12.4: Accessory Organs of the Eye Sponge: Set up Cornell Notes on pg. 45 Topic: 12.4: Accessory Organs of the Eye Essential Questions: What is the function of the lacrimal apparatus? Describe the pathways of the tears. 12.4: Accessory Organs of the Eye 2.1 Atoms, Ions, and Molecules What is the function of the lacrimal apparatus? Describe the pathways of the tears. Get out HW from Tuesday—Pain Handout for signature

Objective SWU: the location and function of the accessory structures of the eye, including common disorders associtated In tables, SW: research their assigned accessory structure and identify their functions

Vision: Crash Course A+P 5m19s P. 44 10 bullets *Special Directions: Stare at ONE star on the flag during the whole opening. Try not to blink or move your eyes. https://www.youtube.com/watch?v=o0DYP-u1rNM

White Board Research Table 1: Eyelids Table 2: Conjunctiva Table 3: Conjunctivitis Table 4: Lacrimal Gland Table 5: Extrinsic Eye Muscles Table 6: Strabismus

Visual Accessory Organs Eyelids Conjunctiva 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 Levator palperbrae superioris – 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

Causes: Viruses Bacteria Irritants such as shampoos, dirt, smoke, and pool chlorine Allergies, like dust, pollen, or a special type of allergy that affects some contact lens wearers Pinkeye in newborn babies, however, should be reported to a doctor immediately, as it could be a vision-threatening infection.

Symptoms: The symptoms of pinkeye differ based on the cause of the inflammation, but may include: Redness in the white of the eye or inner eyelid Increased amount of tears Thick yellow discharge that crusts over the eyelashes, especially after sleep Green or white discharge from the eye Itchy eyes Burning eyes Blurred vision Increased sensitivity to light

Treatment: The treatment for pinkeye depends on the cause: Bacteria: Antibiotics, in the form of eye drops, ointments, or pills. Viruses: Must run its course (4-7 days) Irritants: For pinkeye caused by an irritating substance, use water to wash the substance from the eye for five minutes. Allergies: Allergy-associated conjunctivitis should improve once the allergy is treated and the allergen removed.

Complications: Certain forms of conjunctivitis can become serious and sight-threatening, because they can cause cornea scarring. Caused by gonorrhea, chlamydia, or certain strains of the adeno virus.

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

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 Protection 2m6s P. 44 3 bullets

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

Strabismus is a disorder in which both eyes do not line up in the same direction, so they do not look at the same object at the same time. AKA: "crossed eyes”

Causes: The six muscles of the eye allow both eyes to focus on the same object. In someone with strabismus, the muscles do not work together. As a result, one eye looks at one object, while the other eye turns in a different direction to focus on another object. When this occurs, two different images are sent to the brain -- one from each eye. This confuses the brain.

Causes: In children, the brain may learn to ignore the image from the weaker eye. In most children with strabismus, the cause is unknown. In more than half of these cases, the problem is present at or shortly after birth. Most of the time, the problem has to do with muscle control, and not with muscle strength.

Symptoms: Symptoms of strabismus may be present all the time, or may come and go. Crossed eyes Double vision Eyes that do not align in the same direction Uncoordinated eye movements (eyes do not move together) Loss of vision or depth perception

Treatment: The first step in treating strabismus in children is to prescribe glasses, if needed. A patch is placed over the better eye. This forces the weaker eye to work harder and get better vision. Eye muscle surgery may be needed if the eyes still do not move correctly. Does not fix the poor vision of a lazy eye. A child may still have to wear glasses after surgery. Surgery is more often successful if done when the child is younger. VISION MUST BE CORRECTED FIRST!

Prognosis: After surgery, the eyes may look straight, but vision problems can remain. The child may still have reading problems in school. Adults may have a hard time driving. Vision may affect the ability to play sports. Permanent vision loss in one eye may occur if treatment is delayed. If amblyopia (vision loss) is not treated by about age 11, it is likely to be permanent. Many children will get strabismus or amblyopia again, so the child will need to be monitored closely.

The Doctors: Double Vision and Strabismus 59s-4m55s P. 44 3 bullets https://www.youtube.com/watch?v=iP2VCZzR1Ic