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12.6: Visual Accessory Organs of the Eye. 2.1 Atoms, Ions, and Molecules. Sponge: Set up Cornell Notes on pg. 71 Topic: 12.6: Visual Accessory Organs of the Eye Essential Questions : What is the function of the lacrimal apparatus? Describe the pathways of the tears. Sight.
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12.6: Visual Accessory Organs of the Eye 2.1 Atoms, Ions, and Molecules Sponge: Set up Cornell Notes on pg. 71 Topic: 12.6: Visual Accessory Organs of the Eye Essential Questions: • What is the function of the lacrimal apparatus? Describe the pathways of the tears.
Sight • Visual Accessory Organs • eyelids • lacrimal apparatus • extrinsic eye muscles
Eyelid (palpebra) is composed of four layers: • 1. Skin • Thinnest skin of the body • Protection • 2. Muscle • orbicularis oculi (orbic-u-laris) – closes lid • levatorpalperbraesuperioris – opens lid • 3. Connective tissue • tarsal glands – secrete oil onto eyelashes • Helps keep lids from sticking together
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
Conjunctivitis aka “Pinkeye”: inflammation of the conjunctiva • Caused by bacteria • Highly contagious
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?
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 Protection2m6sAccessory Structures of the EyeStart: 2m36s
Figure 12.24 Extrinsic Eye Muscles
Extrinsic Eye Muscles • Superior rectus • rotates eye up and medially • Inferior rectus • rotates eye down and medially • Medial rectus • rotates eye medially
Extrinsic Eye Muscles • Lateral rectus • rotates eye laterally • Superior oblique • rotates eye down and laterally • Inferior oblique • rotates eye up and laterally
SR= superior rectus • IR= Inferior rectus • MR= Medial rectus • LR= lateral rectus • SO= Superior oblique • IO=Inferior oblique
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