D20 - The muscles of the eye, their innervation, accessory organs of the eye, blood supply of the eye

Question 1

What does the visual organ consists of?

Answer 1

• Eyeball
• N. opticus
• Accessory organs
  
  • Corpus adiposum orbitae
  • Fascia bulbi
    
    • Preorbita
    • Fascia muscularis superficialis
    • Fascia muscularis profunda
  • Muscles of the eyeball
  • Eyelids (palpebrae)
    
    • Superior
    • Inferior
  • Gl. lacrimalis

Question 2

Define orbit

General knowledge

Answer 2

• The orbit is a cavity on the lateral surface of the skull
• Contains the eyeball
• Continous with fossa temporalis and fossa peterygopalatina

Question 3

Give the division of the interior of the eyeball

General knowledge, not directly linked to the topic

Answer 3

• The interior of the eyeball is divided into 3 chambers (camera bulbi):
  
  • Camera anteror (anterior chamber)
    
    • Between cornea and iris
    • Filled with aqueous humor
  • Camera posterior (posterior chamber)
    
    • ​Between iris, ciliary body and lens
    • Filled with aqueous humo
  • Camera viteria (viterous body)
    
    • Largest of the 3 chambers
    • Behind the lens
    • Surrounded by retina

Question 4

N. opticus

Ekstra informasjon

Answer 4

• N. opticus is actually a tract of the brain/CNS
• Pathway:
  • Enters the skull through for. opticum and canalis opticus
  • Cross to the contralateral side at optic chiasm
  • Continue at the optic tract and pass to the lateral geniculate nucleus and thaalmus
  • Projects onto the visual area of the cerebral cortex
  • Terminate in the supraoptic and paraventricular nucleus of hypothalamus

Question 5

Accessory organs

List the accessory organs of the eyeball

Answer 5

1. Corpus adiposum orbitae
2. Fascia bulbi
3. Muscles of the eyeball
4. Palpebrae (eyelids)
5. Lacrimal apparatus (with gl. lacrimalis)

Question 6

Accessory organs

Corpus adiposum orbitae

Answer 6

Supports the eyeball

Question 7

Accessory organs

Fascia bulbi

Answer 7

• Capsule of tendon
• Thin membrane which envelops the eyeball from n. opticus → limbus
• Periorbita (external)
  
  • Splits at orbit margin
• Fascia muscularis superficialis (middle)
  
  • Envelops m. palpebrae superioris and gl. lacrimalis
• Fascia muscularis profunda (internal)

Question 8

Accessory organs

Muscles of the eyeball

Answer 8

• ​M. rectus bulbi
  
  • ​M. rectus bulbi dorsalis
    
    • O: around for. opticum
    • I: anterior to equator
    • ​A: eyeball up
    • Innervation: III. n. oculomotorius
  • M. rectus bulbi ventralis
    
    • O: around for. opticum​​
    • I: anterior to equator
    • A: eyeball down
    • Innervation: III. n. oculomotorius
  • M. rectus bulbi lateralis
    
    • O: around for. opticum​​
    • I: anterior to equator
    • A: eyeball lateral
    • Innervation: VI. n. abducens
  • M. rectus bulbi medialis
    
    • O: around for. opticum
    • I: anterior to equator
    • ​​A: eyeball medial
    • Innervation: III. n. oculomotorius
• M. obliquus bulbi
  
  • ​M. obliquus dorsalis
    
    • O: around canalis opticus
    • I: deep to m. rectus dorsalis
    • A: rotate eyeball
    • Innervation: IV. n. trochlearis
  • M. obliquus ventralis
    
    • ​O: medial wall of orbit
    • I: eyeball posterior to equator
    • A: pull eyeball into orbit
    • Innervation: III. n. oculomotorius
• M. retractor bulbi
  
  • ​O: around canalis opticus (Car: fissura orbitalis)
  • I: Eyeball posterior to equator
  • A: pull eyeball into orbit
  • M. retractor bulbi lateralis
    
    • ​Innervation: VI. n. abducent
  • M. retractor bulbi medialis​
    
    • ​Innervation: III. n. oculomotorius
• M. levator palpebralis
  
  • A: suspension
  • Innervation: III. n. oculomotorius

Question 9

Accessory organs

Eyelids (palpebrae)

Answer 9

• Eyelids:
  
  • Upper lid (most mobile one)
  • Lower lid
  • Third li
    
    • ​Semilunar fold of cojuctiva
    • Lymph nodes are found within the third eyelid
    • Base of the cartilage is surrouded by superficial gland of the third eyelid
• Rima palpebralis: opening between upper and lower lids
• Margo palpebralis: free margins of upper and lower lid
• Caruncula lacrimalis: nasal angle of the eye
  
  • Ca: gl. lacrimalis beneath
• Conjuctival sac: space between lower lid and eyeball, contains mucous and tears
• M. orbicularis oculi: levator muscle of the upper eyelid, extends from for. ethmoidale → upper eyelid

Question 10

Accessory organs

Lacrimal apparatus

Answer 10

• The lacrimal apparatus includes structures that are responsible for production, dispersal and disposal of tears:
  
  • Gl. lacrimalis
    
    • ​Location: between eyeball and dorsotemporal wall of the orbit
  • Gl. palpebrae tertiae
  • Canaliculi lacrimalis
  • Saccus lacrimalis
    
    • ​Marks the beginning of ducuts nasolacrimalis
  • Ductus nasolacrimalis
    
    • ​Goes through os lacrimale and maxilla

Question 11

Accessory organs

Glands

Answer 11

• Sabecous gland (opens into follicles of cilia)
• Ciliary gland (coiled, tubular, sweat gland)
• Tarsal gland (oily, superficial layer of the tear film)
• Lacrimal gland (between eyeball → wall of orbit)

Question 12

Blood supply of the eye

Answer 12

• A. maxillaris → a. opthalmichi externa → rr. ciliares + palpebralis externa → a. malaris → a. lacrimalis
• A. cerebri rostralis → a. opthalmichi interna

​

• Veins are parallel to arteries, but:
  
  • Vv. vorticosae → v. opthalmichi externa

Question 13

Innervation of the eye

Answer 13

• N. oculomotorius (III):
  
  • Sympathetic
  • Parasympathetic
  • Supporting ciliary system
• N. opticus (II):
  
  • ​Sensory
  • _​_Visual perspective
  • No myelinated sheath
  • Actually a tract of the brain
• N. opthalmichi (V₁)
  
  • Principla sensory innervation of eye and orbit
  • → N. frontalis innervates upper lid
  • → N. lacrimalis innervates gl. lacrimalis and temporal canthus
  • → N. nasociliaris → n. infratrochlearis innervates conjuctiva and third lid
• N. maxillaris (V₂)
  
  • N. zygomaticus give sensoryinnervation to lower eyelids
• Controls movement of eyeball:
  
  • N. oculomotorius (III)
  • N. trochlearis (IV)
  • N. abducent (VI)