Sponge: Set up Cornell Notes on pg. 71Topic: 12.6: Visual Accessory Organs of the Eye

Essential Questions:1. What is the function of

the lacrimal apparatus? Describe the pathways of the tears.

2.1 Atoms, Ions, and Molecules

12.6: Visual Accessory Organs of the Eye

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SightVisual Accessory Organs• eyelids• lacrimal apparatus• extrinsic eye muscles

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Eyelid (palpebra) is composed of four layers:

1. Skin• Thinnest skin of the body• Protection

2. Muscle • orbicularis oculi (orbic-u-laris) – closes

lid• levator palperbrae superioris – opens lid

3. Connective tissue• tarsal glands – secrete oil onto eyelashes

• Helps keep lids from sticking together

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4. Conjunctiva (Con-junct-i-va)• mucous membrane; lines eyelid and covers portion of

eyeball• Lubricates eye• Prevents microbes from entering the eye• Protection• Contain an enzyme that has antibacterial properties

• Reduces eye infections• Thin/Freely movable/ transparent

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Conjunctivitis aka “Pinkeye”: inflammation of the conjunctiva• Caused by bacteria• Highly contagious

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Lacrimal Apparatus• Lacrimal gland

• lateral to eye• secretes tears

1. Canaliculi (cana-lik-u-lie)• collects tears

2. lacrimal sac• collects tears from canaliculi

3. nasolacrimal duct• collects tears from lacrimal

sac and empties tears into nasal cavity

Figure 12.23

How does this picture explain why your nose start to run when you are crying?

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• Tear glands secrete excessively when a person is upset or when the conjunctiva is irritated

• Tears spill over the eyelid, nose fills with fluid

The Eyes Natural Protection2m6s

Accessory Structures of the EyeStart: 2m36s

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Figure 12.24 Extrinsic Eye Muscles

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Extrinsic Eye Muscles

Superior rectus• rotates eye up and

medially

Inferior rectus• rotates eye down and

medially

Medial rectus• rotates eye medially

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Extrinsic Eye Muscles

Lateral rectus• rotates eye laterally

Superior oblique• rotates eye down

and laterally

Inferior oblique• rotates eye up and

laterally

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• SR= superior rectus

• IR= Inferior rectus

• MR= Medial rectus

• LR= lateral rectus

• SO= Superior oblique

• IO=Inferior oblique

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• The motor units of the eye muscles have the fewest muscle fibers of any muscles in the body• Move with great precision• Eyes move together

• Align when looking at something