Lecture 10 Eye Muscles

Question 1

What do the intrinsic ocular muscles control

Answer 1

control pupil diameter & helps alter lens curvature to enable us to see near objects

Question 2

What do the extrinsic ocular muscles do (extra ocular)

Answer 2

Move the eye

Question 3

How many extra ocular muscles are there

Answer 3

6

Question 4

Name the extra ocular muscles

Answer 4

Superior rectus
Inferior rectus
Lateral rectus
Medial rectus
Superior oblique
Inferior oblique

Question 5

Where do the recti muscles arise from

Answer 5

Arise from the orbit from an annular fibrous ring

Question 6

Where does the superior oblique muscle arise from

Answer 6

Roof of the orbit posteriorly

Question 7

Where does the inferior oblique muscle arise from

Answer 7

Floor of the orbit anteriorly

Question 8

Where does the elevator palpebral superiors lie and what is its purpose

Answer 8

Just above the superior rectus and elevates the eyelid

Question 9

Where do the rectify muscles insert into the sclera

Answer 9

Anterioirly

Question 10

Where do the oblique muscles insert into the sclera

Answer 10

Posteriorly

Question 11

What are the muscles in the face that close the eyelids

Answer 11

Orbicularis oculi

Question 12

What are the 2 parts of the orbicularis oculi

Answer 12

orbital and palpebral sections

Question 13

Where does the orbicularis oculi arise from

Answer 13

It arises from the nasal part of the frontal bone, from the frontal process of the maxilla in front of the lacrimal groove, and from the anterior surface and borders of a short fibrous band, the medial palpebral ligament

Question 14

Define uniocular

Answer 14

Movement of one eye

Question 15

Define binocular

Answer 15

Movement of two eyes

Question 16

Define intorsion

Answer 16

When the top of the eyeball rotates towards the nose

Question 17

Define Extorsion

Answer 17

When the top of the eyeball rotates away from the nose

Question 18

What is the action of the medial rectus

Answer 18

Adduction

Question 19

What is the action of the lateral rectus

Answer 19

Abduction

Question 20

What are the actions of the superior rectus

Answer 20

Elevation
Adduction
Intorsion

Question 21

What are the actions of the inferior rectus

Answer 21

Depression
Adduction
Extorsion

Question 22

What are the actions of the superior oblique

Answer 22

Intorsion
Depression
Abduction

Question 23

What are the actions of the inferior oblique

Answer 23

Extorsion
Elevation
Abduction

Question 24

Why do extra ocular muscles except for the medial and lateral rectus have more than one action

Answer 24

due to the angle they make with the optical axis of the eye while inserting into the eyeball.

Question 25

Why do the muscles pull the eyeball at an angle

Answer 25

The muscles are attached to the orbital axis not the optical axis

Question 26

What muscle is the only elevator of the abducted eye

Answer 26

Superior rectus

Question 27

What is Strabismus

Answer 27

Squint (misalignment of the eyes)

Question 28

What are the 2 types of Strabismus

Answer 28

* Esotropia (manifest convergent squint) | * Exotropia (manifest divergent squint)

Question 29

What are the functional consequences of a squint

Answer 29

Amblyopia (brain surpasses the image of one eye) | Diplopia (nerve palsies)

Question 30

Name the intrinsic muscles in the eye

Answer 30

Ciliaris Sphincter Pupillae Dilator Pupillae

Question 31

What innervation of the intrinsic muscles

Answer 31

Ciliaris- parasympathetic (oculomotor, ciliary ggl.) Sphincter- parasympathetic (oculomotor, ciliary ggl.) Dilator- sympathetic. (T1, sup, cervical ggl.)

Question 32

What happens to the pupils in increased illumination

Answer 32

Both pupils constrict

Question 33

What happens to pupils in decreased illumination

Answer 33

Pupils dilate

Question 34

Fibres destined to activate the pupillary reflex go where after the optic tract (afferent pathway)

Answer 34

Do not go to the LGB instead leave optic tract to go the midbrain (where IIIn nucleus is situated) Edinger-Westphal nucleus

Question 35

Describe the efferent pathway of the light reflex

Answer 35

From EWN in IIIn nucleus, preganglionic parasympathetic pass through IIIn into orbit. Parasympathetic fibres go to & synapse in ciliary ganglion. Postganglionic fibres go through short ciliary nerves to constrictor pupillae

Question 36

What is the LGB

Answer 36

Lateral Geniculate Nucleus A relay centre in the thalamus for the visual pathway. Receives major sensory input from the retina

Question 37

What condition can cause pupil abnormalities

Answer 37

Horner's Syndrome- pupils look different sizes anisocoria

Question 38

What are some common causes of absent/abnormal pupillary reflex

Answer 38

* Any abnormality of the afferent limb/ centre / efferent limb of the reflex * Diseases of the retina – detachment/ degenerations or dystrophies * Diseases of the optic nerve – such as in optic neuritis (frequently seen in MS) * Diseases of the III cranial nerve (efferent limb)

Question 39

What is the afferent limb of the pupillary reflex made of

Answer 39

Retina, opic nerve, IIIn nucleus (EWN)

Question 40

What is the efferent limb of the pupillary reflex made of

Answer 40

IIIn nucleus (EWN), ciliary ganglion, ciliary sphincter muscle

Question 41

What innervation is damaged in Horner's syndrome and what is the consequence

Answer 41

Sympathetic innervation | Affected pupil cannot dilate so is constricted

Question 42

Horner's syndrome can occur due to the disruption of

Answer 42

* Thoracolumbar outflow of the sympathetic * Sympathetic chain and cervical ganglia * Head and neck – postganglionic sympathetic fibres travel along with blood vessels * E.g. Pancoast tumour of the lungs