Eye Muscles Flashcards
(31 cards)
Which set of muscles moves the eyeball ?
Extrinsic muscles
Name the two sets of extrinsic eye muscles.
Recti Muscles (SLIM) and Oblique
5 of the extrinsic muscle originate in the common tendinous ring. Which one does not? Where does it originate.
- Inferior oblique
2. Originates from the medial orbit surface.
What structure causes the superior oblique to make a right-angle turn?
A fibrocartilaginous loop called the trochlea
How are the extrinsic muscles attached to the eye ball
The extrinsic muscles are attaches along the orbital axis
List the 3 functions of the extrinsic eye muscles?
- Allow eyes to follow a moving object.
- Maintain shape of eyeball.
- Hold eyeball in the orbit
Why do we need the obliques to elevate and depress the eye when we have the inferior and superior recti?
Obliques provide the lateral pull needed to counteract the medial pull of the inferior and superior recti.
Define strabismus and its symptoms.
- A congenital weakness of the external eye muscles
2. Causes the eyes to rotate medially or laterally (“cross-eyed”).
Name and describe one consequence arising from strabismus.
- Diplopia (double vision).
- Unable to focus the images from each eye, so people see two images instead of one.
- Eyes may alternate focusing, or brain ignores input from weak eye.
- May lead to functional blindness.
List the 4 members of the recti muscle group.
- Superior
- Lateral
- Inferior
- Medial
List the 2 members of the oblique muscle group.
- Superior
2. Inferior
List 2 functions of the intrinsic eye muscles?
- Control pupil diameter
2. Changes curvature of lens
List the 3 intrinsic eye muscles.
- Ciliary muscle
- Constrictor pupillae
- Dilator pupillae
Where is the ciliary muscle found?
In the ciliary body.
Where is the constrictor pupillae found?
In the iris at the pupillary border.
What is the orientation of the dilator pupillae and where are they found?
- Radial
2. In the iris
How is the the ciliary muscle innervated?
Parasympathetic branch of oculomotor (III)
How is the the constrictor pupillae innervated?
Parasympathetic branch of oculomotor (III)
How is the the dilator pupillae innervated?
- Dilation controlled by sympathetic branch of oculomotor (III)
- Constriction controlled by parasympathetic branch of Oculomotor (III)
What is the pupillary reaction to increased illumination or close objects?
- Parasympathetic branch of oculomotor (III) causes the sphincter pupillae to contract
- Pupil constricts to prevent light entering.
What is the pupillary reaction to decreased illumination or distant objects?
- Sympathetic branch of oculomotor (III) causes the dilator pupillae muscle to contract
- Pupil dilates allowing more light to enter.
name the 6 extraocular muscles and what nerve innervates them
lateral rectus (CN6) medial rectus (CN3) superior rectus (CN3) inferior rectus (CN3) inferior oblique (CN3) superior oblique (CN4)
what are the anatomical movements of each muscle?
LR = abduction MR = adduction SR = elevation intorsion, adduction IR = depression, extorsion, adduction IO = extorsion, elevation, abduction SO = intorsion, depression, abduction
how would you test each muscle in isolation?
LR = abduct MR = adduct SR = up and out IR = down and out IO = up and in SO = down and in
