Ocular muscles Flashcards
What are the seven extraocular muscles
- ) Lateral rectus
- ) Medial rectus
- ) Superior rectus
- ) Inferior rectus
- ) Superior oblique
- ) Inferior oblique
- ) Levator palpebrae superioris
Which muscles correct the eye movements
Superior oblique and inferior oblique
Which muscle lifts the upper eye lid
Levator palpebrae superioris
L.O.S insertion
- It inserts onto the upper eye li
LPS nerve supply
Facial nerve (sympathetic nerve supply)
What is it called when you get loss of function of LPS
Ptosis
What does the lateral rectus do
Pulls the eye laterally (abduction)
What does the medial rectus do
Pulls the eye medially (adduction)
What does the superior rectus do
Pulls the eye up + medially and rotates it
What does the inferior rectus do?
Pulls the eye down and medially rotate it
Define intorsion
Rotation of the eye
Define extorsion
Rotation of both eyes
What does superior oblique
Corrects the inferior rectus action. The tendon goes through a trochlear (Pulley) and attaches to the globe of the eyeball at the top
What does superior oblique
Corrects the inferior rectus action. The tendon goes through a trochlear (Pulley) and attaches to the globe of the eyeball at the top
What does the inferior oblique do
Corrects the superior rectus action
How to examine eye movements
- ) Sit directly in front of patient (so eyes at same level)
- ) Sit 2 arms lengths apart
- ) Test peripheral vision
How to examine lateral and medial rectus
- Sit in front of the patient.
- Place a finger at eye level about an arms length from their face and move your finger right and left.
- Do this twice, once whilst observing the left eye and once whilst observing the right eye.
How to test superior and inferior rectus muscle
Sit in front of the patient. Place a finger at eye level about an arms length from their face and out to the right side move your finger up and down.
Repeat this on the left side.
The issue
- If the lateral rectus muscle doesn’t work the eye can’t be abducted
- Superior + inferior can’t be tested in isolation
Examination of inferior and superior oblique muscles
- We have to position the eye so that superior/inferior recti are giving max rotation + look for complete correction
Examination of inferior and superior oblique muscles
- We have to position the eye so that superior/inferior recti are giving max rotation + look for complete correction
- Sit in front of the patient. Place a finger at eye level about an arms length from their face and out to the left side move your finger up and down.
Repeat this on the right side.
Semi-circular canal structure
Have:
- ) Superior canal
- ) Lateral Canal
- ) Posterior canal
- ) Vestibule
- ) Cochlea
Where does the semi-circular canallie
The petrous part of temporal bone
Semi-circular canal function
- Has an ampulla (a swelling)
- In this ampulla there is cupula/hair cells and nerve fibres
Function
- The cupula movement generates nerve impulses
- Has cilia
Process
- endolymph fluid moves
- cupula distorts
- distortion detected by hair cells
- neuronal impulse generates
Dizziness
- When the semi-circular canals send signals to brain when there is no movement
Physiological cause of dizziness
After spinning round
Pathological cause of dizziness
Labyrinthitis: inflammation of hair cells (often due to viral infection)
Reflex
- ice cold water in ear
- petrous part of bone is cold
- part is warm
- creates a convection current in canal
- signal to brain is sent
- eyes slowly move towards cold water then jump back to normal position
