EYE

I.   INTRODUCTION
–  eyelids ( palpebrae)

–  external landmarks

1.  Sclera: “whites” of the eye
2.  Cornea:  transparent center part in front of the iris
3.  Iris: pigmented part of eye
4.  Pupil:  opening in iris

–  Lining sclera and eyelid is conjunctiva

*  function:

II.  LACRIMAL APPARATUS
–  produces/collects tears

A.  Lacrimal Gland:
*  produces tears

B.  Lacrimal Puncti: little openings which drain the tears

 

C.  Nasolacrimal Duct: drains tears into nasal cavity

What do you think?  When a person cries, tears spill onto the cheeks and the person gets a runny rose.  Based on your knowledge of the lacrimal apparatus, what is happening?

III. EXTRINSIC EYE MUSCLES

A.  Superior Rectus:
*  elevates eye and moves eye medially (adducts the eye)

B.  Inferior Rectus:
* depresses eye and moves eye medially

C.  Medial Rectus:
*  moves eye medially

D.  Lateral Rectus:
*  moves eye laterally (abducts the eye)

E.  Superior Oblique:
*  depresses eye and moves eye laterally

F.  Inferior Oblique:
*  elevates eye and moves eye laterally

IV.  LENS
–  Lens: biconvex, transparent structure inside eyeball

*  held in place by suspensory ligaments

V.   EYEBALL LAYERS (TUNICS)

A.  Fibrous (External) Tunic:  it is avascular

1.  Sclera:

*  posterior 5/6 of eye
*  function:

2.  Cornea:  curved, transparent structure in front of iris & pupil
*  anterior 1/6 of the eye
*  function:

B.  Vascular Tunic:

1.  Choroid: dark brown membrane

* function:

2.  Ciliary body:  a ring of tissue that surrounds lens

*  smooth muscle tissue
* attaches to lens via suspensory ligaments
*  functions:

3.  Iris:  pigmented, colored part of eye
*  pupil

*  function:

C.  Neural Tunic:  Retina
*  posterior 3/4 of eye

1.  Pigmented Layer: outer layer

*  functions:

2.  Neural Layer: inner layer
*  function: receives light information and converts it into nerve impulses that are sent, via CN II (optic nerve) to the brain

*  contains photoreceptors

Optic Disc (“Blind Spot”): area where the optic nerve exits the eye
*  contains no photoreceptors

Macula Lutea:

lateral to blind spot

*  in center is Fovea Centralis:

VI.  INTERNAL CHAMBERS OF THE EYE

A.   Anterior Cavity:
*  between cornea and lens

*  filled with aqueous humor

B.  Posterior Cavity: 
*  between lens and retina
*  contains vitreous humor

VII.  HOW VISUAL INFO IS PROCESSED

1. Light rays enter eye through the cornea and are refracted (bent)
2. Light rays are further refracted by the lens
3. Light rays focus on retina
4. Light ray information is converted to nerve impulses by photoreceptors
5. Nerve impulses transmitted to the brain via CN II (Optic nerve)

Which extrinsic eye muscle depresses the eye & moves the eye laterally?

a.  superior oblique     

b.  superior rectus 

c.  inferior rectus        

d.  lateral rectus          

e.  inferior oblique

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