Muscles around the Eye

Question 1

What are the functions of the eye?

Answer 1

1. Self-focus light
2. Adjust for light intensity
3. Converts light into electrical impulses interpreted by brain

Question 2

What is the bony orbit?

Answer 2

• Pyramidal bony cavity of facial skeleton
• Lined by periorbita (fascia sheath of the eye)
  > continuous at optic canal, superior orbital fissure, inferior orbital fissure, dural fascia

Question 3

What are the contents of the bony orbit?

Answer 3

1. Eyeballs and their extraocular muscles
2. Nerves and vessels
3. Lacrimal apparatus

Question 4

Which bones make up the orbital margin?

Answer 4

frontal, maxillary and zygomatic bones

Question 5

What are the walls of the orbit?

Answer 5

1. apex
2. 4 walls
   - superior
   - inferior
   - medial
   - lateral

Question 6

What is the superior wall of the orbit formed by?

Answer 6

1. orbital part of the frontal bone
   – has lacrimal fossa with lacrimal gland
2. Lesser wing of sphenoid
   – near apex

Question 7

What is the medial wall of the orbit formed by?

Answer 7

1. Ethmoid bone (ethmoid plate)
2. frontal
3. lacrimal
4. sphenoid (body)
   > Indented by lacrimal fossa for lacrimal sac
   > The two walls are separated by ethmoid sinuses and nasal cavity

Question 8

The inferior wall of the orbit is formed by?

Answer 8

1. Maxilla (orbital surface)
2. Part of zygomatic and palatine bones

Question 9

The lateral wall of the orbit is formed by?

Answer 9

1. frontal process of zygomatic bone
2. Greater wing of sphenoid bone

Question 10

Describe the location of the apex of the orbit?

Answer 10

• at optical canal
• in lesser wing of sphenoid
• medial to superior orbital fissure

Question 11

What are the clinical correlations of the orit?

Answer 11

1. Fracture of the orbit
2. Blowout fracture
   > Intraorbital bleeding causing exophthalmos (bulging eyes)
3. Periorbital Ecchymosis (discoloration of the skin resulting from bleeding underneath)
   > Blows to periorbital causes bleeding and swelling
4. Orbital tumors
   > cause exophthalmos

Question 12

What are the contents of the orbit?

Answer 12

Eyeball
Optic nerve
Ocular muscles
Fascia
Nerves, vessels, fat, lacrimal gland
Conjunctival sac

Question 13

What are the functions of the yebrows?

Answer 13

1. shade
2. shield for perspiration

Question 14

Describe the eyelids?

Answer 14

• skin-covered folds with “tarsal plates” connective tissue inside
• contain tarsal glands that produce an oily substance to prevent eyelids from sticking together

Question 15

Which muscle opens the eye?

Answer 15

levator palpebrae superioris
- only present in the superior eyelid because it is the only one that opens

Question 16

Describe the canthus (corner of the eye)?

Answer 16

• Lacrimal caruncle makes eye “sand” at medial corner
• Epicanthal folds in many Asian people cover caruncle
• Tarsal glands make oil to slow drying

Question 17

Describe eyelashes?

Answer 17

• ciliary gland at hair follicle
• touch sensitive, thus blink

Question 18

What is the conjuctiva?

Answer 18

Mucous membrane that coats inner surface of eyelid (palpebral part) and then folds back onto surface of eye (ocular part)

Question 19

Describe the histology of the conjuctiva?

Answer 19

• Thin layer of connective tissue covered with stratified columnar epithelium
• Very thin and transparent, showing blood vessels underneath (blood-shot eyes)
• Goblet cells in epithelium secrete mucous to keep eyes moist

Question 20

Why is vitamin A necessary in the conjuctiva?

Answer 20

Vitamin A necessary for all epithelial secretions
— lack leads to conjunctiva drying up
> scaly eye

Question 21

What are tears?

Answer 21

contain mucous, antibodies, lysozyme (anti-bacterial)

Question 22

What structures produce and transport tears?

Answer 22

1. Lacrimal glands
   — superficial/lateral in orbit, produce tears
2. Lacrimal duct (nasolacrimal duct)
   — medial corner of eye carries tears to nasal cavity
   > frequently closed in new borns — opens by 1 year usually

Question 23

Describe the flow of tears through the lacrimal apparatus?

Answer 23

Produced by lacrimal gland
> spread over eyeball
> lacrimal lake
> lacrimal canaliculi
> lacrimal sac
> nasolacrimal duct
> inferior nasal meatus

Question 24

What are the 2 groups of muscles within the orbit?

Answer 24

1. Extrinsic muscles of the eyeball
   - extra-ocular muscles
2. Intrinsic muscles of the eyeball
   - control the shape of the lens and size of pupil

Question 25

Name the 3 nerves that innervate the eye muscles?

Answer 25

1. Occulomotor 2. Abducens 3. trochlear

Question 26

Name the extrinsic eye muscles?

Answer 26

1. superior oblique 2. lateral rectus 3. medial rectus 4. superior rectus 5. inferior rectus 6. inferior oblique

Question 27

State the movement, innervation and testing of the superior oblique muscle?

Answer 27

movement = depresses eye + medial rotation innervation = CN IV Trochlear test = look medially and downward

Question 28

State the movement, innervation and testing of the lateral rectus muscle?

Answer 28

movement = lateral rotation innervation = CN VI Abducens test = look laterally

Question 29

State the movement, innervation and test of the medial rectus muscle?

Answer 29

movement = medial rotation innervation = CN III Oculomotor nerve test = look medially

Question 30

State the movement, innervation and testing of the superior rectus muscle?

Answer 30

movement = elevates innervation = CN III Oculomotor nerve test = look medially and upward

Question 31

State the movement, innervation and testing of the inferior rectus muscle?

Answer 31

movement = depresses innervation = CN III Oculomotor test = look laterally and downward

Question 32

State the movement, innervation and testing of the inferior oblique muscle?

Answer 32

movement = elevates eye + lateral rotation innervation = CN III Oculomotor nerve test = look laterally and upward

Question 33

What is intorsion?

Answer 33

medial (inward) rotation of upper pole (12 o’clock position) of cornea > caused by superior oblique and superior rectus

Question 34

What is extorsion?

Answer 34

Lateral (outward) rotation of superior pole of the cornea > caused by inferior rectus and inferior oblique

Question 35

What will happen to the position of the eyes if there is damage to the right abducent nerve - the sixth cranial nerve?

Answer 35

right eye rotates medially

Question 36

What will happen if there is damage to the trochlear nerve - the fourth cranial nerve?

Answer 36

eye rotates laterally and upward

Question 37

What will happen if there is damage to the third cranial nerve - the oculomotor nerve?

Answer 37

eye rotates laterally and downward

Question 38

Name the 3 layers that support and maintain the eye?

Answer 38

1. Outer fibrous layer 2. Middle vascular (pigmented) layer 3. Inner layer

Question 39

What are the consequences of a lesion of the CN III nerve?

Answer 39

complete ptosis - drooping of the upper eyelid

Question 39

State the origin, insertion, innervation and action of the levator palpebrae superioris?

Answer 39

Origin: lesser wing of shpenoid Insertion: anterior surface of the tarsal Innervation: Occulomotor nerve (CNIII) Action: Elevation of upper eyelid