postganglionic fibers pass through ciliary ganglia without synapsing and distribute via long and short ciliary nn to the dilator pupillae and superior tarsal muscle.
64
Q

Parasympathetic innervation to the lacrimal gland

A
  1. Preganglionic cell bodies located in the salivatory nucleus in brainstem.
  2. Preganglionic fibers travel with the greater petrosal nerve (CN VII).
  3. Postganglionic cell bodies in pterygopalatine ganglia.
  4. Postganglionic fibers travel with the zygomatic (V2) and lacrimal (V1) nerves.
  5. Increase lacrimal gland secretions.
65
Q

sympathetic innervation of lacrimal gland

A
  1. Preganglionic cell bodies located in upper thoracic spinal levels (T1-T4).
  2. Preganglionic fibers enter sympathetic chain and ascend.
  3. Postganglionic cells bodies in superior cervical sympathetic ganglia; fibers distributed via internal carotid nerve (deep petrosal nerve).
  4. Greater and deep petrosal nerves merge to form the nerve of the pterygoid canal.
  5. Postganglionic fibers distribute with the zygomatic (V2) and lacrimal (V1) nerves.
  6. Vasomotor; creates more watery lacrimal fluid
66
Q

Pupillary Light Reflex

A
  1. Function – protect eye from excessive light exposure
  2. Afferent nerve – CN II (vision)
  3. Efferent nerve – CN III (GVE-P to sphincter pupillae m)
  4. Shine light in eye (CN II).
  5. Both pupils constrict (CN III).
  6. Direct response – ipsilateral eye constricts.
  7. Consensual response – contralateral eye constricts.
67
Q

Corneal Reflex

A
  1. Function – protect eye from foreign objects
  2. Afferent nerve – CN V1 (general sensation to eye; pain)
  3. Efferent nerve – CN VII (orbicularis oculi)
  4. Puff of air on eye (or directly touching cornea) stimulates CN V1.
  5. Both eyes blink due to contraction of orbicularis oculi (CN VII).
  6. Direct and consensual responses.
68
Q

Accommodation Reflex

A
  1. Function – view near objects
  2. Afferent nerve – CN II (vision)
  3. Efferent nerve – CN III (GSE and GVE-P)
  4. Looking from a distant object to a near object (CN II).
  5. Direct and consensual responses.
  6. Three events occur:
    a. Ciliary muscles contract, cause rounding of lens (accommodation) (CN III; GVE-P)
    b. Pupils constrict (CN III; GVE-P)
    c. Eyes adduct (CN III; GSE)

Neuro 2019 Exam 2 (14 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions